Rack progress
My vacation put a little hold on my rack making, but this week I did get to spend a few hours in the workshop. The gallery is updated.
I’m pretty happy with the progress for a first rack. I wish I had spent more time when making the bends for the rack top, some of them aren’t perfect and it makes the whole thing slightly wonky. The top has a slight twist in it when viewed from the front, it doesn’t all lie in a nice plane. It’ll definately be functional but it might not be pretty.
I’m pretty happy with how the mount to the fork crown came out. It is tricky to get everything to fit when you use a sidepull brake (instead of cantilevers). I should have left my mock-up brake on for the photos.
The other challenging part has been coming up with fixtures for holding things in place while I braze them. I built the rack in this order:
- Make the top
- Make the fork crown mount
- Attach the fork crown mount to the top
- Make and attach the stays to the top
- Make and attach the backstop to the top
Attaching the fork crown mount to the rack top was tricky. I did it by mounting a wheel (no tire) into the fork and putting a long and skinny piece of wood onto the wheel (coming off at a tangent). The end of the wood had a groove which held the front of the rack at the centerline. I useda ziptie around a spoke and the fork blade to keep the whole thing in compression. The rear of the rack was held against the mitered fork crown mount using this compression.
How do others do it?
To get the top straight I”d have put one end in a vise and twisted the other – with tubing that thin you should be able to get it right bare handed (how tough are ya?
Attaching the crown mount I would have tacked one side with the top sitting on a brick (anything fireproof) and the mount bolted to anything that would hold it more or less in position. Then tweak it true and tack the other side. Then check that it fits the bike. Much easier than faffing with the unit on the actual bike.
Or alternatively, I might have brazed the bottom mounts onto the stays and used those to hold the top in place while doing the crown mount (assuming you have at least one welders magnetic clamp to hold that in place while you braze – if not, go and buy one).
Hmm, like this: http://www.thewelderswarehouse.com/acatalog/Magnetic_Welding_Positioner.html
http://www.peerlessusa.com/magnets.htm
but these ones are IMO better – the big one will hold a whole bike
I don”t have a magnet yet, but I”ve been curious about them. Alistair also showed me a cool jig that he made using a test tube holder. I”m going to make a copy of it and will post the results on this blog when it is done.