turbo time
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| posted on 29/9/04 at 04:00 AM |
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Electrical Conduit tubing good for A-arms??
So,
I was strolling through the home depot today (hardware/home improvement store) and walked by the electrical conduit piping/tubing and had to do a
double take. It apparently comes in 3/4", 1", 1 1/4"....and other sizes in 1/4" increments. Anyhow, those sizes are the
I.D.'s. Now, the pipe was labeled as EMT (Electrical Metalic tubing). I think that's what it was anyhow, I'm not so good with
TLA's (Three Letter Acronyms)  . So I had a look at it, and while there was no label on it as to the SWG of it, the 1" version looked
like it was between 1.5 and 2mm wall thickness, about right for A-arms. I can't confirm it until a make a trip back with my vernier caliper
though. I only mention it because it cost about 1/4 of what I paid for the tubing I'm using to make my A-arms. As far as I could tell the only
problem was that it was galvanized, which is unhealthy to weld, but you could wire brush, or grind it off, or wear a respirator to weld it.
So, to the question: Anybody familiar with this stuff if it is made of with some kind of pot metal or alloy that wouldn't work in welding, or if
there are any things about it why it wouldn't work for making A-arms?
I don't really need it, but maybe if it works some folks can save some money in construction costs.
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Tblue
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| posted on 29/9/04 at 05:11 AM |
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I wouldn't. It's low quality steel, it's seamed tubing, it's quite thin in the wall (the galvanising adds to the wall
thickness, but not to the strength) and so is a quarter of the price for a good reason.
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Rob Lane
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| posted on 29/9/04 at 07:45 AM |
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It's also malleable and designed for bending.
First road bump would see car flat on floor as they would bend.
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mangogrooveworkshop
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| posted on 29/9/04 at 07:52 AM |
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Quote
I don't really need it, but maybe if it works some folks can save some money in construction costs..........what u save there you can use for
the huge medical billls later.!
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JB
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| posted on 29/9/04 at 11:42 AM |
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Tubing
I would only use CDS 2 for wishbones.
John
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derf
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| posted on 29/9/04 at 01:12 PM |
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I'd be surprised if electrical conduit would hld a locost up on its own weight without ripping apart.
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Mark Allanson
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| posted on 29/9/04 at 06:16 PM |
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You could always use it for putting your wiring through, probably ideal for that
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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andkilde
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| posted on 29/9/04 at 06:24 PM |
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Hmmn
A shame really as there are all sorts of "connecty" bits available for the conduit. Build a whole chassis with a tubing cutter and a #2
Robertson screwdriver...
Ooh! how about PVC pipe and that lovely smelly glue? "What we have here is a high-tech composite sports car chassis."
Cheers, Ted
[Edited on 29/9/04 by andkilde]
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turbo time
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| posted on 29/9/04 at 06:53 PM |
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Ah, ok
Good info to have, so it's actually made with very low grade, soft steel. Makes sense, it's gotta be cheap(er) for a reason....
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chrisf
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| posted on 30/9/04 at 02:39 AM |
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The Depot stocks pipe, not tube. The other folks are right: You should use cold rolled 1020 DOM for the arms. I don't think the conduit would
last the test drive!
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Hugh Jarce
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| posted on 30/9/04 at 04:58 AM |
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quote:
Originally posted by chrisf
You should use cold rolled 1020 DOM for the arms.
Sorry to be pedantic, but I thought I'd jump in here in case any one gets the wrong idea.
DOM is Drawn Over Mandrel, with the emphasis on drawn. It starts out as a solid hot or cold bar.
ERW (or CREW in US) is rolled from thin strip and Electri Resistance Welded.
That conduit is also rolled, and is of much lesser quality, as it's designed to be easily bent with a plumber's/electrician's
jerker, and only has to support a handful of wires. 
The pay isn't very good , but the work's hard.
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ernie
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| posted on 30/9/04 at 05:13 PM |
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electrical conduit
I have been bending conduit for **** years and it is soft as boot laces
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andkilde
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| posted on 30/9/04 at 08:41 PM |
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quote:
Originally posted by Syd Bridge
Quote
Ooh! how about PVC pipe and that lovely smelly glue? "What we have here is a high-tech composite sports car chassis."
