The 12-speed project started in early sumer 2008 after the first rumors circulated in the Pro Team that Campagnolo is going to launch a 11 speed groupo.
A bit energized to be always one gear in advanced I started the development of the 12-speed system. The adjustment of the transmission ration of the cable retraction to revolving angle was made by proportional reducing the drum radius of the index ring. Prior calculation figured out to choose a center-2-center dimension of 0.5*1.60mm + 2.00mm + 0.5*1.60mm = 3.60mm. this leads to a total cassette width of 41.2mm. this width requires an integrated lock ring into the 11 teeth sprocket and a further shift of the cluster towards the spokes. On the Ergopower shifter I accoutered three problems :
- where to locate the addition slot on the index ring on the 11-speed system I add to the innermost gear the 11th, and it was impossible to add another one, due to the limited rotation angle in this direction. So I decided to add it on the side of the smallest sprocket. This required significant changes of the plastic housing to allow the additional rotation angle. The space for the additional 12th slot was now identified.
- How to maintain the additional rotation of the index ring The bigger total rotation angle needs to be considered and required two additional changes. The ratchet mechanism of the thumb lever couldn't be engaged because there were no teeth to rotat the index ring further than the original outermost position. I decided to cut out sufcient teeth out of an standard index ring and braze it onto my 12-speed I-ring.
The second major change needed to be done on the ratchet teethed ring operated by the lever behind the brake lever. At least one or better two additional teeth need to be added in order to increase the operational revolving angle. - Campagnolo has no equidistant angle increments between each shifting step. To make it worse is the shifting angle increment biggest between generic 9th and 10th gear (second to outermost and outermost). So this force me to find a solution to live with the non-linearity by making the cable retraction to parallelogram inwards swing ration non-linear too. A old solution is know by changing (shifting) the cable fixing point further to the spokes.
The cassette needed to be change significantly on the aluminum spider. It was required to disassemble the sprockets from the carrier and to machine it to achieve the 2.00mm spacer dimension. The assembly was easy by simply riveting the carrier and sprocket with stainless steel rivets together. An integrated look ring into the 11 teeth sprocket leads to a clean lock and sufficient clearance to the drop outs.
- shimaNo 10-speed c-2-c dimension 3.95mm
- Campy 10-speed 4.20mm
- (my) Campy 11-speed 3.95mm
- The cassette can be made either out of Campy 1.75mm wide sprockets with 2.20mm spacer or with shimNo 1.60mm sprockets and generic 2.35mm spacers. For a cleaner look I prefer to integrate the lock ring into the 11 teeth sprocket.
- (my) shimaNo 11-speed ST-78XX 3.95mm
- Campagnolo 11-speed 3.95mm
- (my) Campy 12-speed 3.60mm requires Campy 11 speed chain
- 11 speed cassettes can be assembled to all Campy/Fulcrum rear wheels and Lightweight wheels with Campy or HG rotors. 12-speed cassettes can only be assembled to Campy/Fulcrum rear wheels with a modified HG rotor .
Keine Kommentare:
Kommentar veröffentlichen