Sturmey Archer 5-speed ( sprinter, etc. )

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Brucey
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Re: S.A. 5speed

Postby Brucey » 12 Jul 2014, 8:08pm

sorry, he is just parroting what it says in the SA manual, (albeit with an added 'be sure it goes in before you pedal hard'). Which is, for want of a better word, 'wrong'. What he says to do works OK on a three speed ( and therefore 2-3-4 shifts on 5s) but it isn't really necessary even in those hubs. However that procedure in no way ensures that the gear will go in properly when you are doing sun swapping shifts (i.e. between 1 and 2 as well as 4 and 5, in either direction) on a 5s.

If you do it like that you will be very likely to break your hub. I cannot stress this enough but No Amount of backpedalling or freewheeling will ensure that these shifts go in; they will only go in when you are pedalling forwards, so that is what you have to do before you pedal hard, hence my recommendation. Freewheeling or backpedalling really don't achieve anything other than making sure that you are not pedalling hard when trying to shift; other than that they just slow the shift down, which is really bad news when you are on a steep hill and going 2-1. Pedalling forwards without force is necessary not optional on the sun swapping shifts.

I have dismantled several sprinter internals that came out of bromptons and (despite the fact that they see about half the torque of the same hub when fitted to a large-wheeled bike) they were absolutely jiggered. The commonest faults were worn high gear clutches (from bad 4th gear adjustment and/or shift cable drag -the folding really doesn't help here- ) and worn sun locking (from believing the SA manual shift instructions).

I have a sprinter in a 26" wheel that has now done over 15000 miles (estimated; I've done about half of them) and I nearly broke it myself before I figured out that the SA instructions were a crock. Now, with the correct lubrication, adjustment and shift technique, it is a very slick shifting hub. However, use the wrong technique and you still might break it.


[edit; it is more obvious what is going on here when you use one of these hubs in a large wheeled bike; the hub is turning more slowly under more torque and this means the shifts are slower and any problems are liable to be magnified. Everything happens much faster on a small wheeler, but there is still much potential for hub damage on some shifts.]

cheers
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Sweep
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Re: S.A. 5speed

Postby Sweep » 13 Jul 2014, 12:23pm

Hi Brucey

Thanks for the reply - hell this is complicated isn't it?

Just to clarify something.

I have rechecked your initial advice with regard to the 1-2 and 4-5 shift.

If I say try to compromise between the two bits of advice would that be OK?

HE of Bicycle workshop says pedal back a bit for all changes, then forwards.

In those two changes you say to keep pedalling (I stress KEEP - I think you mean with no pause) under light load.

Is the back pedal doing any harm as such?

If not by doing it aren't I just delaying slightly the forward pedal under light load and therefore not doing anything really different harmful?

I take back my comment up thread - this is clearly as complicated as space ship.

** I am by the way trying to simplify any difference between shifts as the position on my Brommie of the shift lever makes it hard to see which gear I am in - though this could no doubt be sorted with some DIY labelling.
Sweep

Brucey
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Re: S.A. 5speed

Postby Brucey » 13 Jul 2014, 1:47pm

you are quite right in that the 1-2 and 4-5 shifts will only definitely go in under forward pedalling, no real load.

Any freewheeling/backpedalling is still (if you know what you are doing) basically pointless; it won't do a great deal of harm but;

1) the whole gear change will be slower; bad news on a 2-1 shift on a steep hill, you are more likely to conk out or make the gears crunch by pedalling hard too soon.

2) because these shifts usually won't go in when freewheeling, when you move the lever (on a downshift) and the gear doesn't go in, you are loading up a shift control spring somewhere in the hub.

In the ball-locking sprinter the 2-1 shift control spring is a small one that is buried inside the axle. It isn't a very good quality spring, it cannot be replaced, and commonly (on well-used hubs) it has been compressed somewhat. The absolute worst thing you can do is try to select gear 1 when stationary or when freewheeling/backpedalling (especially from gear 3 or higher); this will compress the shift control spring until it is coilbound and if this is done regularly the spring will deform permanently. If this gets bad enough, the gear will slip in gear 1 and nothing (nothing any LBS will do, short of a new axle) will cure it.

I have yet to see one of these springs actually break; what I have experimented with is (using small screwdrivers through the ball holes and animal cunning) spreading the coils out again somewhat, and I have turned a hub that wouldn't work into one that would. But this is not a good way of spending your time if it can be avoided.

