Physics talk

[mossy1200]

I'm not sure how much truth there is in this.

Yes when you pick a wheel up (radio controlled car works good) and accelerate the tyre deforms I know how your so called "centrifugal" force works, but once you put it on a road, with a normal force, things start changing dramatically.

Centrifugal growth can cause tyre diameter to increase 2% on a steel belt and more on older tyre.
At slow speeds inflation pressures can change the distance travelled per rotation also.
A under inflated tyre will cover less distance at slower speeds but will grow taller than a correctly inflated tyre at high speeds.
They are only small amounts.

The same goes for a gearbox driven speedo. As the bike gets faster the percentage of wheel slip increases and the speedo reads faster than true speed travelled. Some bike racing on salt lakes travelling 300 have a rear wheel speed of 330+ losing 30kph or more in wheel spin.

These are all small factors when riding a bike and wouldnt be enough to make a difference at road legal speeds though.

[Oakie]

Some bike racing on slat lakes travelling 300 have a rear wheel speed of 330+ losing 30kph or more in wheel spin.

Is a slat lake like a slat bed?

[Ocean1]

Some bike racing on slat lakes travelling 300 have a rear wheel speed of 330+ losing 30kph or more in wheel spin.

Must remember that next time...


Top Fuel racing slicks can grow 10" in diameter at 300mph. That's a Meter per rev more.

But there's no speedo to worry about, eh.

[mossy1200]

Must remember that next time...


Top Fuel racing slicks can grow 10" in diameter at 300mph. That's a Meter per rev more.

But there's no speedo to worry about, eh.

Its my excuse for doing 286 at the last quarter mile. Im sure I had 14kph of wheel spin going on.

[mossy1200]

Is a slat lake like a slat bed?

Yes. Nobody races bikes on waterbeds.

[Hawk]

want if you are traveling in the opposite direction of the earths rotation does that mean you are still moving, going slower, or faster :brick:

[FJRider]

want if you are traveling in the opposite direction of the earths rotation does that mean you are still moving, going slower, or faster :brick:

That would depend on the settings of your Flux Capacitor ....

[Dave-]

Centrifugal growth can cause tyre diameter to increase 2% on a steel belt and more on older tyre.
At slow speeds inflation pressures can change the distance travelled per rotation also.
A under inflated tyre will cover less distance at slower speeds but will grow taller than a correctly inflated tyre at high speeds.
They are only small amounts.

The same goes for a gearbox driven speedo. As the bike gets faster the percentage of wheel slip increases and the speedo reads faster than true speed travelled. Some bike racing on salt lakes travelling 300 have a rear wheel speed of 330+ losing 30kph or more in wheel spin.

These are all small factors when riding a bike and wouldnt be enough to make a difference at road legal speeds though.

Centrifugal force doesn't exist, so I'm not sure what you're on about there.

But even if your tyre expands by 2% it's pressed on to the road by some mass which is going to be greater than the 2% increase, or so I think, and my very quick calcs would suggest.

I'm actually putting together the idea of the smart-bike which would take your velocity primarily from GPS and/or accelerometer it's only a matter of time before the bike becomes "smart"


Even if you are going down a very steep hill and your movement around the earths circumference is 100 but trig calcs would have you doing a true speed higher than the gps shows.

Does a GPS register distance calculated including verticle climb angles?

GPS reads in 3 dimensions from at least 4 satellites in geosynchronous orbit (which means they don't move relative to the earth) so even when you're going up or down hill you get the magnitude of velocity.

[scumdog]

But even if your tyre expands by 2% it's pressed on to the road by some mass which is going to be greater than the 2% increase, or so I think, and my very quick calcs would suggest.

.

Hmm, from memory those who race dragsters have to calculate tyre 'growth' into the calculations for the correct gearing...have a look at one at rest and then look at the tyre diameter change when the dragster is in 'full flight'.

[Dave-]

Hmm, from memory those who race dragsters have to calculate tyre 'growth' into the calculations for the correct gearing...have a look at one at rest and then look at the tyre diameter change when the dragster is in 'full flight'.

That's cause the ratio of the weight of the car vs the centripetal force of the tyre spinning is lower, so yes I would expect that.

Then again they have a great big wing pressing them on to the track, but that'll only work for ~120kph? at a guess? so before that while the wheel is spinning they may very well have to account for it.

Like I said, I may be wrong, but I'm fairly certain that the expansion of a road bike wheel wont make much of a difference on the force the body provides putting it there, my quick calcs suggested it would, but I had to pull some numbers out of my ass for an arbitrarily thin piece of tyre.

plus I'm electrical engineering, I'll run it buy the mechanical guys.

someone ought to tell me I'm a know it all scientist soon, that's the usual KB way.....

edit: the mechanical guys have just told me they think the tyre will get smaller cause it'll be mushed into the track.

there was a shot at bathurst showing this down conrod straight a few weeks ago, probably on youtube somewhere.

[Coolz]

Dave...your idea that centrifugal force dosn't exist and bikes are getting smarter all the time suggests to me that you have lost that race already!

[onearmedbandit]

Then again they have a great big wing pressing them on to the track, but that'll only work for ~120kph? at a guess? so before that while the wheel is spinning they may very well have to account for it.



Apparently the rear wing at speed generates 5000lb of downward force at speed, yet the diameter of the rear tyres grow a few inches right through the whole run, including terminal velocity.

[Dave-]

Dave...your idea that centrifugal force dosn't exist and bikes are getting smarter all the time suggests to me that you have lost that race already!

Centrifugal force is what they teach you in high school cause your dumb undeveloped teenage brain can't comprehend that the direction of the force is towards the center of rotation.

And it works well for most people. If you want to know more most universities cover it in 100 level physics.

To conclude I think there's other things that attribute to the uncertainty in speedo reading, mechanical slip of the tyre, electronic pulses, the impedance of the inductor on the speedo increases with frequency, temperature, etc, on modern digital tachometers (the thing that shows you revolutions per minute) to save on costs they don't filter the signal, and it can get really saw-tooth shaped if you don't, when you do however you get a much more accurate representation, I know this cause I designed and built one at uni this year.

If you're really worried about it get a GPS, they're fail proof....except for when you cant connect to enough satellites :)

[Gremlin]

edit: the mechanical guys have just told me they think the tyre will get smaller cause it'll be mushed into the track.

there was a shot at bathurst showing this down conrod straight a few weeks ago, probably on youtube somewhere.
The tyre is getting squashed into the track because of the rather large amount of downforce being generated by the car above the tyres. On the flip side, watch drag cars when they warm up their tyres in the staging. Square conventional looking tyres turn into donuts (no RC, leave alone), quite an impressive deformation. I also enjoy the wheel shots from V8 supercars as they're going around corners :crazy:


Dave...your idea that centrifugal force dosn't exist and bikes are getting smarter all the time suggests to me that you have lost that race already!
As Dave said, Centrifugal force doesn't actually exist... hell, I didn't learn much in physics, but at least I remembered that...

[dangerous]

the concorde strechs two foot longer in full flight, hows that farking work brain box's ;)

and ive walked faster than a 767 doing 500kph... honest

[mossy1200]

Centrifugal force is what they teach you in high school cause your dumb undeveloped teenage brain can't comprehend that the direction of the force is towards the center of rotation.

And it works well for most people. If you want to know more most universities cover it in 100 level physics.



You better hold on tight to the merry-go-round or you might fly into the middle.

[jim.cox]

the concorde strechs two foot longer in full flight

That figure seems more than a little far fetched - can you provide a reference?

[oneofsix]

That figure seems more than a little far fetched - can you provide a reference?

Nice challenge :laugh: I thought two foot sounded like what I had heard but a quick google and most results are saying 6 - 10 inches.

www.britishairways.com/concorde/aboutconcorde.htmlConcorde measures 204ft in length - stretching between six and ten inches in-flight due to heating of the airframe.

www.manchesterairport.co.uk › At the AirportConcorde G-BOAC (affectionately known as 'Alpha Charlie') became the second ... During flight Concorde could stretch between 15 and 25 centimetres due to


Perhaps the two foot was the urban myth version.

[pzkpfw]

You better hold on tight to the merry-go-round or you might fly into the middle.

If you let go, you'd fly off (away, at a tangent) in a straight line in the direction you were going. The force, that keeps you going around and around instead of flying off in that straight line, is towards the centre of the merry-go-round. (Similar, in a way, to Earths gravity keeping our Moon in orbit, instead of travelling off somewhere else).

http://en.wikipedia.org/wiki/Centripetal_force

http://en.wikipedia.org/wiki/Centrifugal_force_(fictitious)

http://en.wikipedia.org/wiki/History_of_centrifugal_and_centripetal_forces

[HenryDorsetCase]

If you let go, you'd fly off (away, at a tangent) in a straight line in the direction you were going. The force, that keeps you going around and around instead of flying off in that straight line, is towards the centre of the merry-go-round. (Similar, in a way, to Earths gravity keeping our Moon in orbit, instead of travelling off somewhere else).

http://en.wikipedia.org/wiki/Centripetal_force

http://en.wikipedia.org/wiki/Centrifugal_force_(fictitious)

http://en.wikipedia.org/wiki/History_of_centrifugal_and_centripetal_forcesthank s for these links. And they say you never learn stuff on KB

[huff3r]

In theory ... GPS measures across the Earths surface ... (the earth being round) so one may assume climbing/descending speeds are not entirely true.

Vehicle GPS tracking systems should be entirely reliant on Global positioning changes to log speed across the earths surface. Not repeating speedometer readings.


That's a pretty poor theory, as then an aircraft with a GPS backed up Inertial Reference Unit would be stuffed. GPS can and does give a 3d fix in space using four satellites, but your best bet is 5 or 6 so you know if ones dodgy. So it'll quite happily give you your velocity in any direction, including straight up or down if your driving on a vertical surface :pinch:

[Dave-]

You better hold on tight to the merry-go-round or you might fly into the middle.

Honestly don't worry about it, if you've got this far in life without needing to know it you've either been very lucky, or your livelihood hasn't required the knowledge, you'll get through the rest of life not knowing too.

[oneofsix]

Honestly don't worry about it, if you've got this far in life without needing to know it you've either been very lucky, or your livelihood hasn't required the knowledge, you'll get through the rest of life not knowing too.

wonder if this guy cared in it was Centrifugal or Centripetal, guess he was just glad it worked.

http://www.youtube.com/watch?feature=player_embedded&v=1Igk59dxK2E

[Oakie]

If the curvature of the earth was the only confounding factor, and the radar got him at 62, he would actually be going faster, so ping him for 63.

You could always add the speed of then earth's rotation and do him for about 16062kph (although the 1600kph is at the equator)

[Berries]

You could always add the speed of then earth's rotation and do him for about 16062kph (although the 1600kph is at the equator)
Unless he is going the other way.


Stick that up your doppler.

[mossy1200]

If you let go, you'd fly off (away, at a tangent) in a straight line in the direction you were going. The force, that keeps you going around and around instead of flying off in that straight line, is towards the centre of the merry-go-round. (Similar, in a way, to Earths gravity keeping our Moon in orbit, instead of travelling off somewhere else).

http://en.wikipedia.org/wiki/Centripetal_force

http://en.wikipedia.org/wiki/Centrifugal_force_(fictitious)

http://en.wikipedia.org/wiki/History_of_centrifugal_and_centripetal_forces



You crack me up. You link the very information that shows that you dont understand what cetripetal force is.

Gravity from the mass of the Earth and the Moon attract each other.
The centripetal force is what is stopping them from coming together.

The centripetal force is outwards and not in. The balance of the mass and the cetripetal force is what maintains the distance as an orbit.

The other example is the roller coaster. The carts are on the inside of the loop. Your theory would have the cart on the outside being pulled into the centre. Im feeling safer on my roller coaster than yours.


The faster you revolve an object through rotation the higher the outwards G forces that act on the mass in rotation.
The tyre wishes to leave the centre point and expands with the limiting factor being the strength of the construction.
Turn it fast enough the tyre becomes taller and skinnier.

You need to read your link again im afraid.

[Dave-]

You could always add the speed of then earth's rotation and do him for about 16062kph (although the 1600kph is at the equator)

Heisenberg was out driving one day, he was pulled over by a policeman. The policeman asked, "Do you know how fast you were going back there? Heisenberg replied, "No, but I know where I am."

I once thought about dobbing a police officer in for speeding, I was sitting still on my motorcycle and the world was moving past me!....lol

rastuscat have you had either of those excuses yet? can you tell me a bedtime story about some of the excuses you have heard?

[Oakie]

Unless he is going the other way. Stick that up your doppler.

Thought about that too but it just made my head hurt. A fine for going 15937kph backwards?

[Ocean1]

Heisenberg replied, "No, but I know where I am."

Well he would , wouldn't he, just on principle.

[Dave-]

You crack me up. You link the very information that shows that you dont understand what cetripetal force is.

Gravity from the mass of the Earth and the Moon attract each other.
The centripetal force is what is stopping them from coming together.

The centripetal force is outwards and not in. The balance of the mass and the cetripetal force is what maintains the distance as an orbit.

The other example is the roller coaster. The carts are on the inside of the loop. Your theory would have the cart on the outside being pulled into the centre. Im feeling safer on my roller coaster than yours.


The faster you revolve an object through rotation the higher the outwards G forces that act on the mass in rotation.
The tyre wishes to leave the centre point and expands with the limiting factor being the strength of the construction.
Turn it fast enough the tyre becomes taller and skinnier.

You need to read your link again im afraid.

If you have an object revolving through rotation (what? I know right?) and it's not changing speed, is it accelerating?

[Oakie]

And if you had a steel donut and heated it with a very hot thing, when the steel expanded would the hole in the middle of the donut get bigger or smaller?

(Sorry RC. Hope you don't dream of steel donuts now.)

[mossy1200]

If you have an object revolving through rotation (what? I know right?) and it's not changing speed, is it accelerating?

No but it still wants to leave its axis point hense tire expansion outwards. On a small scale than that of a drag car tire.
Ask a custom bike builder about the damage a tire with not enough guard clearance due to expansion during rotation.

