Thirty Years with a Sturmey Gear.

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Brucey
Posts: 37471
Joined: 4 Jan 2012, 6:25pm

Re: Thirty Years with a Sturmey Gear.

Postby Brucey » 19 Nov 2019, 9:26pm

update; A couple of years ago my ancient, cobbled together SA five speed hub finally developed a major fault. It had been used and abused for several decades/many tens of thousands of miles and had only received new ball bearings and R springs in that time. It was basically a 1964 FW with a (longer) FG axle in it, and a conversion to something close to S5-1 specification (as described upthread), all stuffed into a 36h 3s shell with the correct relief in it for the 5s internal. I think the FG axle came from a 1950s hub. Anyway the axle eventually broke near the axle slot, and I think it broke because the slot had sharp edges which were good stress-raisers. When the axle broke it wasn't dramatic; the back wheel went all floppy, I had no problems stopping and it was clear that I couldn't carry on riding the bike. I had to push it home, which fortunately wasn't too far.

So I threw together a mess of other parts I had knocking around which included an S5-2 planet cage, an S5-1 axle (which I modified to have less sharp edges) and carried on. I took the opportunity to fit a modified sun gear assy which was intended to reduce the parasitic drag. For a couple of years normal service has been resumed.

Until yesterday.

A long time ago someone older and wiser than me mentioned the possibility that, with a SA 5s hub of that vintage, it was possible to get a fault which would cause the bike to be unrideable, indeed the wheel to be impossible to turn without either great difficulty and/or great risk of further damage. However they weren't able to tell me exactly what happened to cause this, and I couldn't imagine what it might be either. Now I know different and furthermore the phrase 'coming to a grinding halt' now has a deeper meaning to me.

I was tapping along in the middle gear, enjoying the sunshine and suddenly there was a terrible sound from the back wheel and it was clear that something dreadful was happening. It felt for all the world like it does on a derailleur geared bike when the chain has derailed itself into the spokes; kind of jerky, incredibly noisy and somewhat alarming. A few curse words, use of the brakes and I had managed to come to a halt, during which time the rear wheel had turned about four or five turns more, with accompanying ghastly sounds.

It soon became clear that the wheel wouldn't even turn without more commotion/damage; something very profoundly bad had happened deep within the hub. So not only was I walking, I was also carrying the bike. I had some tools with me and I briefly considered setting to with them, but I wasn't optimistic that I'd be doing any good.

more to follow....
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

ElCani
Posts: 218
Joined: 5 Mar 2015, 11:24am

Re: Thirty Years with a Sturmey Gear.

Postby ElCani » 19 Nov 2019, 10:18pm

Di2 motor unit failed? :D

mig
Posts: 2165
Joined: 19 Oct 2011, 9:39pm

Re: Thirty Years with a Sturmey Gear.

Postby mig » 19 Nov 2019, 10:43pm

Oh no ! Any original receipts.? :wink:

Brucey
Posts: 37471
Joined: 4 Jan 2012, 6:25pm

Re: Thirty Years with a Sturmey Gear.

Postby Brucey » 19 Nov 2019, 10:52pm

where was I...?...

Oh yes, carrying my bike home. Fortunately it was only a few miles and I had plenty of time to mull things over. I had no idea what had happened, but it must have been pretty bad. Unfortunately I don't have an identical rear wheel amongst my stash of spares, not quite. I could rustle up a 3s internal easily enough and even another 5s internal was likely but I was concerned that the hubshell itself might not be useable, such was the commotion that had gone on inside the hub; there could easily be something major broken. I thought of all the times I'd been tens or hundreds of miles from home and felt grateful that it hadn't happened then. I don't ride so much in remote lanes at night any more but only about ten days earlier I had ridden forty miles or so in the dark and had it happened then, I'd have had a very long walk indeed. I guess reliability is something you take for granted until you don't have it any more. I was fairly baffled as to what might have happened; this internal had done a couple of years, whereas the previous one had done about 35 years with me plus none of it was brand new when I put it together and started to use it.... what was the difference?

Eventually I trudged up my driveway, both sides sore from swapping the bike to the other shoulder every few hundred yards. About 28lbs isn't much at first but it soon gets to you when you are carrying it. I thought about swapping another wheel in, but I was both curious to see what had happened inside the hub as well as keen to knock the job on the head ASAP if I could.

