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Notsure if anyone else has tried this but the standard Ultegra 6770 Di2 rear mech can be controlled by the new Alfine SW-S705 flat bar shifter, and having just bought a One Up 42 tooth cassette ring i started plans to mod the rear mech to cope with a 11-42 cassette.
heres some pics of the finished build, it looks a bit tight on the 42 tooth ring but its set up as OneUp recommend and shifts fine.
the Cassette is a 10 speed XT 11-36 with the 15 &17 tooth sprockets removed and replaced with a Dura Ace 16 tooth sprocket, and the OneUp Components 42 tooth sprocket.
With a Hope 34 tooth chainring up front and Dura Ace chain.
the Alfine SW-S705 shifter has had its clamp machined off and the remaining stub machined to replicate the shape of a Sram matchmaker to fit the R1 brake lever. The shifter wire is then plugged into what is normally the output end of the SM-EW67 control unit which means i can still trim or reset the rear mech, with one of the wires that normally would connect to the shifter cropped and the other extended and routed inside the frame to an internal junction where the battery and rear mech wires connect up. With a direct external battery mount bolted to a custom bracket secured to the down tube bottle bosses so it lays flat on the tube.
The rear mech took a few goes to sort out a good shape, but i ended up with something close to the Sram XX1 or K-edge cage with an offset top pulley, and an MTB mid cage length. So the same cage length as the new Ultegra Di2 GS mech. I've used a modified Ultegra long cage rear plate and Ultegra 11 tooth pulleys, i'm going to try a 13 tooth upper pulley to see if i get a better chain wrap on the smaller cassette sprockets.
The outer cage plate is 3mm thick laser cut aluminium hard black anodised with a brass threaded insert and aluminium spacers for the correct pulley offsets, this is to match up with a standard Ultegra cage so there is no setup problems with shift alignment. This was an easier option than machining the whole cage from 5mm aluminium plate. The P spring is increased in tension and B spring plate is modified as well to increase the spring tension and force the mech to pull in closer on the small sprockets.
having tried a few rough cage plates to sort out the best tension and pulley positions, it was pretty much a case of bolt the whole mech together, fit it to the frame and the indexing was spot on, and just needed the limit screws setting.
One thing is, you must use the PC link and E-tube to update the firmware or the whole lot is dead and won't work, even then it pings up a shifter error in red on the road bike connection check, but it still lets you alter the shifts available and select muti-shift. (Alfine is 8 or 11 speed only)
Next stage is to make the rear mech Shadow+ by fitting a clutch in it, so i can get away without running a front chain device, i've got a trashed Di2 mech of ebay, and have got hold of a needle roller clutch the right size to suit the Shimano rear mech, and i think i've found a clamp that will give me the an adjustable degree of slip to alter the tension for the clutch.
its been foggy all weekend so the photos aren't too hot, but i will get some better ones taken soon, and i got a few spare mech cage plates made if there's any interest.
So to reverse engineer it, and fit it into a Di2 or road P knuckle is a bit tricky but not impossible. The hardest bit has been trying to find a clamp mechanism to replicate the steel band of the shadow +. The answer to this was simple in the end, a spring hose clamp, this locks onto the outside of the needle roller clutch, with the advantage that the 2 ears of the clamp can be loaded up by a locking screw.
i've tried it in the wrecked mech i got of ebay and it seems to work just waiting for a new rear mech to turn up so that i can modify it. I'm thinking i will just swap the P knuckle over with the one of the wrecked mech so i can put it back to normal if it doesn't work.
Just for info 'Rose Bikes in Germany are selling off Ultegra 6770 Di2 mechs and shifters at half price' and have been for a while.
the piece around the outside of the roller clutch is the band spring which is compressed by the cam to load it up.
My version of the same thing, in pieces, Custom cage, standard shimano P pivot pin, its hardened and ground where the roller clutch fits so it seemed easier to buy the part than attempt to replicate it. Needle roller clutch, spring clamp, and a new bearing piece for the P knuckle as this is fixed on the clutch mechs rather than be part of the cage as on a standard road mech.
Now to fit all these bits into the P knuckle.
Also the original Scott derailleur hangers aren't the strongest and are a bit prone to bending when slightly overloaded, so after a couple of rides you may find your gears start to play up, so check the mech hanger is still straight.
I had one bend half way through a muddy 24 hour race, luckily i had a spare.
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