[Ocean1]

And if you had a steel donut and heated it with a very hot thing, when the steel expanded would the hole in the middle of the donut get bigger or smaller?

(Sorry RC. Hope you don't dream of steel donuts now.)

Really?

Depends. :yes:

On the ratio of steel to hole.

[Dave-]

No but it still wants to leave its axis point hense tire expansion outwards. On a small scale than that of a drag car tire.
Ask a custom bike builder about the damage a tire with not enough guard clearance due to expansion during rotation.

No?!? it's not accelerating? haha gotcha

oh man....you honestly have no idea what you're talking about dude.

what else can you tell me about physics? if you hold up a rope with one hand, then pull your weight off the ground with the other, do you fly?


Really?

Depends. :yes:

On the ratio of steel to hole.

No the hole gets larger always.

It's to do with the atoms vibrating faster due to having higher energy and the electromagnetic force (cant remember if it's electromagnetic or vander vaals) binding the atoms stays the same.

Digging up exam questions from 2 years ago here guys.

Who knows which way electrons flow in a circuit? positive to negative? or negative to positive?

[Ocean1]

No the hole gets larger always.

So, a 10mm hole in a 1000mm steel sheet gets larger if you heat the steel?

[mossy1200]

No?!? it's not accelerating? haha gotcha

oh man....you honestly have no idea what you're talking about dude.

what else can you tell me about physics? if you hold up a rope with one hand, then pull your weight off the ground with the other, do you fly?

Im not sure what your trying to prove. You took the topic away from cetrifugal force and added revolving mass centripetal force.

Go take a weight on elastic out into your back yard and spin it in circles and come back in and tell me the elastic didnt stretch.


Or you could just watch it online

http://www.youtube.com/watch?v=PEcMgc2D3do

[Akzle]

So, a 10mm hole in a 1000mm steel sheet gets larger if you heat the steel?
yes.



Who knows which way electrons flow in a circuit? positive to negative? or negative to positive?

:Offtopic::Offtopic:
AC bitch.
(shit don't flow.)

[Dave-]

So, a 10mm hole in a 1000mm steel sheet gets larger if you heat the steel?

yup.

thermal expansion into wikipedia ought to answer most of what you're after.


Im not sure what your trying to prove. You took the topic away from cetrifugal force and added revolving mass centripetal force.

Go take a weight on elastic out into your back yard and spin it in circles and come back in and tell me the elastic didnt stretch.


Or you could just watch it online

http://www.youtube.com/watch?v=PEcMgc2D3do

so can you explain newtons 3rd law of motion to me?




:Offtopic::Offtopic:
AC bitch.
(shit don't flow.)


you're telling me alternating current doesn't flow?

[mossy1200]

yup.

thermal expansion into wikipedia ought to answer most of what you're after.



so can you explain newtons 3rd law of motion to me?

So you still think a tire doesnt expand and increase diameter as revolutions increase?

[Dave-]

So you still think a tire doesnt expand and increase diameter as revolutions increase?

no it does, but not for the reasons you've stipulated.

please, explain how newtons 3rd law of motion applies to your centrifugal force and the centripetal force you understand so little of.

and explain to me, if force is equal to mass times acceleration, that if a tyre is spinning but not changing speed is there a force pushing it outwards? if the acceleration is 0? how does that happen?

[Oakie]

Who knows which way electrons flow in a circuit? positive to negative? or negative to positive?
Left to right?

[mossy1200]

no it does, but not for the reasons you've stipulated.

please, explain how newtons 3rd law of motion applies to your centrifugal force and the centripetal force you understand so little of.

and explain to me, if force is equal to mass times acceleration, that if a tyre is spinning but not changing speed is there a force pushing it outwards? if the acceleration is 0? how does that happen?

Ok Dave your correct the tire expands but not because of cetrifugal force. But the tire does expand.

[Dave-]

Can you get a knee down on on a cop bike?

http://henzilla.smugmug.com/Motorcycles/various-bikes/i-KJSb24F/0/M/GS-knee-draggin-M.jpg


Left to right?

Actually it's negative to positive, Benjamin Franklin got them around the wrong way, but because it's such an integrated engineering standard now and it makes no real difference, no one has dared to change it.

true story.

[Dave-]

Ok Dave your correct the tire expands but not because of cetrifugal force. But the tire does expand.

Im thinking your need to be vocally perfect might cost you a few relationships. Im not sure Newton had a theory on that though.

oh no.

10char

[mossy1200]

Actually it's negative to positive, Benjamin Franklin got them around the wrong way, but because it's such an integrated engineering standard now and it makes no real difference, no one has dared to change it.

true story.

Ok if im incorrect Dave in the reason explain the expansion in a way that we all understand.

Yesterday you mentioned a decrease in diameter but now you state you accpet an increase and im not sure why you have changed your mind on that.


The low effect of down force on a high speed bikes front wheel(where most speedos connect ) or even the rear wheel taking into account bike dont have wings forcing them downwards .

there are so many things that effect the accuracy of a crude for of speedo. Traction against surface( the wheel the speedo will cause negative or positive changes depending on front or rear), expansion or disortion of tyre and theres most likely alot of others.

[mossy1200]

oh no.

10char


Post edited and was out of line sorry.

[HenryDorsetCase]

AC bitch.
(shit don't flow.)
[/COLOR]

then anodising doesn't work, and neither does a lead acid battery.

thanks for clearing that up.

[Spuds1234]

Im no physics major, nor have I taught physics before so this maybe a bit rough, but Im going to attempt to explain this like your 5 (dont be offended). If I make an assumption about what you may or may not know then I might miss something out that will be important to you understanding this.

Centripetal force is always directed toward the center of the curve, centrifugal force is always directed away from the center.

However centrifugal forces are fictitious forces. They don't exist. They appear to be there because if human perception though.

Imagine for a moment that you're on a merry-go-round that is spinning very fast. In order to not fall off you need to hold on. Your applying a force. The direction of that force that your exerting on the bar of the merry go round is actually inwards with respect to the center of the merry-go-round. Now imagine that you let go of that merry-go-round and you fall off. You would fell like you were pulled off by a mysterious force. However an observer that is on the same merry-go-round would see that your flying radially away from the merry-go-round. But an observer on the ground in a stationary reference frame (the dude on the merry-go-round is in a spinning reference frame) would see you fall of tangentially.

People who have done physics know that velocity is a vector (it has magnitude and direction) and in this case, is always at right angle to the centripetal force, we can therefore say, from the viewpoint of the observer in a stationary non-rotational reference frame that the person is really flying away from the merry-go-round due to his inertia, because inertia is the resistance of change in motion, in this case, the person's inertia has overcame the centripetal force, and thereby he will fly tangentially away from the merry-go-around.

The reason that centrifugal force is called a fictitious force is because that it only agrees with the definition of a force (a push or a pull) when the observer is in the same rotating reference frame as the object; while an observer in an non-rotational stationary reference frame does not need to be equipped with the concept of centrifugal force. The existence of centrifugal force is really a matter of fact that which frame of reference that the observers are in.

[Spuds1234]

Go take a weight on elastic out into your back yard and spin it in circles and come back in and tell me the elastic didnt stretch.

Ignoring the elastic completely for a moment, I'll get back to it shortly.

A moving object tends to move in a straight line right? Unless a force acts on that object. When you throw a stone at something, if there wasn't gravity that stone would just fly off into the distance never to land again. Gravity is constantly acting on the stone to make it curve and come back down to Earth. A similar thing is happening when you spin a rock on a string.

To spin the rock on the rope you have to first get it moving. When you apply a force to the rock to make it move its actually moving in a straight line initially (probably for only a very very short distance if the rope is already taught). In order to make the rock move out of a straight line and into a circle, you have to keep pulling on the rope (you can't spin something around without your hand being slightly ahead of the rock). This inward force that your applying to the rope is what centripetal force is. It's an inward force because you're always pulling the rope "down" with respect to the rock (if inward is a negative direction and out is a positive direction, down would be a negative direction).

Your pulling on the rope is applying the same force to the rock. Pulling it inward/down. If you let go of the rope you would see the rock fly away tangentially (ever play with a fox tail as a kid?)

It's that inward force that your applying to the rope with your hand which the rope is then applying to the rock, the force on the rock is inward.

Of course, your hand feels the rope pulling back on it (Newton's 3rd law and all that). That's "centrifugal" force. For the same reason as on the merry-go-round it doesn't exist. If your hand could think, it would certainly think it was there (centrifugal force), but your hand is in the same reference frame as the rock -a spinning reference frame. You know better because you can see with your eyes (which are hopefully not spinning to much at this point) what is happening if you let go of the rope. The rock would fly away tangentially. So there is no centrifugal force (as explained in my other post).

Now if the rope isn't getting any longer (or shorter) when your spinning the rock, it means that the inward force the rope is applying to the rock is equal and opposite to the reaction force that the rock applies in the string rope which must be outward right? So are we back to centrifugal forces being real? No, not in the sense everyone is talking about in this thread with the exception of a few posters.

From Wikipedia:


A reactive centrifugal force is the reaction force to a centripetal force. A mass undergoing curved motion, such as circular motion, constantly accelerates toward the axis of rotation. This centripetal acceleration is provided by a centripetal force, which is exerted on the mass by some other object. In accordance with Newton's Third Law of Motion, the mass exerts an equal and opposite force on the object. This is the reactive centrifugal force. It is directed away from the center of rotation, and is exerted by the rotating mass on the object that originates the centripetal acceleration.

This conception of centrifugal force is very different from the fictitious force. As they both are given the same name, they may be easily conflated. Whereas the 'fictitious force' acts on the body moving in a circular path, the 'reactive force' is exerted by the body moving in a circular path onto some other object. The former is useful in analyzing the motion of the body in a rotating reference frame; the latter is useful for finding forces on other objects, in an inertial frame.

This reaction force is sometimes described as a centrifugal inertial reaction, that is, a force that is centrifugally directed, which is a reactive force equal and opposite to the centripetal force that is curving the path of the mass.

The above might seem a bit convoluted but never the less its true. What the general population thinks centrifugal force is isn't true, the the people that actually understand it cant explain it for shit.

Now back to the problem.

Keeping things simple and assuming that the rock is traveling at a constant speed and your spinning it in a circle above your head.

The rock on the rope is held in circular motion by the tension in the rope. It is this tension that is causing the circular motion.

So what happens to the elastic? Why does it stretch? Simply because until the elastic is fully stretched the inward force the elastic is providing (from your pulling) is less than the reaction force the rock is applying (this force comes from outside factors like gravity and wind resistance, and also things like the rocks inertia which I wont get into). When the outward reaction force on the elastic is greater than the inward force that the elastic provides, the elastic must stretch until both forces are equal and opposite.

If any of this isn't clear, then feel free to ask questions, although I suspect at this point most of what I've said will have gone in one ear and out the other.

Dave- do you have anything to add? You seem pretty clued up on all this shit.

[mossy1200]

Ok so I understand.

But what are we calling the tyres inability to maintain it shape as the revolution speed becomes greater.
I understand that the exit line of an object is straight but the angle of exit is still distancing the object from the axis. So surely this means a retained object has force outwards appearing to be centrifugal force.

Question. What are you calling the resulting stretch?

[oneofsix]

Ok so I understand.

But what are we calling the tyres inability to maintain it shape as the revolution speed becomes greater.
I understand that the exit line of an object is straight but the angle of exit is still distancing the object from the axis. So surely this means a retained object has force outwards appearing to be centrifugal force.

Question. What are you calling the resulting stretch?

Centrifugal force. Whilst this may be a fictional force to the physicist to the rest of us it is the easy way to say and understand it, and the kicker is they also understand you even though they know it is a simplified expression of a complex concept.

Just like saying water freezes at 0C and boils at 100C, only works when it is pure and the pressure is right etc etc etc, but fucked if we care it is close enough for general use.

Gotta have a degree of tolerance, and back to speed ...

[Milts]

272434
Just to help confuse things.

(From http://xkcd.com/123/)

[Dave-]

Dave- do you have anything to add? You seem pretty clued up on all this shit.

By the time I finished study last night (actually it was technically this morning) my brain wasn't much in the mood for explaining tangential, I started a post and wrote "Tangential" and then my brain quit, figured I'd leave it till the morning, plus this stuff is fresh for you, you sat 101 last semester? I sat it like 2 years ago haha.

I would add would be in terms on a tyre on a rim, imagine you lay the wheel down on the ground, and then like a pizza cut it up, except you've got a lot of friends and so you have to make a lot of cuts (luckily this is science so our cuts are infinitely thin) and we keep cutting until we get smaller and smaller pieces of pizza, we keep going until they're arbitrarily small, it's easier if I stop here and you just imagine they're in sections of about 5cm, this wee 5cm cross section piece of tyre has a certain mass, it's very small, maybe 20 grams? 50 grams? it's very small compared to the mass of the whole tyre.

Lets also look at the definition of acceleration, which is change in speed, acceleration is a vector, which means it has both magnitude and direction, in physics to properly identify an objects motion you must specify how fast it's going and in what direction, this is the same for velocity (there was a hilarious joke in the despicable me about vectors - top film) so lets say then that you spin a wheel up to a speed, and you hold it constant at that speed, now think about what your little pizza slice of wheel is doing, it's spinning around, but its also constantly changing direction, therefore its acceleration is non-zero (because it's vector is magnitude AND direction) even though the tyre isn't spinning any faster or slower, it still has acceleration.

It is this acceleration, with the mass of that wee pizza slice, that distorts the shape of the tyre at a tangent, but because the tyre is joined all the way around, all the other wee pieces of tyre do the same thing at exactly the same time, and it looks as if the tyre is moving away from the rim.

In reference to the tyre getting smaller, that was a more real world situation where it's on a road and you have many more forces coming in to play.

