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Old 10-18-10, 07:22 AM   #1
Fish_man
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SA 3 spd wont select low.

Doing up my twenty and Im 90% of the way there except I cannot get the hub to select low gear. Sturmey Archer AW hub 1990 I think

At first I suspected a lubrication issue that it had gummed up and hoped riding it would loosen it up. Then today I stripped the hub, scrubbed and re lubed every part .... zero sign's of wear ( which is surprising for a hub twenty years old)

Tested it off the bike and all three seemed to select fine ... although it's a little hard to tell when your holding the chain and trying to spin a wheel and guess how fast the parts are turning.

Then I put it in on the bike and no dice ... even pulling on the chain manually doest seem to help?

So I'm stumped now ?

Any SA 3 speed expert's ?
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Old 10-18-10, 07:27 AM   #2
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Ive just tried again ... it doesnt appear to select low off the bike either.

One gear ... direct drive and then nothing
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Old 10-18-10, 08:50 AM   #3
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Low is the highest cable tension, is there enough being pulled? ,
screw the cable adjuster in more.
proper length end of indicator spindle line up with edge of axle in .. 1:1/N/2nd?
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Old 10-18-10, 09:10 AM   #4
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You should be able to tell easily off the bike what gear you are in and whether they are working properly. Clamp the axle in a vise by the flats so that the wheel is horizontal. Turn the wheel and hold the cog in place to simulate coasting, then pull the chain all the way out. If the chain is the proper length the end of the rod used to make the 2nd gear adjustment should be well beyond the end of the axle. I don't have a hub available, but from memory I would say about 3mm. At that point stop the wheel and turn the cog so that it drives the wheel. In 1st gear the cog should turn faster than the hub - you will see the cog teeth progress past the spokes. Of course in 2nd gear the cog will turn at the same time, and in 3rd gear the cog will turn slower than the spokes.

If after following the above procedure 1st gear does not work then you need to overhaul the hub again. I would recommend you follow the excellent procedure at the following link.

http://www.youtube.com/watch?v=ea6krXSs-lc
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Old 10-18-10, 09:58 AM   #5
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Follow cny-bikeman's advice, and do a careful bench test hand-turning the sprocket watching it's motion relative to nearby spokes. There are 3 possibilities, slower, same and faster.

Since you've possibly moved the axle or may not have a factory indicator chain setting the shoulder to the end may not work for you.

Start by letting it spring all the way in. That's 3rd and the hub should move faster than the sprocket. Pull out slightly and you should find a dead spot with no engagement, a bit more will engage 2nd, hub turns at the same speed. Now pull the indicator all the way out, and the hub will drop to 1st and spin slower than the sprocket.

The combination of the gears you can get is the key diagnostic clue. If you can get 3rd and 2nd but the hub won't drop to low, the likely cause is that the right side ratchet which drives in 2nd and third isn't disengaging. Most likely the clutch (the + shaped part) and/or the mating bumps on the inside of the right side pawls are worn so that they don't retract completely.
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Last edited by FBinNY; 10-18-10 at 10:07 AM.
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Old 10-18-10, 10:51 AM   #6
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Thanks for all the advice ... Ive tried really hauling on the chain (as hard as I dare) and it still wont even come out of direct drive. I've tried pretty much everything I can think of.

fietsbob - it wont go into gear full stop ..... adjustment cable shifter were the first things i though of ... but even pulling the chain manually It still doesn't go in

Quote:
Originally Posted by FBinNY View Post
The combination of the gears you can get is the key diagnostic clue. If you can get 3rd and 2nd but the hub won't drop to low, the likely cause is that the right side ratchet which drives in 2nd and third isn't disengaging. Most likely the clutch (the + shaped part) and/or the mating bumps on the inside of the right side pawls are worn so that they don't retract completely.
Which part no/ No's - from this (http://www.users.globalnet.co.uk/~hadland/sa/saaw.pdf) drawing is that ? and I will have a really better look at those bit's when I strip it back down.

FB - Like I said the inside of the hub looked near brand new after I had cleaned it.

I will follow that link cny posted tonight or tomorrow and let you know if I get any result's.
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Old 10-18-10, 11:02 AM   #7
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In the schematic you referenced, you're interested in the bumps on the inside of pawls #512, and the outer rim of the clutch #505. In low the clutch pushes the the bumps on one end out causing the working ends to retract from the ratchet ring.

