Hello! My team and I were wondering how to rotate extrusions similar to this video from ElectricWizzz. Thank you!
Generally, the same way you make them rotate them going vertically: using a sprocket or large-enough gear.
Mind you, gravity is going to factor in differently because it’ll be trying to add a thrust load on the sprocket. The way around this is a thrust washer, though a suitably large nylon washer or even a piece of cutting board could get you something Good Enough For FTC™.
The device that you show in that video clip is similar to a “jib crane” (except for the raising up and down part). The key to making it stable is supporting the extrusion to a “mast” with some bearings.
Which building system are you using? Actobotics has a number of very useful components that could be used to support the extrusion on a mast. If you had a solid 1/2" diameter tube secured to your drive base sticking up in the air to serve as the mast, then you could use these pillow blocks installed inside the extrusion to allow the extrusion to rotate around that tube. The tube mast would not need to be that tall to support the extrusion. A mast a few inches tall would allow you to place two of the pillow blocks in the extrusion with a couple of inches spacing between them and you will have plenty of stability. The extrusion can be much taller than that if you want. You just want the bearings to be spaced far enough apart to give you good support to carry the load at the end of the arm and resist the tendency for the whole crane to tip over.
Creating the rotation can be done with a chain and sprocket or large gear as @Billfred suggested. Actobotics sells gears or sprockets with a large enough bore that you could bolt the gear or sprocket to the bottom of the extrusion and still have the 1/2" tube passing through the center.
The pillow blocks will probably also be able to serve as the thrust bearing that @billfred suggested as long as you have some sort of collar on the mast for the lower pillow block to rest against.
There are probably similar ways to do this with other building systems. I am most familiar with the Actobotics set, but VEX and GoBilda have a lot of good stuff as well.
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