Physics talk

[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

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

[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/1....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/1....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.