How a frame is made

Sorry to steel (sic intended) a title but it’s about as perfect as this title could be. I take pictures of almost everything I build. Some see the light of day but most do not. I have a deep connection with building things for my own satisfaction so documentation is rarely on the front burner. I did this particular frame as an experiment. I had been talking to a local MTB racer about building a race frame. We’ve gotten to know each other over the last 6-9 months. He’s an excitable guy. The type of guy that holds the door for little old ladies, says please and thank you, and just checks in once in a while with a pleasant “how is it going”. I like building frames for friends and people who are positive about the world. I don’t have an unlimited number of these in me every year so it’s professional nirvana to be in this situation. It’s my goal to stay in this state. I had been planning to start a really cool build for an expedition style bike. It’s taken a little longer to get the parts than I thought, so with a few days extra time I plugged this frame in the queue with the idea of documentation, but also to see how fast I can weld a bike with keeping the quality high. I have been welding in larger batches that take weeks; this was about doing it in hours. Last Thursday I started cutting tubes at 3pm, had a fully built frame 22 hours later, and a deliverable frame 48 hours after that, I hope you enjoy the pics and the process below. The pictorial is purposefully incomplete but I think it shows my general technique.

The biggest part of the first few steps for me is to miter the tubes. The tight alignment shown below helps keeps the tubes straight once I start welding. The heat of the torch arc and the molten filler will pull any small gaps in an attempt to close them. While misalignment can be corrected in several ways the best thing to do is minimize the gaps altogether.

The process of cutting the tubes involves my knee mill. Keri likes to call it my 3000lb drill press. I have fixtures designed to precisely hold the tubes on center and at the perfect angles for the cutters to do their magic.

Once all of the tubes are mitered, I set up the fixture and see how tight the tubes fit and what adjustments need to be made. There is lots of measure twice and then twice more and cut once going on.

Once everything is tight I go through a process of drilling holes in the head tube and Bottom Bracket to allow the hot gasses to move out of the tubes when they get welded and to allow argon to flow through them to keep impurities from becoming part of the weld.

The next step is an option that allows the use of a 27.2 seatpost in a 31.8 tube without a shim. I weld a stepped collar into the seat tube with an internal 27.2 bore. I then file down the weld and sand smooth. the effect is that you can’t see the junction between the tubes other than a small line of welding filler.

Now that the front triangle is mitered I move to the chain stays. I assemble the stays and drop-outs into the mitering fixture to locate how I want everything to fit.

The dropout end of the chain stays get the first miter, done by hand with a file whose profile matches the dropout. The goal as always is a tight fit.

After the mock-up is done I weld the drop-outs on.

The welded sub-assembly is now carried to the mill and mounted in the vise and the chain stays are cut at angles to fit on the bottom bracket to maximize tire clearance but still leave room for the chainrings.

At this point I head back to the fixture and make sure the stays are the right length. Mitering is important here because any gaps will tend to pull the wheel left or right, compromising alignment of the rear wheel.

After I’m satisfied with all fits it’s time to tack and weld. The first thing I do is tack in two or three locations on each tube around each side of 6 or 12 on a clock face. The tacking and welding is done in such a sequence to pull the frame out of alignment as little as possible or even to pull it back in if necessary.

After the frame is tacked I’ll weld as much as I can in the fixture. The range of motion is limited so after welding in the fixture I’ll finish up on the welding table.
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This is the table shot of the BB. What’s missing is the wider view of the fixture adding argon to the inside of the tubes to create an oxygen-free welding environment.

This is where things stand after welding the front triangle.

The next step is to weld the chain stays on. Getting the drop-outs to stay the correct width again requires a sequence of welding certain parts of the tubes first. The goal is no coldsetting, and for the wheel to sit center. Much proper care was taken in earlier fit up to have the chain stays bend at the widest part of the tire.

After chain stays it’s time to move on to seat stays. I first load the stays into the mitering fixture at the desired spacing and angles.

After mitering I fit up and miter the drop-out end of both stays and weld the first stay on. The little bobble in the filler still bothers me.

And the second stay.

The next part you don’t get to see. It’s a lot of little tedious work like doing the bridges and braze-ons. The good news is that sometimes the client shows up at quitting time with some beer and Keri shows up with more beer and we have a great time.

Sorry, no steps of the paint process. The elves are pretty elusive. All I do is leave the can of color coat on the bench and they do their thing in about 24-48 hours. It’s pretty cool. This is the first of a string of bikes that will be limetime. It’s amazing to me how when one person sees a color, others like it too. My middle son picked the color and it seems to be a hit. If you scroll back in time on this WordPress site you’ll see I swore off green, oops.

I hope you enjoyed the tutorial. It was a fun frame to build. Ciao!

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1 Response to How a frame is made

  1. Guy says:

    Jonathan – Thank-you. I…REALLY…enjoyed the process and seeing it come alive. You know how to build a proper bike my friend. It will be an honor to throw my leg over it. I know bikes are tools and this one has a purpose and that is to carve and attack singletrack. I will race the heck out of it for you and give it everything I got man. Thank-you Jonathan. Cheers.

    …that picture again where I look like a dork with my damn eyes closed. Oh well. See you soon.

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