James
you are obviously correct about the 1420 haveing a clutch, My thoughts were from obsevations of the sectional view, being as the 1400 didn't have a clutch, I don't really see why they needed one, the 1400s motor has more than enough power to cope with the start up loads. I'd always assumed and probably wrongly that the powder clutch was part of a belt drive as in the subsequent models, prior to the centrifugal clutch of the 1450 onwards.
My only other thought and it's only a thought as I'm typing was it more to do with braking rather than torque transmision, as with no interlock back then it would have had to stop the drum from 2850 to rest in was it 10 seconds back then. I would enjoy seeing some exploded views or parts diagrams to fully get this component worked out in my mind.
Great thread, I'm enjoying all this fabulous litrature and advertising. It's enough to make me fancy sorting out my electra (hotpoint) twin tub, just there several Hoovers to be restored first (cue the comments lol).
all the best
Mathew