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PostPosted: October 7, 2008, 12:45 am 
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killernoodle wrote:
The round tubing is all DOM.

That's incorrect.
DOM tubing is round, but there's ERW round tubing too.
I actually have a stick of 1" round ERW in my garage right now...
Like Chet, I don't know what makes you think that 0.095" wall is flimsy, I find it very solid.

If you're thinking of running track days you should definitely check some rulebook like SCCA's or NASA's to see what they require.
This isn't a style item, it needs to be built to spec.

Moti

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PostPosted: October 7, 2008, 1:34 am 
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Blackbird wrote:
killernoodle wrote:
The round tubing is all DOM.

That's incorrect.
DOM tubing is round, but there's ERW round tubing too.
I actually have a stick of 1" round ERW in my garage right now...
Like Chet, I don't know what makes you think that 0.095" wall is flimsy, I find it very solid.

If you're thinking of running track days you should definitely check some rulebook like SCCA's or NASA's to see what they require.
This isn't a style item, it needs to be built to spec.

Moti


All the round tubing I got a quote for is DOM. I wouldn't consider erw an option for suspension stuff, and for rollbar stuff it could make me not pass inspection for a track day.

As for the bike shocks, if you mount them at a flatter angle than regular shocks, you can increase the mechanical advantage. I don't want to do it JRs way, that way puts a strange load in the middle of the tube where its the weakest.

Consider a shock that is 90 degrees or vertical, that same shock mounted at 45 degrees has twice the travel at half the spring rate if I remember correctly. I had a piece of paper lying around here somewhere that had all my calculations.

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PostPosted: October 7, 2008, 2:42 am 
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Ahhh, I thought this was a general comment about round tubing.
I'm going to be using DOM for my suspension arms as well, but I'm probably going to use 1"x0.064" for the arms.

BTW, surprisingly, the rule book of NASA does allow for roll bar (not cage) made out of ERW for HPDE.
Not that it's a good idea or that the rest of the spec worth anything - they don't even require a diagonal or rear legs! :shock:

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PostPosted: October 7, 2008, 5:22 pm 
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DOM tubing can be made from ERW, I think you need to check the specs to see if it is seamless...

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PostPosted: October 7, 2008, 6:16 pm 
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horizenjob wrote:
DOM tubing can be made from ERW, I think you need to check the specs to see if it is seamless...
Is there a such thing as non ERW DOM? Most racing bodies only specify DOM, not seamles IIRC. I could be wrong. I thought DOM was just ERW that had been drawn over a mandrel that work hardens it and cleans out any weld seam protrusion inside. I would imagine it would be quite difficult to fabricate a length of tubing with no weld seam whatsoever. I imagine the end product would cost considerably more too.

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PostPosted: October 7, 2008, 9:18 pm 
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OK, I thought DOM was being talked about as being different then based on ERW. They do make seamless tubing, but I don't see how without drawing over a mandrel. Not counting cast iron pipe....

So they spec it for roll cages because it's work hardened basically, it seems...

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PostPosted: October 8, 2008, 6:12 pm 
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Ok, just got a new quote from the metal supplier

6 24' sticks of 1x1 16ga $25 each $150 total
1 24' stick of 1" OD .095" wall DOM $69
1 24' stick of 1.5" OD .120 wall DOM $115

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PostPosted: October 8, 2008, 7:20 pm 
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chetcpo wrote:
horizenjob wrote:
DOM tubing can be made from ERW, I think you need to check the specs to see if it is seamless...
Is there a such thing as non ERW DOM? Most racing bodies only specify DOM, not seamles IIRC. I could be wrong. I thought DOM was just ERW that had been drawn over a mandrel that work hardens it and cleans out any weld seam protrusion inside. I would imagine it would be quite difficult to fabricate a length of tubing with no weld seam whatsoever. I imagine the end product would cost considerably more too.


All the above. Surprisingly (I agree it seems difficult to make), seamless tubing costs the same as ERW DOM of the same alloy. ERW DOM is more prevelant for mechanical use, seamless is used more for hydraulic, but they do cross over... apparently the weld is not a quality/strength issue in mild steel... I think most chrome moly is seamless, perhaps because of brittle weld seam possibility.

