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Power Computer Tech Info

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power curve graph

The Kinetic Power Computers (T-725W and T-725WL) were designed to work with Kinetic Fluid Trainers. The graph above shows how the wattage measurement on the power computer is identical to measured wattage at the resistance unit roller at a given speed. Here's how it works:

The Kinetic Power Computers operate on the principle that the resistance in the Kinetic Fluid Trainers is speed sensitive. We have based our Power Computers on the premise that the only factor having any impact on the resistance unit is how fast the roller is spinning; independent of rider weight, cadence, crank length or any other factors. After riding a Kinetic Fluid Trainer you would be aware of the relationship between speed and effort. The faster you go, the harder it is to pedal. At Kinetic we have studied this relationship extensively.

We have used our test robot, Crank Armstrong, to analyze the forces experienced by a rider on our fluid trainers. Specifically, we have analyzed the amount of wattage needed to sustain any given speed on our trainer. The end result is a very accurate power curve and a mathematical formula to describe it. The best-fit formula for Kinetic’s fluid trainer is in the form P = Ax + Bx3, where P is power in watts, x is speed in miles per hour, and A and B are constants. With this formula, we can calculate how many watts a rider is producing on our trainer if we know how fast the bike's wheel is turning. 

The Kinetic Power Computers have a rear wheel sensor that picks up speed off the rear wheel and then converts speed to power using the formula. The end result is an accurate estimation (+/- 3%) using some very simple and inexpensive hardware. 

Our computer is not a strain gauge and does not measure torque, so there are a few things it will not do. Unlike the much more expensive systems, the Kinetic Power Computers will not register a spike in wattage from a sudden acceleration. With our computer, the wheel must turn faster before a higher wattage reading is observed. Likewise, our computer will register positive wattage while coasting even though no force is being applied to the pedals. Wattage readings when riding outdoors or any situation when you are not on a Kinetic Fluid Trainer are not accurate because the constants (roller size and amount of resistance) are unknown.

Trainer Compatibility
The Kinetic Power Computers will only provide you with accurate power readings when you are riding a Kinetic Fluid Trainer, no other brand nor our Wind or Magnetic trainers are compatible with the power function on our Kinetic Power Computers.