Sprocket wrench for Gates Carbon Drive, a carbon belt drivetrain for bicycles
The wrench has been used very successfully to apply 30 Nm of tourque on a 20t sprocket. Enough to meet the specs on Rohloff's locking sprocket carrier.
The OpenSCAD file provides a parameter to change the number of teeth, but this has not been tested as I only have 20t available. YMMV.
It is recommended that you first do a test print to make sure it fits your sprocket. Different 3D printers, settings, filaments and sprocket wear all play a significant role. Include only the teeth and the rim, no handle and only a couple of layers thick. See the comments for hints. If it fits, it fits - Yay! Otherwise you'll have to fudge around with the parameters.
The handle is a bit short, but this allows the whole wrench to fit a 140x140 mm build plate. You should increase totalSize if you have a larger build plate to make the wrench easier to hold on to.
There's a surprising amount of pitfalls for making such a tool. Many prototyping iterations were either too tight or too loose. Some of the belt and sprocket dimensions were difficult to meassure accurately and required some trial and error.
You can also get the official wrench from Gates, but printing your own may be cheaper or more convenient. I needed one urgently and couldn't wait for shipping. As such, parts of the sketch are dirty code, but it turned out to work very well.
Clas Ohlson PLA
Added three solid layers about half-way through the print for extra strength. In FlashForge FlashPrinter these settings are (with a 7.2mm thickness at 0.4mm resolution, giving 18 layers):
Interval layers: 6
Solid layers: 3
Used 3 perimeter shells as well as 3 bottom layers and 3 top layers.