Does the Alfine 11 di2 motor have oil in?

[Cavemud]

I recently built a bike up with alfine 11 hub running on di2 with a gates belt drive. It's absolutely brilliant with only the very occasional clunk (say once every five miles if I put the power on too soon after a gear change).

Anyway, I'm now in the process of building another for the wife. When I had the wheel in the wheel jig, I stupidly put the non turn washers on the wrong way around. I realised this evening when I tried to put it in the frame.

One of the washers had jammed on, so I fiddled for a few minutes to no avail.

Eventually I picked up a claw hammer and gave it a little lever, but I was levering against the plastic motow body and there was a little cracking noise.

A few seconds later I noticed a little oil smeared on the face of the motor body

I've taken the motor body off and can't see any obvious damage.

Does the motor body have oil in it? If not it could only have come from the hub then?

The motor body itself is quite flexible and I was only pushing gently, so it's hard to beleive I damaged any of the steel parts behind.

[Brucey]

never had one in bits but I would be very surprised if the servo motor unit was intended to have oil in it. However oil leaks from the RH end of alfine hubs are not uncommon, so that seems reasonably likely to be the source (Knackers belt drives, obviously).

Needless to say using a claw hammer as a prybar against the servo motor casing is not a terribly good idea.

cheers

[Brucey]

OK I've just taken MU-8S40 (shift servo as used on Di2 'cyber nexus' SG-8C56 and SG-8R45 models) apart. Inside it is meant to be bone dry but even on this unit (which had not gone far enough to wear the sprocket before the system failed somehow..... ) there were signs that the chain lube had started to penetrate the servo.

This isn't identical to an alfine Di2 unit (not least because it turns in the other direction) but it is likely to be similarly constructed. I can post some more photos if you like.

Inside the unit there is a small DC motor with a worm gear, driving a reduction gear train comprising mostly of plastic spur gears, with a potentiometer that is used as a 'resolver'. The rear of the servo unit has a steel cover plate held onto the main plastic housing using 8 off #0 phillips self tapping screws.



The yellow thing is a lip seal that is intended to prevent chain lube and dirt from getting into the unit. However if lube leaks out of the hub itself past the bearing seals, it will bypass this seal.

Once the servo is removed, the hub itself differs in the following ways (at least) from one with a conventional cassette joint

a) the locknuts are different
b) the interface to drive the shift mechanism inside the hub is different
c) there is no return spring on the shift mechanism
d) presumably there is a shift control spring to work when the shift proceeds in both directions (rather than just one as per a normal hub)

The plastic servo housing is trapped between locknuts on the hub. If the servo housing sees a lot of force, the plastic parts would likely break.

The alfine 11 servo unit MU-S705 looks like this at the rear (seal removed)



Not sure it comes apart the same way; can't see an obvious array of screws.

cheers

[Brucey]

some photos;

Cyber-Nexus (sounds like something out of Dr Who...)

Note that the static part of the servobox restraint is the same as non-cybernexus hubs (so half a CJ would fit to this part) but moving part of the gear selector engages differently. The hub did so few miles before it stopped working that the sprocket was hardly worn.

servo has seal and removable rear panel

the innards of the servo

There are five wires used from the six in the connector. The terminals are potted on the back of the connector, presumably because water may pool inside the servobox at this point. There doesn't appear to be a drain hole per se, BTW.

The resolving potentiometer is geared to the quadrant gear that drives the hub's shift mechanism. With the quadrant gear in the position shown (which is low gear I think) the resolver has a timing mark that faces exactly downwards. The quadrant gear has a PTFE facing on both sides so that it moves smoothly. This bears against a painted steel part on one side and the unit had moved infrequently enough (in its woefully short service life) that the PTFE coating was undamaged and the paint on the painted steel part was also unmarked.

The rubber gasket had swollen slightly; I assume that this is because the chain lube reacts with the rubber in the gasket. You can buy a new yellow seal for this MU (shown on the MU EV techdoc , not the hub techdoc) but that is the only spare part shown.

It is quite possible that both the hub and the MU shown are in serviceable condition. However the LBS took the view that playing 'spare parts bingo' until they had a working system again was a daft thing to do when they could whack in a clockwork hub and shifter, and make the bike work again, in a fraction of the time and cost. They donated the scrapped parts to me knowing that if I came up with any useful info about these parts, I'd let them know. Plenty of folk must have come to a similar conclusion regarding scapping or fixing these because the last time I looked the Di2 hubs were selling for less on ebay than the clockwork ones.

I may try a scheme whereby I convert the Di2 hub to clockwork shifting, possible with an external return spring for the shift mechanism.

cheers

[Bsteel]

Brucey, thanks for the write up and photos, I've been curious about this unit for while.

There are five wires used from the six in the connector.cheers

Is the two wire can-bus system that is used on the derailleur systems still used for the rest of the system interconnections ?

[Brucey]

Brucey, thanks for the write up and photos, I've been curious about this unit for while.

There are five wires used from the six in the connector.cheers

Is the two wire can-bus system that is used on the derailleur systems still used for the rest of the system interconnections ?

I don't know; this diagram suggests not

but then again there could be a canbus chip buried in the potting inside MU-8S40. I guess I should have done a continuity check on the wiring whilst I had it in bits.

However the Alfine DI2 system doesn't look quite the same layout, so could more likely be a canbus system. I'd say that the mechanical parts may be very similar inside the servo units in any event.

cheers

[Suffolker]

For some time, I've wondered why these hubs seem to be priced well below the mechanical counterparts.

That being so, I've also thought it would be handy if the electronic versions could be made to work in "manual".

I'll be very interested to see what Brucey comes up with.

[Bsteel]

However the Alfine DI2 system doesn't look quite the same layout, so could more likely be a canbus system. I'd say that the mechanical parts may be very similar inside the servo units in any event.

I think those assumptions are likely correct, I hadn't appreciated the age of the 'Cyber Nexus'.