Anyway, I was successful and the bike was back working again about an hour and half later.

However the job was made difficult by the fact that it was very difficult to unscrew the ball-ring. Normally this is easy if gears are still turning; the ball ring drives the ring gear backwards and this either spins the axle or turns the internal wholesale depending on which is easier. However if the gears won't turn and/or the planet cage is jammed against the hubshell, it may be nigh-on impossible to unscrew the ball ring. The saving grace is that if you select gear 1, the high gear pawls are retracted and then the ball ring will usually unscrew.

The fact that the internal wouldn't come out of the hubshell without some persuasion from a hammer I regarded as somewhat ominous. I soon started to find pieces of mangled metal, and it became clear what had happened; one of the low gear pawl pins had escaped (rightwards, the swaging having been ineffective) and had gone into the planet gears. The loose pawl had slid round the slot in which the low gear pawls sit, and had intermittently jammed (wedged) against the other pawl, thus locking the planet cage to the hubshell. This would have been alright by itself but the remains of the pawl pin were intermittently jamming the planet gears. Not good.


The low gear pawl pins are different in the FW/S5/S5-2 hubs; similar but slightly different from one another and completely different from everything else. FW uses pawl pin part K707, S5-1 uses HSA133, and by S5-2 they had declined to sell these parts separately and you could only buy a subassembly including these parts. These pins are about 4mm shank and have an enlarged head so they won't pull through the planet cage leftwards. The pin is riveted (swaged) at the other end so that it won't pull through the planet cage rightwards, so the pawl and the pawl pin are more or less permanently fixed to the planet cage. You can (with some difficulty) change the 'R' spring without disassembly, so barring 'unfortunate events' these parts are in for good more or less.

All the FW assemblies I have seen have been completely trouble-free in this area; I had supposed that (like the joining links in some camchains) the pin was hard everywhere except at the end where it was to be swaged. These low gear pawls can see higher loads than the high gear drive pawls and the high gear drive pawls pivot on hardened pins. Also when in the middle gear or the higher gears, the low gear pawls are overrun so these parts are always on the move, even if the loads are not very high when the low gear (s) is/are not being used.

S5 and S5-2 planet cages are not quite identical but the same kind of assembly is used, and the parts look very similar. The only clue I had that this might be an issue is that I have seen a couple of 'retired' S5-2 planet cages in other people's bits boxes, without one of the pawl pins fitted, reasons unknown.

However recent events have revealed to me that these parts may look the same but they are most certainly not the same. The pawls pins in (I think) some S5-2 hubs are soft all over. Its not clear to me if the HSA 133 part from S5-1 hubs is more like the FW or more like the S5-2 part.

Anyway this means two main things; one good and one bad.

The good is that the pawl pin is soft enough that it is liable to lose ( get chewed up) in a fight with the planet gears and is less likely to cause serious damage to them.
The bad is that it doesn't seem to matter how heavily swaged the left end of the pin is, the material just may not be strong enough to withstand the service loads and it is only a matter of time till the pin escapes and causes the hub to blow up spectacularly.

I have taken some photos of the failed parts and I shall post them before too much longer. I remember checking that the low gear pawl pins were not just about to come loose or escape from the planet cage when I built that internal up; it would be daft not to, so I know that the pawl pin was secure two years ago.

Amazingly the planet gears, sun pinions and ring gear escaped serious damage despite munching on the loose pawl pin.

I can't find K707 for sale anywhere, and so far I have only found HSA133 listed by a bike shop in the USA; not exactly handy. I may make my own parts if I can't source any; the world is no longer brimming over with FW hubs that I can rob for spares.

photos to follow.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Brucey
Posts: 37471
Joined: 4 Jan 2012, 6:25pm

Re: Thirty Years with a Sturmey Gear.

Postby Brucey » 19 Nov 2019, 11:42pm

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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Brucey
Posts: 37471
Joined: 4 Jan 2012, 6:25pm

Re: Thirty Years with a Sturmey Gear.

