Buggy torsional rigidity

[Slunnie]

There are a heap of buggy designs out there, and from what I've seen so far most of the designs seem to just happen, even with the bigger budget builds (that I've seen) out of the US.

From an engineering perspective, there is a huge amount of thought that is put into things like suspension design, but does the same go into chassis. Arranging the tube work to produce strength along the length is fairly common, and likewise at the rear across the back, but how big an issue is it to design torsional stiffness into them. I see a lot of race car designers and even road car manufacturers often comment about the improvements to torsional rigidity so that the suspension can be set up to do the work, but for offroading vehicles the norm seems to be to allow them to move around, with some vehicles like the Unimog moving a significant amount in the chassis requiring everything to float on the chassis.

With buggy design are people designing them somehow to be torsionally stiff, even if for strength and fatigue resistance? I was under the impression that many of the buggies which have a high driveline such as moon buggies seem to not worry too much, but it looked like those with low drivelines such as front engined buggies seem to angulate the lower tube work for clearance, but perhaps this introduces torsional stiffness also???? It just seems like it would be an important aspect when putting 500+hp through a buggy, with Australian vehicles already getting around 400hp such as in Pete's new truck.

[bj on roids]

For a rockcrawler I cant see torsional rigidity being a key factor.

As for high speed stuff, and road handling/driving, I cna see where you are coming from.

[bru21]

mate look at almost any off road racing buggy and they are rigid as. Most have the engines mounted to bulkheads which become part of the chassis. Ivan stewart used the skin of the fuel tank as a structural member.

TT are so rigid its crazy but weighing 5000lbs so they should be!

Mine has to be torsionally rigid to pass as an icv so I have given it some thought. (lots of)

cheers bru

[Slunnie]

Its interesting Bru. I was reading on Pirate I think it was something about some builder that had a reputation for building chassis that would twist around, and how many of the chassis are built like a cardboard box, in the sense that they dont flex front to rear or side to side but they do torsionally. I don't recall who the builder of the twisty chassis were though.

It sounds like much of the torsional stiffness comes purely from the use of material, guessets, strong welds and bits being bolted in rather than triangulation. Even looking at Shannon Campbells KOH09 truck, the frame doesn't triangulate for torsion anywhere forward of the back of the drivers seat, even in the front suspension area which I would have thought would be most prone to flexing.

Obviously enough is had.

Click for high res.



Edit, Bru this question isn't in relation to your buggy of which I'm lovin the build - more me thinking through designs and design differences of different buggies. I'd also been wondering is bevelled floor pans increase the torsional rigidity etc.