In a normal pedal-forwards-no-load 2-1 shift the shift control spring is compressed a little (maybe 3mm) as soon as you start to move the lever; you will feel the resistance in the gear lever and then you will feel the gear go in (with the feet and the hand on the gear lever) and the resistance should change; then you can move the lever all the way to the correct position and then pedal hard. You will be pretty sure that the gear has gone in fully because if the shift starts to go in under (say) half the load it will almost certainly be completed once the lever is moved to the correct position because this applies an increasing spring load to the shift mechanism, which you will feel if the shift baulks in any way instead of completing. [BTW If the shift is hesitant to complete in any way this is a sure-fire sign that there is something wrong in the ball-locking mechanism; e.g. insufficient lube, swarf in the control rod/spring, and/or burrs on the control rod ends where they push the balls out.]

By contrast if you move the shifter fully (2-1) when freewheeling or backpedalling the shift control spring is immediately compressed by 7mm. If you change from gear 3 or higher I think it can be more than that. When the shift starts to go in you will feel it with the feet perhaps but you won't be so sure that it has gone in fully; all you know is that the shift started to go in under full spring load, which is not at all the same thing as it being successfully completed under the reduced load seen as the spring extends. You have no possibility of feeling the changing spring force through your finger on the lever once the index position is reached. If the gear has half-way gone in and it then slips when you pedal hard, this invariably causes some further wear/damage to the sun locking mechanism.

It is quite instructive to change gear with the bike on the workstand, pedalling slowly (if necessary set a brake to drag slightly so that there is some load in the transmission). You will soon get a feel for what causes shifts to go in and what doesn't, all without great risk of damage to the hub.

Things are different in the dog locking sprinter and the current (W) hubs but much of the same logic prevails; the 2-1 and the 4-5 shifts won't go in unless you are pedalling forwards, and clumsy technique risks damage.

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

fatboy
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Re: S.A. 5speed

Postby fatboy » 13 Jul 2014, 5:15pm

Shifting from 1 to 2 and doing the light pedalling is a challenge without grinding to a halt I find. 4 to 5 and back again is a lot easier as is 1 to 2. I have only once found the lever to be stiff on this change and when I felt this I went very easy on it all.

I may be deluding myself here but on a Brompton the basic gearing is such that I reckon I need less pedal turns than I would need on a proper bike.

I also agree that it is hard to see the numbers on the brompton shifter.
"Marriage is a wonderful invention; but then again so is the bicycle puncture repair kit." - Billy Connolly

Brucey
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Re: S.A. 5speed

Postby Brucey » 13 Jul 2014, 5:48pm

fatboy wrote:Shifting from 1 to 2 and doing the light pedalling is a challenge without grinding to a halt I find. 4 to 5 and back again is a lot easier as is 1 to 2. I have only once found the lever to be stiff on this change and when I felt this I went very easy on it all.
interesting... I can't help but wonder if you hub needs a shot of lube or something if that 1-2 shift is as baulky as that.

I may be deluding myself here but on a Brompton the basic gearing is such that I reckon I need less pedal turns than I would need on a proper bike.
, no I think you are right; the hub is turning faster (because the wheel is smaller) and everything happens more quickly.

I also agree that it is hard to see the numbers on the brompton shifter.
they also wear off, don' t they? But then with just five gears I'm rarely in doubt about which gear I'm in anyway.

cheers
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fatboy
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Re: S.A. 5speed

Postby fatboy » 13 Jul 2014, 6:33pm

Brucey wrote:
fatboy wrote:Shifting from 1 to 2 and doing the light pedalling is a challenge without grinding to a halt I find. 4 to 5 and back again is a lot easier as is 1 to 2. I have only once found the lever to be stiff on this change and when I felt this I went very easy on it all.
interesting... I can't help but wonder if you hub needs a shot of lube or something if that 1-2 shift is as baulky as that.

cheers


Of course I meant 2 to 1. The reason you want to change to a lower gear as the going has got tougher and hence getting slower and pedalling lightly makes a lump like go even slower!
"Marriage is a wonderful invention; but then again so is the bicycle puncture repair kit." - Billy Connolly

Brucey
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Re: S.A. 5speed

Postby Brucey » 13 Jul 2014, 6:59pm

even having used SA 5s hubs for many years, I still have to remember to change down to first good and early; it is closer to second gear than second is to third; best to do a pre-emptive shift rather than struggle beforehand...

cheers
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fatboy
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Re: S.A. 5speed