Postby Brucey » 20 Nov 2019, 8:49am

photos of the culprit are below;

Image01507.jpg


The left end of the holes in the planet cage have no counterbore and the swaged part of the pin barely protrude beyond the planet cage. This means that there is barely anything retaining the pawl pin. If the pawl pin manages to drift rightwards inside the hub, the head end starts to interfere with the neighbouring planet gear. The planet cage above has one intact pawl and one empty hole where the other pawl pin should be.

Image01509.jpg


The failed pawl pin. You can see how soft it is by the fact that when it has gone into the planet gears it has plastically deformed. Also evident are wear marks from various adjacent parts; even the R-spring has marked the pin up. [c.f. You basically never see wear marks on the (hard) pawl pins in non-NIG AW hubs, or the high gear pawl pins in FWs/FGs. S5 models etc even if they have done intergalactic mileages.] The left end of this pawl pin has simply plastically deformed under the service loads, hence the smaller diameter. The pin also lengthened slightly

Image01510.jpg


Another view of the left end of the pawl pin where it has plastically deformed in service.

With a ~2.25 input ratio on a 27" wheel and a reasonably strong rider, I estimate that each low gear pawl pin sees about 300lbs force when starting off or climbing with the saddle unweighted.

IIRC the planet cage above (which I used for a couple of years) came from an S5-1 but that I fitted a single pawl pin from an S5-2 to it. Hence the remaining pawl pin is still both intact and snug.

The planet cage I refitted was the FW one which has done many, many tens of thousands of miles. The pawl pins were still snug.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

scottg
Posts: 717
Joined: 10 Jan 2008, 8:44pm
Location: Highland Heights Kentucky,, USA

Re: Thirty Years with a Sturmey Gear.

Postby scottg » 20 Nov 2019, 6:53pm

mig wrote:Oh no ! Any original receipts.? :wink:


Obviously not fit for purpose, postwar rubbish only lasts 30 years,
now a Golden Sunbeam would be ready for another 100 years.
Harummphh. :)
+++++++++++++++++++++++++++++++++++++
Why not the best, buy Cyclo-Benelux.

cycle tramp
Posts: 639
Joined: 5 Aug 2009, 7:22pm

Re: Thirty Years with a Sturmey Gear.

Postby cycle tramp » 20 Nov 2019, 10:43pm

I am sorry to read of the failure of your hub. As I wrote way back in 2012, I was envious of both your mileage on this bicycle and your construction and ownership of this bicycle.
It still remains one of most favourite bicycles on this forum, (such purity of form and function, as well as a clever marriage of differing eras and disciplines) I look forward to seeing its next reincarnation :-)

Brucey
Posts: 37471
Joined: 4 Jan 2012, 6:25pm

Re: Thirty Years with a Sturmey Gear.

Postby Brucey » 20 Nov 2019, 11:17pm

it is back in action; I fixed the hub within a couple of hours of reaching home (*), and was riding the bike again later on the same day.

(*) I was a bit tuckered out having carried the bike, so I didn't set to immediately; the repair was a bit quicker than that.

The thing is, I am anxious to find out what the difference is in the pawl pin parts that are soft and those which are not; the S5-based internal which lasted two years looked much the same as the previous one (modified FW that lasted thirty-odd years of hard use) when I installed it.

It also failed in a catastrophic fashion without any warning; this is a very bad combination. I was maybe doing 15mph when it broke but I could have been rattling down a hill at three times the speed and I shudder to think what would have happened; the planet cage jammed against the hubshell (so it carried on turning with the wheel) but the planet gears didn't want to turn any more because there was a loose pawl pin in the workings; no wonder there was a terrible sound. Additionally I was in second gear at the time which meant that the hubshell was being driven by two things (the planet cage which had jammed , and the ring gear as normal) which will result in incredibly high stresses in the geartrain.

I am hoping to

a) find out the date range of the parts that are not fit for hard service and/or
b) devise a test which allows anyone to identify what parts they have fitted.

I am thinking of a scratch hardness test for the pins, but I need examples of both good and bad parts to go at, and more to the point I need to know the exact date of manufacture of these parts too (I have already had kind souls offering parts to me).

