Sturmey-Archer use and assembly

[dabac]

Hi all,

I'm having my first go at using a S-A 3 spd hub and I'm feeling a bit uncertain about the flattened sides of the axle. Sheldon Brown's site has kindly enough informed me that special washers are required, but the one that came with the hub won't fit the dropout on the frame I'm planning to use(another story) and I'm not too keen on the cutting my own. So...
- how necessary are they?
- can I put a shim as a liner in the dropout instead until the flattened sides of the axle is held firm?
- if I really should cut my own washers, how thick do they need to be?
-Are they needed/recommended on both sides or is one side enough? which one in that case?

 

[garage sale GT]

I am working on a similar project myself, except with an 8-speed sturmey. I filed down the top of an antirotator washer to make it rounded enough to fit an MTB frame.

Yes they are absolutely essential, because the axle takes reaction torque from the gears; i.e. when the wheel goes 4/3 as fast as the sprocket, the sprocket carrier planet gears are pushing against the axle.

Of course, it's possible the dropouts have enough meat in them to prevent rotation even without a close fit, but I wouldn't bet on it. I tried the shim idea too but anticipate problems changing flats in lousy conditions. What if you lose one?

To me, that washer looked like hardened steel, and that stands to reason too. I would guess it has to be either thick or hardened. Or.... I hate the thought of having to drill and file a precise axle shaped hole in a piece of flat stock, but I was thinking of using an external arm which would attach to the chainstay like a coaster brake bike. Again, it would have to be either thick or hardened.

Maybe have someone weld such a bar to your washer, which would then attach to the chainstay like a coaster brake reaction arm?

Knifemaking books are one source of info on how to harden steel at home.

 

[dabac]

.. I filed down the top of an antirotator washer to make it rounded enough to fit an MTB frame.

I'd rather not do that. The AR washer that I've got is VERY special to fit the bike the wheels came from, and if I grind that one down I have no way of putting the donor bike back together if my project doesn't work out.
Not that it's a lot of money, but if my ideas doesn't work out I'd much prefer to pass the donor bike on to some other enthusiast rather than sentencing it to the dumpster

.. Yes they are absolutely essential, because the axle takes reaction torque from the gears; i.e. when the wheel goes 4/3 as fast as the sprocket, the sprocket carrier planet gears are pushing against the axle.

So how come my old 3-spd Shimano didn't have any? Did the reaction arm for the coaster brake also deal with the propelling torque, or did the use of continuous as opposed to interrupted threads make it possible to simply SQUEEZE the dropouts firmly enough to keep the axle from turning?

.. Of course, it's possible the dropouts have enough meat in them to prevent rotation even without a close fit

I was thinking that maybe propelling torque would be big enough to spread the drop outs. I dunno, I've widened cone wrenches and the occasional pedal wrench, so why not? Then again the AR washers would brace against the same surface so there's no avoiding that particular issue.

.. I tried the shim idea too but anticipate problems changing flats in lousy conditions. What if you lose one?

My first thought was to use a U-shaped shim that would line the dropout on both top and bottom side. That would make it easier to find if it should get dropped. Otherwise I can always put in a couple of small spots of welding to keep it in place.

.. ... I hate the thought of having to drill and file a precise axle shaped hole in a piece of flat stock?

Hate is a bit strong, but yeah, I'd like to avoid that too.

.. Maybe have someone weld such a bar to your washer, which would then attach to the chainstay like a coaster brake reaction arm?

I wouldn't have to outsource the welding , but I'm not too keen on messing up the AR washer. Perhaps there's a wrench size that would fit the flattened axle and be used as a reaction arm? It'd then be fairly tiny, and considerably weaker regarding spreading risks as compared to the AR washer...

 

[dabac]

- can I put a shim as a liner in the dropout instead until the flattened sides of the axle is held firm?

Answering my own question here. W/o access to the proper anti-rotation washers I instead shimmed the dropouts until the flat faces of the axle was a nice and snug fit. It turned out that a few strips cut out of an old VCR casing was a close to perfect fit. Rode the bike that way for awhile and everything seems to have held up fine. The hub worked as it should and the dropouts doesn't appear to be spreading.

 

[garage sale GT]

I have had a few old shimanos and they always used antirotators. They are on the inside of the dropout. Also, a previous owner may have lost them, too.

I was concerned any shim formed from strips of metal would crush and deform. Please let me know how those hold up.

Good call on not filing the sturmey antirotator. I think they are hardened; mine cracked, probably from too much torque on the axle nut. However, there is little room for unmodified sturmey antirotators in an mtb dropout because it is so short.

 

[Akadat]

The S-A anti rotation washers are hardened and very necessary. The axle is under a lot of torque, I guess about 1/4 of the power you put into the pedals is trying to rotate the axle. 1st Gear rotates the axle one way and 3rd gear rotates it the opposite.

The flats on the axle means that half the threads are missing, so be careful to not overtighten the axle nuts as they are prone to stripping. I am afraid to tighten them enough to keep the chain in tension and have tension adjusters fitted. (Not quite adjusters in my case, they simply hook over the backs of the dropouts and prevent the axle being pulled off centre; my bike has a S-A hub with a deraileur chain tensioner at the rear, and a 3-sprocket chain wheel). The nuts will never get tight enough to prevent axle rotation.

Making your own anti rotation devices is feasible. Make them out of mild steel and then case-harden them. To case harden, heat to red hot with an oxy/acetylene flame that is fuel rich (an orange flame not quite sooty) for a minute or so, do both sides, then throw them into cold water. They will have a hard skin and a soft core.

Good luck!