I know back bone chassies can be very stiff in torsion but isn't there a risk that they'll bend so that the wheels on one side are closer together than the other?

This particular car has a metal frame in the body tub for crash / rollover / side impact protection.
Rescued attachment F16 chassis front.jpg

Nice pic but i wouldnt be too happy having a crash in that, even if the body is 'safe'

I wouldn't even call that one a backbone. More two subframes connected by a small tube. A real backbone is much larger in cross section and often triangulated.

Like this:



or:



So in answer to your question, it depends on the strength of the backbone, but it's unlikely in a properly designed one while still being more likely than in a decent spaceframe/monocoque. In the one you show the body is going to have to be a decent monocoque to avoid it.

[Edited on 29/11/09 by iank]

Nearly all backbone chassis are really only part of the structure the body stiffens them a lot.

The only backbone chassis I can think of that didn't transfer any chassis loads the body was the Triumph Herald.

here's aproper backbone chassis


that other one looks like it'll twist all over the place. i wouldn't go near it

quote:

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Originally posted by smart51
I know back bone chassies can be very stiff in torsion but isn't there a risk that they'll bend so that the wheels on one side are closer together than the other?

This particular car has a metal frame in the body tub for crash / rollover / side impact protection.

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quote:

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Originally posted by t.j.
The upper ball-joint mounting - wishbone looks tiny to me!

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The front and rear sub-frames are going to be able to apply a huge amount of torsion to that wimpy "backbone". As it stands, I wouldn't even call that a chassis either. If the body is substantial and rigidly bolted to the sub-frames it might be OK but here in Australia the finished chassis would be subjected to a torsion test and the metalwork we see here would fail that miserably. I like the Lotus Europa backbone, even though they rusted like bastards!

No way would I even consider getting in that!

I reckon a few miles around where I live and the potholes would destroy it in minutes!