Chris Burbank's Aluminum SWB - Part 2

Chris Burbank had his new SWB bike, basically an aluminum Rans Rocket clone. Now in rideable form, it had been just an incomplete frame at the last meeting,

The fork is set up for nearly zero trail, ala Mark Stonich, and he likes the results. He isn't too happy with the front brake to chain interference. He was assured that he could mount the brakes behind the fork, so the cable will face the other side, with no problems. This even works with LWBs with large fork rakes, but you get some funny looking brake pad angles.

He splits his riding between this Rocket clone and the Bacchetta clone he showed at an earlier meeting and likes them both.

Main tube is 1.5" x 0.080" wall 6061 aluminum tubing. Originally it had just the main tube between the head tube and the bottom bracket. But when it seemed to flex too much for comfort (especially given the fatigue failure tendencies of aluminum) he added a couple of bracing tubes below the main boom.

Seat adjustment is by sliding along a rectangular bar welded onto the top of the backbone tube. It has holes (for a pin or detent?) to avoid the Rans tendency for the seat to slide out of position.

The driveline has one idler on each run of the chain to avoid the front fork crown and the rear frame tubes. The rear brake mounts are just steel bolts turned down and then threaded into aluminum bosses on the chainstays. Very slick!

He used a roller behind the front derailleur mounting tube to allow a straight run along the top of the main tube and a fairly tight turn up to the derailleur. Mark recalled a rule of thumb about cable failing quickly if it turns tighter than 43 times its diameter. That may come into play here.


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