Cycling UK Forum

SA five speed hubs are a bit of a mixed bag. I never had much love for the S5-1 and S5-2 models, mainly because they had a (to me) slightly crazy method of selecting the gear 1/gear 5 sun pinion, which involved a stronger spring crushing a weaker spring flat. Yet the only thing protecting both sun pinions from perhaps being engaged at the same time (which would result in instant destruction of the hub) was that weaker spring's ability to disengage the gear 1/5 sun pinion, once the LH toggle control was pulled. I therefore avoided these hubs for years, given that I had a perfectly serviceable five speed hub which I'd built by converting an FW, using a simple (much simpler than any SA produced) pushrod on the left side. Because of this I dodged a couple of other bullets;

a) the interrupted low gear drive dog ring in S5-1 alloy hubshells, which broke (just like the similar FM one had, about thirty years earlier) and
b) the 'made from cheese' low gear pawl pins in some (most?) S5-1 and S5-2 hubs.

When my ancient converted FW finally threw in the towel (after many decades and many tens of thousands of miles), the replacement innards were S5-2 based. They lasted about eighteen months before b) bit me in the backside, resulting in what is arguably the worst hub gear blow-up I'd ever personally experienced. At least when the original FG/FW axle finally broke it both gave me warning (there was a very loud noise about a week before it broke altogether, which I am pretty sure was one side of the axle breaking alongside the slot) and after it happened I could at least wheel the bike. When the pawl pins spat the dummy in the S5-2 internal, the bike had to carried; the wheel wouldn't even turn.

Sturmey Archer themselves eventually addressed the S5-2 axle issue by introducing a revised axle (which ought to be found inside all such hubs 08-88 or later, plus inside earlier hubs which have been retrofitted) where the sliding key was behind both sun pinions, so there was only one spring required for the sun pinions and it wasn't possible for both suns to be engaged at the same time.



But this doesn't appear as standard equipment on any parts listing for a hub that I have seen. Mind you, such listings were not always complete at the time; the AT5 (hub brake + five speed in alloy shell) model is mentioned here in the text

http://www.sturmey-archerheritage.com/files/view-1062.pdf

but there are no part numbers or drawing for that variant of the hub listed. For those you have to track down this document;



Which reveals that the 'Elite AT5' used mostly S5-2 internals, but the low gear pawls are plunger pawls, similar (but not identical) to those used in the FG/FB four speed models some decades earlier. The Elite AT5 hub is pretty rare; I think it was only made from ~1985 to ~1990. In ~1991 it was replaced by a 5-Star based model which was so unreliable this was in turn replaced in 1993 by the 'Sprinter' single toggle 5s hub. The 5-star based hub brake is even rarer than its predecessor; the only examples I have seen have been badly broken. However the S5-2 based Elite AT5 hub is an interesting hub because it ought to be a basis from which a reliable 5s hub can be built, since neither a) nor b) above can possibly apply.

Anyway I was recently presented with a faulty Elite AT5 hub which is date marked 07-87. I don't know which version of the S5-2 axle it has in it, even, or what faults the hub possesses, but I aim to find out. I can see that the circlip which retains the sun pinions on the axle has come adrift, and that this alone would be enough to cause major running problems in the hub; it might turn out that this is the only problem, we shall see...

I shall update this thread as and when I get into it.

cheers

Provisional update;

It seems that the secondary sun cup has been forced leftwards and that this overwhelmed the circlip. The circlip had been fitted correctly (sharp edge leftwards) so that isn't the reason for failure. I suspect very strongly that the gears were so badly adjusted that the secondary sun was barely engaged with its cup; the result of this would most likely be that the gear would slip, and when it slipped, it would tend to force the cup leftwards.

There was a fair sized burr on the axle and until this was dressed, I couldn't refit the cup on the axle. The axle is the original type rather than the revised type, and the hub appears otherwise to be in good order.

'Death by natural causes' or 'murder'? -the provisional verdict is 'murder' in this case. One of my mad ideas is to make a fixed length spacer so that the LH cup cannot be pushed off but that isn't so long that you can't adjust the hub bearings if necessary. There may be enough room for a locknut, FG/FB/FW/S5 style, (but with a small spacer and Loctite) instead.

Photos added;





If this is the full extent of the damage it .will have been a very easy repair. The hubshell will polish up well, but will lose its markings in the process. The lubrication port is standard fitment on this hub, but I think they had already deleted it on the AW by this time.

cheers

Often wondered if the 'plunger pawl' carrier from the FG hub(k404) could be modified to locate with the low gear 'splines' integral to the interior of the later s5/2 alloy shell (with the more substantial spoke flange).
Would also need to use the shorter planet cage from the FG (k403)as well.
The 'ears' of the 'plunger pawl' carrier would have to be removed and a male spline machined to locate in the 'splines' within the hubshell that locate the (inadequate) interrupted low gear drive dog ring. All of which would need the use of the well equipped engineering workshop that I lack.

I think it could work like that. But it would surely be simpler to either use an Elite AT5 as it is, or machine an Elite AT5 hubshell (so that most of the drum was removed and there were spoke holes in where the back of the drum flange was), or even remove the LH insert in an AT5 shell and fit it to a standard hubshell.

The other thing you could so would be to bolt the planet cage to the hubshell (which would involve drilling holes through the LH hub insert) so that you had the basis for a 3s fixed gear, with gear 3 direct.

now updated with photos

cheers

I read this useful post, prior to bidding on a ebay AT5 purchase. It was advertised for parts and not working with RH indicator jammed.

