An avid cycling friend of mine approached me about building some bicycle parts. The bicycle manufacturer Niner produces a patent pending stem cap called the Top Cap. We liked the unique idea of being able to snap a bottle cap onto the stem cap but we needed a slightly different angle. We thought we may be able to cater to the single speed and retro bike fans by producing a stem cap with a cork in it.
My first try turned out fairly chunky and ugly. A few more runs got the product fine tuned to what it is today. The clean look is what it’s all about.
The cap is machined from solid stock 6061 aluminum rod and features an actual wine cork. The threaded stud is made from A2 Stainless Steel. To set the headset preload there were two 2mm spanner holes drilled in the side of the cap in order to allow an allen wrench to be used for pre-tension. Each cap takes me about 2 hours to machine plus the time it takes for the finishing.
The finishing process involves Type II anodizing in my garage. After a few tries the caps started to turn out quite well. I still have yet to come up with a clear sealer to help protect the cork, I’ll get around to figuring it out someday. If you have suggestions then send them my way.
The only modification required in order to fit the caps on standard 1 1/8″ headsets is to set the star fangled nut a bit deeper into the fork tube. I machined an install tool to allow for quick setting.
As far as weight goes the cap came out to 28 grams. Some standard aluminum caps with the cap screws that I weighed were in the 17 to 19 gram mark. The cap was not built to compete with the weight weenie market