View attachment 138281
This picture shows the evolution of my clip on chain guard for the 2020/2021 Domane+ HP.
It clips into the motor mount bolt heads (no bolt removal or adjustment required), and the third point of contact is the base of the seat tube where I am using a velcro "Command Strip". This allows the design to be easily removed, and the adhesive attached to the bike to also be easily removed. I have both the 52cm and 60cm frame (smallest and biggest), so the goal is to make the same design work across all frame sizes.
You can see the alignment to the chain is not adjustable, and what I found between the two bikes I am testing that the motor is mounted +/- 1.0 mm and I am targeting roughly 0.5mm tolerances from the guard to the chain. I will either need to make a universal design with a wider chain guard (less likely to help keep the chain on), or create a few different iterations of guard offset from the frame along with a simple measurement tool to determine which one is needed.
I am now going on rides with this installed, but as my chain drop history is about 1 drop every 1,000 miles it will be tough to prove this is working. Also tough to know when the chain event that this is designed to mitigate happens that it doesn't just jam up and break. I don't plan to do extensive design testing trying to get my chain to bounce in different ways. I am just going to start riding with it and periodically look at how it is getting grease marks and chain impact marks.
Next step is to find a better printer filament. Currently this is PLA. I will investigate a black carbon fiber filled nylon filament as an option, and also see what options there are these days to have it commercially printed.
