×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Wheel moment of inertia estimate

Wheel moment of inertia estimate

Wheel moment of inertia estimate

(OP)
Is there a "rule of thumb" that can be used to estimate the moment of inertia of a wheel?  The information available is: wheel weight, wheel diameter, wheel width.  Doesn't have to be exact or model-specific.  Just trying to get a formula that's better than assuming a solid cylinder, shell cylinder, or thick shell cylinder.  Also, the same goes for tires.

Specifically concerned with aftermarket race wheels for production cars like Porsches or Corvettes.  More specifically, the types of wheels made by companies like BBS or OZ Racing.  Any help is appreciated, since only wheel weight is typically reported.

uwaeve

RE: Wheel moment of inertia estimate

About all you can do is attach said wheel to a soft torsion bar and start it rocking (lightly by hand) back and forth like the balance wheel in a watch.  

Some measurement and calculation will then give you a figure for moment of inertia.

RE: Wheel moment of inertia estimate

Get a drawing of a typical wheel and work it out. It is not rocket science.

For an even cruder estimate, obviously the 'average' radius of the material is greater than 0 and less than the rim radius. So choose a figure somewhat less than the rim radius , say 80% and work it out from there.

Alternatively if you have a solid model of the wheel most solid modelling programs will tell you the answer.

For the tyre you will not be far wrong if you think about it as a total of three rings - two sidewalls and the tread.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Wheel moment of inertia estimate

Two rings for the wheel, one for the barrel and the other for the center, with an estimate of how the mass is divided between them based on the given nominal wheel dimensions?

Norm

RE: Wheel moment of inertia estimate

If you have the possibility to hang the wheel as a pendulum, in two cables, knowing the length from the wheel axis to the attachment point, you can easily derive the inertia from the small angle pendulum oscillation time.
The problem is to hang the tire so the pendelum point is the wheel axis.

Jesper Slattengren
www.prattmiller.com

RE: Wheel moment of inertia estimate

If you are purchasing this as an OEM, this information is typically on the drawings or other document. You should request this information from the vendor.

Greg gave a good suggestion to figure it out. I would take it a step further and obtain a "typical" public domain or calculated information for both the mass and rotational inertia. Because mass and rotational inertia are related to each other through a parameter called the radius of gyration, you can take a published or calculated value for this and use your mass to obtain a better estimate for rotational inertia.

Best regards,

Matthew Ian Loew


Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources