I watched this video on building the Mini V Linear Actuator and realized that it is very close to the kind of video camera slider I'd like to build. Edelkrone makes a slider which lets the camera move twice the length of the track. (video) It does this by having a second carriage on the bottom of the track. The top and bottom carriage are linked by a belt and the bottom carriage is bolted to the support (tripod). A short slider on your tripod is great when shooting over-the-shoulder shots. If the actor nearest the camera shifts over and blocks the lens, the shooter can just slide the camera over to keep the far actor visible in the frame. So a 12 inch slider like this would give you 24 inches of adjustment in a very compact package. The track and the carriages would be the same as on the Mini V Linear Actuator. The end caps wold need to be changed to support a larger pulley who's diameter would put the belt at exactly the correct position to attache to both carriages. A longer version of this slider can be used in the conventional way with support on each end. You can angle a slider like this up to 90 degrees if you put weights on the carriage opposite the camera that match the camera's weight. Then you can slide the camera up and down with little effort and it will stay put when released. In addition if you could bolt a motor onto the pulley for motion control or a flywheel to provide smoother motion, you would have a very flexible camera slider package for both time-laps and video. Oh and a carriage lock would top it all off. Any other suggestions?