I lately had some fun and felt in the mood for playing around with numbers a bit. The idea was that highest achievable top speed is relatively easy to measure and even though there's a series of factors at work, the main being aerodynamic drag.
The idea is, when your bike achieves topspeed on level ground this is when its horsepower and the force working against it, even out. So with the topspeed v^2 being known, rho is generally assumed to be 1.2 for air and the only number I was able to find for Cd for a motorcycle was 1.8. You can play around with the cross-sectional area a bit, but a frontal shot of the bike with yourself on it should give you a pretty good idea. I ended up estimating it to around 1.3m2 for my TR1 with me on top of it.
So I played around with a spreadsheet a bit entered the numbers as above and lo-and-behold got some numbers.
A whopping 71hp at the wheel (casually rounded up for bragging rights), which funnily enough is spot on with what the factory claimed for a TR1... Now I know that my calculation figures in 10 percent transmission losses, but no frictional losses, which at this point might be quite some, especially considering the skinny rear tyre, so the power-rating at the crank might be rather irrelevant.
Really curious what the dyno will spit out and show whether this is a usable approximation or not.
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