I went out on my bike on Thursday, only to get caught by that thing in the end. Sky lowering, wind shrieking, air getting sticky, and the bits cutting through them all.
Raindrops? No, something more crispy. Yes this is Hokkaido.
So today I hung in and drew things and stuff.
Sprockets. Those good guys who work closely with the chain. I made the design base for them to get ready for the future release of things like these, some of which will feature our original tooth shape. It’s similar to the ISO standard shape but modified primarily for durability reasons, and the prototype worked well. There are other tooth shapes like the JIS ones, but I don’t like them much.
One reason I’m picky about things like this is the small safety factor in these parts, which means bicycle drive train parts may easily break under regular usage conditions. For instance, bicycle chains have tensile strength around 1 ton. Not much margin there. My 24-tooth front sprocket has 48.6mm pitch circle radius, which renders 3.5 times leverage when used with a 170mm crank arm. If I put my whole 200 or 300kg back strength, the static weight alone will reach one ton. If the positioning is not that efficient, there are other factors such as corrosion, dynamic load, twist, and cold brittleness. Therefore chains keep snapping in winter.
So here comes the better season for the chain. Although I’m not the nicest master for my poor wee chain, I’m looking forward to some spring fun with it nonetheless.