Framebuilding with Dave Bohm: Day 11

I started the day with a pile of braze-ons and not much time to get them adhered to the frame and fork. Brake studs, rack mounts, stay bridges, brake and shifter cable guides all needed a place to call home. I was a little nervous that I wouldn’t get them all on before I needed to pack the bike for shipping back home. Since I don’t have convenient access to an oxy-acetylene rig, I really needed to work efficiently.

The first step was to make some bridges. Using Dave’s sweet tube bender, I was able to create some nicely curved bridges. After brazing those in place, next up were the brake bosses. Since I’m building a randonneur type bike and planning to use some wide tires, I decided to go traditional and use some Mafac Raid brakes. The brakes will easily clear wide tires and supposedly provide excellent stopping power and modulation. The brakes require special brake bosses that I ordered from Compass Cycles, the go-to e-store for all things traditional and rando.

A curvy seatstay bridge makes all the bike geeks swoon.
A curvy seatstay bridge makes all the bike geeks swoon.

The bosses went on without a hitch, so I focused next on brazing the rack mounts on the fork for the Compass randonneur rack. The rack is designed to mount directly to the brake bosses of the Mafac Raid brakes and to a pair of rack bosses lower on the fork blades. Compass supplies the rack bosses too. They look like little tombstones, so I’ll refer to them as tombstones going forward. The tombstones are tricky to braze because they need to be precisely located so the rack struts can attach to them without any undue bending or straining. The only way I could figure to position them properly was to use the brake and rack as my fixture. With the brake and rack mounted on the front fork, the plan was to attach the tombstones without damaging my brand new rack. I had to get in really close with the torch to heat up the area quickly. Luckily the rack nor the brake was harmed. The rack struts did get warm but it didn’t seem to affect the chrome plating.

The Compass brake boss is nearly ready for action. It just needs a spring ring.
The Compass brake boss is nearly ready for action. It just needs a spring ring.
I mounted the Mafac Raid and the Compass rack to use as a fixture to locate where to attach the lower rack "tombstones".
I mounted the Mafac Raid and the Compass rack to use as a fixture to locate where to attach the lower rack “tombstones”.

The next step was to figure out how to braze on the little spring rings for the brake bosses. Making a fully integrated randonneur bike is tough work. Everything requires more thought and extra steps. The production rando frames that include most of this stuff are a true bargain. I applaud companies like Rawland, Box Dog, and Boulder Bicycles for offering a similarly equipped frame for a reasonable price. Okay, back to the stupid little spring rings. These rings attach to the Compass brake bosses and provide a mounting point for the Raid’s spring. Both rings should be positioned on the brake bosses at the same angle to provide even spring tension. Getting this wrong would mean uneven pad wear, and worse, possible brake shoe rub from mis-centered brake pads.

According to the Compass instructions, the spring rings should be mounted directly above the brake bosses. I wasn’t quite sure how I was going to attach them accurately at first. Dave suggested that we do it by eye, but I don’t trust my eye anymore. You should see how well my eye aligned the seat binder boss. I’m not going to show a photo because it’s too embarrassing. I’m sure Dave’s eye is better, but I wanted to go one step beyond the trained eye.

Brass rod weighted with a spring clamp hangs from the hole of the spring ring to help properly align the Mafac Raid's caliper springs.
Brass rod weighted with a spring clamp hangs from the hole of the spring ring to help properly align the Mafac Raid’s caliper springs.

After some thought, I came up with the idea to use gravity as an alignment tool. I would turn the fork upside down with steerer tube pointing toward the ground and use some brass rod to hang some heavy objects off of the spring rings. The rings would be forced by the weight of the hanging objects to both be pointing in the same direction, down! Almost the whole two weeks taking this framebuilding class, I’ve relied on Dave to provide answers and solutions. It felt good to figure something out on my own.

I was feeling pretty proud of myself after successfully brazing on those tricky rings. But as usual, pride is fleeting. Dave pointed out that I brazed on the rear derailleur cable boss backwards. Doh! I’m glad he caught it though. It’s an easy fix when you have a torch handy. I would have been really upset if I had to deal with that when I got home.

With all of the braze-ons brazed on, all I had left to do was finish filing, a lot of finish filing. I was too tired to do any of it, so instead I boxed the bike. When it arrives at home I’ll get to spend some quality garage time filing away before the frame is pretty enough for paint. At my pace I might not be riding this beauty for another year.

My new frameset denuded of all unwanted flux. All it needs is some more file work and it'll be ready for paint.
My new frameset denuded of all unwanted flux. All it needs is some more file work and it’ll be ready for paint.

The past two weeks learning how to build a bike frame from Dave have been really fun and rewarding. Dave is a good teacher and he has an excellent workshop in which to learn. It was nice to have a classmate, Cooper was a fine fellow who made a great frame himself, but I liked the fact that the student to teacher ratio was low. I could get Dave’s undivided attention when I needed it and Dave could work at my and Cooper’s varying paces. Because I had some framebuilding experience coming into the class, I was able to do some more advanced things than someone with no experience. Making my own lugs and building a bilaminate frame was fantastic. I only wish Dave could have magically sped up the finish filing and cleaning steps. Dave had many tools but not the one that does all the glamour work for you. Like all professional framebuilders, you just have to sidle up to the vise, lock your frame in place, and start filing.

Once I’m done with the finish filing, and once the bike gets painted, and once I hang all the pretty parts on my bike, then I’ll post some glamour shots. Until then thanks for reading and let me know if you have any questions about amateur framebuilding.

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