Mechanical components II
Electrical Drive II
Interfacing II
Parallel port D/A converter
Motion Software
Video's II
Platform Drive Calculations
Mechanical components II
Here is an overview of the mechanical components that I used for the platform:

Rack-shelf metal is great for this type of experiment. You can bolt it together easily, make lots of adjustments, and with some cross-beams, a very strong structure can be build. The even spaced holes let you easily make accurate symmetrical constructions.
I used 30x50mm, 2mm thickness material. It was quite cheap in Taiwan, about US$ 1 per meter. You can get it up to 2.5m long. In Europe, check for "dexion slotted angle"

For the cables I used 2.5mm steel cable, that easily holds the total platform weight of about 120kg (including me). Cable tensioners and fasteners are standard hardware stuff.


The chain-sprocket wheel drive generates quite some noise. A much more silent drive can be obtained by using belt-pulley. I used "A" type belt, 2" pulley on the motor that drives a 6" pulley mounted on the drive axis via #22 belt. Then a 2" pulley on the same drive axis moves a 2nd belt that is connected to the cable.  The mechanical drawings of the pulleys are shown on the side. I had these made in Taiwan, hence the Chinese comments.

The motors are real industry DC servo motors. I was lucky enough to find them on the junkyard one day. They are specified as:
Typical power 230W, current 4.4A, 2100rpm@ 52V, torque 1.05Nm. I used this motor with +/- 24V drive voltage. When I increased the voltage to +/- 36V, the platform drive forces got somewhat scary. These motors could rip the whole structure apart. 
You really can get away with much less, depending on the gearing you want to implement. Some alternatives could be electric gate openers, electric screwdrivers, car wiper motors.  

The roll-bearing wheels came from old production line conveyer belt rollers. They are aluminum with V-groove, and inside have double ball bearings with 15mm inner shaft.

For the end-stop switches I used micro-switches, with extended lever, that is pulled down by a rope and a spring.