Hammond delay thingie (was: mysterious delay lines)

[R.G. Keen]

>Speaking of delay like devices  (though I'm not sure this real is one) can
>someone explain how the small motor driven drum inside a Hammond organ that
>has all the wires connected to it works to generate tremolo/varabrato.  I'm
>not talking about a Leslie here, this thing has a wire from each of the draw
>bars connected to it I guess a single output wire, and some rotating part
>inside that's turned by a belt running off the same motor that turns the tone
>wheels.
Sounds like an oil can delay. These work by having an insulating layer
inside the rotating can and a high voltage signal source which deposits
charge on the inside of the insulating surface, somewhat like the
charge depositer in a Van de Graff generator. The charge then rotates
with the can and is picked off some rotational delay later by a (very!)
high impedance input. The oil inside is to keep the charge from
bleeding off into the air inside the can.