So you have gravity pulling your vehicle down at 1G, on a drag car this is higher cause the wing presses it down some more. I theorised that you have your tangential force pressing the tyre out at some force, the acceleration is huge, but the mass is tiny, so the force is fairly normal, if there was no weight on the axle then the tyre would be allowed to expand, would raise the ride height of the vehicle, and change the gearing, BUT we have a vehicle pressing down at 1G, if the force pressing down is greater than the force pressing "out" from the wheel then the tyre will be more squashed than it is expanded, therefore the gearing would go down, I may be wrong on this though.

And then I spoke with a mechanical engineer friend, he explained that as the tangential force hits the road the tyre deforms and the radius gets smaller again, lowering the gearing more substantially, you can sort of see it in this video.

v-DMkO3g2SI


edit: I just had a thought, what's going on in this video isn't exactly as I've described, what I've described is wiped out by the bob and sway of the car going over bumps and braking etc, but the bumps and braking etc gives a good impression of what I'm describing, you can see that as he goes over a bump and the force pushing down on the axle increases the base of the tyre deforms more and more.

now while that's only happening to the bottom of the tyre, the rest of the tyre is expanding sure, but you'll find the gearing is based on the average (halfway), as it turns out from the mech student, the tyre gets more smaller due to this deformation than it gets larger due to tangential force, therefore at speed the tyres gearing goes down. and the speedo should reflect this.

But because they don't use an active filter on modern digital speedos you wont see this cause it's lost in the signal noise.

I feel we've achieved something here today. Back to network protocol design!

[Spuds1234]

By the time I finished study last night (actually it was technically this morning) my brain wasn't much in the mood for explaining tangential, I started a post and wrote "Tangential" and then my brain quit, figured I'd leave it till the morning, plus this stuff is fresh for you, you sat 101 last semester? I sat it like 2 years ago haha....

Na did all my physics stuff last year, so a lot of what I wrote above I had to look up. For all intents and purposes this year has been 3/4's maths and fuck all physics. Next year will change that though I think.

As for the tyre shrinking or growing thats well out of my area of expertise, but I suspect if the tyre was off the ground (like that video of the RC car a page or two ago) that what your seeing is much like the rock on the rope. The tyres sidewall acts like a stretchable rope, and the part of the tyre that contacts the road acts like a rock. So the tyre would expand in this case, but here we're completely taking out the affects of the cars mass and the force that the tyre was exerting on the ground.

What happens when the tyre is on the ground with the weight of the car pressing down on it? Im not sure. Its well out of the realms of what I know and I cant find any material online that even begins to explain it.

[Dave-]

What happens when the tyre is on the ground with the weight of the car pressing down on it? Im not sure. Its well out of the realms of what I know and I cant find any material online that even begins to explain it.

There's a book in the EPS library on tyres, there'll be something in there about it, you're probably sitting less than 100m from it :D

[Spuds1234]

Speaking to my flatmate, he reckons that the radius of the tyre shrinks because of plastic deformation caused by the forces the tyre exerts on the road (due to both the tyres rotation and the mass of the car) and then at speed, the tyre does not have enough time to come back to its original shape in one rotation.

So basically if you look at a tyre on your car, you notice that the bottom part of the tyre is squashed more than the top part. Now what happens when you spin that tyre really really fast like what is happening in the video Dave- posted?

All those small parts of the tyre (that Dave- mentioned) get squashed a bit each time the tyre goes through 1 revolution, but now the tyre is rotating so fast that those small parts of the tyre cannot expand back out to their original position before they are squashed again. So it looks like the tyre is contracting.

This seems to make no sense intuitively when you first think about the problem because when you think about it its hard to imagine a tyre going that fast. Its not something you look at every day. Unlike the situation when your spinning a rock on a rope (because who didn't do that as a kid in some form or another).

This seems to make sense as you'll notice in that Bathurst video when the car speeds up the tyre gets deformed and squashed and the radius of the tyre seems to shrink. Then when it slows down or the weight on the tyre decreases (when it lifts off the ground) the radius of the tyre increases. When the tyre is off the gound we're back to a rock on a stretchy rope kinda problem and when the car slows down each small section of the tyre is allowed to return to its original shape because its not immediately getting squashed again.

[mossy1200]

Why do you think the bike gets forced down heavier onto the road at speed when a bike has no wings to force it onto the road?
The front wheel of bikes I have riden seem to get lighter the faster you go.
I also dont understand why we are comparing a race car wheel braking and moving over bumps to a motorcycle front wheel at 200 or more.
Idd say the only time a motorbike wheel has compressed for extended time is front during braking and rear during acceleration.:shit:

[Akzle]

thanks mann!

[Dave-]

Why do you think the bike gets forced down heavier onto the road at speed when a bike has no wings to force it onto the road?
The front wheel of bikes I have riden seem to get lighter the faster you go.
I also dont understand why we are comparing a race car wheel braking and moving over bumps to a motorcycle front wheel at 200 or more.
Idd say the only time a motorbike wheel has compressed for extended time is front during braking and rear during acceleration.:shit:

you're entirely right.

a bike doesn't get heavier, but the physics involved means the tyre shrinks. also a few guys mentioned drags cars and I believe the original discussion was in a car/truck to do with cruise control/limiters....

the front wheel will get lighter during acceleration due to a torque at the back wheel.

the race car wheel video is an analogy, there aren't any videos on youtube with a motorcycle wheel at speed which show a representation of what I'm describing to you.

braking yes, also cornering on a cambered corner.

I see we have our own physics thread now, I was considering starting one so next time someone talked about centrifugal force I'd just link them to the thread.

Anyone happen to know what the maximum lateral G a bike can pull in a corner is? I bet you'll be surprised how low it is.

[mossy1200]

Hey. I never started a new thread. I just took the original thread off topic. Id rather just have an infraction than be responsible for this thread.

When everyone thinks your stupid dont open your mouth and confirm it.

[bogan]

So, a 10mm hole in a 1000mm steel sheet gets larger if you heat the steel?

Well, my oven isn't that big, and neither is me torch, so it would depend entirely on where the heat was applied. In fact in some cases I think you could get the hole (if it were quite a bit biger than 10mm) to shrink.


a bike doesn't get heavier, but the physics involved means the tyre shrinks.

How so? With nice wide sticky bike tyres you'd have both the centrifugal force, and the heat-pressure trying to push out the center, counteracted only by the extra weight transfered to the rear wheel, and that only applied to a few percent of the circumference at any one time.


Anyone happen to know what the maximum lateral G a bike can pull in a corner is? I bet you'll be surprised how low it is.

I think its around 1.2 for sticky road tyres, though the motogp guys get up around 1.5 iirc.

[Gremlin]

Hey. I never started a new thread. I just took the original thread off topic. Id rather just have an infraction than be responsible for this thread.
Yours was the second post that took it off at a tangent, but more comprehensive and better to start a thread... This discussion needed it's own thread, it was off all on it's own.

However, you are always welcome to an infraction if you want?

[mossy1200]

you're entirely right.

a bike doesn't get heavier, but the physics involved means the tyre shrinks. also a few guys mentioned drags cars and I believe the original discussion was in a car/truck to do with cruise control/limiters....

the front wheel will get lighter during acceleration due to a torque at the back wheel.

the race car wheel video is an analogy, there aren't any videos on youtube with a motorcycle wheel at speed which show a representation of what I'm describing to you.

braking yes, also cornering on a cambered corner.

I see we have our own physics thread now, I was considering starting one so next time someone talked about centrifugal force I'd just link them to the thread.

Anyone happen to know what the maximum lateral G a bike can pull in a corner is? I bet you'll be surprised how low it is.

I only started talking about a bike tyre ballooning after speeds exceed 200kph.
Theres also many more factors such as original pressures. Eg drag car expansion is excessive due to tire design to grab the road on take off then expand. This giving traction and torque followed by reduced resistance on road followed by increased gearing. All important in the drag scene.
A 2% increase on a steel belt road bike tyre is a smaller amount but can effect speedo reading.
I believe that most bikes on both front and rear wheel would not have any or much more downforce at speed with avergae joe riding it. most in my opinion would see a reduction of downforce.

[mossy1200]

Yours was the second post that took it off at a tangent, but more comprehensive and better to start a thread... This discussion needed it's own thread, it was off all on it's own.

However, you are always welcome to an infraction if you want?

Im good for a while thanks. When I get within 1 infraction of losing my KB licence do I get a warning letter?

[Gremlin]

Im good for a while thanks. When I get within 1 infraction of losing my KB licence do I get a warning letter?
In KB land you have to do impressive things to lose your licence (and then it's permanent). Instead, you just lose features, more and more as your points climb...

[Akzle]

Well, my oven isn't that big, and neither is me torch, so it would depend entirely on where the heat was applied. In fact in some cases I think you could get the hole (if it were quite a bit biger than 10mm) to shrink.

sorry brogan. factoid is factoid.
the atoms around the hole are packed as tight as they're gonna get. 'twill expand outward. to freedom.

[mossy1200]

In KB land you have to do impressive things to lose your licence (and then it's permanent). Instead, you just lose features, more and more as your points climb...

That didnt take long. You just infracted me for something else.
Could be worsa. Bad gwama and spellin mistakes could be infracturiZed also.

[bogan]

sorry brogan. factoid is factoid.
the atoms around the hole are packed as tight as they're gonna get. 'twill expand outward. to freedom.

Sorry Greeny, the textbook only goes so far once you get into the real world.
If you have a bit of flat bar and heat it, it'll expand out each side right. So if you have a big disc with a large hole in the center (this can be thought of as a curved bit of flat bar) and heat only the sides, they will expand similarly to the flat bar, going inside and outside. the top and bottom will of course get further apart, but the minor diameter will get smaller. Its only when you heat the whole (not the hole) thing the shape stays the same, and the length increases the circumference and therefor diameter.

[Dave-]

I only started talking about a bike tyre ballooning after speeds exceed 200kph.
Theres also many more factors such as original pressures. Eg drag car expansion is excessive due to tire design to grab the road on take off then expand. This giving traction and torque followed by reduced resistance on road followed by increased gearing. All important in the drag scene.
A 2% increase on a steel belt road bike tyre is a smaller amount but can effect speedo reading.
I believe that most bikes on both front and rear wheel would not have any or much more downforce at speed with avergae joe riding it. most in my opinion would see a reduction of downforce.

Yup, and at speeds above 200 you'll start seeing the tyre shrink.

There are many many more factors, right down to the elasticity of the steel in the belts.

yes a 2% increase would, but it doesn't increase.

And you're right with the last remark too, bikes dont produce down force because the wings smack the ground in a corner and the down force in the corner does whacky things to the centripetal forces because you're leaning the bike over.



How so? With nice wide sticky bike tyres you'd have both the centrifugal force, and the heat-pressure trying to push out the center, counteracted only by the extra weight transfered to the rear wheel, and that only applied to a few percent of the circumference at any one time.


Asked and answered.


Well, my oven isn't that big, and neither is me torch, so it would depend entirely on where the heat was applied. In fact in some cases I think you could get the hole (if it were quite a bit biger than 10mm) to shrink.


We assume the heat is evenly distributed.

and no the hole will expand.

read this: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thexp2.html

Also think about cold welding. and heating things up, then slipping them over things and waiting for them to cool down.

[bogan]

Asked and answered.

err, again, how so?

The extra weight is what, 1kN max. Total centrifugal force (4.6kg tyre doing 54m per second) is 50kN by my reckoning (though maybe I've got some units mixed up?). Obviously only around 1.4kN (3%) is directly acting against the weight at one time, but that is enough, plus the momentum of the rest as it comes around makes it fucking plenty.


We assume the heat is evenly distributed.

Why? is your oven that big?

[pzkpfw]

You crack me up. You link the very information that shows that you dont understand what cetripetal force is.

Wrong.


Gravity from the mass of the Earth and the Moon attract each other.
The centripetal force is what is stopping them from coming together.

Wrong. With respect to the Earth, the Moon would really like to just continue off in what would appear to be a straight line - see "velocity" in the diagram linked below. (At least for a while; it'd still be bound by the Sun). The force of Gravity (calling it a force is kind of debatible too) from the Earth, towards Earth, is what makes the Moon continually fall towards Earth instead of continuing in that straight line - and away.

(The Moon also attracts the Earth of course, which is why they actually both orbit the mutual barycentre.)


The centripetal force is outwards and not in.

Wrong. Where in those links to mainstream science is that stated?

e.g. see this diagram on that page on centripetal force. Note the direction of the arrow. http://en.wikipedia.org/w/index.php?title=File:Centripetal_force_diagram.svg&page=1


The balance of the mass and the cetripetal force is what maintains the distance as an orbit.

Rubbish. (In the context of your explanation).


The other example is the roller coaster. The carts are on the inside of the loop. Your theory would have the cart on the outside being pulled into the centre. Im feeling safer on my roller coaster than yours.

No, you don't understand.

At any moment in the loop, if the loop vanished, the cart would continue off in a straight line (not quite straight, it would fall due to Earths gravity).

What makes the cart continue in the loop, is the force applied inwards on the cart by the track.

The force applied by the cart to the track (outwards), is the fictitious centrifugal force.


The faster you revolve an object through rotation the higher the outwards G forces that act on the mass in rotation.

Wrong.

The faster you rotate an object, the more the bits of it want to fly off in a straight line. Thus the more force you need to apply to keep it all rotation.


The tyre wishes to leave the centre point and expands with the limiting factor being the strength of the construction.
Turn it fast enough the tyre becomes taller and skinnier.

That's what you'll see, but you describe the cause incorectly.


You need to read your link again im afraid.

Nope. You do.

[Dave-]

err, again, how so?

The extra weight is what, 1kN max. Total centrifugal force (4.6kg tyre doing 54m per second) is 50kN by my reckoning (though maybe I've got some units mixed up?). Obviously only around 1.4kN (3%) is directly acting against the weight at one time, but that is enough, plus the momentum of the rest as it comes around makes it fucking plenty.



*deep sigh*

a 250kg bike weighs 9.87 * 250 = 2467.5N = 2.5kN

centrifugal force doesn't exist, what you're calling centrifugal force is actually a tangential force involving the mass of the tyre and the constant change in acceleration from the rotation of the wheel, if you read this thread, by the end of it you'd know this.

