Make:

Pour some Goog on 'linear actuators'.

If you drop your AC requirement, there are (literally) tons of motors
available that run on 12 Volts DC and have exactly the speed and torque
characteristics you need.

Automobile power-window motors. Check the online surplus sites,
or your local junkyard.

You can get an AC-to-DC 12 Volt DC power supply and be all set.

Cool thanks guys. Ya I was just saying AC cause it would be ultimately hooked up to an AC outlet in the home/office, but ya, going with a AC/DC converter hopefully wouldn't be too difficult. I just don't know much about this stuff so I have a lot of research. Unfortunately there aren't many documented projects out there online that are anything like this that I can learn from.

I believe that you should be thinking about big gear reductions. You will have to lift a desktop and everything that -might- be on top of it. That could easily top 200-300 pounds. With a gear (or chain or belt) reduction, the speed will be reduced but the force will be increased. What's more, given the random things that could be on a desktop slower is probably better.

I think that more important that the motor selection is how are you going to drive it, and make absolutely certain that it can't fall back down.

The easiest way would be to use a basic linear actuator, like these ....

https://www.surpluscenter.com/sort.asp?UID=2009110211475770&catname=electric&keyword=EALD

But they are pretty pricey. Personally, I'd be looking at something like this ...

https://www.surpluscenter.com/item.asp?UID=2009110211475770&item=5-1074&catname=electric

and driving things through a 3:1 or 4:1 chain reduction. On the same site as those two motor links you can find plenty of roller chain and sprockets under the 'power transmission' tab.

John

If you are looking for a remote control option as well you could consider using a satellite receiver (that has DiSEqC motor control capability) and a DiSEqC motor. This would enable you to store multiple positions too.