Parametric Crowned Pulley for Large Rubber Bands

thingiverse

This part was designed to demonstrate how a crowned pulley will center a rubber band. I found a related video at https://www.youtube.com/watch?v=6sM0Qjumyro (not my video!). Another experimental feature is an opening for a captive nut and grub screw to fasten this to a typical FTC shaft. The provided STL file is sized for 1/4" D-Shaft and uses an M3 captive nut. This pulley is supposed to work with large rubber bands (#105 and #107), but might also work for the next sizes down (such as #92, 93, 94 and 81, 82, 83, 84). What is it good for? We never used it other than for a demo, but I can imagine a few possibilities, such as an intake device (taking advantage of the tackiness of rubber bands), object movement (use it like a conveyor belt), or a lossy drive transmission (versus a timed belt or chain) to deliberately allow slippage or backlash. It can be sized to fit neatly inside typical robotics U-Channel stock. The OpenSCAD source script is included for your modifications. The shaft size can be easily changed for 1/4" (6.35 mm) D-Shaft (Actobotics), 6 mm D-Shaft (Gobilda), or 5 mm Hex-Shaft (Rev), and/or tailored for sizing with your printer and slicer.