GTAW Chromoly bike frame....any advice, FILLER? TRICKS?

[Johnson]

I just ordered a tube set of double butted chromoly tubes for a bike I'm going to build. I have heard that 309L is ok, but some say use 70s6. Any bike builder out there with tricks or ideas that have made thin wall CrMo welding turn out nice? Thanks

[Rambozo]

I just ordered a tube set of double butted chromoly tubes for a bike I'm going to build. I have heard that 309L is ok, but some say use 70s6. Any bike builder out there with tricks or ideas that have made thin wall CrMo welding turn out nice? Thanks

Perfect timing.

[Tanh]

Nice! I was waiting for this one too. Now all that's needed is a way to cut and fit up the tubes. Gives me a great idea for a bike trailer as a project for the summer.

[Rambozo]

Nice! I was waiting for this one too. Now all that's needed is a way to cut and fit up the tubes. Gives me a great idea for a bike trailer as a project for the summer.

Try this for a neat way to make the fishmouth joints with a paper template.

http://metalgeek.com/static/cope_custom.pcgi

[Tanh]

Wow. Didn't expect to get an answer till daybreak. It's 1:30am here and I'm in the shop. It's a slow night so surfing takes up a lot of the time.

That's great idea, thanks for the link. I'm just wondering how one would cut the pattern once printed out. I've been tossing around the idea of a hole saw on a drill. Then there's not much use for the pattern anyways though.

[Rambozo]

Wow. Didn't expect to get an answer till daybreak. It's 1:30am here and I'm in the shop. It's a slow night so surfing takes up a lot of the time.

That's great idea, thanks for the link. I'm just wondering how one would cut the pattern once printed out. I've been tossing around the idea of a hole saw on a drill. Then there's not much use for the pattern anyways though.

There are a lot of tubing notchers that use hole saws. Others use a punch and die. But the paper and die grinder will also work. With thin wall tubing, you can even make pretty good time with just a rat tail file.

[Tanh]

It may not be as pretty but that seems the route to take. Paper and die grinder that is. I just never thought of that. I have a few used endmills I can strap to a drill that'll work too. Things are really coming together now. In my mind that is.

I've yet to watch Jody tig the tubing but I'm wondering if it could be done with stick if you're careful enough. Maybe grind down a bit afterwards then glass and paint to cover. It wouldn't look near as nice but would function just as well I'm sure.

[Rambozo]

It may not be as pretty but that seems the route to take. Paper and die grinder that is. I just never thought of that. I have a few used endmills I can strap to a drill that'll work too. Things are really coming together now. In my mind that is.

I've yet to watch Jody tig the tubing but I'm wondering if it could be done with stick if you're careful enough. Maybe grind down a bit afterwards then glass and paint to cover. It wouldn't look near as nice but would function just as well I'm sure.

Depends on the tubing wall thickness. Some of that bike tubing is damn thin. I've never seen stick rods smaller than 1/16", so that might be tough. I know some bikes are brazed.

[youngnstudly]

I use empty toilet paper rolls and paper towel rolls for notching tubing since it holds up for a lot longer. If you can figure out the circumference of your tubing (diameter multiplied by 3.14), you can divide the stretch out by 2 and mark the cardboard roll in halves. At that point those marks can be used for getting more consistent notches that are exactly 180 degrees apart. Any present weld seams in the tubing (if equipped) can help when clocking your notches too.

I'll be honest here. As a sheet metal worker, I always had an excess of used Wiss snips laying around, and I used to use those for cutting up to 16 gauge capacity (mild steel or stainless) tubing and conduit. Now I use the hole saw and drill press method with a decent vise, since snips are too hard on my hands.

[MuttonHawg]

Several years ago I visited a bike builder, and they had a custom jig they built onto a drill press to notching the tubing. The jig was a vertical plate with clamps so the angle of the tube (with respect to the hole saw mounted in the drill press) could be set in the jig for a very precise cut with very little setup time. This gave a very precise setup, and the builder could do the TIG welds entirely with very little filler (titanium bikes). When I learn to TIG, especially aluminum, I plan to build a jig similar to this when I start doing bicycle work.

[youngnstudly]

To me, the toughest part of notching tubing is getting both of the ends notched square (or whatever the exact angle is that you want for that intersect), and getting both notches in line with one another on one length of tubing. I normally use 2 drill press vises on a flat surface to clamp my workpiece, then remove one of the vises so that the setup fits on the drill press table.

However, it still seems like a chore to keep things aligned, level, and straight! In reality, I just need to build more clamps and fixtures as I see a need for them, and work in a few degree wheels for accuracy.

Using tools I have, to build tools I need, just so I have what I need to create actual (non tool related) projects. That's just swell.

[Rambozo]

And part 2



With hammer time!

[zoama]

Tubing for Jody's bike project video was provided by Everlast forum member zank of Zanconato Custom Cycles.

[youngnstudly]

That mill setup for notching tubing is very cool, as is Jody's fixture table. The best part of the video was seeing the awesome welds done by both men though! Very impressive, to say the least!