I'm not sure where you got 3% from or what it has to do with anything.

but to answer you question.

the tyre gets smaller because as the tyre connects with the road it deforms, it takes some amount of time for the tyre to undeform and 1 rotation of the wheel isn't long enough at +200kph so before the tyre can reform. It's forced to deform again and the radius of the tyre is reduced.

yes my oven is big enough. or you can just leave the 1m^2 plate in the sun.

[pzkpfw]

...

Here's a test - swing an object around you on the end of a string. At some moment, let go of the string. Look at the object at the moment you let go. Look at what direction the object goes in. Think about what forces were acting on that object before and after letting go.

The key point, is that the object will keep going in the direction it was going at the moment of letting go.

It won't go off in a direction directly away from you.

Say you are swinging it clockwise (seen from above) around you, and let go when the string is due South. The object will fly off West - not South.

This is because at (just before) the moment of letting go, the object is travelling West, and the centripetal force (towards you) is acting North, to keep the object moving in a circle. {90 degrees before that, the object was East of you, moving Southwards, and the centripetal force you are applying by the string is acting West}.

If the centrifugal force were real, and acting away from you, you'd expect that object to fly off Southwards.

[bogan]

*deep sigh*

a 250kg bike weighs 9.87 * 250 = 2467.5N = 2.5kN

centrifugal force doesn't exist, what you're calling centrifugal force is actually a tangential force generated by the mass of the tyre and the constant change in acceleration from the rotation of the wheel, if you read this thread, by the end of it you'd know this.

I'm not sure where you got 3% from or what it has to do with anything.

but to answer you question.

the tyre gets smaller because as the tyre connects with the road it deforms, it takes some amount of time for the tyre to undeform and 1 rotation of the wheel isn't long enough at +200kph so before the tyre can reform it's forced to deform again and the radius of the tyre is reduced.

Yes but the rear has half that to begin with, add another 100kg from the front.

Centrifugal force is simply a description of a perceived force equal and opposite to the centripetal force. I bet people in space stations would just think down was directly away from the center of rotation; I bet when they were designing space tables they would have to withstand a downwards force "generated by the momentum and rotation force which is equal and opposite to the centripetal force at any given time"; and I bet those space dudes would get tired of writing all that and just come up with a shorthand notation for it, oh if only there was some word already in use that most people understood immediately ;)
The fact you don't use it in simple physics calculations is irrelevant.

the 3% is three percent of the circumference with a 50mm contact patch. If the rotation isn't long enough for the tyre to deform one way, tell me how 3% of that time is long enough for it to deform the other?

[Spuds1234]

Here's a test - swing an object around you on the end of a string. At some moment, let go of the string. Look at the object at the moment you let go. Look at what direction the object goes in. Think about what forces were acting on that object before and after letting go.

The key point, is that the object will keep going in the direction it was going at the moment of letting go.

It won't go off in a direction directly away from you.

Say you are swinging it clockwise (seen from above) around you, and let go when the string is due South. The object will fly off West - not South.

This is because at (just before) the moment of letting go, the object is travelling West, and the centripetal force (towards you) is acting North, to keep the object moving in a circle. {90 degrees before that, the object was East of you, moving Southwards, and the centripetal force you are applying by the string is acting West}.

If the centrifugal force were real, and acting away from you, you'd expect that object to fly off Southwards.

We covered this and I explained it in detail although it is a wall of text and I dont think many people will read it. Now we are onto expansion of a motorcycle tyre at what I assume is to be the following speeds 100kph, and 200+kmh so we can work out what affect this will have on the speedo reading or something.

I think thats how this all got started?

[mossy1200]

Here's a test - swing an object around you on the end of a string. At some moment, let go of the string. Look at the object at the moment you let .......... expect that object to fly off Southwards.

Yes understood and never denied but this angle that the objects travels is always increasing its distance from the axis point. i never stated it left in a line from axis to disconnection point but it still moves away from the axis. It no longer wants to remain in orbit when nothing retains it. What I ment to show is that when the force increases with increase in speed the diameter grows dependant on the ability of the tyre to stretch and distort. the result is the tyre if not strong enough will balloon out and lose width as a result.

As per post one I called this ----- Centrifugal growth ------

So if the term is incorrect please tell everyone what the correct name for this is.

[bogan]

As per post one I called this ----- Centrifugal growth ------

So if the term is incorrect please tell everyone what the correct name for this is.

You muppet, this one is way better :bleh:

"growth generated by the momentum and rotation force which is equal and opposite to the centripetal force at any given time" :confused: :wacko:

[mossy1200]

Centrifugal growth A tire rotating at higher speeds tends to develop a larger diameter, due to centrifugal forces that force the tread rubber away from the axis of rotation. This may cause speedometer error. As the tire diameter grows, the tire width decreases. This centrifugal growth can cause rubbing of the tire against the vehicle at high speeds. Motorcycle tires are often designed with reinforcements aimed at minimizing centrifugal growth.[citation needed]


http://en.wikipedia.org/wiki/Tire

Taken from link Wikipedia half way down the content heading name Centrifugal Growth .

[Drew]

I'm quietly confident, that Dave is wrong in thinking the tyre outside circumference decreases as the rotational speed increases, but I'm intrigued by the theory.

[Dave-]

Yes but the rear has half that to begin with, add another 100kg from the front.

gotcha divide by 2.


Centrifugal force is simply a description of a perceived force equal and opposite to the centripetal force. I bet people in space stations would just think down was directly away from the center of rotation; I bet when they were designing space tables they would have to withstand a downwards force "generated by the momentum and rotation which is equal and opposite to the centripetal at any given time"; and I bet those space dudes would get tired of writing all that and just come up with a shorthand notation for it, oh if only there was some word already in use that most people understood immediately ;)
The fact you don't use it in simple physics calculations is irrelevant.

You didn't say you were in a non inertial reference frame!

next time you're talking physics I'll assume you're spinning. makes sense.


the 3% is three percent of the circumference with a 50mm contact patch. If the rotation isn't long enough for the tyre to deform one way, tell me how 3% of that time is long enough for it to deform the other?

If 1 rotation isn't long enough for the tyre to reform, then how does it deform so quickly in the first place?

OOOOH good question.

I'm starting to think that it doesn't stay deformed.

I think it deforms more than if it were just sitting still, the tangential force hitting the road squashes it some more, but then at the other end of the contact patch that same force. and this would lower the average radius of the tyre, but by fuck all, it might even negate the tangential force "pushing" the tyre off the rim.....

I've spent too long considering this, need to carry on with study.

[mossy1200]

I'm quietly confident, that Dave is wrong in thinking the tyre outside circumference decreases as the rotational speed increases, but I'm intrigued by the theory.

Ill say I agree with the decrease but only during extreme acceleration or deceleration because the stretch if you had enough power would be both out and exerted against the rim to road surface pulling the tread around the point it would normall sit at a straight line through the axel. But im thinking you would need a very underinflated tyre and a huge amount of power to do so while accelarating to have this distortion reduce the diameter when doing high speeds. I cant see it happening at constant speed.

[bogan]

You didn't say you were in a non inertial reference frame!

next time you're talking physics I'll assume you're spinning. makes sense.

It shouldn't be relevant, you need to be able to consider things from both viewpoints, inside and outside the system. A good book series I found (which deals with this sort of thing) is, fuck I've forgetten the name, it was a steampunk style book where the world was a giant balloon and everyone lived on the inside and had to spin up habitats with old school tech, I'll dig up the name if you're interested.


If 1 rotation isn't long enough for the tyre to reform, then how does it deform so quickly in the first place?

OOOOH good question.

I'm starting to think that it doesn't stay deformed.

I think it deforms more than if it were just sitting still, the tangential force hitting the road squashes it some more, but then at the other end of the contact patch that same force. and this would lower the average radius of the tyre, but by fuck all, it might even negate the tangential force "pushing" the tyre off the rim.....

I've spent too long considering this, need to carry on with study.

If it is hitting the road tangentially there will be no impact force transmitted...

[Dave-]

[citation needed]

Derp.

Oh well, it was a nice theory, shame it's not backed up by a reputable source.

[bogan]

Derp.

Oh well, it was a nice theory, shame it's not backed up by a reputable source.


[Many, Many citations needed]

Pot, kettle much?

[Drew]

All the talk about physics has become boring because of the pissing contest, so I'll spoil it with real world fact.

The sidewall of a road tyre is quite well equipped to fight distortion through the force exerted by acceleration. But since it cannot sufficiently maintain it's shape in a cross sectional sense, the tyre's rolling radius increases.

[mossy1200]

All the talk about physics has become boring because of the pissing contest, so I'll spoil it with real world fact.

The sidewall of a road tyre is quite well equipped to fight distortion through the force exerted by acceleration. But since it cannot sufficiently maintain it's shape in a cross sectional sense, the tyre's rolling radius increases.

I just wish I could say it like Drew.


Manufactures believe in it and try to minimise it.
Custom bike builders allow for it for a different reason(clearance on close guards)

[Dave-]

"It is discovered that the increases of internal damping and speed will barely cause tire-road contact length to change."

we're talking 2.5 degrees either side of vertical, up to ~180kph

fascinating read, pity none of you can see it.

Zeng-Xin Yu, Hui-Feng Tan, Xing-Wen Du & Li Sun (2001): A Simple Analysis Method for Contact Deformation of Rolling Tire, Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility, 36:6, 435-443

http://www.tandfonline.com/doi/abs/10.1076/vesd.36.6.435.3543

So, as the contact patch increases, the minimum radius must decrease, this is basic trigonometry.

It's ok chaps, no hard feelings, we use science to be right, not prove we're right.

[bogan]

So, as the contact patch increases, the minimum radius must decrease, this is basic trigonometry.

The problem still is that it's basic text book trig, not real world application. Rubber is flexible and stretchy, so the both the radius and contact patch can increase simultaneously. Have you forgotten the whole discussion revolves around (see what I did there) the centrifugal forces stretching the tyres circumference?


It's ok chaps, no hard feelings, we use science to be right, not prove we're right.

And those who properly apply it to the real world to do something useful care not about being right at all, for that becomes self evident.

[Drew]

"It is discovered that the increases of internal damping and speed will barely cause tire-road contact length to change."

we're talking 2.5 degrees either side of vertical, up to ~180kph

fascinating read, pity none of you can see it.

Zeng-Xin Yu, Hui-Feng Tan, Xing-Wen Du & Li Sun (2001): A Simple Analysis Method for Contact Deformation of Rolling Tire, Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility, 36:6, 435-443

http://www.tandfonline.com/doi/abs/10.1076/vesd.36.6.435.3543

So, as the contact patch increases, the minimum radius must decrease, this is basic trigonometry.

It's ok chaps, no hard feelings, we use science to be right, not prove we're right.Are you retarded?

Watch a drag cars tyre expand, and the contact patch increase in area at the same time.

[Dave-]

The problem still is that it's basic text book trig, not real world application. Rubber is flexible and stretchy, so the both the radius and contact patch can increase simultaneously. Have you forgotten the whole discussion revolves around (see what I did there) the centrifugal forces stretching the tyres circumference?


This was accounted for.

on the topic of contact patchs

Did you know the area of the contact patch is irrelevant to the grip the vehicle has on the road?


Are you retarded?

Watch a drag cars tyre expand, and the contact patch increase in area at the same time.

You can watch TV all you like Drew and draw whatever conclusions you would like from what you see.

[bogan]

This was accounted for.

on the topic of contact patchs

Did you know the area of the contact patch is irrelevant to the grip the vehicle has on the road?

In your head, or in the article somwhere between you quote and your conclusion?

Oh not this shit again, rubber in addition to be stretchy, is also adhesive. It's why drag cars get more grip from running larger contact patches. FFS man, pull that text book out of your arse and stretch your legs in the real world once in a while.

[Dave-]

In your head, or in the article somwhere between you quote and your conclusion?

Oh not this shit again, rubber in addition to be stretchy, is also adhesive. It's why drag cars get more grip from running larger contact patches. FFS man, pull that text book out of your arse and stretch your legs in the real world once in a while.

In the article, I cant quote too much from it otherwise I'll lose my access privileges.

Here's the equation for the frictional force, can you please point out where it says "area" or "A" or something squared?

http://www.worsleyschool.net/science/files/hula/equation1.JPG

[Drew]

In the article, I cant quote too much from it otherwise I'll lose my access privileges.

I think they'd be rapped with that result, if you are this beligerant on that site as well.

[bogan]

In the article, I cant quote too much from it otherwise I'll lose my access privileges.

Here's the equation for the frictional force, can you please point out where it says "area" or "A" or something squared?

Well with a lack of evidence, I'll assume you're jumping to an oversimplistic and erroneuous conclusion, as has been the trend thus far.

Adhesion is not part of friction. They are two different components that contribute to a tyre's grip.

[Drew]

Well with a lack of evidence, I'll assume you're jumping to an oversimplistic and erroneuous conclusion, as has been the trend thus far.

Adhesion is not part of friction. They are two different components that contribute to a tyre's grip.Ooohhh, lets start discussing how friction can be detrimental to grip. Just for fun.

[onearmedbandit]

Did you know the area of the contact patch is irrelevant to the grip the vehicle has on the road?



Apparently it does though...


In terms of simple physics F = V mu... If you double the contact area, then the pressure will halve (per mm2) so the friction per mm2 will halve. However, you have twice the area of contact patch so that cancels out the halved pressure. The conclusion is that basic friction is independent of area, it only needs vertical load and a co-coefficient. You can do whatever you want with the area from a stiletto to a surfboard, the friction force will be the same.

However life is more complex than simple physics. The most obvious point is that tyre rubber is adhesive, so if you double the area you double the amount of adhesion (gross approximation). So wide tyres do have more grip than thin tyres.

The bit in bold I like the best.

http://www.f1technical.net/forum/viewtopic.php?f=6&t=12762

[bogan]

Ooohhh, lets start discussing how friction can be detrimental to grip. Just for fun.

Helmet friction is correlated with a tyre grip minimum?

Or the more serious answer of carcass flex and heat buildup pushing the tyre outside its designed limits.

