Nerdy Question.......

[george graves]

Dumb asses...Just frinking measure it...

Find a lift, put the car up into the air 8 feet or so.

Get some light ribon from the fabric store(wide enough not to slip into the cracks of the tread)

Wrap the thread around a front wheel a few times

Add a little bit of weight to the free end of the ribon. Keep adding untill the the wheel will just start to move, then remove a tiny bit of weight(this part will make up for friction of the wheel bearings)

Then add 10 pounds of weight to the ribon, and measure the acceleration of the wheel as it rotates.

(OR SOMETHING LIKE THE ABOVE) - anyways, that how it would be done in the real world by an engineer(most likely on a low friction bearings, and a computer measuring the accelerations(alpha) of the wheel...

Or sorry about the dumbass comment...(just a joke)

[Z3Jonathan]

It's not a simple integral unless your wheel looks like a hockey puck

I never said it would be simple. I said it'd take a few ( :P = understandment) It'd be a royal bitch to figure for all the different materials in a tire.......

Jonathan is probably right, not worth worrying, but something I was pondering.

You could probably do the wheel without too much trouble.... atlho creating the model would probably require having direct access to a wheel to measure from.

The tire is obviously not worth trying to model, and its so thin anyways, I would make the assumption and idealize it as a doughtnut with constant properties (read: density).

Jonathan

[Z3Jonathan]

Dumb asses...Just frinking measure it...

Find a lift, put the car up into the air 8 feet or so.

Get some light ribon from the fabric store(wide enough not to slip into the cracks of the tread)

Wrap the thread around a front wheel a few times

Add a little bit of weight to the free end of the ribon. Keep adding untill the the wheel will just start to move, then remove a tiny bit of weight(this part will make up for friction of the wheel bearings)

Then add 10 pounds of weight to the ribon, and measure the acceleration of the wheel as it rotates.

(OR SOMETHING LIKE THE ABOVE) - anyways, that how it would be done in the real world by an engineer(most likely on a low friction bearings, and a computer measuring the accelerations(alpha) of the wheel...

Or sorry about the dumbass comment...

That takes all the fun out of it!!!!!!!

EDIT: That method would also take into effect the moment of inertia of every rotating part (lugs, brake disk, rolling elements of the bearing, hub, etc)... but these would be constant from wheel to wheel.

Honeslty if an engineer was really intersted, he'd probably just find it in the solid model, since he'd probably have access to that anyways, and then idealize the tire.

Jonathan

[rs4pro3]

Hum I thought Autocad gave the moment of inertia, our teacher showed us some hidden tool where it would calculate all that engineering. Drawing it out in autocad would be hard to do for sure.
Hum you're making me interested in sitting down and calculating it out.

[rwh11385]

Damn. George's logic rocks me.

But that is the easy way out. We like the overly complicated approach!

[Z3Jonathan]

Hum I thought Autocad gave the moment of inertia, our teacher showed us some hidden tool where it would calculate all that engineering. Drawing it out in autocad would be hard to do for sure.
Hum you're making me interested in sitting down and calculating it out.

I could be wrong... the Material Properties tool might do it. Been a while since I've fooled around with that tool for anything other than finding the volume of a solid. Honestly, in the 6 years I've been using AutoCAD, I can count on my hand how many solid models I've created.

Jonathan

[george graves]

Oh hell yea, if you had a model of the wheel in autocad, with the density of the mental used to make the wheel by all means..let the computer calculate it for you...

Anyone got a autocad file fo my borbet type c's?

:up: