Bicycle cadence sensor ring for road bicycle

thingiverse

My E-bike conversion kit came with a cadence sensor magnet ring that was too small for my road bike, so I created a custom one as my first design. This model uses 25 neodymium magnets (5mm diameter x 4mm high) and mounts on a chainring where the spacing between the closest bolts is 64.7 mm. To generate with OpenSCAD, follow these steps: openscad -Dpart=ring -o ebike_cadence_sensor2_ring.stl \\r ebike_cadence_sensor2.scad\\r openscad -Dpart=rcap -o ebike_cadence_sensor2_cap.stl \\r ebike_cadence_sensor2.scad\\r openscad -Dpart=nuts -o ebike_cadence_sensor2_nuts.stl \\r ebike_cadence_sensor2.scad\\r openscad -Dpart=bolts -o ebike_cadence_sensor2_bolts.stl \\r ebike_cadence_sensor2.scad\\r For the nuts and bolts, ensure that the library "threads-library-by-cuiso-v1.scad" is accessible. The SCAD file contains variables at the top where you can adjust the number of magnets, bolt hole spacing, size of the pockets for the magnets, etc. Note that certain combinations will be incompatible (will overlap) with specific bolt hole numbers. For example, 24 magnets won't work with 5 bolt holes. To assemble: Press magnets into the holes. If the holes are too loose, you can use epoxy. If they are too tight, you can drill them out a bit more or adjust the magnet hole size in the SCAD file. Assemble on top of a steel object (such as a file cabinet or cast iron skillet) to prevent magnets from jumping out and attracting each other. Once the magnets are in place, slide the slip ring into position to hold them secure. Mount between the frame and the chainring with the flat side facing the chainring and the open holes facing the frame. Secure with rectangular-head bolts and nuts. I encountered issues with a weak connection between the bolt and the head, which was resolved by printing that particular STL file with 100% infill. Attribution: The bolts and nuts in this build utilize threads-library-by-cuiso-v1.scad (not included – available on Thingiverse). Note: I made last-minute cleanup changes to the code after my previous print (to make the ring a bit wider), so I haven't test-printed this latest version yet.