Cycling UK Forum

I've had one of these for years, its been really reliable.
But now theres no juice, a multimeter tells me the coils are open, I get infinite resistance across the (clean) terminals.
Same with the QR tight or loose.
Looks I need to make a tool to get the guts out, I see new guts are available.
Is this a common problem with these, I see on youtube that there are some soldered joints around the axle.
I've been through all weather with this and some floods however the wire gauge seems a bit on the heavy side to rot through.

The wire runs through a slit along the axle. It is likely open circuit there. You can disassemble it and often solder a new wire in. When you do take it apart, make careful note of the alignment and order of the stack of plastic and metal parts that form the contacts to the cable. Note that some earth through the frame, others not. The frame earthing types must be connected the correct way around if you have any earthing in the rest of the circuit.

Open circuit would suggest a break in a wire somewhere. But I did notice someone once had a wiring problem - viewtopic.php?t=95655 - that was resolved by swapping the wires. Might not work here (as it wouldn't measure open circuit) but is worth a try. There was also something about tightness of nuts, which suggests that the body is being used as part of the circuit for that model, which introduces another place where the circuit can break.

Note that to open the shell entirely you probably need the Shimano TL-DH-10 octagonal spanner, which is quite expensive. I once tried using a large adjustable spanner and it only succeeded in marring the flats. You'll need to open the shell to replace the internal assembly, but if you're inspecting the wire (and cleaning cups/replacing bearings on the right hand side) you might not need to open the shell - although it'll certainly be a fiddly operation compared to changing the internal assembly.

It may be possible to loosen off the internal assembly by turning the wheel around so it rotates backwards. Run it like this for a few miles and check the tightness.
viewtopic.php?t=121871

as per the previous reply there now two different versions of most shimano hub generator models, with and without an earth return. the older versions all had an earth return and in these models the connector to the hub is designed so that the RHS of the plug is offset from the wheel centreline by about 8mm or so. The silvery part of the hub connector is ground and is connected to the axle. I presume there is a soldered joint somewhere inside, but since I've never had to mess with it, I don't know more. In more recent designs the connector is more offset, and both wires exit the hub via an axle slot. In both designs any wires that use the slot are soldered to the connector.
Shimano's corporate blind spot appears to trapped volumes. These are no real concern provided temperatures are constant and atmospheric pressure does not change. Unfortunately both things are very likely to happen, and when they do, it doesn't really matter how good the seals are, it is only a matter of time before the hub inhales water via the bearings. Once water is inside the hub it takes a very long time to dry out and in the meantime it typically causes considerable corrosion.

The solution is relatively simple; just excavate a vent groove or two the hubshell. It is best if the grooves are made across the screw threads that the centre screws into. The sides of the vent slots can be rendered hydrophobic by coating them in waxoyl. By the simple expedient of
screwing in the centre whilst the is a piece of cord in the slot, then pulling the cord out, you can be reasonably sure the slot is unobstructed. Because they are hydrophobic rainwater should never enter via the slots, but if there is ever any liquid water in the hubs, it will soon centrifuge out via the slots when the bike is ridden. Once the vent is installed, there should be much less corrosion inside and the bearings should be happier too
FWIW it is not at all difficult to make a wrench for this job. All you need is a ~2" square of 1/8" steel sheet. Correct use of drill, hacksaw and file should leave you with a 32mm octagonal hole, more than capable of exerting the ~200 ftlb torque this part often needs. The wrench is best held in place using a shaped piece of wood, such that it its over the connector. The wood can be held in place using track nuts or QR skewer. The wrench can be held in a bench vice.

I notice that one of the 2 contacts on the outgoing power connector has one that is electrically connected to the QR axle, so one side is grounded.
I'll be able to make more sense of the vent holes when I get it apart.
Ad for that I have a 3/4" drive socket set that probably has a socket the right size, its metric, inch and bsw.
I plan to attack it on Satday.

Most sockets are hexagonal. You need an octaganol tool.

rjb wrote: ↑23 May 2024, 9:51pm Most sockets are hexagonal. You need an octaganol tool.

I successfully unscrewed one still in the wheel using a very large bench vice. Of course I dribbled some easing oil into the threads first.

Why don't they make the fitting the same as some other Shimano part of about the same size, such as a bottom bracket? Or do they want to sell more tools?

Have a look at Bruceys tool in this thread. And the Shimano version.
viewtopic.php?t=138762#p1500296

plancashire wrote: Why don't they make the fitting the same as some other Shimano part of about the same size, such as a bottom bracket? Or do they want to sell more tools?

octagons of 32 mm and 36 mm are commonly used in headsets, so a headset spanner ought to fit. Unfortunately the centre might unscrew with such a spanner on a new hub, but on a used hub removal is usually not possible unless you use a full octagon tool of some kind. More recent shimano designs use a large splined tool instead. Another special tool....

Thanks for the reminder about the octagon, that would have been a swearword or 2 tomoz.
I agree using a open end spanner is just going to chew up the ally housing, I have bi-hex sockets, but they are not going to fit either.
Using a chain grip was another idea but I see the flats on the octagon are sloped so they'll just slide off.
With my drill press and die grinder I guess I could make something from 3.2mm steel plate, it'll take a while to do though.
My cowboy side wants to pull the connector housing off and drill some holes in the octagon and use a pin wrench, but I'm resisting the temptation.

Does anyone know if the 36mm octagon thread is a left or right hand thread.

It is a right-hand thread, turn clockwise to tighten. So was my Shimano T785 dynamo hub, as was an older cheap Sanyo hub that I opened up, built just like the Shimanos, with a threaded cap on the side. I'd say they are all right-hand threaded.

Here is a photo of my Shimano Hub cap, and the tool I made to undo it, just welding eight separate bits of steel.
Edit: you cannot really see in the photo that it is a right-hand thread, but I can confirm it is.

I made an ally tool by bashing an octagon of the right size, and this loosened the cap no problem.
It appears the open circuit was mainy too much silicon cack inside the connecor housing, isulating most of the grounding washer, so only a tiny bit of corrosion stopped conduction.
2 problems however, the bearings are galled, and before using the tool I made I used a headset spanner and ruined the cap, it will go back on but the seal will need to be removed or cut back.
I might try straightening with a socket or something, but I think the hub is probably only going to be good for the summer, better that nowt till I get a replacement.