I need an estimate for the polar moment of inertia

[wz07bw]

Folks,

I need to estimate the pitch moment of inertia of a vehicle for Vehicle Sim.

I have the corner weights as well as track and wheelbase. My first thought was to treat the vehicle as a dumbell with two different size masses.

The pitch moment would be the sum of the mr2 with r being the distance between the cg and the front and rear axles respectively.

Any ideas.

Jim

 

[GregLocock]

That's not a bad approach, rule of thumb is that it is the same as the yaw inertia, or a bit less, and the NHTSA publishes a list. Sorry haven't got the link.

Cheers

Greg Locock

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

 

[cibachrome]

What's the vehicle? Maybe its laying aroung here. Other option is to easure it yourself...

 

[PTwizz]

The corner weights and track wheelbase are not enough to determine pitch moment. E.g. a mid engined car might have a far lower pitch moment for the same corner weights than a front or rear engined car.

Pete.

 

[wz07bw]

Thanks everyone. I fully understand that I don't have enough to determine the polar moment. I was hoping someone had a good rule of thumb.

I do have the NHTSA paper with their data and some of it seems a little off with respect to weights.

Thanks anyway.

Jim