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Sturmey Archer Hubs

Construction Tips
Calamity
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Sturmey Archer Hubs

Postby Calamity » Mon Jan 05, 2015 11:28 am

Technical question: Older Sturmey Archer gear hubs e.g. AW series are cheap and plentiful. Anyone here familiar with their workings?

I want to find out the feasibility of converting one to left hand drive. Could it be as simple as reversing the two sets of pawls in their respective ratchets?

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dralphs
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Re: Sturmey Archer Hubs

Postby dralphs » Mon Jan 05, 2015 10:30 pm

I think probably not as the ratchet teeth will be the wrong way round

but take a look at http://sheldonbrown.com/sturmey-archer/aw.html
or
https://chestercycling.wordpress.com/20 ... er-aw-hub/

there is also lots of diagrams and documents on the SA heritage site, eg for yours look at
http://www.sturmey-archerheritage.com/i ... ail&id=837
Dave
Falcon Notnray Racing
www.yarntonscouts.org.uk

Calamity
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Re: Sturmey Archer Hubs

Postby Calamity » Tue Jan 06, 2015 10:34 am

Thanks for the links dralphs. I see what you mean now about the teeth.

The right hand ratchet looks like it might be reversible by parting off the threaded part of the R.H. ball cup and welding it back on flipped over, assuming it's made of steel.

The left hand (low gear) one might be more tricky as it's integral to the shell on the newer hubs, according to the 1973 service manual. On older drawings the L.H. ball cup and ratchet appears to be threaded into the shell, but from what I can see from various photos, the later ones have no means of unscrewing it if that was still the case.

I wonder if the tooth ring might just be pressed into the shell. If not, maybe new teeth could be broached in-situ somehow. Or maybe I could just remove those pawls all together and blank off the lowest gear.

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Re: Sturmey Archer Hubs

Postby Calamity » Wed Jan 07, 2015 4:44 pm

I procured myself a rusty 1985 vintage AW hub yesterday evening to pull apart. Lots of rust, water and gammy grease inside meant it was past its best so I don't feel too bad about sacrificing one in the name of science.

Happily the small low-gear pawls are bisymmetrical and will simply go back in the other way round. The larger ones that the clutch mechanism interact with are handed, but I think a kiss with the grind wheel will put a sufficient chamfer in them to make them operate the opposite way. The holes for the pawl pivots (4mm on my particular model, a real mixed bag of measurements and thread sizes) need to be redrilled to make the pivot heels line up with the square holes behind them though and this is as far as I got last night.

Image

The ring gear is made of really hard stuff. A freshly sharpened cobalt HSS bit barely scratches the surface. I guess this is probably key to their reliability. I'm going to borrow a solid carbide bit to try on it next.

The teeth inside the ratchets may well be just as hard. I was thinking of making a broach from an HSS blank and progressively scrape the little wedge shapes out, but I might have to make something that takes a carbide insert instead.

Image Image

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dralphs
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Re: Sturmey Archer Hubs

Postby dralphs » Tue Jan 13, 2015 10:17 pm

Glad you are making progress
I suspect the ratchet may be case hardened, worth googling to see if anyone knows
Dave
Falcon Notnray Racing
www.yarntonscouts.org.uk


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