BikeRumor: What are the benefits of this design in regards to: weight, pedal efficiency, handling?
I’m making a steel machine for the big guy, so, it could be lighter. The pedal efficiency is great considering that you’re applying torque to the suspended member, a damn compromise to gain the SS ability. But that ICR stuff makes a 6” travel bike pedal like a 2” travel bike, so that’s progress. Handling is top notch since you get to determine the geometry you like.
BikeRumor: Are the frames vertically complaint and laterally stiff?
Vertical compliance is good due in part to no seat stays and a slack seat angle. There’s plenty of lateral stiffness, but there’s a touch of torsional flex in the back, also due to no seat stays. I think that the most important place for good stiffness is between the handlebar and BB because that’s where the machine receives all the highest torque input from the rider.
BikeRumor: Could you give a rudimentary description of how the linkage works?
The design is unified to in order to run the single speed. BB movement is not cool so I use a pair of links to trace out a ICR (instantaneous center of rotation) path through the BB location. The early stroke effective pivot point is pretty far back so the bike is very active in or out of the saddle. In the midstroke, where the pedaling efficiency is most important, the effective pivot is concentric with the BB (notice minimal BB movement in the video) but moving forward to a stiffer position rapidly. For one inch of midstroke wheel travel, the ICR advances forward three inches. The result is good progressiveness at the crank and a falling rate in the saddle.
Despite popular belief that a URT locks out when standing, this one does not. Single pivot URTs had major issues and went extinct. I’m just applying modern pedaling efficiency enhancing technology to the URT, and
it works well. It starts out neutral like any non-URT but develops the stiffer at the crank/plusher in the saddle behavior gradually through its travel.
BikeRumor: What type or riding or segment of riders are you targeting?
They’re all good. Custom builders who do it for the fun of it can accommodate a pretty wide spectrum of bikes/styles. The only area I haven’t done is road bikes. They’ve been refined so much over all the years that I can’t add much to it.
BikeRumor: What builder’s works do you really admire?
I like the pioneers’ works. Old school. Leitner, Lawwill, Busby, Castellano, Klassen, Saiki. I’d like to get my name in there eventually. As for today, Santa Cruz’s VPP is still king. I’d like to approach them soon with a new twist on that concept, we’ll see where it goes.
BikeRumor: Obligatory: Whats your take on 650B wheels?
Interesting, my most recent build is on a pair of those wheels (pictured above). Hmmm…here’s some dry wit- my emotions lie somewhere in the middle on 650B wheels. I myself might run one up front one day when a light casing 2.6 or 2.7 tire becomes available, but I like shorter chainstays and I need the strength of a 26” in the back.
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