Abstract: A bicycle crank assembly comprises pedals, crank arms, an axle and a chainring assembly. The pedals, crank arms, and axle are coupled to the chainring assembly through an elastic element in the form of a U-shaped spring. This elastic coupling allows relative angular rotation between pedals and chainring proportional to the force exerted on the pedals by a bicycle rider. The proportionality constant, or elasticity, is adjustable by repositioning the spring within its supporting structure. The elasticity may be thus adjusted to enable accurate calibration of measurement instrumentation associated with the crank assembly, or for any purpose for which an adjustable elastic coupling is desirable.

Abstract: A bicycle crank assembly comprises pedals, crank arms, an axle and a chainring assembly. The pedals, crank arms, and axle are coupled to the chainring assembly through an elastic element in the form of a U-shaped spring. This elastic coupling allows relative angular rotation between pedals and chainring proportional to the force exerted on the pedals by a bicycle rider. The proportionality constant, or elasticity, is adjustable by repositioning the spring within its supporting structure. The elasticity may be thus adjusted to enable accurate calibration of measurement instrumentation associated with the crank assembly, or for any purpose for which an an adjustable elastic coupling is desirable.

Abstract: An instrumentation system for measuring the instantaneous pedal force and power exerted by the rider of a cycle is described. Being small and lightweight, it is intended to be mounted on the cycle and to operate while the cycle is ridden. The pedal crank assembly is modified to provide an elastic support for the chainring assembly, allowing a small relative rotation between pedals and chainrings when force is applied to the pedals. This rotation is a function of the magnitude of the force and is detected by angle detectors, consisting of angle indicators rotating with the pedal crank assembly and stationary sensors mounted on the cycle frame. These angle detectors measure the relative rotation at 25 or more positions distributed around a revolution of the pedal crank assembly. Electrical signals from the sensors are coupled to a microprocessor. The processor compares the signals, computes the applied pedal force and power at each measurement position, and displays and/or stores the results.