Sprocket wrench for Gates Carbon Drive

thingiverse

Sprocket Wrench for Gates Carbon Drive, a carbon belt drivetrain designed specifically for bicycles. Note: After using this wrench several times, I'm starting to question its design. Since it only engages the teeth on one side of the sprocket, it tends to slip off, which is very frustrating. The short handle also makes it difficult to apply enough torque. To prevent this, I usually wrap a piece of nylon webbing around the handle and attach it to the rim, but it can still slip off. This wrench has been successfully used to apply 30 Nm of torque on a 20t sprocket, meeting the specs for Rohloff's locking sprocket carrier. The OpenSCAD file includes a parameter that allows you to change the number of teeth, although this hasn't been thoroughly tested since I only have a 20t sprocket available. It is recommended that you first print a test version of the wrench to ensure it fits your sprocket perfectly. Various factors such as different 3D printers, settings, filaments, and sprocket wear all play a significant role in this process. For a test print, include only the teeth and rim, omitting the handle and printing only a couple of layers thick. Refer to the comments for hints on how to achieve the best results. The handle is intentionally short to allow the entire wrench to fit within a 140x140 mm build plate. If you have a larger build plate, consider increasing totalSize to make the wrench easier to hold onto. Creating this tool proved to be more challenging than expected, with many prototyping iterations resulting in either too tight or too loose fits. Accurate measurement of belt and sprocket dimensions required trial and error, as some measurements were difficult to obtain. For those in need of a sprocket wrench quickly, printing your own may be the most convenient option. Although I needed one urgently and couldn't wait for shipping, parts of the sketch contain dirty code, but it ultimately worked very well.