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Author: Subject: Seamed vs Seamless
SimonNOS

posted on 12/11/02 at 07:30 PM Reply With Quote
Seamed vs Seamless

Does it make much difference weather you use seamed or seamless tubing for the wishbones?

Seamless is stronger right? But can you get away with seamed?





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ProjectSRP

posted on 12/11/02 at 08:11 PM Reply With Quote
If I were you I would try and get some DOM tubing. Not only is seamless DOM stronger because of the cold working but also a higher grade of steel is usually used. Can't be too safe when it comes to suspension.
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Lars

posted on 18/12/02 at 12:40 AM Reply With Quote

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Lars

posted on 18/12/02 at 12:43 AM Reply With Quote
it seems quite hard finding seamless tube, does anyone know if seamed will be strong enough.

I've seen a pic in the book where the trailing arms are made using seamed tubing, and also some people on this site use seamed oval tubing???????

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chrisg

posted on 18/12/02 at 06:34 PM Reply With Quote
Hydraulic supply places usually have seamless.

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Viper

posted on 18/12/02 at 06:45 PM Reply With Quote
any decent steel stockholder should have CDS (cold drawn seamless) that's what i have used for mine, 25mm O/D 18swg but the wishbones tiger supplied me (not using them) are a lot heavier i am guessing they are 10swg and i believe they are seemed...






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Viper

posted on 18/12/02 at 06:46 PM Reply With Quote
oh and i paid £12.00+vat for 6 mtrs






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Liam

posted on 19/12/02 at 01:38 AM Reply With Quote
I'm using the same seamed oval that MK uses on his wishbones. I rather doubt it's gonna just fall apart, probably not even in an accident that rips a wishbone off - then it's academic anyway. I'm not worrying about using seamed.

I will, however, be getting my wishbones professionally [TIG] welded. That's something really worth thinking about. The quality of welding is far, far more critical than the seamed-vs-cds issue when it comes to the wishbones.

IMO of course.

Liam

[Edited on 19/12/02 by Liam]






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Rorty

posted on 19/12/02 at 05:10 AM Reply With Quote
Of the seamless "mild" steel tubing, CDS is the strongest, followed by CDW/DOM.
Then there is welded mild steel tube (ERW), which shouldn't be confused with black/galvanised pipe, which is also welded. You should only be using tube.
You could use ERW, but it would be worth doing a few sums first to check suitability. I would have thought 25.4mm x 2.6mm ERW would do the job.
I would only use CDW/DOM and CDS. It's dimensionally more acurate, and inherently stronger. OMO.






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Dick Axtell

posted on 19/12/02 at 02:32 PM Reply With Quote
quote:
Originally posted by chrisg
Hydraulic supply places usually have seamless.)


MK told me never to use the seamless hydraulic tubing, because it's been heavily annealed. This means that it bends easily, (for hydraulic circuits - used it myself in rig-building), and will therefore do so under "bump" loading.

Be warned - others have discovered this to their cost!!

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philgregson

posted on 20/12/02 at 04:06 PM Reply With Quote
I must admit that I was just going to use ERW like the rest of the chassis (but round obviously). If you stick a bit in the vice and bash F*** out of it (Highly technical I know and perhaps taking the technological approach too far. ) you can cause more damage than I would want to see on my car and it's primary failure mode doesn't seem to be one of falling apart at the seams.

Now I know that this probably is only an approximation of the wishbone loadings on a locost but it indicates to me that the welded seam is probably not too much of a problem. If we were applying pressure from the inside it might be a diferent thing - but we are not.

Once again I might be talking rubbish but your views would be appreciated.

Phil.

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interestedparty

posted on 20/12/02 at 05:26 PM Reply With Quote
quote:
Originally posted by philgregson
Now I know that this probably is only an approximation of the wishbone loadings on a locost but it indicates to me that the welded seam is probably not too much of a problem.


Seems reasonable to me. After all, we are all relying on the strength of welded joints, why should the wishbone tubes be any different? Might be important if weight was a critical issue, and the thinnest possible tube was needed

John





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Alan B

posted on 20/12/02 at 11:02 PM Reply With Quote
Guys consider a seamed tube that has come "unseamed" unlikely, but bear with me.

I t will stiil have the same tensile strength as full tube and the full compressive strength. The three things that are afected adversly are a) torsional stiffness, b)beam stiffness, and c) buckling strength.

Consider a), this should not be an issues, as there should be no torsional loads on any wishbone tube.
b) again should not be an issue, there are no bending loads (except for the lower wishbone I guess)
c) depends a lot on the tube length. a relatively short tube with a thick wall should not be affected too much.

So I would say with a good choice of material, seamed tube should be OK IMO. Although DOM/seamlees is better.

I'd also agree with Liam that quality of welding is a bigger concern than tube selection.

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