Parametric Chain Link Drive Pulley

youmagine

Human: I felt a strong urge to create small chain drives for some of my models, but wanted to use classic chain link style chairs rather than proper chain drive chains. I looked up other 3D Printing model repositories and found that nobody had made a model for this before. After scratching around with a pencil to figure out what parameters I needed, I jumped into OpenSCAD and came up with two parametric models. One has a neck, holes, and nut slots for screwing it onto a shaft while the other is just a disk with chain recesses which can be easily adapted to other pulley body designs. Both are included here. The chain size and number of link pairs determines the size of the pulley. So the important variables to fiddle with are; Llength: This is the outside length dimension of a single link Lwidth: This is the outside width dimension of a single link Lthickness: This is the diameter of the link "wire" N: The number of chain link pairs around the pulley. Please note this is pairs of links not the number of single links. The pulley neck size is controlled by the following parameters; Pwidth: Width of the pulley main drum which the chain recesses are cut into PstemD: This is the diameter of the pulley attachment neck There's nothing to stop you putting dimensions in here that can't accommodate the retaining screw or the shaft. We leave that to you, the user, to figure something sensible. PneckL: This is the desired neck length AxleD: This is the axle diameter ScrewD: This is the retaining screw diameter There are a bunch of other parameters that you may wish to tweak too; Ptol: Is the printing tolerance. It is used to provide a bit of space around the chain profile so that chain will fit into the recess despite a bit of spread from the extruded plastic PtolThk: This is a printing allowance for the "radially" orientated link thickness. This allows a bit of extra on either side of the link slot so any sagging of the printed filament can be easily removed or at least won't interfere with the link sliding into the slot. Wclr: On either side the the tangential link is a cutout slot. This parameter just controls the size of this slot. CutD: There are some very stylish decorative holes in the end of the pulley. This parameter controls the diameter of these CutN: This controls the number of these extremely stylish holes Hopefully this is all clear enough. I feel the model will work well for larger chains where the printing tolerances are less of a factor in the final printed shape. I trust this will be useful to you.