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Suspension help
b14wrc - 14/6/12 at 11:27 AM

Getting ready to order all my steel for locost.

For suspension arms, is 19.05mm od x1.6mm CDS suitably strong enough for use on all my wishbones?

Rob

Theshed - 14/6/12 at 01:28 PM

No

Alan B - 14/6/12 at 01:37 PM

I'd lean towards no, but it depends on the design really. Keep bending loads off them and they should be OK.

Theshed - 14/6/12 at 01:40 PM

After my unhelpful response I have been looking at your photo archive to see what you are building. With a mid engine you will be putting a lot of force into your rear lower wishbones. I would definitely use larger (frist choice) of thicker (second choice) tubes in the lower wishbones.

b14wrc - 14/6/12 at 02:12 PM

Lol. I thought that was going to be the answer.

I looked at 22.23mm od 2.6mm wall thickness for the lowers, but thought this would be too much over kill.

What sort of size tubing would you recommend I do the bottoms expecting I can use the 19mm stuff for the top wish bones?

Thanks, Rob

Ps, not ordered it yet.

But as a rough price, all the tube to make my chassis, 80 od metres, £240 delivered.

Theshed - 14/6/12 at 02:26 PM

I am using 28mm x 1.6mm in my lower wishbones but with no bending load whatsoever. I am using T45 tube but the advantages are marginal.

I did not spend hours on stress analysis but just looked at what others were doing. I would wait for one of those clever young engineers to pop up!

phelpsa - 14/6/12 at 08:18 PM

3/4" 16swg is plenty assuming a) you can weld properly and b) you aren't putting any massive bending loads into the wishbone.

7/8" 16swg should be find for a standard 7 style lower wishbone as long as you dont mount the damper half way along it!

28mm T45... are you building a tank? :O

[Edited on 14-6-12 by phelpsa]

b14wrc - 14/6/12 at 09:11 PM

I'm going to run push rods to the bottom ball joint and have inboard shocks at the front. So limiting the bending. However, with mid engine and probably a bit more weight than the average, I am steering towards beefing up the bottom arms. I havn't done any maths on it, but like many, trying to use similar to what others have already done.

Thanks for the help.

Rob

Theshed - 15/6/12 at 06:09 AM

"28mm T45... are you building a tank? :O"

Yup! An 800Kg 750BHP Methanol breathing tank on 10" and 14" slicks......

Seriously though whilst theoretically if bending loads are avoided very thin/small tubes could do the job surely the reality is that a tiny kink/ding/distortion caused by welding etc will put the tube in bending and for road use if you do not want to spend forever inspecting the wishbones a little extra weight here is worth peace of mind. Practically it is very hard to avoid some bending loads in most designs. The extra cost will be tiny.

phelpsa - 15/6/12 at 07:20 AM

quote:
Originally posted by Theshed
"28mm T45... are you building a tank? :O"

Yup! An 800Kg 750BHP Methanol breathing tank on 10" and 14" slicks......

Seriously though whilst theoretically if bending loads are avoided very thin/small tubes could do the job surely the reality is that a tiny kink/ding/distortion caused by welding etc will put the tube in bending and for road use if you do not want to spend forever inspecting the wishbones a little extra weight here is worth peace of mind. Practically it is very hard to avoid some bending loads in most designs. The extra cost will be tiny.


If there are no bending loads at all then you could get away with very small tube (1/2" ). 3/4" in that application has enough RF to put up with weld distortion etc causing minor bending loads, it is not a very thin or small tube at all! The main advantage of going to bigger tube is that it allows a greater weld area, how confident are you in your welding?

[Edited on 15-6-12 by phelpsa]

b14wrc - 15/6/12 at 11:21 PM

Ask me when the build is done!

Think the 22mm or 25mm will be looked at for lowers.