[Drew]

Helmet friction is correlated with a tyre grip minimum?

Or the more serious answer of carcass flex and heat buildup pushing the tyre outside its designed limits.Yeah, I was hoping it would go on for a bit, and then bring up overheating.

[bogan]

Yeah, I was hoping it would go on for a bit, and then bring up overheating.

My bad, it's tough at the top sometimes :shifty: :whistle:

[schrodingers cat]

You sure know a lot of theories Dave.
Best you stay at school and leave the real world to the rest of us.
All that education and no fucking idea :-)

[Ocean1]

Adhesion is not part of friction. They are two different components that contribute to a tyre's grip.

What causes adhesion?

[Dave-]

Apparently it does though...



The bit in bold I like the best.

http://www.f1technical.net/forum/viewtopic.php?f=6&t=12762

Going to need a better source than another forum OAB, seriously I could just cite myself on another forum and say "Oh look, I agree with myself!"

Have a read of this chaps, what do you reckon? I realise it's wikipeida, and I'm not saying it's true...
http://en.wikipedia.org/wiki/Tire_load_sensitivity

Race Car Vehicle Dynamics is in the EPS library, I'll have a browse Thursday arvo after my exam and cite from the genuine article rather than a wikipage (haha imagine that!)

Formula 1 Technology is out and due back on the 9th.

Come to think of it I should really update that wikipedia page on tyre deformation.....

[BMWST?]

Centrifugal force is what they teach you in high school cause your dumb undeveloped teenage brain can't comprehend that the direction of the force is towards the center of rotation.

And it works well for most people. If you want to know more most universities cover it in 100 level physics.

To conclude I think there's other things that attribute to the uncertainty in speedo reading, mechanical slip of the tyre, electronic pulses, the impedance of the inductor on the speedo increases with frequency, temperature, etc, on modern digital tachometers (the thing that shows you revolutions per minute) to save on costs they don't filter the signal, and it can get really saw-tooth shaped if you don't, when you do however you get a much more accurate representation, I know this cause I designed and built one at uni this year.

If you're really worried about it get a GPS, they're fail proof....except for when you cant connect to enough satellites :)

and the built in fudge factor by the us military which changes day to day

[BMWST?]

the phenomana of a tyre with low pressure having a smaller diameter than its correctly inflated brother is used by car manufactures to moniter tyre pressure.The wheel revolutions can be monitored with the abs hardware so if one wheel is spinning consistently faster than the others then the systems warns you that you have a flat tyre

[SMOKEU]

This thread is seriously anti lulz.

[mossy1200]

Im not the brightest guy in the world but idd like a big fat sticky contact patch telling me I have grip. Biscuit tyres and hp dont do alot for me other than skids.

[bogan]

What causes adhesion?

Chemicals, fuck knows which ones, there's probably at least three of them in there. I just scraped through with 7th form chem so its beyond my field of expertise.


Going to need a better source than another forum OAB, seriously I could just cite myself on another forum and say "Oh look, I agree with myself!"

He wasn't quoting it for scientific fact, just cos they explained it well. Are you really struggling with the concept of adhesion, or are you just being deliberately obtuse now? If its the later, I would say an 'I must be right' ego is one of the biggest impairments to learning, and at your stage you should have a lot to learn, and nothing to get in the way.

[Drew]

Im not the brightest guy in the world but idd like a big fat sticky contact patch telling me I have grip. Biscuit tyres and hp dont do alot for me other than skids.Interesting, have you considered the front contact patch on a large bike, and the load distribution between it and the rear whilst tipping into a turn?

[Akzle]

the answer is π.

funnily. it's also the question.

[Dave-]

He wasn't quoting it for scientific fact, just cos they explained it well. Are you really struggling with the concept of adhesion, or are you just being deliberately obtuse now? If its the later, I would say an 'I must be right' ego is one of the biggest impairments to learning, and at your stage you should have a lot to learn, and nothing to get in the way.

No, I'm usually wrong, but then I go and find out and I become right, you just happened to catch me on something I was once wrong about.

Judging by your wee personal user title you can probably tell me something about ARQ protocols?

[mossy1200]

Interesting, have you considered the front contact patch on a large bike, and the load distribution between it and the rear whilst tipping into a turn?


you seen the fizzer after testing front end contact footprint stickness. It unloaded the content of my wallet and made my wife cry.

[Ocean1]

Chemicals, fuck knows which ones, there's probably at least three of them in there. I just scraped through with 7th form chem so its beyond my field of expertise.

Partly correct.

This part:
fuck knows

At least, as of a year or so ago nobody knows.

A few shrewd suspicions, to be sure. But that's it.

[scracha]

He wasn't quoting it for scientific fact, just cos they explained it well. Are you really struggling with the concept of adhesion, or are you just being deliberately obtuse now? If its the later, I would say an 'I must be right' ego is one of the biggest impairments to learning, and at your stage you should have a lot to learn, and nothing to get in the way.

I can't lurk anymore. You're obviously struggling with the fact he's educated and quoting scientific fact.
Friction is 100% independent from the area of contact.

The coefficient of friction is dynamic, partly due to the way a wide tyre deforms and changes temperature.

[onearmedbandit]

Going to need a better source than another forum OAB, seriously I could just cite myself on another forum and say "Oh look, I agree with myself!"



See this quote Dave



He wasn't quoting it for scientific fact, just cos they explained it well. Are you really struggling with the concept of adhesion, or are you just being deliberately obtuse now? If its the later, I would say an 'I must be right' ego is one of the biggest impairments to learning, and at your stage you should have a lot to learn, and nothing to get in the way.

If a wider surface area doesn't provide more 'grip', then can you explain to me why I've experienced otherwise? I realise the 'friction' doesn't change. But explain why a car with the same weight, same power, will lose 'grip' earlier on asphalt with narrower tyres? That's my experience in the real world.

[mossy1200]

Im thinking that if the brains are designing abs,traction control and launch control etc on bikes I might be better off with an older bike.

Rider feedback sounds safer than someone get his/her math wrong.

[Kickaha]

That's my experience in the real world.
The real world dosn't count if a forumla in a book somewhere says different

[onearmedbandit]

If a wider surface area doesn't provide more 'grip', then can you explain to me why I've experienced otherwise? I realise the 'friction' doesn't change. But explain why a car with the same weight, same power, will lose 'grip' earlier on asphalt with narrower tyres? That's my experience in the real world.

I may have found the answer to my question. Ok does this work for you then Dave?


So do wider tyres give better grip?

If the contact patch remains the same size and the coefficient of friction and frictional force remain the same, then surely there is no difference in performance between narrow and wide tyres? Well there is but it has a lot to do with heat transfer. With a narrow tyre, the contact patch takes up more of the circumference of the tyre so for any given rotation, the sidewall has to compress more to get the contact patch on to the road. Deforming the tyre creates heat. With a longer contact patch and more sidewall deformation, the tyre spends proportionately less time cooling off than a wider tyre which has a shorter contact patch and less sidewall deformation. Why does this matter? Well because the narrower tyre has less capacity for cooling off, it needs to be made of a harder rubber compound in order to better resist heating in the first place. The harder compound has less mechanical keying and a lower coefficient of friction. The wider tyres are typically made of softer compounds with greater mechanical keying and a higher coefficient of friction. And voila - wider tyres = better grip. But not for the reasons we all thought.

http://www.carbibles.com/tyre_bible_pg3.html

[Spuds1234]

This also explains it pretty well (the wider tyre thing). Perhaps a bit more simply.


Mehcanisms of Tire grip.

Friction
Mechanical Keying
Adhesion

As they are madr from deformable rubber, tires dont exactly follow basic friction theory. So to just say that F=mu*r is strictly wrong. Although it basically does floow this during the elastic range.

Tires only give grip when they are at the correct temperature. this is the most important thing you can remember about tires .


Now on to business.

Tires are the most important part of the suspension, either they are designed to fit it, or the suspension is designed around the tire.

People who say wider tires make more grip because ;''there is more rubber on the road' are wrong. They are both wrong that it makes mroe grip and that there is more rubber on the road.

When you make a tire wider, you alter the contact patch to be wider , but it reduces in length. So depending on sidewall stiffness, a wider tire can actually give less rubber on the road.

The main reason for tires being the size they are is actually heat management. Wider, low sidewall tires will cool better than narrow tall tires. If you can;'t get a tire up to temperatie it will give no grip, if you get it too high you will cook the rubber and ruin the set of tires.

Back to contact patch, you can safely assume that contact patch stays roughly the same area with wide or narrow tires (as long as the load stsys the same). Narroe will have longer contact patches and wide tires will have shorter.



The reason why F1 tires are wide is primarily so that they dont cook (remember they arent just wide, they are fairly high sidewalled), but they ten dto have wider contact patches because they will give better grip going round corners.

A wide tire will generate more lateral force per slip angle making cornering better. F1 cars DO NOT have wide tires for linear acceleration.


Conversely (Mike im goin to have to disagree with you here) drag racers acutally use the tires not becuase of the width, but the tallness. As we know a wider contact patch gives better cornering performance, a narrow but long contact patch is what you want for linear acceleration.

so strangely, drag racers will actually be better with narrow tires. So why do they use wide tires? (remember the most important gip aspect of tires) Temperature! They want as longer contact patch as they can get, but need the width for cooling. (eith 4000+ horsepower you do kind of build temp rather well)

But if you look at the contact patch shape between say, an F1 car or drag racer. (both are considered to use wide tires). The F1 patch will be wider and shorter for good cornering, the drag patch will be longer and narrower (relatively) for good linear acceleration.


So to sum up: Wider tires are not always better. They dont always give better traction. It depends on the car, the situation, the conditions.

Eg. Rally cars use wider tires when on tarmac rallys, and use (surprisingly) very thin tires on ice rallys.
F1 cars used to use narrow tires until aero began to be used in the 60's.
Drag racers acutally want tall tires, width is there to stop the tire being destroyed.

I found it here http://www.physicsforums.com/showthread.php?t=330790

[jonbuoy]

Centrifugal force doesn't exist, so I'm not sure what you're on about there.

But even if your tyre expands by 2% it's pressed on to the road by some mass which is going to be greater than the 2% increase, or so I think, and my very quick calcs would suggest.

I'm actually putting together the idea of the smart-bike which would take your velocity primarily from GPS and/or accelerometer it's only a matter of time before the bike becomes "smart"



GPS reads in 3 dimensions from at least 4 satellites in geosynchronous orbit (which means they don't move relative to the earth) so even when you're going up or down hill you get the magnitude of velocity.


Are you sure? GPS Speed Over Ground is exactly that. It doesnt use altitude for the calculation.

[bogan]

No, I'm usually wrong, but then I go and find out and I become right, you just happened to catch me on something I was once wrong about.

Judging by your wee personal user title you can probably tell me something about ARQ protocols?

But this same point keeps coming up, what you find out about being textbook right, only gets you to almost being real world right. Thats when you have to listen to people with real world experience, and fit their observations into your model rather than just posting simplist equations.

No, even googled the acronym, still don't care.


Partly correct.

This part:

At least, as of a year or so ago nobody knows.

A few shrewd suspicions, to be sure. But that's it.

Huh, thats kinda cool they haven't quite figured it out yet.


I can't lurk anymore. You're obviously struggling with the fact he's educated and quoting scientific fact.
Friction is 100% independent from the area of contact.

The coefficient of friction is dynamic, partly due to the way a wide tyre deforms and changes temperature.

I don't think I ever said friction was dependant on contact area, just that grip was; grip = friction + adhesion

[Dave-]

But this same point keeps coming up, what you find out about being textbook right, only gets you to almost being real world right. Thats when you have to listen to people with real world experience, and fit their observations into your model rather than just posting simplist equations.



Just checking here but...

when you say "textbook right" you mean scientifically proven?

and when you say "real world experience" you mean observation right?

[bogan]

Just checking here but...

when you say "textbook right" you mean scientifically proven?

and when you say "real world experience" you mean observation right?

Textbook right, is when a myriad of factors are left out so the answer is solvable using only the major factors (which is fair enough otherwise it would be overwhelming and exams would take days). Like how they ignore air drag/velocity in most ballistics problems, or ignore adhesion and mechanical interlocking in grip problems, or ignore temperature fluctuations in components and fluids...
You'll get the marks, but you also need to realise how much these ignored secondary effects change the real world result. It's why people like Drew laugh at you when you try to explain what he's observed for ages doesn't happen; don't forget that scientific theory often begins with an observation.

[Dave-]

Textbook right, is when a myriad of factors are left out so the answer is solvable using only the major factors (which is fair enough otherwise it would be overwhelming and exams would take days). Like how they ignore air drag/velocity in most ballistics problems, or ignore adhesion and mechanical interlocking in grip problems, or ignore temperature fluctuations in components and fluids...
You'll get the marks, but you also need to realise how much these ignored secondary effects change the real world result. It's why people like Drew laugh at you when you try to explain what he's observed for ages doesn't happen; don't forget that scientific theory often begins with an observation.

You didn't go to university huh?

[Drew]

You didn't go to university huh?Bloody hell, you're a dick.

I typed out half a page trying to get you to CONSIDER our point of view. I deleted it and felt better straight away.

To have a debate, requires both parties trying to see the other side. Otherwise it's just arguing, and that is as productive as masturbating with a cheese grater. Slightly amusing, but mostly, painful.

[ducatilover]

You didn't go to university huh?

:facepalm: Fuck, even I did.


So, I haven't remembered everything in this, but has anybody actually given the correct anwser as to why the drag tyes grow so much? I don't recall seeing it and it's not centripetal force.
I imagine it'd be the same reason why bike tryes will grow under severe acceleration and high speed riding.

Sidewalls are stressed more than people think even in acceleration, this creates heat, tyre and air inside tyre expands. (It's easy to see the incredible stress a tyre is under when you're throwing ~8000hp at it)

Thank you.
I should have taken physics at uni though, it looks fun (more hot chicks in Psych and Sociology though)

[Drew]

:facepalm: Fuck, even I did.


