Schedule 40 Black Steel Pipe Chopper Frame

[gmc123]

Hey guys, I tripped across this forum looking for information on schedule 40 black steel pipe and the possibilities of using it for a chopper frame. I just can't see spending an arm & leg on the 4130 or DOM material that I'm probably going to mess up anyway. If it is feasible to use, what should I expect in regards to bend & weld characteristics?

I would certainly appreciate any input from those willing to share their knowledge- as you can see I have none...

I'm having a tough time pricing the stuff; just assuming that it is in fact cheaper.

The welder I have is a Hobart 125 amp. Mig with no gas....

Thanks in advance.
gmc

 

[metengr]

GMC123;
I would not recommend using carbon steel (black iron)pipe for your motorcycle frame. For safety reasons, the motorcycle frame should be constructed of low alloy steel tubular material that can provide sufficient strength and toughness for the type of stresses that the frame would be exposed to during riding. From what I remember, most motorcycle frames are built using tubular AISI Type 4130 low alloy steel, as a minimum.

AISI type 4130 alloy steel is weldable provided certain precautions are followed. Namely, a preheat and stress relieving.

 

[GRoberts]

I believe that most motorcycle frames that are built out of steel tubing would be made from 4130 or other high strength tubing in order to keep the weight down. A mild steel frame could be built strong enough, but it would weigh 2-3 times as much, or more. The main problem I see, is that with the small home mig welders, without an experienced welder, (and sometimes with), the heat input can be low enough that a great looking weld can not even be fused with the base metal. Especially if the base metal gets to be a little thicker, as would be required when using mild steel in the place of high strength steel. If you decide you have to build a frame with a little mig welder, make sure you destructively test (successfully) a good number of welds before you start doing anything your life depends on. The best way, since you will most likely be doing fillet welds, is to back bend them until they break, and then take a good look at the break to make sure you got fusion clear to the root of the weld, and observe for other defects too.

 

[gmc123]

You guys have been most helpful. I will take metengr's advice on steering clear (no pun intended) of the iron pipe. I actually got the idea looking thru a showcase of fames for sale made of the same stuff, scary isn't it. As for GRobert's advice, sounds like he's been there and done that with the do-it-yourself welders. I appreciate the advice and intend to thoroughly check my welds no matter what material I use, especially the ones my backside is sitting on.

PS:
After reading GRobert's post I had a bad visual of hitting a pot-hole in the road and the front forks breaking off due to poor weld penetration.....I hope that I don't dream about this tonight when I go to sleep.

Thanks again for your time guys.
gmc