Recently I heard about using exercise bikes to generate electricity. It is more or less like a bi-cycle fixed in a training stand. They convert the rotation of the wheel into electrical energy. The scenario is that they take some W watt of power from that model. In their case a disc like arrangement is used to transfer the rotation to a dynamo or a generator (I am not sure about, what is the difference between using a dynamo and DC generator). My question is if I use a shaft kind on arrangement on either side of the same wheel and connect it to two different dynamos, will I get 2W watt of power or will the two dynamos separately contribute (W/2) watt of power and thus contributing the same W watt of power. If I make an arrangement such that both the wheels get rotated when you peddle the bi-cycle (Assuming both the wheels are not in contact with the ground i.e both the wheels lie above the ground as a training stand is used). Having one shaft on either side of the two wheels, Therefore, getting output from 4 shafts and using four different generators, will I get 4W watt of power or will the power from each dynamo be (W/4) watt of power, thus contributing the same W watt of power.