Mid-drive detail.
The mid-drive consists of a double-freewheel assembly: 16t track sprocket and 14t BMX freewheel mounted to a one-way clutch (FC-20/HFL2060) that slips over the 20mm output shaft of the planetary gearbox on the motor. Chain tubes serve a triple role of keeping the chain clean, keeping the chain from fouling on the rest of the bike, and keep the chain aligned to the sprockets. The TOP derailer is used as a medium-capacity (28t) chain tensioner.