onsdag 4 april 2012

Spaceframe comparison

Finally it seems I have the spaceframes modelled up. Above is a picture of the original IMSA frame

And here is a picture of Pauls spaceframe. I know the frames aren't exact, as an example they lack suspension pickup points. But they're both close enough for now. Further refinement will be made.

 The point was to compare the torsional rigidity of the frames and then work to find improvements for Paul. The picture above shows how I set the analysis up. A virtual part was attached to the front rectangular beam which will house the attachment points for the front shock absorber. This part was then rotated 1 degree around the longitudinal axis. At the rear rectangular beam, another virtual part was applied and this was clamped.
I do know this is not really the correct way to do it if you want values to compare to the real world, but for comparing spaceframes and see if improvements can be made I felt it would be good enough, especially since there's a limit to what I can actually do on my computer.

For Pauls spaceframe, we suspected that the engine would act as a cross brace. I decided to model this by adding an infinitely stiff virtual part connecting the engine mounts.

For the analysis, a full-on 3D analysis seemed appropriate. To speed up the computations, the mesh size was set to 20mm with a sag of 10mm using parabolic elements. Material was set to steel.
And the results?
For the IMSA spaceframe pictured at the beginning of the post, a moment of 6168Nm was recorded.
For Pauls spaceframe, not including the effect of the engine/transmission, the moment was 6824Nm.
When the transmission was taken into account, the moment increased to 8139Nm.

I am confident that we can find ways of increasing torsional rigidity for Pauls car. As a reference, speedlab have their corvette racecar up at 18000Nm/deg

Now, next on the to do list is finding improvements

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