Printed and run on an HTD 315-3M belt: both 5 mm bores carry a D-flat under one M4 set screw in a captured nut, the 60-tooth pulley runs on six spokes, and both print their flanges in place.
Using the CheapCAD Tools connector, design a two-pulley timing belt drive: HTD 3M belt, 10 mm wide, about 81.94 mm between centres, with 2 mm of extra face width beyond the belt. Pulley 1: 40 teeth, 5 mm bore with a D-flat 0.5 mm deep, 0.2 mm print compensation, a hub 20 mm across and 10 mm tall with 1 M4 set screw in a captured nut. Pulley 2: 60 teeth, 5 mm bore with a D-flat 0.5 mm deep, a hub 20 mm across and 10 mm tall with 1 M4 set screw in a captured nut, and 6 spokes 5 mm wide on an 8 mm web round a 20 mm spoke hub, a 5 mm rim under the teeth, 3 mm fillets at the rim and 4 mm at the hub. Both pulleys: printed flanges 3 mm thick reaching 4 mm past the teeth, the top flange printed in place on breakaway print supports. Check the design, apply any Auto-fix it suggests, then export both pulleys as STL and give me the download link.
Paste it into Claude, ChatGPT or any AI app with the CheapCAD Tools connector, and it designs this drive with you, checks it and hands you the files. How to connect your AI.
HTD-3M-40T.stl — pulley 1, 40 teeth, without supportsHTD-3M-60T-P2.stl — pulley 2, 60 teeth, without supportsHTD-3M-40T-w-supports.stl — pulley 1 with breakaway supports under its top flange: print this oneHTD-3M-60T-P2-w-supports.stl — pulley 2 with breakaway supports under its top flange: print this oneFree STLs are CC BY 4.0, exactly the design that was printed for the photos, with its print compensation (pulley 1 0.2 mm). Open the design to change anything, tune the fit for your printer, or download STEP, DXF, SVG and the belt.
| Pulley 1 | Pulley 2 | |
|---|---|---|
| Pitch diameter | 38.20 mm | 57.30 mm |
| Outside diameter | 37.44 mm | 56.53 mm |
| Outside diameter, as built | 37.04 mm | 56.53 mm |
| Root diameter | 35.02 mm | 54.11 mm |
| Groove depth | 1.21 mm | 1.21 mm |
| Pitch line differential | 0.38 mm | 0.38 mm |
| Belt width | 10.00 mm | 10.00 mm |
| Face width (belt + clearance) | 12.00 mm | 12.00 mm |
| Minimum face width | 12.00 mm | 12.00 mm |
| Flange outside diameter | 45.04 mm | 64.53 mm |
| Flange past the OD | 4.00 mm | 4.00 mm |
| Minimum flange height | 1.59 mm | 1.59 mm |
| Flange inward of the groove | — | 5.00 mm |
| Minimum flange overlap | — | 3.00 mm≈ |
| Belt | 105 teeth · 315.00 mm | |
| Centre distance | 81.94 mm | |
| Drive ratio | 40 : 60 · 1 : 1.5 | |
Read from the generator's Dimensions panel for this design, which opens with no warnings.
Ready for an FRC robot: the bore fits REV ½" rounded hex shaft, with SH-50 retaining-ring grooves on both faces and a splined washer under each ring so nothing walks along the shaft.
Built like a machined part: ISO 773 keyways sized to 12 mm and 20 mm shafts, M5 set screws to lock them, and flanges drawn as bent metal plates instead of printed rims.
Splined like a gearbox shaft: ISO 4156 involute splines in module 1, with a flat root at 30° on the small pulley and a fillet root at 37.5° on the large one.
Heavy-duty HTD 8M on splined shafts: straight-sided ISO 14 splines carry torque no set screw could, and the 36-tooth pulley is spoked around its spline hub.