Free hub dummy to DIY a single-speed cog for virtual shifting, such as the Zwift Cog. My initial motivation was to save the cost of an additional cassette - of which only one sprocket would then be used :( But I’ve also noticed a significant improvement in terms of sound emission in contrast to a full cassette (and probably even compared to the v1 Zwift Cog, since noise was reported to be equal or even worse).

This DIY-Cog is designed for the 5th sprocket of a Shimano 12-speed road cassette in combination with the small front chain ring (chain line, see picture 3) and to be used on the 11-speed HG free hub, usually supplied with smart trainers like the Wahoo Kickr Core. Spacing-wise you probably could also use an 11- or even 10-speed sprocket (i.e. different width) but I’m not sure how the chain line would deviate (different gear combinations might be necessary).

I’ve uploaded two versions; v1 is the two-part ‘standard’ and v2 has two additional 1mm-shims to be printed in TPU for even more dampening (though, during my testing, it didn’t make a huge difference). In case you need a different gear combination, chain line or free hub design, I've uploaded the .stp-files for you to modify!

Disclaimer: While I provide all data and information to the best of my knowledge, I take no responsibility for any damage - whether to your accessories, bike or body! If you choose to install printed parts to your bike, that's entirely on you!