Fantastic explanation. That is exactly what I needed to get me going. As I was reading through it, I started getting flashbacks of the physics courses I took in university.
Basically, given that I will likely purchase a Gear Head DC motor (built-in gear reduction), I would need a model with a minimum of 1.25 Kg/cm (assuming a 1 cm radius gear/drum), and appoximately 24 rpm rotation speed ( 2 cm diameter gear/drum would pull 6.28 cm of cable per revolution, so for 1 inch per second, it would need to turn 2.54/6.28 revolutions per second). Sorry to drag this back into metric, but the Gear Head motors I'm looking at have their torque ratings in grams/cm.
For my purposes (and assuming I got it right - and noting the fact that I always try to err on the high side of my estimates), I located a Gear Head DC motor, with 2000 grams/cm of torque, 132:1 gear ratio, and a speed of 42 rpm (which would allow me to achieve close to 2 in/s - best case senario).
The drawer will be built into my desk, so it should be fairly close to level (allowing for the 6 degree incline should compensate for any slope in the floor of this ancient house I'm in). Also, the control circuit I designed for this uses a latching gate switch to supply power to the motor (bi-directional for open/close using a single switch) which resets via 2 roller switches placed at the extremities of the allowable drawer positions. The roller switch positions are adjustable in the assembly to allow coast-to-stop adjustments so the drawer doesn't halt abruptly when opening/closing. The only thing I haven't figured out yet is how to detect a stall condition, for cases where the assembly has jammed, or there is an obsticle in the way too heavy to push. I assume it would have something to do with monitoring the current through the motor, and resetting if it reaches the max rating of 340 mA.
Thank you very much!