Postby fatboy » 13 Jul 2014, 7:00pm

Brucey wrote:even having used SA 5s hubs for many years, I still have to remember to change down to first good and early; it is closer to second gear than second is to third; best to do a pre-emptive shift rather than struggle beforehand...

cheers


Found that out the hard way on Cheddar Gorge!
"Marriage is a wonderful invention; but then again so is the bicycle puncture repair kit." - Billy Connolly

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breakwellmz
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Re: S.A. 5speed

Postby breakwellmz » 15 Jul 2014, 8:15am

One of the traditional advantages of a hub gear over a derailleur was that you could always change down multiple gears when stationary, is this a myth now exploded?
I have always been in the habit of leaving a SA hub in a high gear if left at rest for long periods to ensure springs don`t remain compressed whilst inactive,it seemed the right thing to do.
Does this`advise for use`apply to other IGHs as well?

Brucey
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Re: S.A. 5speed

Postby Brucey » 15 Jul 2014, 9:31am

Stationary shifting performance varies with the hub. On an SA 3s hub it is OK to stationary shift to gear 1 and similarly it is OK to shift from 4 or 3 to 2 in a 5s.

Most downshifts in shimano nexus 7, nexus 8, alfine 8 are OK to be done stationary too.

From the very first, SA 4s hubs were a little iffy on 1-2 shifts and this has been carried over into every SA 5s design on 1-2 and 3-4 shifts. [In fact the 5s designs are worse on 1-2 than the 4s design, because one of the suns is different; it transmits drive in one direction only] . Similar arguments apply to the Sachs 5s designs too, and for similar reasons.

In the SA and Sachs designs the sun pinions see driving torque both ways, so can't be set to be freewheeling in one direction. This means that you can't have two suns engaged at the same time, not without there being some potentially tremendously exciting things going on.

By contrast the Shimano hubs only ever drive the sun pinions one way, and each is allowed to freewheel in the other direction. This means that if two are engaged at the same time, one drives and the other freewheels, and you shouldn't ever get a slippage or a loss of drive.

The downsides of the shimano approach are that;

1) you need many more pinions etc for any given number of gears; e.g. a Nexus 7 is about as complicated inside (in terms of the number of gears) as two SA 5s hubs are; this can also make the gear inefficient.

2) the shift control has a small stroke and the slightest error in manufacture or adjustment (or just a cable problem....) means the gear will go out of adjustment, which is what usually breaks them; hovering between gears is bad for any IGH, no exceptions.

cheers
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breakwellmz
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Re: S.A. 5speed

Postby breakwellmz » 29 Jul 2014, 7:57am

I think i may have broken mine yesterday.
There was an almighty`CRACK`in 4th gear as i stood on the pedals, followed by a surprising amount of vibration feeding back through the pedals.Smooth in the gears above and below.It feels very much like a tooth missing off a gear.
That`ll be coming apart later :cry:

Brucey
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Re: S.A. 5speed

Postby Brucey » 29 Jul 2014, 9:35am

oooh errr.... that doesn't sound good.

Odd that the other gears seem OK; the same parts (some each) are used in gear 5 and gear 2.

If gear 5 is OK the fault is probably in the gear 4/gear 2 sun pinion or its locking.

Good luck with the stripdown.

cheers
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Sweep
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Re: S.A. 5speed

Postby Sweep » 29 Jul 2014, 5:06pm

sorry to hear that,er, breakwell.
Do keep us posted on how you get along.

We'd all be interested.

No idea where you are but if in London I'd consider taking it to Bicycle Workshop.*

* Caution: I know Brucey doesn't seem to rate some of their advice.

I stress that I'm not criticising Brucey.
Sweep

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breakwellmz
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Re: S.A. 5speed

Postby breakwellmz » 1 Aug 2014, 12:05pm

Took the innards out this morning,gave them a good wash`n rinse with Paraffin in a clean container.
No metallic bits or anything else came out in the wash, nor any sign of damage.Certainly not what i would call smooth when actuated in hand,certainly compared to my Nexus hub.
It`s now assembled and set up back in the bike, but will wait for the rain to stop before trying it out.
It`s this one BTW-
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breakwellmz
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Re: S.A. 5speed

Postby breakwellmz » 2 Aug 2014, 4:27pm

Squirel 005 (Small).jpg


The test run was short!
I think the initial`crack`the other day must have been the plain section of this gear splitting but holding together, hence no debris but rough running.
It`s definitely buggered now though :lol:
Some very thin sections amongst the broken bits, just ripe for being case-hardened all the way through.The circlip was notably brittle-one of the`ears`coming off in the process of its removal.