BTW, you can build the hub with the right end of the axle standing in a vice (do not crush) and testing most of the function before putting it back into the shell.
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Old 10-18-10, 11:04 AM   #8
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All else fails whole core can be purchased , just put it in the Hubshell..
I heard even newer NIG designs are interchangable.
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Old 10-18-10, 12:08 PM   #9
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this is driving me nut's now ...... No sign of wear .. everything is engaging disengaging correctly (as best I can tell)

How does the 1st gear work ?

3rd gear is through the planetary gears the clutch (505) engages the planetary gear pins (50 x 4)

2nd gear direct drive The clutch moves up and presses against the gearing paw (512)which transfers drive direct to the ball ring and thus to the wheel.

1st gear ??????

I just cant see how it SHOULD work .... so I cant find what the problem is.
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Old 10-18-10, 12:21 PM   #10
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no wait 2nd gear the clutch engages with the gear ring 511a and the gearing pawla are forced out and engage on a spring
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Old 10-18-10, 12:45 PM   #11
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Here's the short version of how SA hubs work.

There are two sets of driving pawls, right (high) and left (low). Right and left sides are on carriers connected to each other via the planetary, so that the left side always rotates at 3/4ths the speed of the right. Because it's driven via an over-running (tech-speak for freewheel) the hub will always turn as driven by the faster right side ratchet, over-running the slower left side ratchet.

So,
in 2nd, (1:1) the clutch engages the right side carrier which drives the shell at the same speed
in 3rd, ( high, 4:3) the clutch engages the planetary cage via the planet gear pinions, turning the cage, which in turns the right side carrier (via the planetary) at 4/3rds the speed of the input. Note that in both 2nd and 3rd the left side pawls are being overrun by the faster turning shell, which gives you the characteristic slow freewheel click.

got it so far? (if not reread and look at the schematic until you do, before continuing.

in 1st (low, 3:4), and here's the secret, the clutch engages the right side carrier the same as in 2nd, but to prevent the carrier from driving the hub, it also presses on the lever end of the pawls withdrawing into the carrier and dis-engaging them from the shell. This allows the right side carrier to drive the left side carrier at 3/4ths speed via the planetary, and allows the left side (slower) ratchet drive the hub.

The key is that 1st and second are the same, except that in 1st the right (faster) ratchet is disengaged.

Once you understand the principle, you should be able to diagnose your problem.

As I said, it helps to built it up and review your work before sliding it back into the shell.
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Last edited by FBinNY; 10-18-10 at 12:51 PM.
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Old 10-18-10, 12:57 PM   #12
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I was having a problem with an SA hub a while back. It seemed to be shifting in only the two gears you mentioned. I had to check, re-check, double-check several times. I eventually realized my shifter was a bit rusty and the cable and ratchet mechanism was catching on the inside of the shifter. After disassembling it and cleaning/lubing the insides, then re-adjusting the spindle and cable length, I had three working gears. Good luck.
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Old 10-18-10, 01:20 PM   #13
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wow .. Thanks FB.. I think Ive pretty much understood that on the 3rd of 4th read through.

It's getting late now so I think I will have another look tomorrow with fresh eye's and mind.

and to think a few short hour's ago I was scared of taking it apart ... now I'm fairly sure I could do it blindfold lol
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Old 10-18-10, 02:20 PM   #14
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If you have indeed pulled on the chain while the wheel was coasting (wheel turning, cog not) and the indicator/shift rod does not move out beyond the 2nd/direct drive postion, it sounds like the clutch is sticking, rather than the drive path for 1st not working. I would a burr or similar on the axle slot area where the clutch slides.
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Old 10-18-10, 02:59 PM   #15
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Quote:
Originally Posted by cny-bikeman View Post
If you have indeed pulled on the chain while the wheel was coasting (wheel turning, cog not) and the indicator/shift rod does not move out beyond the 2nd/direct drive postion, it sounds like the clutch is sticking, rather than the drive path for 1st not working. I would a burr or similar on the axle slot area where the clutch slides.
This is a possibility, but rare on a used hub, where the sliding key track tends to get worn smooth. But it's worth considering, and is one more argument for bench testing the basic function before putting the shell on. Testing in a vise w/o the shell allows you to see exactly what's not working right, and dwal with it. Obviously you cannot test the left side ratchet this way, but almost all else is possible.
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Old 10-19-10, 07:26 AM   #16
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Well I seem to have three gears now ... I couldn't tell you what the problem was .. but I stripped it right back again re-built it following the drawing exactly and it was working so I quickly got it all back together before it failed on me again.

Big thanks for everyone that helped.

I now have a even bigger respect for the designer's and builder's of these wonderful little hubs.
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Old 10-19-10, 11:05 AM   #17
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I suspect your axle was not correctly centered. I could be wrong.
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