So between classes, work at the shop, and other hobbies, I've been working on this little thing for the past five months. I can finally showcase it now that it's pretty much done!
Nicknamed Project "Rotory" Cutter, the goal was to use as few non-bike parts as possible while keeping the design clean and cohesive.
Voila. The idea of making a pizza cutter came to me when my cheapo cutter started rusting after I sharpened it. Turns out a rotor makes for a nice blade when sharpened.
The blade is a Campagnolo AFS/Centerlock 140mm rotor. They are the only stainless centerlock (centerlock>6-bolt) rotor that I could find that are also completely round (no serrated edges, etc) They also happen to be a nice brand that I would happily own. To sharpen the rotor to a knife's edge, I mounted the rotor to a cheap dummy hub, put the hub-cassette-rotor combo on my beach cruiser, and spun the cranks while simultaneously holding a stainless-specific lathe file to the rotor. The result is sharp enough to cut you if not careful.
The rotor is mounted to a Novatec D791 CL hub that was cut in half. It is mounted backwards (flipped) for blade centering purposes.
For corrosion resistance and in anticipation of contamination, the bearing in the hub has been replaced with a full ceramic Si3N4 bearing that has a nylon cage and uses no lubricant. The added hardness protects it from contaminants pitting the races. If it cracks on me, I always have a stainless bearing waiting for me to fall back onto.
The bearing itself is pressfit, and securely held in place with the hub's endcap retainer lockring (along with the help of a nylon washer), which has been trimmed down to recess fully into the hub shell.
The original hub endcaps have been modified to act as spindle spacers, braced against the bearing's inner race.
The spindle-bearing stack is held together with the use of a ZTTO 15mm Thru Axle (originally had a WolfTooth one, but that one didn't come out as nicely due to errors on my part). The thru axle's internal bore of 8mm was (painstakingly) enlarged to 9mm using a guided drill, and then bottom-tapped with M10x1 in order for a corresponding Trek suspension pivot bolt to thread in from the other side of the handle, effectively compressing the stack. Thru-axle length was carefully shaved in order for the axle to bottom out on the handle and not crack the inner race. Torque to 3Nm and held together with edible loctite (very hard to find), same loctite was used for the bearing-retaining lockring.
The handle is a handmade carbon fiber piece. The core/center was laid up over a ramp and compacted with a matching plate from above. Thickness was made to be 5mm. The layup is a mixture of 2x2 twill and 3k plain weave based on the carbon I had on hand, and a unidirectional skin layer was applied on top for aesthetic purposes.
Weight weenie holes were drilled in increasing sizes using a stepped bit and careful drum sanding following my printed template.
The rim (the woven bit on the edge) was cut from a sheet of 3mm 2x2 twill weave carbon and laminated to the core/center. The stacked plies were then wet-sanded to the shape of the core (the rim's outer edges were rough, and the center layer's shape was final, so basically sanded down until they were flush and no more). I originally wanted to apply a UD layer to the rim too, but I found the contrast between woven and UD to be quite pleasing, so I kept it.
Filets were then applied to all corners, and 1000 grit sanding sponges took care of all the micro-scratches. It is buttery smooth when held in the hand.
Today at the shop, we christened her by ordering and cutting 3 pizzas.
This wouldn't be weight weenies without a weight figure. The whole assembly weighs 245g
And while we're at it, here's the parts list:
Bike parts used:
- Novatec D791SL-CL centerlock front hub and its various components
- Campagnolo AFS 140mm rotor
- ZTTO 15mm Thru-Axle and accompanying stainless shim washer
- Trek M10 rocker pivot bolt
- Shimano centerlock lockring (The cheap OEM one since its profile is lower)
Non-bike parts used
- Nylon washer, 28mm OD, ID cut to 24-ish
- 2x2 twill weave/3k plain weave carbon fiber and resin for handle
Had a lot of fun making this, and it's also going in my portfolio for when I apply for internships. If you enjoyed seeing this, consider dropping a comment so it gets more exposure