NHRA doesn't even specify DOM as I recall. Just a choice of Mild Steel (.118 wall for all diameters) or Chrome Moly (various wall thickness from .049 to .094 depending on diameter and location). SCCA is kinda confusing, says you can use DOM or Chrome Moly but not ERW... I would assume by DOM they mean ERW DOM is OK, but it's not clear.

It's amazing that sanctioning bodies AND companies selling tubing, even those specializing in racing, are so vague and too lazy to be more explicit.
Maybe they're confused too. :shock:

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PostPosted: November 17, 2008, 11:24 pm 
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What exactly are the different types of 16 gauge 1 inch square tubing available?

I called around and found P&O and Cold Rolled. Are there other types and what are good which should one avoid?

I checked the book both old and the new Gibbs one and I can't find any discussion over different types of tubing.


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PostPosted: November 17, 2008, 11:46 pm 
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DOM means "Drawn over mandrel" which happens after the tube is welded. I don't think they make seamless DOM. (I may be wrong)
Seamed tubing in general is not weaker than seamless.
DOM in whatever form is held to a higher tolerance than non DOM.


Read this, it's a really good coverage of the differences of seamed vs seamless tubing. It is in regards to bike frames, but the technology is very similar if not the same.

http://www.anvilbikes.com/?news_ID=21&catID=3


@asennad
spaco (from rec.crafts.metalworking) wrote:
Hot Rolled vs. Cold Rolled, What’s all the Fuss About?
----------------------------------------------------------------
Here’s an email that I received today. It asks a pretty common question:
“> Hello Pete, need some help understanding the difference between hot
> rolled and cold rolled steel, and the reasoning for the preference
for one
> over the other???? Can you please answer this question????? “

Theoretically, the only difference between hot rolled and cold rolled
steels is that hot rolled steel is rolled to its final dimensions while
hot enough to scale (over 1700 degrees F) while cold rolled steel is
rolled to its final dimensions well below 1000 degrees F.
So----- If you are making ½” square hot rolled steel, you have to
estimate what the final size will be after the product cools, whereas
you can finish the cold rolled steel to much closer tolerances right in
the sizing rollers and that is what you get.
There are some other things to consider, too:
-The finished tolerances on hot rolled steels are looser than on cold
rolled. Not only the plus or minus tolerance from nominal size, but
the "square-ness" of the product. And, I can tell you from personal
experience that there’s a lot of out-of-tolerance A36 (hot rolled steel)
out there. So, if you need a specific size and you are going to go to a
“surplus” place, bring your ruler, square and micrometer to make sure
you get what you need.
- I have been told that, in order to get the cold rolled steel to come
out with a nice finish, they might use "cleaner" ingots from which to
roll the product. This means that you’d get fewer slag or carbon
inclusions with cold rolled steels.
-Note that I haven't talked about the chemistry of the steel at all.
You can cold roll or hot roll 1045 and you can perform either process on
C1018. But since we often talk about using "mild" steels, the two
steels that we end up having around most often are C1018----which is
quite often sold in cold rolled form and A36 which is always hot rolled.
-One other difference that may be of interest to the blacksmith is
that if you buy "1018”cold rolled steel", you can be pretty sure that it
has 0.18% carbon content and few other impurities. But the spec for A36
can let the carbon content go as high as 0.29% and
it can contain many more impurities. More carbon makes it harder to forge.
-You generally have to pay about twice as much money for cold rolled
steel as for hot rolled steel, for reasons which are probably obvious
from the above.
So far, you are probably feeling that, in dealing with mild steels,
cold rolled steel is clearly the better stuff to have if you can afford
it. Well, yes, usually, but---- since the hot rolled steel IS rolled
while hot, it has a chance to normalize after the last rollers,
so it is pretty much stress free when you get it. But machinists who
usually buy cold rolled steel, often have the stuff twist and warp on
them as they machine the first side or two. This is because the cold
rolled steel actually work-hardens in the rolling process.
For blacksmiths, this isn't much of a problem, since we are usually
going to heat it up and reform it anyway.
Finally, in my experience, the more popular (to the steel yard)
sizes of mild steel usually come in both cold and hot rolled. I buy
hot rolled whenever I can for blacksmithing. Except if I'm going to put
a LOT of work into a piece. Then I buy cold rolled steel to minimize
the possibility of having a crack appear in the shaft of my fancy flesh
fork after about an hour of forging and an hour of filing and chasing.
But in some sizes, for instance 1/4" square, the steel yards in our
area only carry it in cold rolled, at twice the price of hot rolled----
so if I want any of that for S-hooks and for nails, etc., I'm stuck with
the higher priced stuff--- unless I want to order a ton or two to get
it in hot rolled form!

