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Elvin · May 21, 2011, 03:30 AM

Guys,does anybody know how to use Solidwork 2010 simulation to analysis torsion for car chassis?? Actually I done already but I no sure is it correct or not, can anyone help me to check?? Total weight of car plus driver is 190kg, so I diveded to 4 because eqully share by 4 wheels mean each tyre will withstand 475N. I fix 2 wheels behind and add one upward force(475N), one down force(475N) for the two front wheels.I had attached my analysis result. Is it correct?? Thanks for help

jcaron2 · May 21, 2011, 09:48 AM

I haven't used SolidWorks so unfortunately I can't help you there. However, I think your analysis should be set up a little differently. I would fix all four wheels (since they're limited by the ground). Then I'd distribute the ~1900N of downward force in several places. You'll have to estimate the locations based on the weight distribution. For example, if the weight of the driver accounts for 700N, you'll need to apply 700N of downward force somewhere near the driver's center of gravity. I'm assuming the driver sits just in front of the arched section, so maybe the force would be in the center of the cross-bar in front of that sections? Or perhaps divided proportionally between two of the cross-bars, if the driver sits somewhere between them. Then you can do the same for the battery and motor if you know or can estimate their weight and location. After that, I'd divide the remaining force (from the weight of the rest of the chassis, components, etc.) into maybe eight or ten locations throughout the chassis. You should be able to make a very rough (but educated) guess as to how to apportion them. If nothing else, just dividing evenly should be a fairly decent estimate. It's also possible that SolidWorks can spread the force evenly throughout the frame, rather than having to specify a number of point sources. I just don't know, since I've never used it.

Either way, it looks like a very cool project! Have fun!

Elvin · May 21, 2011, 11:21 PM

Thanks! But I think that is a bending moment analysis instead of torsion (since 4 wheels are fixed)... what I need to know is if I've calculated the torsion with appropriate force?

jcaron2 · May 22, 2011, 07:06 AM

Aaah. Got it. Sorry about that. :)

Unfortunately I guess I'm no help then.

ebaines · May 23, 2011, 11:41 AM

Torsion analysis of the frame chassis should be based on two things:

1. Twisting torque introduced as the car turns through a corner, due to the differing suspension stiffness between front and rear. For example if the rear suspension is stiffer than the front, then the rear outside tire will take more of the cornering load than the front outside tire. This causes a twisting moment in the chassis. To calculate the amount of torque in the chassis that this causes you need to know the equivalent spring rates for the rear and front suspensions. But in general this may account for a twisting moment of perhaps +/- one half the nominal weight on the wheels.

2. Impulses due to one tire hitting an obstacle in the road (pothole, for example). This causes an impulse shock to the suspension for that wheel. One way to model this is to determine the force required to deflect the suspension by, say, 3 inches, and apply that additional force to that corner. To keep things in equilibrium you can model the other 3 points of the suspension as fixed in your software. I think your approach of modeling the front as taking a force of +475N on one corner and -475N on the other is not too bad, though it's really a worst case.