On Sun, 17 Apr 2016 01:27:49 -0400, "Carl Ijames"
wrote:

"Ed Huntress" wrote in message
.. .

On Sat, 16 Apr 2016 10:09:18 -0700, wrote:

On Sat, 16 Apr 2016 07:21:30 -0400, Ed Huntress
wrote:

On Sat, 16 Apr 2016 12:59:10 +0700, John B.
wrote:

On Fri, 15 Apr 2016 17:02:48 -0400, Ed Huntress
wrote:

On Fri, 15 Apr 2016 16:14:43 -0400, "Jim Wilkins"
wrote:

"Ed Huntress" wrote in message
news:6th2hbl749sltd6m6rbfc7hqcunral6th1@4ax. com...
On Fri, 15 Apr 2016 12:35:08 -0700, Larry Jaques
wrote:

On Fri, 15 Apr 2016 06:01:39 -0500, Karl Townsend
wrote:

I've got a project where i need over a hundred feet of 1.38 ID by
1.625 OD DOM tubing.

Turns out this is almost exactly the same size as 1 1/4 water pipe,
MUCH less expenisve.

Need to do a lot of machining and some bending of a small tab. Will
water pipe work as well?

I'd seen the term "DOM" mentioned a few times recently, and finally
decided to find out what it was. Here are some of the sites I
visited
in my research which might be of interest to you, Karl.

http://tubular.arcelormittal.com/ima...l_DOMSpecs.pdf

https://www.rme4x4.com/showthread.ph...s-D-O-M-tubing

http://metalsupermarkets.com/blog/di...seamless-tube/

https://www.youtube.com/watch?v=buu3Ytubp1s

http://www.jalopyjournal.com/forum/t...tubing.286487/

http://products.anssteel.com/item/st...un-1-1-4-2272?
http://products.anssteel.com/item/steel-pipes/galvanized-standard-steel-pipe/g-1-1-4-2272?&bc=100|1002|1016|1047|1049

http://www.industrialgroupco.com/ass...ifications.pdf


Pipe seems to be made from a mutt steel; whatever they find. If I
were making a simple bench or something for intermittent use or of a
light-duty nature, I'd use pipe, the cheapest.

If I wanted a chassis for a vehicle of some sort, I'd definitely
want
to go with DOM. It has a much higher safety factor. 1020 seems to
be
the standard the 4-wheelers use.

I'd also avoid 4130. Chromoly is nice, but is way too expensive and
too finicky for proper welds.

Not really. It's easy to weld with O/A or TIG. You just have to know
how it behaves, and if you won't learn that, I wouldn't want to ride
in anything you welded, anyway.

1020 is (or was) used on NASCAR racers, for two reasons: The weight
restrictions allow(ed) you to use tubing so heavy that you're at the
limit of practical strength anyway, even with 1020; and if (scratch
that -- "when") you crash it, you can cut out old tubes and replace
them without worrying about it.

--
Ed Huntress

I didn't have any trouble welding 4130 aircraft tubing tees for
practice.

Wasn't there a problem with chrome-moly frames so strong and stiff
they overstressed and killed the driver instead of progressively
absorbing energy?

--jsw

No, it's just somebody's old tale. I've heard it before, too.

First, the stiffness of 4130 and 1020 are almost exactly the same (as
is true of all steels, except for the slightly less-stiff stainless).
Second, there isn't *that* much difference in strength. (yield is
around 65 ksi for normalized 4130; 54 ksi for DOM 1020). The
ductility, elongation and ultimate tensile strength are better for
4130 than for 1020 in the hard-drawn condition. 4130 tubing is almost
always used in the normalized condition; 1020 in the hard-drawn
condition.

So you get some more strength and a lot more ductility with 4130. Your
welds can be somewhat stronger because hard-drawn 1020 loses a lot of
its strength from heating at the weld. 4130 is very slow-quenching --
on the verge of air-hardening, and, in thin sections (like the
light-gauge tubing used on aircraft and smaller race cars), it *is*
air-hardening. Strength *at the weld* is pretty good.

It can get tricky with thicker sections. There is a lot of voodoo
surrounding 4130, but the major welding equipment suppliers can clear
that up for you if you ask. They also have info about it on their
websites.

