chrisf
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| posted on 9/3/04 at 08:03 PM |
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Suspension materials
I'm looking for advice on A-arm materials. Currently, I plan to use 3/4", .125" DOM. I plan on using heim joints for the suspension.
Rather than thread the the male heim joint into the DOM, I want to weld a 4030 threaded tube adaptor. Is this the adviseable materials to use or can I
get away with something lighter--ie thinner wall, etc?
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Terrapin_racing
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| posted on 10/3/04 at 12:01 PM |
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Drawn Over Mandrel with tube insets should be fine. If you want to go a bit OTT you can also get them nitotec's as I did.
cheers
Rob
http://www.nitrotec.co.uk/properties/properties_frames.htm
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cymtriks
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| posted on 10/3/04 at 08:37 PM |
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better tubes
Go up in tube diameter before increasing the wall thickness. The lower wishbone tubes are loaded in bending and the book design relies on that big 1/8
inch plate to stop it from folding up over bumps. Moving the coil pickup closer to the hub is a good thing, check out a Caterham, it gets much closer
than the book design and is less loaded as a result.
A one inch 14 gauge tube or 16 gauge tube would be stronger and lighter than the 3/4 inch 1/8 wall tube.
The 16 g tube can take 25% more load and the 14g one can take 33% more load.
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Alan B
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| posted on 10/3/04 at 08:55 PM |
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Most of my rear suspension links are 1" 16g tube with welded in threaded bungs (1/2-20 UNF).....no bending loads on any though....seem very
strong indeed....
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batfasturd
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| posted on 10/3/04 at 08:58 PM |
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well the kit i bought just had normal welded seam tube apparently in 16swg.
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Alan B
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| posted on 10/3/04 at 09:03 PM |
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Nothing much wrong with ERW (welded tube) IMO.....in 20 years of usage I've never seen a failure (seam split)....I think it is pretty well made
these days
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JoelP
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| posted on 10/3/04 at 10:18 PM |
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certainly hope so! my bones are 16g 3/4 inch round ERW, plus the 3mm plate is a bit chopped about. I think this will be the first thing i replace, cos
its not very good...
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Mark Allanson
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| posted on 10/3/04 at 10:56 PM |
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Spose 15mm copper pipe and yorkshire fittings are out of the question then?
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Terrapin_racing
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| posted on 11/3/04 at 09:15 AM |
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I know of a failure on rear training arms on a Mallock that were 3/4" 1/16g and these had to be beefed up.
However it was pushing out over 200bhp.
Check out the Nitrotec treament I mentioned earlier. I judge at Formula Student and I see it appearing on thinner and thinner gauge tubing all the
time!
I honestly do think we are prone to over engineering - but not a bad thing for road use.
I attach an interesting article for interest
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Terrapin_racing
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| posted on 11/3/04 at 09:19 AM |
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PS: Just saw the copper tubing post 
Interestingly enough I have seen a prototype chassis made up in 15mm copper and solder fittings - beats wood mock up I suppose!
so there........
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chrisf
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| posted on 11/3/04 at 01:47 PM |
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Thank you all for the advice. I am now clear as to what the A Arms will be made of. My current plan is to build the suspension out of the 1"
DOM. I really want to build this car so I can enjoy it next summer. When it is complete, I will start experimenting with Ti tube and the suggested
coating. That is the dream anyhow...
--Thanks all, Chris
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Bob C
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| posted on 11/3/04 at 01:48 PM |
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We have to over-engineer, or we'll die! As amatuer builders we do one or two cars in a lifetime & there's no way we can do all the
analysis and testing Mr Ford does on his new models - it's generally a case of "if it looks right" & make it way too strong.
I'm doing an IRS for my locost. OK I can estimate static, sideways and braking forces but my biggest concern is "pothole" stress
trying to rip a wheel off, I think all I can do is make it really strong! So I'm putting 1" sq. tube down the transmission tunnel top as
well. If I'm still posting here in 3 yrs time then it must be over engineered!
cheers
Bob C
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Terrapin_racing
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| posted on 11/3/04 at 02:06 PM |
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You'll need it over engineered with those roads around Knutsford Bob 
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Bob C
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| posted on 11/3/04 at 04:25 PM |
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ahh you've visited then.....
actually there's some nice roads hereabouts, my commute to congleton is V pleasant (not fast mind you). Too many roads ruined by gatsos &
their ilk - the cat&fiddle road has its own police helicopter on nice days!
Bob C
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chrisf
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| posted on 11/3/04 at 04:42 PM |
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Good to hear BobC is dealing with the pot holes. I'm relying a bit on his suspension design!
I forgot to add that, after all the hard work, it looks like heim joints are not in the cards. For all the material, the cost would be about $100
USD/corner. Not locost at all. So, it looks like Delrin will win out.
[Edited on 11/3/04 by chrisf]
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