onesmalldrop

I understand how to adjust the 3-speed Sturmey shifter on a Brompton that I'm currently working on, but something seems odd: is it normal for the cable to be completely slack (no tautness whatsoever) when in third gear? If I add enough tension for the cable to be even slightly taught in third, then when I shift to second, the indicator pin is out almost a full half centimeter past the axle, rather than the specified 1mm. The shifting does seem to work fine with the totally slack cable in third, but it seems unusual. Anything to worry about? (I'm wondering if it could be an issue with the shifter itself letting out way more tension than it should in that shift from 2 to 3...)

Dan Burkhart 

totally slack in third is fine as long as you are almost completely taut in first with just the tiniest bit of pull left on the indicator chain.

onesmalldrop

Right on, thank you!

FBinNY 

The indicator spindle is aptly named because that's what's used to indicate correct cable LENGTH (commonly and incorrectly called tension)

Everything else is irrelevant.

Dan Burkhart 

When the correct indicator for the specific axle length is present this is true but Parts get mixed and matched over the years and sometimes the incorrect indicator is made to work but the marks become meaningless.

Gresp15C

Granted, I'm replying with the IGH expert above me, but "standing on the shoulders of giants," and all that. I've dealt with mix 'n' match indicators, and have found this page useful:

https://www.sheldonbrown.com/sturmey-archer_tech.html

It discusses the method that has always worked for me.

FBinNY 

Agreed, also a problem after a poor rebuild that has the axle out of position.

However, the OP stated that it worked fine when adjusted per the indicator.

I might add that a slightly off adjustment can cause a hub to seem OK, yet running with partial engagement, increasing internal wear and tear.

FWIW - FULL cable slack in the "slack" condition is SOP system design. It makes for more generous tolerances in manufacture and operation. We see this thinking in just about everything from bicycles to aircraft.

GamblerGORD53

I would unscrew it and start over. Make sure the indicator is screwed all the way in and backed off half a turn.
I really have no idea what to look at for positioning. It just doesn't matter with the 3 speed.
I adjust it like Dan said. I put it into third and tighten it till there is a bit of slack. Then it will be tight in 1st.

dutchster

I'm on my third SA hub rebuild. My approach to 'adjustment' is what works for me. I've had the back wheel on and off many times during each rebuild. Here is what I do:

I adjust the cable length so there's a massive amount of slack in third gear. With the bike upside down, I turn the pedals and go through the gears. Very often, I get second gear going up but it gets missed going down. I twiddle the adjuster to take out some slack. I twiddle on (shortening the effective cable length) until second is achieved in both up and down changes. Today, I set it with just one twiddle, just like the last time and the time before that and ... it's rather intuitive. I finish by checking that the indicator spindle can be pulled out just a tad when in first. It always can, when I use my method.

Weird and wonderful!

PS:

When it's all working well, there is still a LOT of slack in third, just a bit less than when I started the adjustment. I don't think 'factory settings' apply after decades of use/misuse.

FBinNY 

Happy to hear you have it dialed in. But, for the record, and for anyone else who finds this thread ------

Time and wear aren't factors here. The factory settings are purely about position, namely sliding the clutch directly in line with what it engaged. That never changes unless a human changes the axle's position from original.

Possibly the single most common cause of AW hub failure is poor adjustment. With only partial angagment, the clutch slips under load, edges get chipped when it catches again.

Andrew R Stewart 

While I learned the adjustment method of the indicator chain's shoulder WRT the axle end I also learned to find the "central point" of adjustment in 2nd gear. This method serves me well when working on repairs that have non standard parts. I set the lever in 2 and using the cable length adjuster I find the cable adjuster setting when the pedaling just begins to skip. The adjuster lock ring is positioned against the barrel, not tight but to indicate that barrel position later. Then i unwind the barrel and find the point of slipping into 3rd gear. The adjuster thread between the lock ring and the barrel is the range of cable that will get you 2nd gear. I set the cable length/adjuster barrel to the mid point of this range and double check the shifting and gear engagements.

I also watch the relative rotational pace of the cog WRT the hub shell (teeth WRT spokes) to judge which gear the hub is in. 1st gear will have the spoke rotating behind the cog teeth. 2nd and they will rotate at the same speed. 3rd has the spokes advancing faster then the cog teeth. Andy

oldbobcat

I think of it this way.Third gear is the default, no-cable-tension, position. The internal spring automatically shifts the hub into third. To adjust the cable, tighten it until you can hit second and first solidly, without slipping out or overshooting.

Dan Burkhart 

For the old star clutch type (pre NIG) I look at it the other way. When the clutch is fully retracted in first, it deactivates the ring gear pawls. The shift to second reactivates them to engage with the hub shell but the star clutch is still engaged with the ring gear. If the shift to second has the clutch advancing no further than necessary to allow the pawls to engage while still allowing the cable to go completely slack in third so the clutch is firmly settled on the planetary carrier the adjustment is correct.

FBinNY 

It's interesting how every experienced SA "expert" has his (or her) own voodoo adjustment method.

Mine relies on the assumption that the clutch rides on a plain bearing, so ideally thrust is limited to no more than what the internal spring generates. So, I shift to low, tighten the cable until it's taut, then back off a hair. I want to end up with 0.5mm or so of lever travel beyond the 1st gear click position. From there, all the other positions will be OK, and the cable will be slack in 3rd.

It's similar to how auto clutches are adjusted so the cable is not supporting the clutch until the pedal is pressed.

oldbobcat

Right. 1st is a reduction gear, second is direct drive using the pawls, and third increases the ratio. But it's the movement of star clutch that motivates the gear change, and that's determined by the pull of the cable.in opposition to the spring. The spring pushes the clutch into third and the cable pulls it back into second or first.

Gresp15C

I think a good thing to remember is that the gear spacing on a SA hub is based on the internal dimensions of the mechanism, and the corresponding dimensions of the shifter. Whatever method you choose, it's either consistent with how the hub works, or it's wrong. The multiple "right" ways of doing it, all get you to pretty much the same place.

The small amount of play in 1st gear serves a purpose. If the cable is held completely taut, the relatively delicate threads of the indicator rod will eventually pull out of the axle key. Been there. This is also why you thread the indicator in, and then back it off by 1/2 a turn. If you find that it needs to be that tight in order to stay in 1st, then the hub is due for a rebuild. Been there.

I find, especially when servicing a tire while on a ride, that just checking for a tiny bit of play when pulling on the cable by hand is a quick way to know that the bike is ready to go.

JohnDThompson 

And then you need to open the hub to replace the axle key.

Some SA hubs used a two-piece indicator rod, where instead of the indicator threading into the axle key, the axle key was trapped between the two pieces of the indicator rod. Less likely to strip, and if it does strip, can be fixed without opening the hub.

Gresp15C

Yup. But I was up and running with a new replacement part for a 40 year old hub, a week later.

tcs

An appeal to tinkerers and pack rats: please keep the original indicator with the hub.

Question for whoever back in the day separated the unique, extremely rare L-120AZ indicator from my SW MKII: what were you thinking?