A few days before I left on a family road trip to move me into Michigan, I was scrambling to finish the latest iteration of my camera slider. My end goal was to set up a motion-controlled shot of the milky way at a stopover in Coudersport, PA. After motorizing my EMT-conduit based slider with a pulley system and being completely dissatisfied with the results, I realized I needed to use a completely rigid drive system. The only thing that fit the bill that I could get from Home Depot was threaded rod. It was actually a solution that I had been leaning towards earlier, but the cost of using a high-precision acme rod or ball screw was absurd for a hobbyist like me. So I decided to take a risk on a 1/2″ steel rod with no rated hardness and no guarantee of straightness and see what could be achieved.
I spent some time over the span of a few days building a track for the threaded rod to turn in. Having finished my internship at Lakehurst, swinging by McMaster-Carr to pick up a few parts on my way home was no longer practical, and $5 shipping on $3 of parts did not appeal to me. Amazon was of no help. So I had to forego using a proper set of ball or sleeve bearings.
The stepper motor was rather crudely bolted/glued my original EMT conduit slider and mated to a gear reduction. I had a nut captivated by the camera platform pulling the entire thing along. Because the threaded rod was not perfectly straight, and because it wasn’t rigid enough to keep itself from bowing under its own weight, the camera platform exhibited a sort of gallop as the rod pushed and pulled up, kind of like a camshaft. Weighting the camera platform helped dampen out some of the motion, but without a small sandbag or two, it would be impossible to eliminate the rocking.
From the video, you can see that it is possible to stabilize out a lot of the jittering. Since the distance between each image was a matter of millimeters and the offset purely translational, stringing together the images at 24 FPS made it really easy for an image stabilization algorithm to align each frame.
I still consider Cheapo Slider 2.0 a failure though. While I could easily cut together a usable timelapse, there were a number of faults, not the least of which was my refusal to spend a large sum of money on a motion-controlled system.
- Threaded rod: If you’re going to use a threaded drive system, you need to ensure that it’s perfectly straight, deviating at most by a few tenths of an inch per yard. If I could redo this with a bigger budget, I would almost certainly go for high-precision acme rod, probably with a diameter of 3/4″ or even 1″. The material could be steel, but I think even aluminum would be fine. The sheer diameter of the rod would provide enough resistance to bending (larger moment of inertia, even if the hardness is inferior to steel’s). I’d be looking at anywhere between $40 to $120 for this sort of upgrade though. Of course, this is assuming I’d even want to use threaded rod again.
- Resetting: Not possible. Because you can’t just pop the nut off the threaded rod and install the camera wherever the heck you want, if you need to reposition the camera in the middle of a shot, you’re out of luck. Even spinning my stepper motor as fast as I could, moving my camera back to its starting position from about 2 feet away took 5 minutes. This was geared down way too much. I had about a 6:1 reduction going from the stepper motor to the shaft, and the 1/2″ coarse threading is 13 threads per inch. This thing was SLOW. I may re-use the system to make a CNC router though.
With those two glaring flaws in mind, version 3.0 will use either a timing belt drive, pull itself along a rack gear, or simply drive on a track. I’ll probably end up running the rig on right-angle brackets using ball-bearings like many Youtubers have done. However, I have decided to focus my efforts on the pan-tilt head, as well as a Halloween prop in the mean time… and… you know… Grad school…