All Heinzmann motors are built to the same basic plan.. The motor is spoked directly into the bicycle / tricycle rim.
So why is the Heinzmann motor so good?
The Magnets: The magnets in a motor are one half of the torque-producing system - they produce the magnetic field which the coils act against. The stronger a field you can fit into a small space, the better. Heinzmann only use the best quality rare-earth magnets, for the highest possible magnetic flux density.
The Coils: The coils are the other half of the system - and the trickiest bit! The trick is to fit as many coils in as possible, able to carry the largest current you can manage. Heinzmann's coil designs are very sophisticated (and very secret!), but manage to squeeze in a lot more power than all the textbooks say is possible - up to 3 horsepower in some motors!
The Bearings: The bearing which a motor and gearbox run on are vital - they are going to get a lot of abuse and no maintenance! Heinzmann only use genuine SKF sealed bearings, not cheaper far-eastern imitations.
The Gears: The gears are the only real wearing parts in a motor and gearbox, so they have to be good. Heinzmann's are made out of hardened steel, with a helical tooth pattern to reduce wear. In the lower-power motors, Heinzmann make the intermediate cog out of tough nylon to reduce noise - even these last three years or more of daily use.
The Castings: Although it's bigger than a standard hub, there's no superfluous metal in the Heinzmann hub - everything is machined down to save weight without sacrificing strength.
The Thermistor: This is the bit almost all other systems miss out! The Heinzmann motor has a built-in thermistor which keeps an eye on the motor temperature.