Having received and started the forensics, it's problem, AFAICS was mainly being gummed up with gunge. But the low gear pawls pockets are somewhat chipped and one of the low gear plunger pawls is very damaged. It seems to be post 8-88 having the later single spring arrangement on the suns...and is the 6 3/8" axle which should be good for 130 and possibly 135mm dropouts. So the Axle is useful. But to get this hub running I'm thinking new nice sharp edged plunger pawls are needed as the chips on the pawl pockets will mean that pawls with rounded edges are more likely to slip.

The original plunger pawls ( HSA383) would seem to be "unobtainium". The low gear plunger pawl ring looks more or less identical to an FG, so I could try robbing those from my spare FG, but I recall those were a bit rounded on the shoulder. So I have a question for the engineers. Is there an alternative that would be suitably hard ? Doesn't have to be hollow...as the FG's aren't.

RE Springs, as different length springs may be required, I have previously bought lengths of compression spring and shortened for unobtainable K hub springs, so a spring to fit seems dooable.........but is there some non SA hardened pin that could be used ? I can check the sizing of stuff...but I don't understand hardening and what to look for.

Also, Brucey refers to the post 8/88 changes resolving an axle issue. Hopefully I have this axle.....but what was the change to the axle itself ? I've done some measurements that seem useful to trap on this post as a reference:

Low Gear Plunger Pawl Dimensions:

3 hollow plunger pawl with an internal seat for spring
- pawl = 23.7mm long x 4.7mm diameter
- internal shoulder/seat for spring set at 7.7mm from open end

Springs = 16.75 - 17mm long; 2.7mm OD ; 0.31 - 0.33mm wire tightly coiled circa 50/50 metal to gap.

The plunger pawl hole on the planet cage is 25.2mm deep.....and also seems 4.7 mm diameter...so close fit.

Done a bit of searching. Best so far in size are these at 3/16" x 5/8".....but may be too tight a fit.

https://www.cromwell.co.uk/shop/fastene ... ZAQAvD_BwE

Say case hardened.

Shoulders seem rounded though and I presume really want a nice flat end for the plunger pawl.

I can’t be a lot of help to you but, short of a better answer, why not try the Colwood Wheel Works?
https://colwoodwheelworks.co.uk/

The SA five speeds have an unenviable reputation - I had poor experience of one too - and hence I use a three speed AW. Yes, the three speed has limited capabilities, but I use mine daily and get great utility out of it …

It might be that the innards of a different version of the five speed gear will interchange with what you have.

Yes, Colwood was my first port of call. Currently can't supply the AT5 pawls and due to only having a limited supply of the FG pawls is reserving those for his inhouse repairs.

Have just dismantled an FG to compare the plunger pawls. Same diameter. Look more robust. probably my best option with an appropriate spring....but I don't want to rob my FG. ( the hole the plunger resides in on the FG is fractionally wider, may be wear, and much deeper, but with a shoulder at circa 19mm for the 3/16" ball bearing)

(May be a problem though as both the AT5 and FG pawls diameter measured to just below 4.7mm, and the AT5 hole 4.7mm.......so a 3/16" diameter pin may be too tight if it is actually the 4.763mm it should be)

So any source of a hardened pin that might substitute still useful.....as original spares hard to source.

my suspicion is that the '4.7mm' dimension is actually 3/16". You may be able to make an excellent replacement plunger pawl by using the shank of a HSS drill bit Such drills have hardened flutes but the majority of the shank is left soft and can be machined. If you get lucky, you can cut (via grinding) a HSS 'blank' which is only hard at one end and use that to make a new plunger pawl. It is important that all three plungers are sprung identically, so it is probably best if all three springs are replaced at the same time.
Jim's idea of using a modified internal of this sort inside a S5/1 hubshell is a good one. I think the parts can be prepared using the SG method, so no fancy workshop is required. just a drlll and an angle grinder. Because of the way the hubshell is loaded (with a dog in every slot), the usual fatigue failures should not happen. The parts can be further enhanced by using adhesive bonding eg. by using epoxy resin to bond the modified pawl plate in position.

FWIW the revised axle is quite different, having a slot for the sun pinion key far to the right of where it is in earlier versions, largely precluding the possibility of both gear trains being engaged simultaneously, even if the springs break.

I've now got a spare set of FG plunger pawls and springs....hoping that they may work OK with the chipped pawl ring. They certainly have squarer shoulders.

I was thinking I would need to trim the FG springs....as shown ...to illustrate only..... FG's at the back; AT5 one at the front..... they have different stand heights. BUT the FG springs are actually not quite as strong...even when you push the pawl to compress it to the same height as the AT5 pawl/spring.

So I will not trim the FG springs....and use the complete FG set as is.

I am presuming that is more important that the set of pawl springs match in strength ....than the particular stand height when uncompressed ? I presume they are never not touching the pawl run when over running in 3,4 &5.

As bought had no brake plate/ shoes. NOS ones arrived. Have put hub back together with FG plunger pawls and brake plate.

Brake seems to rub a little. Looking at leading/ trailing edges of shoes 3 have same degree of chamfer( top photo), the third has less and uneven( 2nd photo).

Do I just file carefully the 3rd to match.....and if still rubbing shallow the angle on that chamfer a bit ?