Power and Speed
Power, Given Speed calculates power at some given
speed. Speed, Given Power calculates speed at some given power.
If a rider has less weight going up a hill, how much faster will
the rider be? Air density can make as much as a 10% difference
in speed. These calculations are made assuming forces are in
equilibrium and a rider has reached steady-state conditions.
Measure rotational inertia. It's easy. Which wheel
would be best for a climb? Which for a sprint?
Forces not in Equilibrium
More often than not, forces on a rider are not
in equilibrium. This happens at the start of a time trial or
short track event such as a 500 m TT or a Kilo. Under these conditions
speeds change as time progresses. Plots of speed, distance, and
acceleration show how these parameters change with time.
In sprints a rider's power output peaks rapidly
and drops off. This is commonly measured with a Wingate
Test. One can create a equivalent sprint Power Profile
and use it in subsequent calculations.
A model of pedaling a bike is presented. In concept,
the Model lets one make assumptions
regarding strength of the thigh and shin muscle groups and converts
these assumptions into power at the pedals. The Model can be
used to investigate optimal seat height, optimal crank length,
effect of "keeping the heel down," or improving muscle
strength. Plots of forces at the pedals and of strength of muscle
groups are presented.
©1998 Tom Compton