I know a well known racecar constructor who mocks up spaceframes in just this manner! Easier to bend than steel, and cheaper. No mistakes or
corrections then when you go to the steel.
Cheers,
Syd.
Hmmn, cool, that's a good thing to tuck in the dark recesses of the noggin for future reference.
Didn't realize PVC would hold a bend.
Cheers, Ted
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drmike54
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| posted on 1/10/04 at 03:20 AM |
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A buddy of mine made a VW powered Dragster and Dune Buggy from water pipe a few years ago. The water pipe is a lot stronger then conduit. But neither
is made for structural use. 
Started Welding the chassis!!!!
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Hugh Jarce
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| posted on 1/10/04 at 04:50 AM |
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quote:
Originally posted by Syd Bridge
Hugh,
I think you'll find that DOM starts life as a strip, is then erw joined into a tube, then heated and 'Drawn Over a Mandrel' to
normalise the weld area and even up wall thicknesses.
How strange, I'm in total agreement with Syd!
My mistake, DOM is indeed rolled from a strip and welded. I had CDS on my mind.
Incidently, CDW (cold drawn welded) is another version of DOM.
The pay isn't very good , but the work's hard.
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leto
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| posted on 1/10/04 at 07:23 AM |
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I don't think welding in cold drawn steel is a great idea. The heated parts will be softer than the rest and the mechanical preform will become
unpredictable.
Cheers!
“I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
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Hugh Jarce
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| posted on 1/10/04 at 07:58 AM |
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quote:
Originally posted by leto
I don't think welding in cold drawn steel is a great idea. The heated parts will be softer than the rest and the mechanical preform will become
unpredictable.
Cheers!
The carbon content isn't that great in CDS/CDW/DOM/ to make a significant difference. Most (round) tube framed race cars are made from this
material and they're perfectly satisfactory.
It's a different story with high carbon steels and alloy steels tubes such as 4130.
The pay isn't very good , but the work's hard.
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Peteff
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| posted on 1/10/04 at 09:23 AM |
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Ernie
I have been bending conduit for **** years.
Four figures eh Ernie! Did you wire up this cave we live in then ?. I used conduit at the back of the car to form the hoop that the back panel rivets
to. It was black not galvanised and was found in a scrapyard. I think that's about the limit of it's usefulness for cars.
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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leto
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| posted on 2/10/04 at 07:02 AM |
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quote:
Originally posted by Hugh Jarce
quote:
Originally posted by leto
I don't think welding in cold drawn steel is a great idea. The heated parts will be softer than the rest and the mechanical preform will become
unpredictable.
Cheers!
The carbon content isn't that great in CDS/CDW/DOM/ to make a significant difference. Most (round) tube framed race cars are made from this
material and they're perfectly satisfactory.
It's a different story with high carbon steels and alloy steels tubes such as 4130.
From what i understand CDS/CDW/DOM are all work hardened to increase yield strength. An area close to a weld will be annealed and lose this extra
strength. This will only be significant if you designed against fatigue. In racing fatigue is not high priority issue, on a road car i believe it
should be. The higher grade steel used in CDS/CDW/DOM will on the other hand give increased strength.
Cheers!
“I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
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JB
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| posted on 3/10/04 at 07:53 AM |
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CDS
You can buy CDS either "hard as drawn" or "annealed"
JB
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Hugh Jarce
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| posted on 3/10/04 at 08:14 AM |
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JB, you beat me to it!
CDS/CDW/DOM is used by thousands of car builders around the world for competition and "everyday" cars.
The point about using (any) hardened material is valid on paper, but in the real world, welding these types of tubing doesn't really drtract
from the performance of the material.
4130 is totally different though.
The pay isn't very good , but the work's hard.
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leto
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| posted on 3/10/04 at 01:55 PM |
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I am trying to figure out how much of CDS/CDW/DOM superiority over ERW is based on fact and how much is tradition. This question is more valid in
here, as the corresponding tubing to CDS and ERW are made of the same grade steel.
As i don't trust tradition, wide spread use isn't an argument of much value. The point that “welding these types of tubing doesn't
really distract from the preformans of the material” is very interesting. I would very mush like to hear more about it.
Cheers!
“I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
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