I hope this is more of an answer than just added confusion,
Pete Stanaitis
--------------

Later addition:
There is a third choice; P&O,or "Pickled and Oiled". This material is
basically A36 that has been acid dipped to remove scale and then oiled
to prevent rusting.


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PostPosted: November 18, 2008, 1:45 am 
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I should add I wanted to know why my tubing - cold rolled- appears to have the seam in the corner of the tube while I see most frames use tubing with seams in the middle of the tubing.

And what's the difference in price?


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PostPosted: November 18, 2008, 12:53 pm 
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I don't know about the seam in the corner tube, but I have seen it before and built set pieces out of it.

From Engineer to Win by Smith (contradicting what I said earlier)
Quote:
Carbon steel tubing can be ordered as COLD DRAWN SEAMLESS, in which case it will be drawn from SAE 1018 steel; as DRAWN OVER MANDREL (DOM) in which case it will be drawn from 1020 steel, be just as strong and just as well finished and a good bit cheaper. It also comes as ELECTRIC RESISTANCE WELDED (ERW) tube, which is produced from SAE 1020 steel unless the wall thickness is 16 gauge or lighter, in which case it is made from SAE 1010. HOT FINISHED SEAMLESS tubing is made from SAE 1026 and is considerably less expensive than cold drawn tube. It is also not as strong, scaly and less dependable. COLD DRAWN AND BUTT WELDED TUBE is found occasionally in some sizes and is considerably stronger and better finished than ERW. One thing that has to be watched out for is that the industry bends a lot of carbon steel tubing to make ots of things and so most carbon steel tubing is available in the annealed condition - woe to him who does not detect it before he builds the part. I have a very good friend who once got an entire roll cage cut, bent, fitted and tacked before he realized that his merry men were working with annealed boiler tube. The other thing that we don't want is "free machining tubing." I currently use round carbon DOM mechanical tubing for most things other than suspension links (there I use E4130N and stress relieve and heat treat after welding). For roll cages I use either 4130 or DOM 1020. I do not want to know about hot-finished tubing because I do not want to clean it. I am old enough to remember the days when English ERW tubing was Liable to split along the weld seam. As a matter of principle (or, possibly, stubbornness) I do not use ERW or butt welded tube on the race car; although, since it is a lot cheaper, I use it all over the trailer and the shop.


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PostPosted: November 18, 2008, 5:19 pm 
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The info from "Engineer to Win" looks very good, but I wonder if it is somewhat specific to his suppliers or the period the book was written.

His comment on annealed tubing was also interesting. Since the DOM tubing is often made from ERW, and the two basic differences are better control of inside diameter and higher yield point, this confirms that the higher yield point from work hardening is what people are looking for in the roll cage material...

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PostPosted: November 18, 2008, 6:46 pm 
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Data seems to be from the late 80s early 90s.

He does say a number of times that materials were bought due to supplier availability as long as they fit the structural requirements. He also said that he never kept material around that he wouldn't use as structural elements of a race car so that no one could "accidentally" build something out of it.

I totally trust the guy from Anvil, so I think the comment about ERW being bad at one time but being avoided due to stubbornness seems valid. With how little tube we use in 7s which could be seamless we might as well spend the money.


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PostPosted: November 21, 2008, 6:31 pm 
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My copy of Engineer to Win was published in 1984... so his knowledge predates that, more than a quarter-century... and his comment, "I'm old enough to remember..." implies that weld seam quality was not an issue even in 1984. Process control has no doubt improved since then too; the reliability of a tube's seam weld should far surpass the "shop welds" at the ends of the tube. Nobody seems to worry that DOM roll bar tubing has a weld seam.

Cold vs. hot rolled. Working with and welding cold rolled seems like you're working on an aircraft project in a clean room compared to hot rolled, which makes you feel like you're working in a blacksmith's shop. I'll always make a great effort to obtain 1018/1020 cold rolled for just about anything I do.
.

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