Original Grey Technic motor from 1977: 6216a

[Steffen]

I think what Magnus wanted was to make the hierarchy of combined parts easily usable:

topmost of course is a complete motor assembly.
it should be composed of 2 things:
- a complete motor housing
- an axle combination of metal+plastic axle portion

the complete motor housing then again would be composed of
- the front
- the back

and the axle combination mentioned above of course of
- the metal portion
- the plastic portion

This will make this part most useful for animators etc.
and at the same time allow to use the complete motor easily in inventories etc.