Pipe and tubing...

[kliff]

Yeah, pretty new around here, but been building and welding for a while now, and I've heard the question a hunert times before. My answer is way far from being scientific, with all the stress ratios, shear factors, and all the mathmatics... just what I've been exposed to, seen, done, and experienced for going on 40+ years now. I'm sure there will be some engineers to explain alll the details I left out...LMAO, and that's cool

JJust wanted to pass it along to maybe help a new guy with a welder trying to figure out what to buy for his next project...

They ain't the same animal. They have definite different tensil stregths, and different deminsions.


PIPE

For example 3/4" black iron, available at Lowe's, Home Depot, etc...is designed to carry gas, oil, water, and even steam. It's strength is based upon bursting pressure, as for dimension, 3/4" B.I. is approximately 1.00" O.D.
ALL black iron pipes have this descepancy. Schedule 40 being the lightest you'd want to use in any frame constrction( and the preferred wall thickness) Schedule 80, the heaviest, thickest wall, nearing 3/16" thick.

TUBING

ERW... is a welded seam pipe, most commonly used by motorcyle manufacturers on productiom bikes, scooters, golf carts, also hand trucks, framing and bracing. Stick or M.I.G. welding work great. MMinimum thickness for frames .125"(1/8)

DOM... Drawn over mandrel, non-welded fabication of pipe, mucho stronger, "Higher End" vehicles and equipment. Stck or M.I.G. also great, gassless M.I.G., beautiful, and strong Minimum thickness for frames .125" (1/8)

CHROMOLY... better know your welding if you mess with this stuff, beautiful welds can lead to ctystallization cracking later. HELI-ARC....aka T.I.G. only! Minimum thickness, I've seen some air frame and fuel dragsters down to .090" possibly thinner...great weight saver, strong as all get out, EXPENSIVE, and touchy when welding.

All tubings bend GREAT on a mandrel bender($3500.00 and MORE), can be touchy on the HF Pipe bender($129.00), I've ruined more than a couple of pieces

Pipe bends good, on a pipe bender, don't rush it, go slow... I HATE bending anything!

[roysheepdog]

thanks good post.

[BuggyMaster]

great info, thanks!

[Snoopy]

How do you feel about 1 - 1/4 X .095 in either erw or dom for a minibuggy frame.
Total estimated wieght of about 500 pounds and around 40 to 50 HP engine ? You said a minimum of .125. I agree with that if using 1 inch but I would like to know your thoughts on going a little thinner but a little larger in diameter. Thanks for a reply

[metalstudman1]

I've used this size before and you need to provide lots of intermediate/diagonal supports for spans over 24" that carry weight or have lateral loads, also is very touchy when trying to weld it if not saddle cut perfectly.There are parts of your kart/buggy that will need a heavier tube for dynamic movement. Rear swingarm support,rack-n-pinion,seat platform for instance.That's basically the size tubing that the Yerfdog Spiderbox uses. What style buggy/kart are you building and what type of terrain will it be driven on?

[Snoopy]

My goal is to use an sae style buggy as my design. I plan to have a complete Z400 front end and an IRS rear using early 80's vw type 2's with inboard pucks and a 6 spline center.
My brother is twisting my arm pretty hard to use a solid axle rear and not IRS. Either way I should be around 500 pounds and 50 HP give or take a little.
We ride eastern indiana or southern ohio, tight woods, generally under 30 mph but beat the snot out of our current rides. I thought the larger diameter would offer more strength but you really have me thinking about the welding aspects of .095.
Both tubes imention are pretty much the same wieght per foot so no gain or loss there. A little more meat to weld on would be nice. DOM is nearly twice as much as ERW, would you have a huge prefference there ? And I fully understand the differences but would ERW be good enough is more the question.

[metalstudman1]

DOM by far better- all the way around. My real frankenbuggy is 1-1/4" sched. 80.DOM (gas pipe)(current weight 376 lbs.) It's heavy but solid.Yes it expensive but how much will it cost to have your chassis fold up on you out in the south forty? You almost need to be a structural engineer to design a solid frame from .095 unless it's chromoly. Kliff says that chromoly is hard to work with but I've never had an issue other than the COST.An alternative tubing to price- find a local Fire protection sprinkler company and see what they'll sell you a 10' or 21' stick of pipe, nearly all there pipe-thread or clamp style is DOM.

[Snoopy]

Thanks for the comments and suggestions. I have tube suppliers but I'm pretty sure I'll go with 1.0. and . .120 wall. Thanks again. I'll start a build log when I can. Snoops

[AceFab]

Adding my 2 cents on the subject.
I have built and raced buggies in a few series and super thick wall tubing is not really needed for strength and durability as much as proper design. I raced a single seat 1600cc car in the desert that weighed 1200 pounds and it was built with 1-1/2" OD x .095" wall DOM (ERW was allowed in the SCORE rulebook), some of the bracing was 1" x .095" wall. If you used Chromoly the wall thickness could be .083". This rule applied for vehicles weighing up to 2000 pounds if memory serves me correctly. I built a Class 7 Ford Ranger and used 1-3/4" OD x .134" wall DOM and that was a 3000 pound vehicle. I think the rulebook only required .120" wall for that class though. So, with a little planning and good construction techniques you can build a strong, durable, and light chassis. Generally the smaller OD tube the greater the wall thickness needs to be to obtain the same strength as a larger OD tube with a thinner wall.

[metalstudman1]

Agree a 100% Acefab-And a valuble 2 cents. Most of us just aren't engineers!!! Stock buggies from the factory are mostly 16g-14g ERW that I've seen. For simplicity and room for error on incorrect bracing and critical load points for the DYI guys I still would recommend DOM thick wall. Most of us are not certified welders either so imperfections there come into play when strength important. I error on the heavy side when I'm not sure about something- but that's just me!!

[AceFab]

I'm with you metalstudman1! Whenever I'm not sure about the strength needed for something I tend to over-build with heavier materials and more bracing. It may be a bit slower because it is heavier but brother it ain't gonna break... That's one thing I enjoy about this forum is that everyone is very helpful and there's lot's of knowledge here too. I always learn something every time I look around the forum, lots of talented folks here. I love checking out all the great mods you do with your buggies.