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The Rotor Crank system offers improvements in a cyclist's efficiency and power development, and is simple enough to be retrofitted to almost any bicycle. The Rotor system optimizes the angular rate of each crank independently in addition to providing variable effective chainring size. Varying the angular rate of the legs may sound a little odd at first, but it actually makes a lot of sense. Just as the swimmer's arm is slower when it is in the water, pulling against the load, and faster when it is recovering through the air for the next Power Phase, the Rotor System enables the cyclist to spend more time in the Power Phase. By virtue of its mechanical linkage, the Rotor System allows the cyclists to spend more time generating power during one revolution. The variance in angular rate is subtle to the rider, however, making the Rotor Crank System easy to adapt to. You might think that spending more time in the power stroke is going to make the cyclist more tired. Actually, the opposite is the case. The kinematics of the Rotor system enable the cyclist to develop more power for a given level of effort by increasing the effective chainring size for the pedal down-stroke (power phase) while decreasing the effective chainring size for the pedal up-stroke. The graph below shows that the power generated by a cyclist with a conventional crank system is not consistent around the entire pedal stroke (blue curve). A conventional crank arm is a fixed length, making the power generated by the cyclists directly proportional to the power generated by the leg for an entire revolution. The figure also shows a computational analysis of the benefits of the Rotor system (red curve) with a rider expending the same amount of effort as the blue curve. You can see that the Rotor system provides increased power for the majority of the revolution.
The Rotor System offers two significant improvements over the conventional crank technology. Each of the improvements help draw more power from a cyclist's legs.
This eliminates the dead spot that occurs when the cranks are vertical, with one leg at the end and one at the beginning of the down-stroke.
The benefits of the Rotor System have been evaluated in the laboratory by Dr. Cordova of the University of Valladolid, Castilla-Leon. In his research, Dr. Cordova performed back-to-back comparisons of the Rotor system and conventional cranks. He found that for a given effort level, the Rotor system increased power up to 16%. He also found that for a given power output, the Rotor system reduced lacate production by 15% and heart rate by 5%, indicating improved efficiency. He concluded that the Rotor system is a real advantage. The mechanical linkage of the Rotor system does weigh as much as 460 grams more than competing crank/bottom-bracket sets depending on the level of the crank. But, if Dr. Cordova's findings are even half right, the added weight of the Rotor system is easily offset by the net increase in power and efficiency provided to the rider. Rotor Components is cooperating with other known Universities and scientists, and is encouraging further in depth testing and comparisons of the Rotor system cranks to traditional cranks and other inventions claiming to provide benefit to the cyclist. |