So, I haven't remembered everything in this, but has anybody actually given the correct anwser as to why the drag tyes grow so much? I don't recall seeing it and it's not centripetal force.
I imagine it'd be the same reason why bike tryes will grow under severe acceleration and high speed riding.

Sidewalls are stressed more than people think even in acceleration, this creates heat, tyre and air inside tyre expands. (It's easy to see the incredible stress a tyre is under when you're throwing ~8000hp at it)

Thank you.
I should have taken physics at uni though, it looks fun (more hot chicks in Psych and Sociology though)Not to my understanding.

The tyre is pretty much un supported in it's tread ceter. The momentum of any section of that tyre tries to carry on forward in a straight line from any spot in the circle. It can do this a littel bit due to flexability in the construction. Bingo, the outer diameter of the tyre increases.

You can carry on arguing it as much as you like Dave, but I have SEEN this with my own eyes. New chain and sprockets on a mates bike, and a new tyre at the same time. Went 190/55 instead of 180/55 on the rear hoop, and had the axle quite a long way further forward. Was all sweet till we got the the motorway, and his bike starts smoking like it's blown up. FUCK!!! Slow down and the smoke is coming from the tyre. Why? Can't figure it out, musta had something caught between tyre and swing arm. Take off, and repeat the process.

Tyre expansion happens! I don't give a fuck what you THINK is MEANT to happen, because I have WATCHED what does happen.

[bogan]

You didn't go to university huh?

Hahahahahaha, 8 years and counting sonny :bleh:


Sidewalls are stressed more than people think even in acceleration, this creates heat, tyre and air inside tyre expands. (It's easy to see the incredible stress a tyre is under when you're throwing ~8000hp at it)

But the expansion starts and stops a bit rapidly for heat conduction through rubber I would think? Still, with that much surface area it'll definitely have made significant changes by the end of the strip.

[ducatilover]

Not to my understanding.



That's my (obviously limited, I look at tits to much) understanding in relation to drag car tyres, which are designed to grow, through expansion, from heat generated by work. Stand next to one during a burn out, the tyres grow, and stay that size, then they grow more going down the run
Get slightly too much wheel slip on one side, it'll hop around and slam you off the track, why? Heat from wheelspin. The tyre that hooks up less will expand more, you can see it

[Drew]

Hahahahahaha, 8 years and counting sonny :bleh:



But the expansion starts and stops a bit rapidly for heat conduction through rubber I would think? Still, with that much surface area it'll definitely have made significant changes by the end of the strip.

Increased pressure pushes the side wall out as well. So no dice on that increasing the circumerence.

[schrodingers cat]

Pressure comes up 1psi for approx every 6 degrees of temp.

With all this high level university talk the function of tyre construction esp sidewall cord layout has been ignored

Q: What is the difference between University and Polytech

A: At University you're taught to wash your hands after you've been to the toilet

At Polytech you get taught not to piss on your hands

[Drew]

That's my (obviously limited, I look at tits to much) understanding in relation to drag car tyres, which are designed to grow, through expansion, from heat generated by work. Stand next to one during a burn out, the tyres grow, and stay that size, then they grow more going down the run
Get slightly too much wheel slip on one side, it'll hop around and slam you off the track, why? Heat from wheelspin. The tyre that hooks up less will expand more, you can see itThe circumference isn't being expanded with the heat, the tyre is being inflated by it. So the bottom bit isn't as flat (straight) after the burnout.

[ducatilover]

Hahahahahaha, 8 years and counting sonny :bleh:



But the expansion starts and stops a bit rapidly for heat conduction through rubber I would think? Still, with that much surface area it'll definitely have made significant changes by the end of the strip.

During the "war, the tyres" process they rears will be doing over 120mph :headbang:

[Drew]

Pressure comes up 1psi for approx every 6 degrees of temp.

With all this high level university talk the function of tyre construction esp sidewall cord layout has been ignored

Q: What is the difference between University and Polytech

A: At University you're taught to wash your hands after you've been to the toilet

At Polytech you get taught not to piss on your hands
I have mentioned tyre construction, it's not pertinant to making my point, to delve into the specifics.

[ducatilover]

The circumference isn't being expanded with the heat, the tyre is being inflated by it. So the bottom bit isn't as flat (straight) after the burnout.

So it's the hot air and inertia stuffs going round and round in circles making the drag tyre taller? (apart from distortion from the bazillion NM of torque)

WHY ARE THERE SO MANY POSTS AT ONCE!!!!!!!!

[Drew]

So it's the hot air and inertia stuffs going round and round in circles making the drag tyre taller? (apart from distortion from the bazillion NM of torque)

WHY ARE THERE SO MANY POSTS AT ONCE!!!!!!!!My description earlier as to why the center of the tyre grows, happens as the RPM of the tyre increases. The burnout is used to make the tyre surface sticky, they just start the tyre low on pressure, because the increase is a side effect.

Yeah, posts seem to have appeared without warning.

[bogan]

Increased pressure pushes the side wall out as well. So no dice on that increasing the circumerence.

Yup, it'll push everything out, so what was a squarish section gets rounded, allowing the center part to push away, increasing the circumference. Then again, this video shows drag tyres are just fucking crazy, look at the size of the rim locks on those fuckers!

<object width="420" height="315"><param name="movie" value="http://www.youtube.com/v/mfJejgODr3E?version=3&amp;hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/mfJejgODr3E?version=3&amp;hl=en_US" type="application/x-shockwave-flash" width="420" height="315" allowscriptaccess="always" allowfullscreen="true"></embed></object>

[ducatilover]

My description earlier as to why the center of the tyre grows, happens as the RPM of the tyre increases. The burnout is used to make the tyre surface sticky, they just start the tyre low on pressure, because the increase is a side effect.

Yeah, posts seem to have appeared without warning.

Well, fuck me, playing with them and being well wrong :( I'd been told it was heat that makes the tyre expand. But, if it's just purely down to tyre speed, it could also make sense


These things happen when you live where I do though, sheep on the mind.

[Drew]

Yup, it'll push everything out, so what was a squarish section gets rounded, allowing the center part to push away, increasing the circumference. Then again, this video shows drag tyres are just fucking crazy, look at the size of the rim locks on those fuckers!

Drag tyres are made to do weird shit alright.

You're right with the circumference thing on a car tyre, I was only thinking about bike tyres when I said it.

[bogan]

This one is also very interesting...

<object width="420" height="315"><param name="movie" value="http://www.youtube.com/v/3_lnCEMSB6c?version=3&amp;hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/3_lnCEMSB6c?version=3&amp;hl=en_US" type="application/x-shockwave-flash" width="420" height="315" allowscriptaccess="always" allowfullscreen="true"></embed></object>

[Dave-]

edit: I just had a thought, what's going on in this video isn't exactly as I've described, what I've described is wiped out by the bob and sway of the car going over bumps and braking etc, but the bumps and braking etc gives a good impression of what I'm describing, you can see that as he goes over a bump and the force pushing down on the axle increases the base of the tyre deforms more and more.

now while that's only happening to the bottom of the tyre, the rest of the tyre is expanding sure, but you'll find the gearing is based on the average (halfway), as it turns out from the mech student, the tyre gets more smaller due to this deformation than it gets larger due to tangential force, therefore at speed the tyres gearing goes down. and the speedo should reflect this.

But because they don't use an active filter on modern digital speedos you wont see this cause it's lost in the signal noise.

I feel we've achieved something here today. Back to network protocol design!

How the fuck did this get so convoluted?

To be honest I'm not even sure what we're arguing about now.

The contact patch expands, which lowers the radius of the tyre as I stated, as I also stated though it's blown away by the other factors, which I did actually make mention of, but to see the subtly of it you have to strip back all the other factors.

Are we in agreement?

[scumdog]

:facepalm: Fuck, even I did.


So, I haven't remembered everything in this, but has anybody actually given the correct anwser as to why the drag tyes grow so much? I don't recall seeing it and it's not centripetal force.


It's 'cos of the 'flingy-out-because-of-surface-velocity' fenomina, easy to explain eh!
Don't ask me to explain 'running-over-your-own-tread' fenomina though, it's a little trickier..

[ducatilover]

It's 'cos of the 'flingy-out-because-of-surface-velocity' fenomina, easy to explain eh!
Don't ask me to explain 'running-over-your-own-tread' fenomina though, it's a little trickier..

Could you please explain it in such eloquent terms (you said not to, I had to ask)
I want to quote it as verbatim next time I'm knocking some physics major tart off. :2thumbsup

[mossy1200]

Funny shit happens after 88mph.

Tires get a bit taller and thinner because the weight wants to be further out . The fact there is a gas in the tire that doesnt mind the change in tire shape is the reason its able to do so.

[bogan]

as I also stated though it's blown away by the other factors, which I did actually make mention of

Funny, we must have all missed those parts?


"It is discovered that the increases of internal damping and speed will barely cause tire-road contact length to change."

we're talking 2.5 degrees either side of vertical, up to ~180kph

fascinating read, pity none of you can see it.

Zeng-Xin Yu, Hui-Feng Tan, Xing-Wen Du & Li Sun (2001): A Simple Analysis Method for Contact Deformation of Rolling Tire, Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility, 36:6, 435-443

http://www.tandfonline.com/doi/abs/10.1076/vesd.36.6.435.3543

So, as the contact patch increases, the minimum radius must decrease, this is basic trigonometry.

It's ok chaps, no hard feelings, we use science to be right, not prove we're right.

Hmmm, missed them again it seems...

[bogan]

Funny shit happens after 88mph.

And if you ride with doug, funny shit happens well before then too :whistle:

[Dave-]

Funny, we must have all missed those parts?



Hmmm, missed them again it seems...

Yes bogan, but here all I was doing is providing a citation, I would have assumed you'd read the whole thread ok? I'm sorry I forgot to mention it the 2nd time.

Also sorry for being a dick.

I've just done 14 hours a day for 8 days straight.

The something does decrease the radius of the tyre, but this gets wiped out by god knows what other forces are flying around and fucking shit up, which is why guys like drew are so amazing cause they know the sum of the fuck ups.

Are we all in agreement on tyre deformation now?


Funny shit happens after 88mph.

Tires get a bit taller and thinner because the weight wants to be further out . The fact there is a gas in the tire that doesnt mind the change in tire shape is the reason its able to do so.

funny shit actually happens near the speed of light, not even kidding.

Who wants to know what happens when you turn your headlights on at the speed of light?

[ducatilover]

Funny shit happens after 88mph.

Legit enough for me, three movies made about it. How many movies made about certifudge petals force?

And if you ride with doug, funny shit happens well before then too :whistle:

You don't want to see what happens when I hit 100mph :facepalm: (a fence happens)

[mossy1200]

funny shit actually happens near the speed of light, not even kidding.

Who wants to know what happens when you turn your headlights on at the speed of light?

Thats silly. If your riding that fast headlights are a waste of time. Theres no way you could stop even if you did see a hazard.

[ducatilover]

Who wants to know what happens when you turn your headlights on at the speed of light?

Are you on a private road? You fucking hooligan

My theory, is your headlight turns on, but you don't see it (meh, closed road)

[Dave-]

Are you on a private road? You fucking hooligan

My theory, is your headlight turns on, but you don't see it (meh, closed road)

nah, photons do this cool thing where no matter what speed you're traveling at, they travel at the speed of light.

So if you're standing still and a photon goes past you, it does so at 200,000km/s

If you're walking along a road, and a photon goes past, it does so at 200,000km/s relative to you.

If you're driving in a car at 200km/h a photon will, to you, be going 200,000km/s

If you're traveling at 200,000km/s a photon will accelerate away from you at 200,000km/s

So if you turn your headlights on at the speed of light....they come on....duh? what did you expect would happen? lol

[bogan]

Are we all in agreement on tyre deformation now?

Not only are we in agreement, we're learning :D


My theory, is your headlight turns on, but you don't see it (meh, closed road)

You're quite right, for you to see the light it must be reflected off something, and since you would arrive at that something at the same time as the light; the only seeing would be done by any bystander observing your fiery mess.

[bogan]

So if you turn your headlights on at the speed of light....they come on....duh? what did you expect would happen? lol

But how do you turn them on? Applying the theory you're using would mean time stops completely for the person traveling the speed of light, making it impossible for even an electronic circuit to turn on the light. Of course applying that same theory would mean light speed is not actually achievable, but I assumed you were ignoring that part of it?

[ducatilover]

nah, photons do this cool thing where no matter what speed you're traveling at, they travel at the speed of light.

So if you're standing still and a photon goes past you, it does so at 200,000km/s

If you're walking along a road, and a photon goes past, it does so at 200,000km/s relative to you.

If you're driving in a car at 200km/h a photon will, to you, be going 200,000km/s

If you're traveling at 200,000km/s a photon will accelerate away from you at 200,000km/s

So if you turn your headlights on at the speed of light....they come on....duh? what did you expect would happen? lol

Can I buy moar photons for my lights?
Wouldn't this mean a photon is capable of traveliing fater than light? and if so, can you show me

[Dave-]

But how do you turn them on? Applying the theory you're using would mean time stops completely for the person traveling the speed of light, making it impossible for even an electronic circuit to turn on the light. Of course applying that same theory would mean light speed is not actually achievable, but I assumed you were ignoring that part of it?

yeah there's a few flaws...

[Drew]

Yes bogan, but here all I was doing is providing a citation, I would have assumed you'd read the whole thread ok? I'm sorry I forgot to mention it the 2nd time.

Also sorry for being a dick.

I've just done 14 hours a day for 8 days straight.

The something does decrease the radius of the tyre, but this gets wiped out by god knows what other forces are flying around and fucking shit up, which is why guys like drew are so amazing cause they know the sum of the fuck ups.

Are we all in agreement on tyre deformation now?The sum of the fuck ups is reasonable...The fuck ups are counter intuitive a lot of the time.

No body brought up that since it's spinning, doesn't the wheel create it's own gravitational 'pull'?


funny shit actually happens near the speed of light, not even kidding.

Who wants to know what happens when you turn your headlights on at the speed of light?This is gonna get silly.

