Moment of inertia and turning performance

[Michael Corsetto]

Originally Posted by BJC

Drop definatly is a huge part of the equation. Too much and you rock back and forth, to little and the wheel scrub makes it difficult to turn. This is again why tortional stiffness is SO important. With a flexable chassis you end up with dropped wheels while turning and raised wheels when your not: the worst of both worlds.

Any advice on how to maximize torsional stiffness in a frame? Just beef up the gussets? Add a second frame layer a few inches up? I know this is kind of a vague question, considering all of the different frame construction methods, just wondering how teams typically negate this (if at all).

Some of my own observations:

Welded tube frames are always rock solid in my experience. 1662 uses 1"x1.5", 1/8" wall tubing welded frame. No flex whatsoever. This is consistent with many WCD around California.

1678 uses 8020 extrusion frames, and they flex like mad. Maybe it was just the gussets we used, but I have a feeling that the 8020 beams are less able to resist torsional forces. (If I remembered everything I learned in mechanics of materials 4 years ago I might be able to figure it out... ) Last year we had to create a pyramid strut system to our arm apex in order to remove the torsion experience while turning.

How is the kitbot frame's torsional stiffness? I don't have much experience with it.

Awesome thread, all this talk about frame flex has got me thinking!

-Mike