I'm about to make some rear wishbones out of 20mm x 2mm CDS.

Everyone seems to discuss front but not rear bones. I'm wary of making them too strong just incase of an 'off' and damaging the chassis.

Opinions? Increase to 2.5mm or stay the same?

strength comes from the diameter as well. 20mm is very small. personaly I would use min 25mm and u would be better with 28.75 or 30mm.
you could then drop to 1.5mm thick. depends how good your welding is.
use 20mm as cross brace but dont need 2mm 1.5 is good.
bet I get lots of disagreement.

I used second hand landrover drop link tube, quality metal that is thrown away as you can buy new with ball joints which is easier than getting the old joints moving, have you any 4x4 garages local?

I guess it's around 25mm diameter, only used for the lower bones as these also carry the shocks on my car, the tops are 3/4" 16swg ERW.

No reason for the rears to be any more substantial than the front, when you crack the brakes on hard the loading on the front is more than the rear every suffer.

I thought 20mm was the bare minimum, Westfield looks 22mm, but I bet they use ERW rather than CDS - not sure what wall they use.

So I'm up to 25mm, no need to go bigger than that. 1.5mm seems thin, 2mm sounds right?

My fronts are going to be 32 x 16 x 2mm top and bottom.

Yes Mark, there is Landrover place close by, but he's an ar$e by all accounts!

its not only the arm size which can be a problem . a bigger size tube gives a better joint for welding

Yes, I agree, but welding 2mm wall or the smaller radius isn't an issue.

My concerns are making the wishbones so strong, that if I do fall off the road, the chassis takes the hit and not the bones.

I'm debating 25mm x 2.5mm now!

My Westfield Mega had 3/4" 14g ERW front and rear. Circa 2002 vintage.

I've used this material for all my wishbonery since. They do bend, but unfortunately they do also take the chassis brackets with them. They're also strong enough to punch a hole in the back panel and through a carbon seat and bruise your spine - if you back the car into a barrier at Combe.

I'll be using 25.4x2.03, or 1.6 if i think i can get away with it. Car will be 7-800kg and 3-400hp though

Of course if you'd have wishbones designed with the load path down the tube instead of REiB you can use thinner wall as there won't be any real bending force on it.

20x2 CDS will be more than adequate.

Good to have you back, my Duratec font of knowledge!

quote:

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Originally posted by flak monkey
20x2 CDS will be more than adequate.

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even 20x2mm will be stronger than your chassis. 2mm cds tube that is triangulated vs 1.6mm erw box section that has brackets welded onto it with no triangulation or bracing behind! i dont know were people keep getting this stupid idea that the wishbones are a sacraficial item. put simply on a locost they are not!

if you want to make something sacrifical then it should be properley designed in, generally sacficicial items have a very short design life and are replaced every race. personally i wouldnt want a wishbone that was designed to give way on a road car, the uk roads are getting so bad they will just bend. think back a few years and loads of people were having problems with origonal locost wishbones bending.

Ash, thank's for your condescending input.

Stupid, not really, I repaired a locost with just wishbone damage. Admittedly it depends on the angle of impact, but I've heard a few accounts of just wishbone repair.

Take it as you like, the facts won't change. It wasn't intended to be condacending.

It's a bit of free advice you have your own free will and can take it or leave it. I honestly don't mind I will continue on as normal. :-)

I just wanted to throw a bit of thinking onto the pie, that may or may not influence you. Wasn't you one on here asking the question because you wasn't sure? I'm easily confused.

I'm not really one for cock swinging, it oddly feels fitting here so be gentle I'm gonna give it a first go. I have built them, drove them, raced them, bumped them, smashed them and fixed more of them, than I can remember. heck I have even written a couple of books about it all so kinda have some idea. If experience is not good enough then there is always the row of letters after my name to fall back on plus Ceng tag at the end

Oooh that was exciting I feel all aroused

Whatever you decide enjoy building it and have fun finding out :-)

well said ashg LOL , iv'e only been posting for a while , but this forum is better than the school yard for fights !

ps : I would still prefer to use 25 mm + and have them not part company from the car

oh the controversy !!!!!!!!!!!!!

Hey if you want to swing your dick carry on, touched a nerve have I?

Yes I asked for peoples opinions and I had some interesting replies. And yes, I appreciate your views too.

What I didn't ask for was the 'stupid idea' comments.

quote:

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Originally posted by ashg
If experience is not good enough then there is always the row of letters after my name to fall back on plus Ceng tag at the end

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If you want to save your chassis in an impact you are better off using more appropriate sized fasteners than M10/M12...

Either way, on the road a good safety factor would be preferable to running a weak link in case of a bump.

I'm using the tube off land rover rear arms, not sure what size but they nice and thick. About 1 1/4" OD with thick walls.

I saw some steering arms off a truck at a truck garage and thought they would be really strong to make arms with...