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I have been interested in this type of thing for a long time for electric assisted bicycles. So I have gained some knowledge about how these technologies work.

I have owned two types of bicycle hub motors and also small but powerful permanent magnet motors. There are brushed hub motors with gear reduction which are similar to the motor hidden in the down tube, and then there are brushless and gearless hub motors where the electronic controller creates a rotating magnetic field similar to what the inventor showed with the rim.

A geared motor can generate considerable torque, but makes quite a bit of noise and needs more frequent maintenance. A brushless motor is nearly silent, but the torque is very low by comparison. An electric bicycle with a geared hub motor can climb a hill by itself. A brushless hub motor is not very helpful if you let your speed drop. This is because if the rotating magnetic field is going faster than the magnets it is trying to pull it quickly becomes ineffective, and the slower the magnetic field is rotating the less amount of power can be transmitted through the motor.

There is almost no chance that any of these solutions have any application for cheating in bicycle racing. First, with the batteries the weight penalty would be prohibitive for any racing application where the race was more than just a few miles. Dragging ten extra pounds around for a hundred miles is going to take a lot more energy than what the batteries would hold.

Second, any system which could put out enough extra power to make a difference at critical times would also generate considerable heat, especially if the components were hidden in the frame tubes.

Third, any geared system putting out a decent amount of power will generate a detectable amount of noise.

Fourth, any ungeared system hidden in the rims would add weight in the worst possible place. Rotating mass absorbs more energy during acceleration than stationary weight. The most critical place to reduce weight on a bicycle is in the tires and rims.

Fifth, and most importantly unlike the human body where performance enhancing substances can be difficult to detect even in during an autopsy, a hidden motor in a bicycle would be very, very easy to detect. As someone earlier mentioned, permanent magnets put out strong magnetic fields which would be easy to detect. A boy scout’s compass would be one way, but a little bit of iron or steel powder would stick to the rims or tubes of any bicycle with hidden magnets or motor. One would have concrete evidence even without using X-rays, MRIs or ultrasound, or disassembly.

So its fun to speculate about stuff like this, but the practicality is just not there as soon as anyone suspects these types of devices are available.