Any rollcage designer types in these parts?

[Davi]

I want to make a sort-of roll cage for a buggy, but I'd also like to build in some weak points as sort of crumple zones - having been in a shunt in a roll-cage-on-wheels before, I'd prefer some area to have a little 'give'next just in case there is a next time!!! If anyone on here knows their onions and wouldn't mind imparting a bit of knowledge, be much appreciated!

[Carpal]

You want the crumple zones to be outside, rather than part of, the safety cage.

[GroundEffect]

As said above, you don't want to intentionally weaken your space-frame. Create crumple zones out of various designs of deformable structures. That's what FEA is for.

[cossy400]

Where are you?

Have a look at tornado motorsport ltd.

He gets very good reviews.

[Davi]

Sorry I didn't explain that very well - indeed, I don't want the crumple zones to be within the cage, BUT by the nature of the vehicle (beach buggy) there is nothing outside of the rollcage to really absorb an impact.

This means in any shunt you're effectively hitting with the strongest part of the vehicle, which hurts! So... what I'd like to do is make some bolt on secondary cages for front and back that extend past the 1mm thick piece of plastic they call the body that are like big bumpers, so will crumple but still provide protection.

I thought about just making them in narrower walled tube but not sure if that's enough or if I need to build in weak points?

[PhillipM]

Put a kink in the tubes leading to them and as you say, make sure they're thinner walled than the main structure, problem solved.

[anonymous-user]

The problem with "simple kinked tubes" is that once that weak spot has yielded, the loads fall off and no more deceleration occurs. You want multiple "weak spots" such as in a carbon composite or, on more of a budget, an alluminium honeycomb panel to collapse in a progressive manner. Plenty of race cars use inteligently oriented honeycomb pannels as a crumple structure outside of the main cage etc

[PhillipM]

Yes, but this is a beach buggy, so I'm guessing he wants something he can stick on with a arc welder and a hammer, and pull straight when it's bent

Edited by PhillipM on Thursday 13th September 20:09

[Davi]

PhillipM said:

Yes, but this is a beach buggy, so I'm guessing he wants something he can stick on with a arc welder and a hammer, and pull straight when it's bent

Edited by PhillipM on Thursday 13th September 20:09

basically, wot he said :P I want to go a *little* more technical than a kink if possible, but there does need to be a certain amount of idiot with hammer about it!

[PhillipM]

Couple of foam filled crash boxes off the front of most modern cars with a plate to bolt them to, and weld a beam/tube across in front of them, all you need to do is unbolt then and bolt a new set on if you bend them?