[MuttonHawg]

That mill setup for notching tubing is very cool, as is Jody's fixture table. The best part of the video was seeing the awesome welds done by both men though! Very impressive, to say the least!

And for me, the worst part was watching that poor bike frame get demolished at the end - tragic!

[Johnson]

Great that Jody had a video on that....also curious could I just use a spindle sander with correct diameter spindle to fishmouth the tubes? Anyone done it that way? I bought my tubes from Nova. For double butted 4130 they where $113 shipped. They also sell higher end tubing for more, but I wanted a "bit" thicker for my first frame build. I have also done some more research and found out some of the worlds best bike builders have build bikes with a hacksaw, file, and torch all in there vise! Makes me think this is doable I guess eyeballing the headtube to the seat tube works well to keep the bottom bracket and headtube in the same plane. We'll see! I have my 250EX coming in a week or two and I'll start the buikld then...I'll include picture, for good or worse

[youngnstudly]

And for me, the worst part was watching that poor bike frame get demolished at the end - tragic!

I didn't want to bring that point up as I cringed while watching! Thankfully Jody had the decency to speed up that portion of the video! He said he didn't want us to watch him getting out of breathe, but I assumed that really meant he had to stop and cry (out of respect) for destroying such wonderful craftsmanship!

I actually enjoy seeing (real world) stress testing done though. My welding instructor taught us that if you can weld something up once (for stress testing purposes), you can always weld the "real deal" up and make it just as nice as the original item that was "sacrificed." It still makes me cringe though.

Think of the poor aspiring cyclist that would have LOVED to get that frame that Jody welded up! All in good fun, I guess. The video was much more effective than if he were to weld up a simple practice joint and destroy it. Outrageous television makes for good ratings, right?

[youngnstudly]

Great that Jody had a video on that....also curious could I just use a spindle sander with correct diameter spindle to fishmouth the tubes? Anyone done it that way? I bought my tubes from Nova. For double butted 4130 they where $113 shipped. They also sell higher end tubing for more, but I wanted a "bit" thicker for my first frame build. I have also done some more research and found out some of the worlds best bike builders have build bikes with a hacksaw, file, and torch all in there vise! Makes me think this is doable I guess eyeballing the headtube to the seat tube works well to keep the bottom bracket and headtube in the same plane. We'll see! I have my 250EX coming in a week or two and I'll start the buikld then...I'll include picture, for good or worse

I would think that a spindle sander would work well for notching the tubing as long as you could clamp it down (or clamp a few pieces of angle "fencing" down to keep the tubing exactly where you want it to be). My upcoming project is to build a belt sander that has different diameter rollers for notching tubing. I've seen a few good videos on youtube which I may borrow some ideas from.

That will be down the road a ways though as I am currently busy with other things in my life!

[MuttonHawg]

I actually enjoy seeing (real world) stress testing done though. My welding instructor taught us that if you can weld something up once (for stress testing purposes), you can always weld the "real deal" up and make it just as nice as the original item that was "sacrificed." It still makes me cringe though.

I would've been interested to see a few strength-related tests as well - like a torsional twisting test (insert long bars in the head tube and the bottom bracket shell, twist like crazy). However, he beat-the-snot-out-of-it-with-a-hammer tes does stress the welds in a very extreme (if not real-world usage) way. When I visited the factory that makes titanium bikes, apparently they do a cold set after all welding is done. In order to correct for a fraction of a degree of out-of-plane, they have introduce a HUGE twist in the frame, and then it springs back to almost exactly the same position as before. It's amazing how springy titanium is!

Part of why I'm interested in welding up bike frames (specifically, tandems for me to race on) is for some ideas I have for experimental designs. It's much easier to wrap my head around a couple hundred bucks for a tubeset that I weld myself, rather than a couple thousand dollars for a custom tandem frame, when I know that it might not work at all. Plus, if the design fails, then I can cut it up and reuse the tubes to build a little bike for my nieces or nephews!

I have some ideas on how to create some homebrew jigging for fitting and assembling bike frames quickly and easily using something like that table Jody uses, but without using shims. I'll save that for when I actually get around to that phase of my welding career, rather than hijacking Johnson's thread any more. Sorry!

[zank]

If it makes you guys feel any better, the frame itself was always simply meant as a prop and the tubes were picked accordingly. And you'd hate to know how many frames I've cut up and twisted and destroyed in the name of research. All part of the gig. The fact is that there is still a lot of work left to do after the frame is welded before it's ready for paint. Jody wasn't really interested in finishing the frame. We joked that some guys might feel like smashing it with a sledgehammer if it's their first time welding 0.032 wall tubing. But thank you to everyone who watched it! It was certainly my pleasure to be a part of the project. Anything I can do to give back to Jody (aside from buying tig fingers and t-shirts). I've learned a ton from him over the years.

I'm looking forward to having an inverter soon. I can't wait to spend some time with pulse and AC waveshape adjustments.