> Ah, that would be Acme threads (cue the Roadrunner! :-)
>  The only trouble with them in a domestic environment is
> that they're pretty noisy

Would they be, if greased ? I don't know if they still make
windows with the screw opener-closerer. Probably do,
didn't stop making them just because I stopped noticing.
I remember top windows at school when I was a mixed infant
(still not thoroughly unmixed - work in progress) that you had
to crank with a long pole

A winch, as you suggested, would be fairly easy. I made a
curtain opener for someone once, (hmm whatever happened
to THAT little money-spinner ?) and that needed about 3kg
pulling force, bi-directional. Which doesn't sound a lot for a
hooman but is for a small motor. I found the motor & gearbox
from a very cheap 14.4V cordless drill worked great. Used
thin nylon rope (2.5mm ?), bit stretchy but OK

But this is all assuming that Mr Davis actually wants things to
disappear. Good trick if you can do it, impresses visitors and
whatnot

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