I was wandering about this theme:

If we would build a Locost type chassis and instead of use the typical square tube of 25mm and wall thickness of 1,5 we intend to use a 30mm square one.

To mantain the same strenght and have not the same wall thickness (because the weight) what would be the right wall thickness?

Please I ask people that can make some calculations and have some experience in the mater.

Regards
Amadeu

If you changed the cross bracing to a smaller guage material, and used 30 x 30 box section you would have minimal difference in weight.

I have attached a scan of a steel book showing data sheets for square hollow section. The wall thickness's of 16 swg is not included however this should help as a guide.

Thanks,

Dan

1.5 divided by 30 multiplied by 25 gives a wall thickness of 1.25. Rough and ready calculation but near enough for our purposes, and would give the same weight per metre.

It will all depend on what is available though

Don't go below 1.25mm wall thickness.

As already said a car built using 30x30x1.25 will be about a 1.5 kg heavier than 25x25x1.5.

30x30x1.5 will still only add about 7 kg compared to 25x25x1.5.

Weight savings from using thinner walled ERW are trivial not worth it for a road car.

Also all this has very little effect on the stiffness of the chassis --- although using 30x30 has stiffness beneifits particularly in the cockpit sides area.

But be aware changing to 30x30 erw has a lot of consequences when it comes to actually building the chassis .

My advice just stick to 25x25x1.5 and use some of the improved version of the book plans that are available.

[Edited on 9/5/08 by britishtrident]

[Edited on 9/5/08 by britishtrident]