I have been building this motorized slider for a long time now. Recently I have got it finished. Maybe it is not polished or could be always better however it does its job. Here are its features:
Max Load: unknown :-D (lifts DSLR on fully deployed Manfrotto Magic Arm)
Travel Length: 111cm
Full length: 150cm
Travel Time: 4min - 2h
Transmission: 6mm steel screw
Speed control: PWM controller, gearbox 1:1, 1:4
Power source: 10 AA batteries (12-16V)
Motor: 12V, 0.19 Nm
Real speed is approximate and depends on how used up are the batteries
It is heavy - 9kg.
It is too long for my car's boot
and now advantages:
Power source is lightweigth and easily available. It is also detachable and one can use for instance car's 12V power source
It is very, very stable - can hold DSLR on fully deployed Manfrotto Magic Arm in any direction without conterweight
All cabling, control system (PWM controller) and motor are in one box inegrated with the rail
Can travel at any direction, even upside down (however there is no such need as the camera can traverse end of the slider usinf Magic Arm).
Cheap and simple!
Music background - Max Loginov - Secret Insland