I went back to the landscaping job last summer so the bike project got put on hold until fall. The frame work had stalled at the point where I was trying to decide how to fix the rear triangle for brazing. Richard Talbot had used a wheel and a string for alignment and brazed his rear triangle without a fixture, I was not feeling confident enough to try that. Tim Paterek had generously provided detailed plans for a nice fixture which could be manufactured in a machine shop. Since I didn't have access to a machine shop I kept looking for another solution.
Rear Triangle
I had a little cash on hand but not enough for a professional fixture so I settled for the Jiggernaut, a fixture made from MDF by a company in Minnesota. It took awhile to setup and all measurements had to be carefully checked, but it worked. After brazing the jig was only lightly charred.
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| Rear Triangle Fixture |
As far as I can recall, the order of operations for this part of the frame construction went like this. I crimped the chain stays for a little extra tire clearance then brazed the plugs into the seat stays. The seat stays where checked for length against the drawing. The dropouts were brazed into the chain stays, then the seat stays. You then end up with two V shaped pieces which are relatively easy to cold set if necessary.
The Jiggernaut kept the frame in alignment while I tacked the chain stays at the bottom bracket sockets. I double checked the setup with a known good rear wheel. The rim has to be centered between the stays. I have vertical dropouts so there isn't much room for error at this point. If the dropouts are off by 1 mm then the rim is off center by about 3 mm. More brazing and double checking. The cantilever bosses were added in a fashion similar to what was done on the forks except the rear bosses are double beveled. I added a chain stay bridge made from left over tubing I ovalized and mitered. For the seat stay bridge, a brake bridge I had purchased was used. Next time I think I'll look into re-enforcements where the bridges join the stays.
Braze-ons
In order to stay true to the original concept there was still a few bits that had to be brazed onto the frameset. I wanted to be able to mount fenders, lights, racks, etc. and did not want any zip ties or clamps on the frame for the finished build. To accomplish this I used the following braze-ons....
WATER BOTTLE BOSS 4
CANTILEVER BRAKE BOSS 4
CABLE HOUSING STOP 3
SHIFT LEVER BOSS 2
REAR RACK BOSS 2
CHAIN HANGAR 1
I had also considered adding brake cable hangars, a pump peg, low rider bosses, and a front derailleur mount, but decided against these.
This made for sixteen more brazes. There is the potential to trash the frameset at this point if you accidentally burn through a tube, but this is the order of operations used by inexperienced builders. Now that I'm at this point of the construction I understand how to get the braze-ons in the right place before the frame is joined togethor. In any case heat control is paramount and there can be no clamping or pressure on any of the bits while brazing.
CABLE HOUSING STOP 3
SHIFT LEVER BOSS 2
REAR RACK BOSS 2
CHAIN HANGAR 1
I had also considered adding brake cable hangars, a pump peg, low rider bosses, and a front derailleur mount, but decided against these.
This made for sixteen more brazes. There is the potential to trash the frameset at this point if you accidentally burn through a tube, but this is the order of operations used by inexperienced builders. Now that I'm at this point of the construction I understand how to get the braze-ons in the right place before the frame is joined togethor. In any case heat control is paramount and there can be no clamping or pressure on any of the bits while brazing.
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| Canti Boss |
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| Cable Housing Stop |
Finishing Touches
I'm not prepared to get into painting right now and there's a powder coating business near my place so it was just a matter of deciding on the color. My first decent road bike was a blue Bertrand, I still have it. Also, I had in mind Toyota racing blue to match the new Tacoma on my wish list. Soooo... blue it is. I simply picked the blue swatch closest to the blue of my minds eye.
My final roadblock was the cost of the cutting tools needed to face, chase and ream the frame in preparation for installing the equipment group. They are simply out of reach for me so this was done by my local bike shop. Support your LBS!
As for racks, I have a Blackburn which fits nicely, but I would like to construct one from chrome moly tubing, customized for this bike. I rarely do anything the easy way.
Hopefully my next blog will outline the pros and cons of this bike, if it is even rideable. Cheers....njc
My final roadblock was the cost of the cutting tools needed to face, chase and ream the frame in preparation for installing the equipment group. They are simply out of reach for me so this was done by my local bike shop. Support your LBS!
As for racks, I have a Blackburn which fits nicely, but I would like to construct one from chrome moly tubing, customized for this bike. I rarely do anything the easy way.
Hopefully my next blog will outline the pros and cons of this bike, if it is even rideable. Cheers....njc
