Tigers
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| posted on 2/8/04 at 06:54 PM |
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Tube size for A-arms
Hi Locost gurus!
I have one question - I can't decide what type and size if tubing should I use?
As there is no much choise for me it makes it more complicated.
I can get 29x3mm DOM, but it seems to be too heavy, right?
I can get the 28x1.5mm (or 30x1.5) welded, but isn't it too weak? Book suggests 25x1.5mm but DOM, so maybe if I increase diametter, it will be
stiffer anyway?
Is it so important to use drawn tubes?
Thanx,
Janis
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JoelP
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| posted on 2/8/04 at 07:02 PM |
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i personally would choose 25x2mm of any sort of tube. people advise against ERW due to the weak spot at the weld, but TBH i think if it is well
designed and made i wouldnt be concerned. I am currently running on 19mm square 16g ERW, that didnt break on the test run, even though it is blatently
much weaker than most recommendations. hence i will upgrade to 25mm round, and increase the walls to 2mm.
though i would be happy with this i would await more expert advice and then bear in mind that it is your life, 'caveat artifex'
etc...
maybe caveat machinator would be better grammer...
[Edited on 2/8/04 by JoelP]
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dblissett
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| posted on 2/8/04 at 07:58 PM |
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tube size
i have gone for 25mm 12 gauge dom not only is it much stronger it just seems to look right when welded to the wishbone bush tubes.
i think that the wishbones are one of the most heaverly load parts and there was a thread about some wish bones bending
these were fitted to a 7 with a rover v8
the conclusion was that the standard 19mm was'nt strong enough for the extra weight
good luck dave
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pbura
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| posted on 2/8/04 at 08:32 PM |
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Some guys have used (sorry to use the old money here) 1" round for the uppers and 1" X 1-1/4" oval for the bottom. Sort of a neat
solution for beefing up the lower bones IMO.
Caveat compactor!
Pete
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Tigers
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| posted on 5/8/04 at 05:28 PM |
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Thanx, guys!
I decided to use stainless steel 25x1.5mm tube for wishbones as my father (he is an engeneer) advised not to use cold drawn tubes because it was very
low quality steel - wery heavy and easy to bend.
Next question - what will happen if I weld together stainless steel with ususal steel? Will the welding area rust heavely? And what kind of wire
should I use for welding - stainless of ususal?
Thanx again,
Janis
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JoelP
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| posted on 5/8/04 at 08:20 PM |
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beware the chromates!
the fumes off welded stainless are toxic. Be cautious when (if) you attempt it. also, some people say that some stainlesses are low quality too. just
cos it doesnt rust doesnt mean its tough!
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dblissett
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| posted on 5/8/04 at 08:30 PM |
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i belive that welding two different metals together requires a lot of skill i wouldent trust my welding of stainless and mild steel on my wishbones
why dont you keep it all the same material
type 907 has built his chassis out of stainless may be he can advise with the welding
cheers dave
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paulf
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| posted on 5/8/04 at 08:50 PM |
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I wouldnt use stainless steel at all, I work with stainless every day and find that it is much more likely to develop stress and fatigue cracks and is
generally lower in strength.
If you are going to use it then it would be best to use thicker material and weld with nickel chrome electrodes deigned for dissimiliar metals.
Paul
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type 907
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| posted on 5/8/04 at 11:36 PM |
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Hi Chaps
For s/s to steel you should use a 309 rod. This is a 25/20 chrome/nickel.
Care should be taken not to "puddle" the weld too much to minimize dilution. Minimum penetration is what your after.
HOWEVER, it 's my advise when fabricating in s/s to use the same material throughout. I have used 1/2" nb sch 10 (22.2 o/d x 2.5 wall)
grade 304 for my bones, 3/4" n/b sch 10 for the lower rears.
Hope this helps. U2U if you need more info
Paul G
Too much is just enough
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Hugh Jarce
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| posted on 6/8/04 at 02:47 AM |
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quote:
my father (he is an engeneer) advised not to use cold drawn tubes because it was very low quality steel
CDS has been in use for dozens of years for race car chassis and suspension. Its the second material of choice to 4130 chrome moly tube.
Leave stainless tube to chemical and milking plants.
The pay isn't very good , but the work's hard.
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Tigers
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| posted on 6/8/04 at 09:10 AM |
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Hmmmm... This confuses me eaven more Then probably I'll stick with thicker stell tubes. Will be easier although heavier. And proably
it's better for wishbones to bend than to break, right?
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Peteff
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| posted on 6/8/04 at 09:32 AM |
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It's actually best for them to do neither. Mine are 2mm wall 19mm CDS and are strong enough for road use, therefore anything stronger than that
should be almost indestructible, which is not always a good thing as you will rip or bend sections out of your chassis in the event of a severe
kerbing. Don't overdo it.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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