I find it utterly baffling that they made the FW for decades and made it practically bombproof in this area, then managed to comprehensively mess things up when trying to make similar parts later on.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Greystoke
Posts: 238
Joined: 8 May 2018, 7:41am
Location: Lincolnshire

Re: Thirty Years with a Sturmey Gear.

Postby Greystoke » 21 Nov 2019, 6:27am

I suspect the bean counters got involved

Brucey
Posts: 37471
Joined: 4 Jan 2012, 6:25pm

Re: Thirty Years with a Sturmey Gear.

Postby Brucey » 21 Nov 2019, 9:19am

Greystoke wrote:I suspect the bean counters got involved


could be. Some kind of sub-species of the genus 'Idioti' at any rate.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Brucey
Posts: 37471
Joined: 4 Jan 2012, 6:25pm

Re: Thirty Years with a Sturmey Gear.

Postby Brucey » 21 Nov 2019, 9:29am

Image

Nay! (or do I mean neigh...?) despite riding one for years I have not yet turned into a quadruped.

this shows an FW hub in cross section; no room inside for loose pawl pins!

Image

The FW hub ain't perfect; common causes of trouble are that the control rod is vulnerable to breakage and that the main clutch spring doesn't always manage to overcome cable friction and thus seat the clutch in gear 4 properly. Both problems are mitigated by conversion to 5s.

This shows the pawl pin K707 (or HSA133 on later S5 hubs) being fitted

Image

Once fitted, the thin end of the pin is swaged (flared) in situ so that it won't come out.

This shows how much overlap there is (not much) between the head of the pawl pin and the nearest planet gear

Image01515.jpg


and this shows how the pawl pin can escape (rightwards in the hub) once the swaging is lost and head is gone (worn away by the planet gear?)

Image01516.jpg


seconds after it get to this point, you ain't going nowhere...


cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Brucey
Posts: 37471
Joined: 4 Jan 2012, 6:25pm

Re: Thirty Years with a Sturmey Gear.

Postby Brucey » 21 Nov 2019, 11:20am

this photo shows an FW (or very early S5 perhaps) internal.

Image

one of the things that you can see is that the planet cage has much thicker ribs than the later S5 part (see previous post). One of my concerns is that the S5 part may be susceptible to failure by fatigue at high mileages; it is almost certainly much more highly stressed, and has lots of nasty sharp edges which can easily start fatigue cracks.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

cycle tramp
Posts: 639
Joined: 5 Aug 2009, 7:22pm

Re: Thirty Years with a Sturmey Gear.

Postby cycle tramp » 22 Nov 2019, 11:11pm

Brucey wrote:it is back in action; I fixed the hub within a couple of hours of reaching home (*), and was riding the bike again later on the same day.

It also failed in a catastrophic fashion without any warning; this is a very bad combination. I was maybe doing 15mph when it broke but I could have been rattling down a hill at three times the speed and I shudder to think what would have happened

I find it utterly baffling that they made the FW for decades and made it practically bombproof in this area, then managed to comprehensively mess things up when trying to make similar parts later on.

cheers



I'm glad to hear the news that the bike is back in action, and that you are unharmed - I've never heard of a hub failing in such a way, and had always imagined no matter how bad the damage that coasting to a controlled halt was always an option. Do you think we expect too much of our bikes - to cope with such mileage? With the the best of intentions we put them together and pedal them to mileage beyond perhaps they were intended by the manufacturer's expectations? Is the best way to guard against any catastrophic failure to take the air industries approach and view every part of the bicycle as parts which should be replaced once a specific mileage is reached?

Brucey
Posts: 37471
Joined: 4 Jan 2012, 6:25pm

Re: Thirty Years with a Sturmey Gear.

Postby Brucey » 22 Nov 2019, 11:27pm

the pawl pin part that failed was probably one of the lowest mileage parts on the bike. It failed because it was badly made, nothing much to do with how many miles it had done (only a few thousand).

Going on past evidence I would have perhaps bothered to inspect the hub internals after ten years or so, and would expect to have found nothing untoward when I did so.

I don't think that QA on bike parts is as good as it could be. However to apply aircraft industry type QA to all bike parts would almost certainly cost too much.

I guess that this incident was about the same as the rear mech going into the spokes on a derailleur geared bike...?

cheers
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