Product Description
This cog is intended to be printed in plastic (e.g., "White strong and flexible"). It fits standard hyperglide splines, such as those on the Brompton one- and two-speed hub. The teeth fit a Gates Carbon Drive Centertrack belt.
The flanges on each side of the cog teeth provide some additional strength. The three radial holes are sized for M3x0.5 set screws, which sit in the circumferential groove on the Brompton hub (which normally holds a retaining ring). I threaded the holes with an M3x0.5 tap, but one probably could twist a set screw into the plastic without first tapping the holes! A 4-mm long set-screw works well.
This makes for a good fit on my Brompton with a 60-tooth beltwheel in front and a 113-tooth belt, although I did file out the dropout by about half a millimeter -- I needed a little bit more tension to keep the belt from skipping teeth under load. Also, it's best to use the smaller, 12-tooth idler because this 14-tooth cog is pretty small -- there's not much clearance between the belt and the chainstay. . See also http://dkprojects.net/belt_drive_brompton
This works very well, and is very light. The jury is still out (as of June 2015) on whether it will hold up in the long run -- I've only been using it a few weeks. I don't think the teeth will wear out, but I'm not sure about the edges of the hub splines.
