southpawboston

I built up an S-A AW for my winter bike, and on my maiden voyage discovered that the cog was slipping under torque. On closer inspection, I realized that the cog itself was not engaging the splines of the driver. I had placed the cog too far out by using three spacers to try to match the chainline of my crankset, and in doing so brought the cog too close to the end of the splined section, and intruding into the channeled area where the lockring seats. The lockring itself was not entirely seated as a result.

You can see the three spacers and not fully seated lockring in this pic:



In hindsight, I should have realized the cog could slowly dislodge the incompletely seated lockring, which it did within two blocks of riding (these things never manifest on the workstand!!!). As a temporary fix, I removed one spacer. Now the cog is fully engaged on the splines and the lockring fully seated in its channel. The cog no longer slips. But now there is a slight wiggle to the cog, it is not seated snugly between the spacers and the lockring. I could probably get the cog snug and retain full seating of the lockring by replacing the two spacers with three thinner ones (I haven't measured their thickness), but is this necessary? Will the slight wiggle cause wear to the driver splines? Or to the keyed nubs on the cog?

Andrew R Stewart 

A slight wiggle usually won't cause the chain to try to derail (the main concern). Single speed (1/2x1/8) chain is not designed to want to derail so it really takes a large misalignment for it to do so. As long as the chain ring and the hub cog are pretty well lined up you'll likely be fine. BTW the rear cog can have it's chain line changed by both the cog/spacers arrangement as well as flipping the cog around so it's dished in the other direction. Andy.

fietsbob

As long as the snap ring is in place it wont come off.

there should be 2 spacers, those washers and the dish in the cog lets you shift the chainline around a bit.

tcs

And Sturmey offers flat, dished and deep dished cogs.

FBinNY 

Transfer one of the three spacers to the outside to stabilize the sprocket. When correctly mounted, the smap ring isn't pocketed at the bottom of the groove, but pushed out against the side of the groove to provide reaction force compressing the sprocket/spaecr stack.

southpawboston

The chain, chainring and cog are 3/32 on this setup.

This cog is actually a Suntour, but fits the three splined driver perfectly. With two spacers and the cog's dish, the chainline is okay. The problem is that the front chainring used to be part of a road double, and it's the outer ring I'm using in this setup. Ideally the chainring would be further inboard.

The problem with 3 spacers, regardless how they're ordered with the cog, is that the lockring is pushed to far out of its channel to stay there. Any lateral force and it can pop out. With two spacers, the lockring seats tightly but there's slight slop, and therefore no compressive force against the cog.

FBinNY 

Shop (search) for a thinner spacer, or cut one from shim stock, plastic, or even a piece of card stock, so there's some thrust against the snap ring and the outside of it's groove. (if you use paper, soak it in oil before using, and it'll last eons.

Otherwise, if there's a local machine shop, bring the ring and a few beers and ask if he can take it down to half (or whatever you need) on his surface grinder. This is about a 1 minute job, since most shops have a grinder with magnetic chuck and all purpose wheel read to go 24/7.

BTW- If the driver diameter is 1-3/8" (35mm) I can send you (I think) a 1mm aluminum spacer I used to make for BB cups.

Andrew R Stewart 

"The chain, chainring and cog are 3/32 on this setup." Southpawboston

Well there's your problem. No righful SA should ever be used with a skinny winny chain Andy.

fietsbob

Just after being around 100+ years the S-A 3 spline fitting type has been a multinational standard.

Shimano introduced the 9 spline , more recently.. a second type , also used now.



For Brompton, Sachs made a 2 cog driver and a 13 & 15t 3/32 cog, for the B derailleur scheme.

It has a 3 gaps, a skip tooth design, for shifting ,, in AW3_ 3 spline.

https://www.sjscycles.co.uk/brompton-...iso-prod22346/

LittleJon

Normally, a little wiggle is no biggie. But since it already slipped off, I'd just check the three inner dogs on the cog and the indents on the hub driver for wear. If they look like there's plenty of meat there, roll on.

tcs

Just something for you to think about.

Andrew R Stewart 

Cyclo, many years ago, made two and three cog units for SA drivers. I never had one but remember them on the wall of a shop I worked for in the 1970's. Wish i had picked one up...

Instead when i got around to playing around with dérailleur shifting and AWs i just mounted two standard cogs back to back. the shifting was pretty poor what with the tooth profiles. Grinding a chisel on a couple of teeth helped. Andy.

arex

I like that idea, I'm gonna steal it.

southpawboston

The inner dogs did get chewed/rounded a little from slipping... but I think there's plenty left. The driver is unmarred (hardened steel?).

LittleJon

That would certainly avoid a lot of time spent fiddling with flathead screwdrivers, not to mention a lot of swearing. Did you just happen to have a circlip in the right size? Where can one find something like that?

fietsbob

It's* sitting out too far..? maybe one spacer has to go , so the snap* ring beds into the groove
properly.


the other snap ring has its own pliers , and would be something from the auto parts
and machine fastners world ..

had one in the early 60's, used it in a 3x3x3 drivetrain, adding a triple crank.

thing worked with an 1/8" chain.. Huret Alvit chain shovers.

tcs

It's a std. size (IIRC 1.375") and my Home Depot had them. Great so far. I'll report back in 20~30,000 miles and let everybody know how it worked out.

tcs

No big deal, but as a matter of history, Sturmey introduced the three-spline in the early 1950s. Before that, most of their cogs were thread-on, like track cogs still are today. The three spline pattern cogs are used with and interchangeable on Sturmey 2, 3, 4, 5 & 7-speed hubs, Fitchel&Sachs (& SRAM) 2, 3, 5 & 7-speed hubs, Shimano 3, 4, 5, 7, 8 & 11-speed hubs and various brands of single speed coaster brake hubs.

surreal

I got a thread-on w/lockring Velosteel. Lovin' the convenience. But, I'm a hit up the home depot for that trick circlip TCS posted above, for the other IGH/ CB bikes.... Looks to be the custard.