I need to make a shuttle car that travels along a single axis for part of a project, and after looking at the prices of linear motion slides (ouch!), I was thinking a simple platform on wheels that travels along two steel rods to keep it straight, and then have a servo powering it along with a gear rack (like these servocity.com/html/gear_racks.html). The rod part is easy (assuming I get them aligned right!), but I’d need some wheels that would be concave to fit over the rod, and basically use it as a “rail”. Anyone have some tips as to where I could find something like that?
Hmm, new idea. Instead of doing that, I’m thinking of just having some chain glued down to be the “rail” (tinyurl.com/ymfxg2) to move my platform up and down the stationary chain “track”. Anyone tried this before and maybe provide feedback as to the effectiveness? I’m probably gonna need additional gearing to get my needed distance of travel, but that shouldn’t be too terribly difficult. Anyone used chain as a rail/guide before?
wow, excellent find with those servo chains and servo horns, i think that would work well too, just make you yo secure the chain down well
Thanks for providing the links to the chains and sprokets. While I fully agree your plan will work on a flat surface, the bars and gear rack will allow you a lot more options and to exercise a lot more force in the axis of the application (since you did mention linear actuators, this might be important). You also don’t need wheels at all. Most people use a rod and gear rack for making the axis on a homemade CRC mill or plotter. The bars don’t use wheels like a railcar, but are mounted through holes. Generally a circle of ball bearings is used to help make movement frictionless. If that’s too much trouble there is a special plastic (can’t remember the name) that provides a very low friction coefficient for such uses. However, just a hole slightly larger than the bar and some lubricant will do if all else fails, or if friction and exact positioning aren’t as important. This will probably give you better results than the track and also allows you to mount the thing in any position since you’re not relying on gravity.
If this doesn’t need to be long, you might want to look at the setup in discarded printers and if you could purpose that to your needs. They have a bar and mount. Some people actually find bigger printers and use this as a basis for a CRC machine with a useful range of 12"-16".
Anyway… hope this was helpful.
You can get small concave plastic wheels with bushings at the hardware store. They are used on sliding doors that roll along tracks.
Alternately, if you can find thin wheels that don’t have absolutely square edges to them, placing two on an axle side-by-side should create a ‘groove’ between them that could ride on the rail in question.
Thanks for all the tips, I’m sure this will all come in handy.
What method did you end up using?
One way to make your own concave wheels is to use a plastic wheel of the appropriate thickness and mount it on a drill press. Turn the press on to spin the wheel and use a piece of sandpaper wrapped tightly around a wood dowel the thickness youw ant your groove, and sand the groove into the edge of the wheel. If you setup a jig for the dowel you will get a more accurately even groove.