Monday, December 13, 2010

First steps to frame number 2

I'm planning on building a frame. My second frame. I'm also planning on moving out of Chicago come may. I'll be moving to bike touring for several months and of course this is the perfect time to build a new bike for it. I've got the dead of winter, and all the time one could ask for. I've decided the bike will pretty much replace the ill fitting bike I made in Doug Fattic's class. Though I intended on that bike to be more of a 650b commuter this one will be a super touring bike. Not quite expedition. I'll be using those 650b wheels as well as other parts and the lighting system from that first bike. Sorry goose (goose is its name) you'll be on the hook for some time.


Fork blade mandrel



One of the things I needed to get in order was a fork bending mandrel that gave me at least 65mm of rake. I've decided to go again with low trail front end geometry, which requires greater fork rake. The whole operation was easier than I had anticipated. All one needs is a fork with a pleasing radius to trace, a block of maple, some sort of band saw to cut the radius and a small variety of rat tail files. I filed this mandrel for imperial oval blades. I filed a variable radius into the block, if you were to file a "V" it would probably accept other variety of blade styles. In filing I attempted to match the radius of the blade as it conformed around the mandrel.

For the question of finding the right fork to trace I used a 1961 Schwinn Paramount fork to model after. You can either trace the inside or the outside of the bend. I choose the inside. After transferring the curve from paper to block and then cutting off the excess wood the next step is filing. Since I chose the inside radius of the fork after filing I ended up with an even tighter radius, which I anticipated and am pleased with. If you traced the outside edge of the fork you'd probably end up with a curve closer to the original.

After the first few tests and some modifications I ended up with a fork rake max of 110mm. After cutting off the flat section of the rake I get about 80-90mm of rake. This mandrel will be adequate for the fork I am building and will look pleasing to my eyes, perhaps to others as well.