On Bicycles, and.... what else is there?

Last time I made an off-the-cuff prediction each rider in today's Boulder Creek to Saratoga Gap Low-Key time trial would be passed, or be passed, by around 2 riders on average. That was based on the assumption riders varied by around 0.5% each in the sequence and that riders varied week-to-week by 2%. These were low estimates, I concluded, after examining the data. For this post I actually did a numerical simulation, using numbers derived from Low-Key historical data. For each starter, I generated a normally distributed "true speed", with sigma = 14.4% about a mean (derived from historical data). For each rider, I then ran a "qualifying climb" in which speed varied normally with sigma = 4.2% from true speed (derived from my score history). Note this was based on the old scoring system, % of median, which includes an artifact that some weeks tend to yield different amounts of score spread than others. So it's probably an over-estimate. I assigned ...

Specialized just revealed a super-cool prototype (it's been called a concept bike, but this seems very functional, nothing concept about it): a tandem version of the Shiv . Wow! Photos stolen from BikeRadar : Interesting phasing on those cranks. One of the cool aspects of this bike is the shaft drive: Super-aero, clearly. But at what cost? Any drivetrain has losses. Losses are generally considered to be proportional to transmitted power, although it's been experimentally shown that for a bicycle transmission efficiency is higher at higher chain tension than at lower chain tension. This is fairly trivial: aspects of drivetrain loss are not necessarily proportional to transmitted power, but rather proportional to chain motion. In any case, a fixed gear drivetrain, such as on the timing chain on a tandem, is quite efficent. For example, 98-99% is typically claimed. An alternate for the timing chain on a tandem is the Gates belt drive. This also claims to be as efficient ...