Interesting fact about a wheel.

**GSVR** · 19th February 2008, 15:04

Originally Posted by Hitcher

The Bogan's Guide To Physical Laws. Please make it stop.

I'm dissapointed in you Hitcher. You couldn't help yourself could you. What are you going to do next move it to PD or merge it with another thread?

**Hitcher** · 19th February 2008, 15:08

Originally Posted by GSVR

I'm dissapointed in you Hitcher. You couldn't help yourself could you. What are you going to do next move it to PD or merge it with another thread?

A deliciously tempting prospect. I was thinking "Jokes & humour"...

**GSVR** · 19th February 2008, 15:13

Originally Posted by Hitcher

A deliciously tempting prospect. I was thinking "Jokes & humour"...

Maybe you should quote the bits you find funny and say why? I could do with some more laughs.

**NighthawkNZ:Me** · 19th February 2008, 15:22

Originally Posted by madandy

Click on the Yellow text!!!! wound and wound, wound and wound.
Who let the geeks out?

Some people have no sense of humour...

he gave me a juicy red rep for it...

kewl

**Hitcher** · 19th February 2008, 15:29

Originally Posted by GSVR

Maybe you should quote the bits you find funny and say why? I could do with some more laughs.

No. I want this Living Hell to cease.

**Badjelly** · 19th February 2008, 15:37

Originally Posted by Hitcher

No. I want this Living Hell to cease.

Then why poke the inert corpse?

**avgas** · 19th February 2008, 15:38

Originally Posted by Finn

Hmmmm, maybe we should attach our engines directly to the wheel and get that sucker turning 14,000 rpm's.

haha then a bmw would spoke itself

**avgas** · 19th February 2008, 15:39

Originally Posted by madandy

Click on the Yellow text!!!! wound and wound, wound and wound.
Who let the geeks out?

The troll obviously
quick get the hall monitor to round em up

**GSVR** · 19th February 2008, 15:39

Grabbed this out of a real geeky forum but it explains whats going on in my head visualizing the wheel in rotation. American tire = tyre

If we are lucky someone will show up who knows a good online or other textbook chapter on rotation/ang.mom.

But until that happens...

The picture of the tire is an instantaneous one. Pretend you had a camera that could take a picture of the tire just as it rolled past you and that it would show, painted on at each point, a little arrow that is the instantaneous velocity of that point-----at the instant the shutter clicked.

The snapshot of the tire would be all covered with little arrows.

The point touching the road would have a zerolength arrow.

The point at the top of the tire would have a horizontal forwards pointing arrow twice the length of the one at the center of the hubcap

Up the center of the picture would be layer after layer of arrows getting longer the higher off the road, till reaching the top of the tire. Their length would be proportional to height.

Just like on a regular stationary turning wheel the speed of a point is proportional to how far out from the center.

None of the arrows in the snapshot are correct except for that one instant (well, the center of hubcap arrow stays the same but the rest dont)

The very next instant you would need to erase them all and draw the picture over, because a new point would be touching the ground. But the picture would look the same! It will always look,
for just that one instant, like rotation around the point touching the ground.

One can ask, well OK but what is the big deal? why should a physics teacher want me to realize this. But as long as one doesnt get off onto that and just looks at the tire it is not such a hard picture to get. Actually I like it---it helps solve something in an elegant way, doesnt it? Did this discussion help at all?

**avgas** · 19th February 2008, 15:48

Originally Posted by GSVR

Did this discussion help at all?

Good point!
Well kind of....but no - as long as tyres dont fly to bits....no one really "pays-for-research".....unfortunately for us the wheels and tyres havent disintegrated for these reasons in a while (80's?).
However i would be interested to know the difference between sitting the wheel weights in the centre circumference in comparison to towards the edge.
Or the effect of carbon defects on carbon wheels at these speeds.

**GSVR** · 19th February 2008, 15:58

And heres a little bit more...

To undertsand tyre, move with it. Then in your system of reference the tyre center is not moving (0), the tyre bottom is moving back (i.e. with -v versus you) and the tyre top - forward (with +v). Now return back to non-moving system (=add v to all), and you'll get 0 at bottom, v at center and 2v at top.

(Called addition of velocities due to coordinate transformation from moving to non-moving system).

In non-moving system tyre is seen as rotating around its bottom ( instant axis of rotation constantly moving forward with tyre).

**Badjelly** · 19th February 2008, 15:58

Originally Posted by Badjelly

Then why poke the inert corpse?

I take it back. I saw the corpse move!

Seriously Hitcher, if you don't like the thread, don't read it. Are you secretly worried there might be something on it that you would find interesting, so you have to keep checking it? If so, don't worry, I assure you there's no chance of that happening.

**Badjelly** · 19th February 2008, 16:00

Originally Posted by GSVR

It will always look,
for just that one instant, like rotation around the point touching the ground.

Amazing, eh? (No I am not taking the piss.)

**Hitcher** · 19th February 2008, 16:06

Originally Posted by Badjelly

Seriously Hitcher, if you don't like the thread, don't read it. Are you secretly worried there might be something on it that you would find interesting, so you have to keep checking it? If so, don't worry, I assure you there's no chance of that happening.

It's like a train wreck. Morbid fascination, if you will. I'm waiting for the Flat Earth Society to arrive and erect a stall.