BTW, the Brits, including Lotus, Cooper, Vanwall, etc., used 1020 or
its equivalent for race cars through the '60s, and they performed as
well as 4130 cars. They bronze-brazed their chassis joints, for the
most part. Chassis stiffness is the issue, unless you care about the
safety of your drivers, which some didn't. g 1020 is just as stiff.

If I remember correctly Norton built some of their racing frames using
"bronze-welding" and claimed that the brazed joints were an advantage
as they were less stiff then welded joints and didn't break as often
:-)

Oh, yeah, that was another source of voodoo. g Many or most of the
one-off and low-volume Brit race cars were, supposedly, bronze
"welded" during the '50s and into the '60s. Bronze "welding" in that
parlance was brazing with a weld-like buildup of filler metal at the
joint.

The old authorities said there was no meaningful difference in
strength between that method and fusion welding. I think it was
treated in the classic chassis book:

http://www.amazon.com/Racing-Sports-.../dp/0837602963
That's a great book and every time I read it I get all enthusiastic
about building my own single seater car.

Me too. And I got my copy in 1965.

I was surprised to learn from
some local race car builders that the book is still used a lot by
builders. The issue of 4130 as opposed to mild steel is covered in the
book and from the the book's point of view the chrome-moly steels
should only be used where the extra strength is needed, for example in
some suspension components, and not in the frames because there is not
enough advantage in rigidity and crashworthiness and a big
disadvantage when it comes to joining with heat.
Eric

Costin and Phipps wrote a great book, but take anything they say about
welding or 4130 with a fat grain of salt. In fact, take anything said
about it by anyone in 1962 with a grain of salt.

For some reason, the Brits were slow to accept fusion welding -- O/A
or TIG -- for tube frames. They were slow to accept TIG, in fact. And
they were slow to adopt 4130.

They may have had some good reasons, but my feeling, having studied a
great deal about it over the past 50 years, is that they were a bit
caught up in popular misconceptions. There are some such
misconceptions floating around in the US, too, such as a need to
pre-heat even thin tubing before TIG-welding it, and the supposed
"grain opening" of 4130 if you braze it. These stories have been
debunked.

Note that Brit homebuilt-aircraft builders aren't allowed to weld
their own tube frames unless they're CAA certified welders. In the US,
our EAA runs classes in welding 4130 with O/A and with TIG, and
hundreds of aircraft have been built that way. I think we have a more
extensive experience base with both the materials and the processes.

But I don't really know. I hope to get out to Jay Leno's garage again
next year, and I'd like to ask Bernard, the garage manager, about it.
He ought to know the whole story on the Brits. Also, the motorsports
instructors at Lincoln and Miller should know very well what works and
what doesn't.

BTW, we have an article coming up on when and where you can use
lift-start TIG, later this year in Fab Shop. I think it will contain
some discussion about 4130.
================================================= ==============

For five/six point roll bars and 10 point roll cages that get installed into
production vehicles to augment the factory structures the NHRA requires
1-3/4" OD tubing with minimum 0.118" wall thickness for mild steel and
minimum 0.083" wall thickness for 4130 chrome moly tubing. Mild steel
welding must be "approved MIG wire feed or approved TIG heliarc process" and
4130 chrome moly welding by "approved TIG heliarc process". No grinding on
welds permitted. Welds must be free of slag and porosity. For full tube
frame vehicles there are more rules on OD and wall thickness depending on
where in the frame the tube is installed. So for the five and six point
bars and 10 point cages mild steel is most common, and if you want to save
75-100 lbs you can step up to 4130 for an extra $500-1000. Unlike
roundy-round cars (NASCAR and dirt tracks) it is extremely rare for a drag
racing car to hit anything so repairability isn't really a concern.

-----
Regards,
Carl Ijames


That's kind of interesting. I'd like to know how NHRA arrived at their
rules for thickness and acceptable welding techniques.

There's a lot of talk about the problem with "cold starts" when
welding 4130, which refers to MIG, primarily. But some kit planes have
MIG-welded 4130 frames.

Over the years I've seen lots of comments and conclusions from people
who build frames, but they rarely do any actual testing. I have a
connection with a guy who works for a major welding-equipment company
who supposedly has lots of testing data on tube frames for aircraft
and cars. I have too much on my plate now to pursue it for an article,
but I hope to get to it eventually.

--
Ed Huntress