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?
I dabbled a bit on this a while back. The key is minimizing the overhead such that the slide moves as much as possible relative to the length of the unit. I was able to achieve an 800mm movement with a 500mm beam (1.6x). (For reference, Edelkrone's range from 1.14x to 1.49x) The problem I ran into was the amount of leverage a camera setting 400mm off to the side puts on the head of the tripod was enough to cause the end to dip noticeably as the camera moved to either end. (I didn't realize how shabby my tripod was prior to this experiment.) Some photos attached. I used wire instead of belt as it helped keep the overall length to a minimum. It worked fine for a GoPro but as I could never really find a way to properly support it I never really considered it a success. Currently working on a double compound table model which resolves the support issues and should give me 1125mm of movement in a 500mm package (2.25x).
Thanks for the quick reply. I like how you mounted your pulleys and used wire instead of a belt. I was thinking of that but it makes some of the other features I wanted less likely to work well. So are you saying the deflection was due to your tripod, not the OpenBuild V-slot?
Yes, it was the $39 tripod. But there is also the potential for some deflection with the Openbuilds parts. It all comes down to how it is built. The stouter you make it, the less the potential deflection. Wider wheel spacing on the bottom mount also helps.
Rick, How were you able to place a pulley on both ends of the V-Slot linear rail? Also, I would like to motorize the slider by implementing the belt and pinion setup. Is there a way you can show this? Thanks!
@Ferds, I used a router and an end mill bit to cut small slots through the center portion of the V-slot (2nd photo) and then drilled and tapped some through holes (3rd photo) where I ran set screws through to serve as the axles for the grooved bearings used as pulleys. Motorizing it is possible but it begins to defeat the idea of getting as much length of run out of as short as possible length of material. The pulleys would need to be set out beyond the length of the rail which adds length with no increase in run distance. Attached is a sketch showing moving the pulleys out where a motor could be attached using short sections of 3/4"x1-1/2" aluminum tubing but it adds 3" to the overall length. You could probably get away with using 3/4" square tubing at the non-motorized end thus bringing the overall length addition to 2-1/4" but it still adversely affects the length to run ratio. Note, you will need to use smaller diameter idler pulleys than the ones from the Openbuilds store. Smaller idlers are easily found online.
@Rick 2.0 First of all thanks for your reply....I really appreciate it! Regarding the location of the motor, would it be possible to place it on the static carriage and set it up like a belt and pinion similar to the image on the bottom? However it will be on the wider side of the rail
