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.

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.

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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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.!

I would only use CDS 2 for wishbones.

John

I'd be surprised if electrical conduit would hld a locost up on its own weight without ripping apart.

You could always use it for putting your wiring through, probably ideal for that

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]

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....

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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Originally posted by chrisf
You should use cold rolled 1020 DOM for the arms.

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I have been bending conduit for **** years and it is soft as boot laces

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Originally posted by Syd Bridge

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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.

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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.

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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.

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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!

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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!

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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.

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Originally posted by Hugh Jarce

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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!

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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.

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You can buy CDS either "hard as drawn" or "annealed"

JB

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.

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!