I respectfully request that you read the post from #1 before going off at a tangent.
Electric drills have changeable gearing to facilitate dcorrect drilling speeds
This statement is only 50% correct. The gearbox is to allow the motor to operate at an optimal RPM and torque range while the chuck turns at a lower speed. A speed controller allows you to slow the speed, so why fit a gearbox?
Slow your hand drill down by force and see what happens, even with forced ventillation the drill will overheat.
Again, why is a good electric drill equipped with a speed controller fitted with a gearbox? It's quite simple, when the armature is slowed down the back EMF decreases, more current flows, and the motor overheats. Solution, fit a gearbox, up the armature rpm and decrease the chuck speed.
Electric car motors do not have changeable gears
Who's talking about electric cars?
No what I want to do is to build a “C5” from scratch.
The C5 is a bike and not a car, and to remain within the EU regs. it is limited to 250W. Cars are not limited to 250W, and if they were they would
definitely need a gearbox.
When climbing steep hills the motor slows down and overheats, a gearbox would alleviate this problem somewhat. RHB-C5C suggested a
variomatic gearbox, is would be a very good solution as it would keep the motor at optimal rpm and torque, lowing the power consumption and heat problem. BUT, very costly. This leads to variomatic vs., stepper motor, I would go for the stepper motor.
This info on motors is based on the fact that I'm referring only to torque motors. Stepper motors and their control systems, would be great on a 'future' C5, are very expensive in proportion to torque motors and their control systems. Battery plus switch plus relay plus motor configurations are not posible.