Wednesday, July 8, 2009

More About Trainers

The more expensive trainers let a rider select simulated conditions and from these conditions calculate the average power needed for a measured speed. There is some entertainment value to selecting parameters, but once this selection has been made, the resistive power is a constant function of speed.

Less sophisticated trainers have one speed versus power curve and resistive power is always the same at the same speed.

In both cases pedaling feel is not realistic. It's unrealistic because the acceleration within the pedal stroke is not realistic. Trainers, even ones with large flywheels, can't duplicate the acceleration profile of riding outdoors. It takes a much more sophisticated approach.

People ask if one can simulate outdoor riding with a flywheel and trainer-type resistance. I did a study of this and concluded that it was just not possible because a flywheel and resistance approach can't duplicate the acceleration within a pedal stroke that characterizes riding outdoors. Accelerations of some trainers in the analysis were off by a factor of as much as 1000.

The PFS measures acceleration and recalculates resistive power 1000 per second within the context of the simulated conditions. It controls the instantaneous resistance using a computer-controlled electronic brake. The result is a much more effective way to spend one's limited training time.

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