Thanks guys. The trolley/track was about $150 all up I suppose (not counting time machine, steppers, gimbal). You could probably build it all from loose bits lying around an average well stocked workshop. The motors were from an EQ3 retro fit kit, about $295 I think, but im left with the controller that came with it.
The time machine controller was a lot more, I deliberately have no idea what that cost. It was made useing 3
PICAXE chips ( 1 master/LCD controller and 1 each per axis), 2 stepper driver chip sets, LCD and box/switches etc.the programing includes the pauseing between images and took weeks. It also handles exposing in bulb mode.
Pauseing is not required if you take say less than 20 sec exposures at a push, 10 secs would be fine. Then the whole project would be quite easy. Just get the EQ3 2 motor with controller kit from Bintel and use the controller that come with it (it even comes with a battery box, gears, clutches). Its a 2 axis drive with 3 settable speeds, no electronics construction, wiring or circuits required at all then. The trolley would be quite smooth too, without start/stopping. You would also need an exposure timer, but they are cheap now off ebay. All not that hard for a handyish handy person ;-)
Phil hart has taken many award winning timelapses with continuose motion like this.