On a five-year old BWR gear hub, I need to replace the axle key — its threading went soft, so the control rod no longer holds —, and one of the pawl springs that broke.
I'll use the opportunity to replace the ball bearings, but I'm stuck at how to remove the one on the left-hand side. What's the procedure?
Flat blade screwdriver under the bearing clip seal thingy that holds the balls in. Prise it out and the balls and cage just lift out from the left side.
Since i'm at it, I have another, related question. Strangely, Sturmey-Archer says that even the right-hand side bearing race is a HSA284, although the seven balls are wider on the RHS, are loose, and don't seem specific to SA.
Can't comment on that, sorry. Mine is a CS-RF3 The balls are the same left and right according to the diagram. HSA284 6.4mm balls Item 2 same as yours.
Mine is a cassette hub but I've not yet stripped down the cassette carrier to look inside.
A bit of cleaning with a Q-Tip revealed two pieces of metal: I assume they are part of the race that broke. The same thing happened on an Alfine 11 gear hub:
So it appears that the RHS also uses an HSA284 ball bearing race, just like on the LHS, which would explain why I saw loose bearing balls when I pried open the BWR for the first time last year.
… the next question being: How to insert the replacement HSA284 on the RHS?
I tried with a flat screwdriver just like before, but it doesn't come out. Should I try harder?
Dunno from a photo, but at a guess, what I might consider, is coming at from the inside. If you can get the thing upside down and push your screwdriver through, you might make contact with the securing ring thingy and tap it out.
You may have to tap gently all round a bit at a time. It looks like it's a way in, so after a few taps it'll be out far enough to get at from the RH end.
yes, the clipped 1/4" balls are the same in almost every SA hub going back to 1930-something, possibly longer. Some Brucey top tips;
1) Don't damage the labyrinth seal when removing it; you may find that a replacement part is differently toleranced and doesn't fit very well.
2) If the clipped balls break up in the hubs you own, this is a sign that something (loading, lubrication, adjustment or simple mileage) isn't favourable for this bearing type.
3) If you don't like the clipped balls in SA hub bearings, you can replace them with (9 off IIRC) loose balls instead, in most cases. However this does necessitate greater care when reassembling the hub. Obviously you don't have to remove the labyrinth seal if you are fitting loose balls.
FWIW it is not uncommon to see failed clips in IGHs of all types. Some folk seem to be able to do mega miles with no problems, others seem to destroy them fairly quickly. It might be the way the bearings are adjusted; I wondered about preload (and it still might be that), but the traditional SA specification appears to be to run the hub fractionally loose.
I've replaced the clipped balls with loose in many SA and shimano hubs. However in many shimano hubs, unless something is added to the assembly (eg a plastic washer) it is possible/easy for a ball to drop inside the workings as the hub is assembled, which is probably going to be fatal.
Since I have a couple of spare ones, I don't mind putting a new HSA284 ball cage instead of loose bearing balls, but… how to insert the new one in there?
From the outside, first removing that piece I assume is the labyrinth seal and is sitting in the way?
the seal just pries out using a screwdriver. However the seal may be damaged by so doing. In you situation I'd break up/remove the remains of the old clip and use loose balls for sure.
Not the same as your hub quite (and what's in a name? Brampton, Brompton, it is all made by SA) but the same bearing parts;
as I mentioned above, not all HSA102 are made exactly the same way; often you will find one that is an impossibly loose or impossibly tight fit in the hub.
Note also that the wear life of a x9 loose ball setup is a lot better than a clipped ball setup.
For other newbies' benefit: Since the cap is likely to be very tight, the solution is to push it out by applying the screwdriver's end from the other side and hit its head with a mallet.
Still, I'll follow your advice and stick to loose balls. It could only work better now that I removed the remains of the semi-broken bearing cage
the dust seal will either move or be wrecked, possibly both. You obviously need to support (elevate) the part else the dust seal has nowhere to go, either. Also note that method doesn't work on every installation; you would need a cranked drift in many cases.
IIRC the tool least likely to cause damage is often a metal tyre lever, used as a prybar.
FWIW whenever you are inside a NIG type hub, it is advisable to check the fit/integrity of the actuator plate. If it is cracked and/or too loose it ought to be attended to. In a hub that had mashed its bearings I'd probably just replace it anyway.
Those metal labirynth-seals, are best removed with a suitable diameter of metal wall plug. by doing so, you exert a uniform pressure and the seal will come off without any distortion. Also, better thn a screwdriver is an old allen-key (6 and 8mm are good for this) that has been cut about 45º where it bends. For holding the hub, just get a thick piece of timber and make a series of holes with your hole-saws; usually 30, 35, 40mm are enough.
It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are...
Regarding pawl springs and toggle keys/control rods:
If the thread between the toggle key and the control rod fails, it is usually best to replace both parts. The reason for this is that even with new parts, the difference between the OD of the control rod and the ID of the key thread is very small. If you do decide to re-use one of the parts, it is best to check the dimensions carefully, comparing them with new parts.
If you want to slow wear down between the two parts, it is possible to wind a little PTFE tape round the control rod thread, such that it becomes a more snug fit in the toggle key (NB this won't 'repair' a worn part but it will slow wear in parts that are still good). Once thus assembled, the thread won't fret and wear so quickly in use. There is no shift control spring in this style of SA hub; this means that downshifting under load is the thing that is most likely to directly overload the connection.
Pawl springs (or 'R' springs, HSA120) are used on both low and high gear drive pawls in old AWs but are only used on high gear drive pawls in more recent hubs like the BWR. Spontaneous breakage is rare; it is most commonly the case that the spring wears on the sides (from rubbing) and then breaks. Various things to do with how the hub is set up can increase the rubbing on the side of the spring, including how the spring is set; small differences to the exact shape of the spring can cause or reduce side rubbing, because the spring is twisted out of shape when it is loaded. It is also possible for springs to get broken if there is debris inside the hub, or the high gear drive pawls are pushed sideways (axially) when under load.
So if an R spring is broken, it is best to check the other parts carefully; often you will find that the high gear drive pawls are imperfect in some way, and ought to be either replaced or the ends reground. If you regrind the pawl tips, it is imperative that that the pawls are kept the same length as one another.