[Drew]

can you show meNo no no young bucky.

It has been mathmatically proven only. There's no way to display the results without propelling something to the speed of light, and then turn on the lights.

[schrodingers cat]

nah, photons do this cool thing where no matter what speed you're traveling at, they travel at the speed of light.

So if you're standing still and a photon goes past you, it does so at 200,000km/s

If you're walking along a road, and a photon goes past, it does so at 200,000km/s relative to you.

If you're driving in a car at 200km/h a photon will, to you, be going 200,000km/s

If you're traveling at 200,000km/s a photon will accelerate away from you at 200,000km/s

So if you turn your headlights on at the speed of light....they come on....duh? what did you expect would happen? lol

Proof please.

[oneofsix]

No no no young bucky.

It has been mathmatically proven only. There's no way to display the results without propelling something to the speed of light, and then turn on the lights.

Hold up. If a photon travels away from anything at the speed of light then if the light creating the photon is travelling at say quarter the speed of light then the photon emitted would have to be doing 1.25 times the speed of light and therefore it would/should be provable with the photon emitter travelling at less than the speed of light when you turn the lights on.

[Drew]

Hold up. If a photon travels away from anything at the speed of light then if the light creating the photon is travelling at say quarter the speed of light then the photon emitted would have to be doing 1.25 times the speed of light and therefore it would/should be provable with the photon emitter travelling at less than the speed of light when you turn the lights on.

I reckon they need to start at the speed of kight, because the one thing geeks agree on, is that funny stuff happens at the speed of light.

[Drew]

Hold up. If a photon travels away from anything at the speed of light then if the light creating the photon is travelling at say quarter the speed of light then the photon emitted would have to be doing 1.25 times the speed of light and therefore it would/should be provable with the photon emitter travelling at less than the speed of light when you turn the lights on.
Is the speed of light, a photon's terminal velocity though?

Just occured to me and it's too hard to edit posts from my phone.

[oneofsix]

I reckon they need to start at the speed of kight, because the one thing geeks agree on, is that funny stuff happens at the speed of light.

Sounds like a cop out. If they haven't proven that a photon starting from an emitter travelling at quarter the speed of light will exceed the speed of light then why give a monkeys about the funny stuff that happens at the speed of light. It could be that part of that funny stuff is that a proton gathers mass and can't exceed the speed of light so their maths is all just theory.

[MisterD]

Hold up. If a photon travels away from anything at the speed of light then if the light creating the photon is travelling at say quarter the speed of light then the photon emitted would have to be doing 1.25 times the speed of light and therefore it would/should be provable with the photon emitter travelling at less than the speed of light when you turn the lights on.

Nope. What you need to let go of, is that time is some kind of constant. It isn't and it varies depending on the observer.

This isn't just theoretical either, GPS satellites travel fast enough that compensation has to be built-in for relativistic effects...it's probably a good job they don't have tyres.

[pzkpfw]

Yep, been known for many many years now. (And shown by experiment).

The speed of light (in a vacuum) is a constant; and it's time and distance that bend to make it fit.

If I'm "still" and a ship passes at (what I consider) 0.5c, and the ship shines a light ahead; both I and the ships crew will measure that light as being at c.

What makes it "work" is that I and the ships' crew will measure time and distance differently.

It's hard to make our brains grok it, because we spend so little time at speeds near what we'd measure as close to the speed of light. (Yes, even those of you who own GSXR's).

[oneofsix]

Nope. What you need to let go of, is that time is some kind of constant. It isn't and it varies depending on the observer.

This isn't just theoretical either, GPS satellites travel fast enough that compensation has to be built-in for relativistic effects...it's probably a good job they don't have tyres.

Good point. I was thinking speed but of course speed is distance over time.

OK ok pzkpfw no need to run it in, its a great commuter and fast enough for ticket collecting if not for light bending. :lol:

[bogan]

Yep, been known for many many years now. (And shown by experiment).

The speed of light (in a vacuum) is a constant; and it's time and distance that bend to make it fit.

If I'm "still" and a ship passes at (what I consider) 0.5c, and the ship shines a light ahead; both I and the ships crew will measure that light as being at c.

What makes it "work" is that I and the ships' crew will measure time and distance differently.

It's hard to make our brains grok it, because we spend so little time at speeds near what we'd measure as close to the speed of light. (Yes, even those of you who own GSXR's).

and distance? I thought it was only subjective time that changed, or do you mean the ship stretches out as it approaches light speed?

[imdying]

and the built in fudge factor by the us military which changes day to dayThat was turned off over a decade ago; accuracy is no longer degraded at all.

/edit: Here you go :) http://en.wikipedia.org/wiki/Selective_Availability#Selective_availability

[Akzle]

i'm going to re-link this here. cos it's cool.

http://htwins.net/scale2/

[Ocean1]

and distance? I thought it was only subjective time that changed, or do you mean the ship stretches out as it approaches light speed?

It does. In fact if you ignore just the impossibility of actually observing it an object falling into a black hole would appear to stretch and stall, never actually reaching the event horizon.

Edit: in fact the ocupants would be in serious trouble from the same problem but different reason: they'd be torn apart by the variable gravity over the length of their body.

[bogan]

It does. In fact if you ignore just the impossibility of actually observing it an object falling into a black hole would appear to stretch and stall, never actually reaching the event horizon.

Edit: in fact the ocupants would be in serious trouble from the same problem but different reason: they'd be torn apart by the variable gravity over the length of their body.

Yeh, just when he said distance it sounds more like the distance travelled by the ship, rather than the ships length changing.

You would get massive red or blue shift at the point though, and it'd probably just fade out due to the time differential effecting the light emissions, actually, it would probably fade out going through the spectrum (i think it'd be blue shift).

Do the occupants stretch that much? isn't it only the viewer perception of them that gets stretched.

[p.dath]

Centrifugal growth can cause tyre diameter to increase 2% on a steel belt and more on older tyre.
At slow speeds inflation pressures can change the distance travelled per rotation also.
A under inflated tyre will cover less distance at slower speeds but will grow taller than a correctly inflated tyre at high speeds.
They are only small amounts.

The same goes for a gearbox driven speedo. As the bike gets faster the percentage of wheel slip increases and the speedo reads faster than true speed travelled. Some bike racing on salt lakes travelling 300 have a rear wheel speed of 330+ losing 30kph or more in wheel spin.

These are all small factors when riding a bike and wouldnt be enough to make a difference at road legal speeds though.

It's worse than that. Often different parts of a tyre spin a different speeds - which is related to tyre deformation. The effect is most pronounced when accelerating, braking, or when experiencing lateral force on the tyre.


Here is another one that I had trouble with initially. For a tyre to rotate, it has to slip. So at any point in time you are riding, you tyres *are* slipping. And as you cross the point of coming off, all that has happened is the slip has exceed the grip. Once you come to the understanding that moving tyres are permanently slipping you start to take on a different appreciation of how they work.

[imdying]

For a tyre to rotate, it has to slip.To rotate, or to change speed of rotation?

[Dave-]

Proof please.

There's lots of material out there because it was published by Einstein


Is the speed of light, a photon's terminal velocity though?

Just occured to me and it's too hard to edit posts from my phone.

Yes, or so the current belief lies, I think there was some talk a wee while ago in quantum about a sub atomic particle that slows down as it reaches the speed of light or something hilariously weird like that.


and distance? I thought it was only subjective time that changed, or do you mean the ship stretches out as it approaches light speed?

So the length contraction is relative to the position of the observer, if you're on a spaceship doing 0.8c things look shorter to you, if you're on a stationary space ship and one goes by you at 0.8c then it's stretched.

I think. I can't remember and my level 1 physics text book is buried at the bottom of a box under a bunch of other boxes.

For anyone interested the twin paradox is quite a good read:

"If we placed a living organism in a box ... one could arrange that the organism, after any arbitrary lengthy flight, could be returned to its original spot in a scarcely altered condition, while corresponding organisms which had remained in their original positions had already long since given way to new generations. For the moving organism, the lengthy time of the journey was a mere instant, provided the motion took place with approximately the speed of light." - Albert Einstein

Explained in a bit more plain english:

"If the stationary organism is a man and the traveling one is his twin, then the traveler returns home to find his twin brother much aged compared to himself. The paradox centers around the contention that, in relativity, either twin could regard the other as the traveler, in which case each should find the other younger—a logical contradiction. This contention assumes that the twins' situations are symmetrical and interchangeable, an assumption that is not correct. Furthermore, the accessible experiments have been done and support Einstein's prediction. ..." - Robert Resnick

http://en.wikipedia.org/wiki/Twin_paradox

Also interesting is the Helios Probes, which hold the record for the fastest man made objects
http://en.wikipedia.org/wiki/Helios_(spacecraft)

The Helios probes got up to 252,792 km/h which is pretty fuckin' fast, that's around the equator in about 10 minutes.

speed of light is 1.079x10^9 (a billion kilometers per hour) so the fastest man made objects have achieved about 0.02% the speed of light....aka....fuck all.

[bogan]

Here is another one that I had trouble with initially. For a tyre to rotate, it has to slip. So at any point in time you are riding, you tyres *are* slipping. And as you cross the point of coming off, all that has happened is the slip has exceed the grip. Once you come to the understanding that moving tyres are permanently slipping you start to take on a different appreciation of how they work.

You mean that the different parts of the contact patch are 'slipping' in different directions so it can sit flat on the road, with a net slip of 0? Or that it is always slipping a tiny tiny bit?

[pzkpfw]

and distance? I thought it was only subjective time that changed, or do you mean the ship stretches out as it approaches light speed?

Distance also changes. You don't see yourself change, but if you go very very fast, another observer will see you get shorter, in the direction of travel. You will "see" the Universe getting shorter.

You'll have heard that if you went "very very fast" to the next star over, that you'd think less time had elapsed than someone left behind would think. Well, you'd also have travelled what was to you a shorter distance than that person back home would measure.

http://en.wikipedia.org/wiki/Length_contraction


Edit: Darn you Dave-, and your fast typing.

[Dave-]

Distance also changes. You don't see yourself change, but if you go very very fast, another observer will see you get shorter, in the direction of travel. You will "see" the Universe getting shorter.

You'll have heard that if you went "very very fast" to the next star over, that you'd think less time had elapsed than someone left behind would think. Well, you'd also have travelled what was to you a shorter distance than that person back home would measure.

http://en.wikipedia.org/wiki/Length_contraction


Edit: Darn you Dave-, and your fast typing.

:)

interestingly though because the stars are so massively hugely far apart, even compared to the speed of light, the distance between the points barely changes.

So at the speed of light the stars don't streak through the sky all awesomely....they just sort of sit there going "you're only going the speed of light, it's still going to take you 4000 years to get here...."

[bogan]

Distance also changes. You don't see yourself change, but if you go very very fast, another observer will see you get shorter, in the direction of travel. You will "see" the Universe getting shorter.

You'll have heard that if you went "very very fast" to the next star over, that you'd think less time had elapsed than someone left behind would think. Well, you'd also have travelled what was to you a shorter distance than that person back home would measure.

http://en.wikipedia.org/wiki/Length_contraction


Edit: Darn you Dave-, and your fast typing.

Won't the observer see you get longer? Cos if your distance to the star gets shorter, the meter ruler on the ship has to get longer right? It all makes sense, it just seems more like a secondary effect of the time dilation than a phenomenon in itself.

[schrodingers cat]

There's lots of material out there because it was published by Einstein



I'm afraid I can't allow that answer Dave.

Thus far ACTUAL behaviour at the speed of light has not been proved.

Please refrain from confusing yourself further

[Dave-]

I'm afraid I can't allow that answer Dave.

Thus far ACTUAL behaviour at the speed of light has not been proved.

Please refrain from confusing yourself further

Yeah you're right, we wont know for sure until we do it.

And we won't come even close to achieving this until we stop waring with each other.

edit: was that a 2001 space odyssey reference there too?

[Ocean1]

Yeh, just when he said distance it sounds more like the distance travelled by the ship, rather than the ships length changing.

You would get massive red or blue shift at the point though, and it'd probably just fade out due to the time differential effecting the light emissions, actually, it would probably fade out going through the spectrum (i think it'd be blue shift).

Do the occupants stretch that much? isn't it only the viewer perception of them that gets stretched.

From their perspective frequency shift is irrelevant. And the difference in gravity over even 1m is enough to tear anything that large appart close to an event horizon.

And not even very close.

[MisterD]

Rock fan-dom was definitely over represented on my Physics degree course.

<iframe width="420" height="315" src="http://www.youtube.com/embed/lFPLgGWMndc" frameborder="0" allowfullscreen></iframe>

[Drew]

Told ya it was gonna get silly.

Anyhoo, about the tyre slipping. It would certainly be doing that, if it didn't have any 'give'. The tyre is bendy, so that the rubber at the outer edge of the contact patch, although part of a smaller radius relative to the center, distorts to save from being dragged across the road surface....I think.

Funny thing about physics aye, Dave is learning it backwards to my understanding.

Someone like me, (prolly a touch more cleverer, but any observer is equal at this point), observed some shit happening and thought to himself. "I wonder how the fuck that works"? (This is where the not so clever guys like me become less equal). Then proceeded to work backwards from the result to factor as many forces as he could to get a theory. Now, we knew the result at the start (we're all equal again), but Dave (or anyone else reading what was found), has learned the forces at work, and come up with a tyre that gets smaller the faster it spins, (they can't be as bloody clever as they think either). Weeeeeeeeee, round and round we go!

[GTRMAN]

Then there was Quantum physics, which kind of turns this whole conversation on it's head.


Let me know when you guys solve the ninth chevron:msn-wink:....

[Drew]

Then there was Quantum physics, which kind of turns this whole conversation on it's head.


Let me know when you guys solve the ninth chevron:msn-wink:....The first one is in texas. Travel north from it on the main highway, and count them till you get to nine.

You're welcome.

[bogan]

Now, we knew the result at the start (we're all equal again), but Dave (or anyone else reading what was found), has learned the forces at work, and come up with a tyre that gets smaller the faster it spins, (they can't be as bloody clever as they think either). Weeeeeeeeee, round and round we go!

To be fair though, in this case it was more to do with the denial of centrifugal force than a fault with the textbooks data.

And the times round we go the closer we get, right? :shifty:

[Drew]

To be fair though, in this case it was more to do with the denial of centrifugal force than a fault with the textbooks data.

And the times round we go the closer we get, right? :shifty:It is an annoying term, (centrifugal force), and we would all be better off if the prick that came up with it had simply given it a little bit more thought at the simple level, before galavanting off with pages of bloody mathmatical giberish as to how it can be measured.

The formula Dave is working to might not be wrong, it is clearly incomplete though.

[oneofsix]

It is an annoying term, (centrifugal force), and we would all be better off if the prick that came up with it had simply given it a little bit more thought at the simple level, before galavanting off with pages of bloody mathmatical giberish as to how it can be measured.

The formula Dave is working to might not be wrong, it is clearly incomplete though.

nah its a great term that represents what normal people observe and sums several more complicated real forces together. Just like speed isn't real but is a simple relative term.

[Drew]

nah its a great term that represents what normal people observe and sums several more complicated real forces together. Just like speed isn't real but is a simple relative term.Perhaps, but we all get taught now that it doesn't exist. The reality is simple enough, yet people still call momentum, centrifugal force. To add insult to injury, they fuck it up and pronounce it centrifical.

[oneofsix]

Perhaps, but we all get taught now that it doesn't exist. The reality is simple enough, yet people still call momentum, centrifugal force. To add insult to injury, they fuck it up and pronounce it centrifical.

Nah I left school before it got to that stage :whistle: and what you mean its not centrifical? :innocent:

[Drew]

Nah I left school before it got to that stage :whistle: and what you mean its not centrifical? :innocent:Fifth form physics, was the only reason I stayed the whole year. Loved that shit, but found out at sixth form level, it requires a smarterer person than me.

[Dave-]

I once corrected someone about centrifugal on another forum and got 5 pages of bitching, moaning and name calling, so whenever I read it on here I just ignore it, kiwibiker is a particularly volatile atmosphere when it comes to physics and knowledge, I think it's the cross section of society who're drawn to motorcycles, but I'm not a psychologist (ducatilover is right though, I did psyc104 last year, fuck there's some tail in that paper :drool:) so I can't say what it is exactly.

I've read centrifugal on here heaps, I was going to post about it in that "stupid shit you've over heard in kiwibiker/motorcycling" thread but knew better of it, another guy in another thread was sharning about how centrifugal force makes the ride height of his blackbird come up, ignored it, cause I knew it'd result in 5 pages of bitching and name calling.

Looks like my hypothesis was right.

Does anyone know what causes (or caused) the static and noise you see on a detuned TV and hear on a radio between stations?

[mossy1200]

I once corrected someone about centrifugal on another forum and got 5 pages of bitching, moaning and name calling, so whenever I read it on here I just ignore it, kiwibiker is a particularly volatile atmosphere when it comes to physics and knowledge, I th................................................ ..>>>



remember original post says ( centrifugal growth ).

I understand the exit line of an object that leaves a rotating orbit is straight and leaves at the angle it was last travelling.

But this would also indicate that seeing the angle is in a percentage away from the centre then the result of a tire that is more likely to expand out due to the air within having almost no ability to prevent it as long as the pressures stay the same ( exclude heat for the moment )

The side wall of the tire will resist the angle away force because trying to twist the rubber in that direction is very hard but for it to become thinner and taller isnt hard at all.

Newer tyres with steel belts will limit the growth. Lets say 2% as an example where an older ply tire isnt as stiff and the effect maybe be 5%.

tyre manufactures do what they can to limit the effects to provide as constant a shape as possible but cant remove centrifugal growth 100% due to the air content within the tyre unless they make solid rubber tires (airless).

[Drew]

I once corrected someone about centrifugal on another forum and got 5 pages of bitching, moaning and name calling, so whenever I read it on here I just ignore it, kiwibiker is a particularly volatile atmosphere when it comes to physics and knowledge, I think it's the cross section of society who're drawn to motorcycles, but I'm not a psychologist (ducatilover is right though, I did psyc104 last year, fuck there's some tail in that paper :drool:) so I can't say what it is exactly.

I've read centrifugal on here heaps, I was going to post about it in that "stupid shit you've over heard in kiwibiker/motorcycling" thread but knew better of it, another guy in another thread was sharning about how centrifugal force makes the ride height of his blackbird come up, ignored it, cause I knew it'd result in 5 pages of bitching and name calling.

Looks like my hypothesis was right.

Does anyone know what causes (or caused) the static and noise you see on a detuned TV and hear on a radio between stations?The Blackbird guy deserved to be told he was a fuckin moron, and to go have his shock serviced.

Hmmmm, the static. Radio noise caused be electrons bouncing around in everything? That's about as random as I can dream up short term. Gimme a box of Heiuneken, and I'll come up with something most folk would believe.

[jonbuoy]

http://en.m.wikipedia.org/wiki/Hafele–Keating_experiment

[Drew]

http://en.m.wikipedia.org/wiki/Hafele–Keating_experimentHmmmmm, how come we don't think that gravity has an effect on atomic power source, instead of time.

It is a small leap to say form that experiment, that time has mass of some sort (if we don't think that atoms are effected by gravity instead of time), that can be altered. Soooooo, how come time travel doesn't get invented? Chocolate fish for the first person dumb enough to say "yet" about the invention of time travel.

Personally, I think that the atomic clock being effected by the different gravity. Ya know, since atoms work kinda the same and planets with orbits and shit. But I'm no physicist, one of those cunts prolly thought of why my suggestion is stupid.

[bogan]

Hmmmmm, how come we don't think that gravity has an effect on atomic power source, instead of time.

It is a small leap to say form that experiment, that time has mass of some sort (if we don't think that atoms are effected by gravity instead of time), that can be altered. Soooooo, how come time travel doesn't get invented? Chocolate fish for the first person dumb enough to say "yet" about the invention of time travel.

Personally, I think that the atomic clock being effected by the different gravity. Ya know, since atoms work kinda the same and planets with orbits and shit. But I'm no physicist, one of those cunts prolly thought of why my suggestion is stupid.

Predictability is the simple answer, the velocity-time based corrections used in the GPS system work. So the boffin's theories work there, and there would certainly be gravity differences too, so since they haven't accounted for those it must not have an effect.

The theory is mass does pile up at relativistic speeds, I guess in a similar way to the distance change, the apparent mass does too. But I'm not sure how you could go back the other way, antimatter maybe? Someones bound to figure it out eventually right :shifty:

[Dave-]

The Blackbird guy deserved to be told he was a fuckin moron, and to go have his shock serviced.

Hmmmm, the static. Radio noise caused be electrons bouncing around in everything? That's about as random as I can dream up short term. Gimme a box of Heiuneken, and I'll come up with something most folk would believe.

it's electromagnetism left over after the big bang, turns out if you fire a frequency off into space is spreads out really really wide and that's the noise you see on the TV and hear on the radio.

anyone know what portion of the electromagnetic spectrum humans can perceive?

The famous Buckminster Fuller quote will suffice (that line from that incubus song)

[Drew]

Predictability is the simple answer, the velocity-time based corrections used in the GPS system work. So the boffin's theories work there, and there would certainly be gravity differences too, so since they haven't accounted for those it must not have an effect.

The theory is mass does pile up at relativistic speeds, I guess in a similar way to the distance change, the apparent mass does too. But I'm not sure how you could go back the other way, antimatter maybe? Someones bound to figure it out eventually right :shifty:Dude, we've covered that I'm too stupid to grasp any of this.


it's electromagnetism left over after the big bang, turns out if you fire a frequency off into space is spreads out really really wide and that's the noise you see on the TV and hear on the radio.

anyone know what portion of the electromagnetic spectrum humans can perceive?

The famous Buckminster Fuller quote will suffice (that line from that incubus song)
Prove it.

[Dave-]

Dude, we've covered that I'm too stupid to grasp any of this.


Prove it.

http://en.wikipedia.org/wiki/Cosmic_noise

Note: not a reliable source.

[ducatilover]

Well, instead of being a desk jockey, I lowered the front guard on the ZX6 to have 2mm clearance, if it shreds and hits my face at 230km/h (or sooner, place bets) I'll buy Drew the choc fish, if it doesn't and I lean over the front with my verniers, and it's more than 2mm, Dave gets choccy fish
Tyre is a Pilot Power at 36psi cold on a reasonably humid Eketahuna day

I think Drew will win

[Dave-]

Well, instead of being a desk jockey, I lowered the front guard on the ZX6 to have 2mm clearance, if it shreds and hits my face at 230km/h (or sooner, place bets) I'll buy Drew the choc fish, if it doesn't and I lean over the front with my verniers, and it's more than 2mm, Dave gets choccy fish
Tyre is a Pilot Power at 36psi cold on a reasonably humid Eketahuna day

I think Drew will win

no no no no

you have to have the wheel spin up at a nice easy rate, on perfectly flat ground in a frictionless vacuum.

surely this is reasonable?

[ducatilover]

no no no no

you have to have the wheel spin up at a nice easy rate, on perfectly flat ground in a frictionless vacuum.

surely this is reasonable?

Sounds easy enough? :lol:

[jonbuoy]

Dont worry - its all a simulation anyway

http://discovermagazine.com/2011/jun/03-our-universe-may-be-a-giant-hologram

http://www.wired.co.uk/news/archive/2012-10/11/universe-computer-simulation

[schrodingers cat]

Prove it.

A parasitic learner then, not an original thinker...:weep:

[Drew]

http://en.wikipedia.org/wiki/Cosmic_noise

Note: not a reliable source.Sooooo, you're using an unreliable source to convince me of something? That's prolly not going to work.


A parasitic learner then, not an original thinker...:weep:Pardon?! Relax man, it was a joke. I don't want to know if it is, or is not, resonance from the big bang. It makes no difference to me, or my understanding of the universe. I cannot apply it to anything I do.

Has got me wondering though. If it is enssentially an echo, wouldn't it be getting quieter?

[Dave-]

Sooooo, you're using an unreliable source to convince me of something? That's prolly not going to work.

Pardon?! Relax man, it was a joke. I don't want to know if it is, or is not, resonance from the big bang. It makes no difference to me, or my understanding of the universe. I cannot apply it to anything I do.

Has got me wondering though. If it is enssentially an echo, wouldn't it be getting quieter?

I'm not trying to convince you of anything, neither of us is on trial here, believe what you want?

[Drew]

I'm not trying to convince you of anything, neither of us is on trial here, believe what you want?Answer the question, is the white noise getting quieter?

[pzkpfw]

Answer the question, is the white noise getting quieter?

It's coming from everywhere. Eventually it'll all be gone, but for now the stuff we receive today has simply come from slightly further away than the stuff we received yesterday. There will be some tail-off, but how noticible? That's beyond me to answer.

[Dave-]

It's coming from everywhere. Eventually it'll all be gone, but for now the stuff we receive today has simply come from slightly further away than the stuff we received yesterday. There will be some tail-off, but how noticible? That's beyond me to answer.

It'll run out one day....

[Berries]

It'll run out one day....
And $500 says Sanitarium will then stop anyone else importing some to fill the gap.

[pzkpfw]

It'll run out one day....

Yeah, that's what I meant by "Eventually it'll all be gone".

[schrodingers cat]

Sooooo, you're using an unreliable source to convince me of something? That's prolly not going to work.

Pardon?! Relax man, it was a joke. I don't want to know if it is, or is not, resonance from the big bang. It makes no difference to me, or my understanding of the universe. I cannot apply it to anything I do.

Has got me wondering though. If it is enssentially an echo, wouldn't it be getting quieter?



Actually I was referring to Dave for employing my strategy of demanding proof when he over extended himself. He used the same strategy on you hence the comment directed at him.
I also understand the static to be cosmic noise
For all we know he 'echo'may be geting quieter - but on a cosmic scale

[bogan]

I heard this, and figured it must be posted here...

"In theory, there is no difference between theory and practice; in practice there is"

:lol: At the very least this should be put up in all engineering workshops at universities...

[jonbuoy]

it's electromagnetism left over after the big bang, turns out if you fire a frequency off into space is spreads out really really wide and that's the noise you see on the TV and hear on the radio.

anyone know what portion of the electromagnetic spectrum humans can perceive?

The famous Buckminster Fuller quote will suffice (that line from that incubus song)

Its not all from the big bang, some is spewed out by our own and other suns and some is from lightening storms and man made sources.

[Drew]

Its not all from the big bang, some is spewed out by our own and other suns and some is from lightening storms and man made sources.
Sooooo, it's getting louder?

[mossy1200]

Sooooo, it's getting louder?

If everyone used their clothes dryer at the same time and then we all ripped clothes apart on Dec 21 would scientists confirm that the sudden increase in static noise was the end of the world about to happen?

[jonbuoy]

Sooooo, it's getting louder?

I dont know, it gets louder with solar flares and some frequencies ranges are getting pretty crowded. Arent stars still being born?

[Drew]

I dont know, it gets louder with solar flares and some frequencies ranges are getting pretty crowded. Arent stars still being born?

I have no idea whatsoever.

[Dave-]

Its not all from the big bang, some is spewed out by our own and other suns and some is from lightening storms and man made sources.

oh of course.


I dont know, it gets louder with solar flares and some frequencies ranges are getting pretty crowded. Arent stars still being born?

Sort of, technically we're still being born, but some/most of the stars being born in the night sky were born millions of years ago, it's just taken that long for the light to reach earth.

[Dave-]

Who knows why I keep chewing out tyres?

[Drew]

Who knows why I keep chewing out tyres?Because you think you're a track hero?

[bogan]

Who knows why I keep chewing out tyres?

Cos you like the taste?

[p.dath]

Who knows why I keep chewing out tyres?

Try changing into second.

[bogan]

Try changing into second.

hahaha, you just got p.burned :crazy:

Serious answer though, maybe the tyre shrinks so much with speed it's rubbing on the rim? :shifty: