Sturmey Archer RX-RD3 ..good idea...??..

[SA_SA_SA]

interesting: but didn't it(the 1-2, 4-5 slipping) defeat the point of the NIG parts in the red band sprinter a bit

[Brucey]

I agree, it did.

But arguably the NIG thing was to allow a 'safe' 3s coaster brake hub and (as in previous generations of hubs) the 5s ones may just have inherited the 3s driver, actuator plate and all.

cheers

[Bsteel]

For the past 10+ years the SA 3s hub eg X-RD3
http://www.sturmey-archer.com/files/catalog/files/307/PART%20LIST%20-%20X-RD3.pdf

has been fitted with a thing called an 'actuator plate'. This exists for one purpose only; without it, when you are in top gear and you wheel the bike backwards, the clutch is being driven backwards by both the gear ring and the planet cage, but at different speeds. If the clutch doesn't ride up against its spring (which it arguably should do, there are ramps on the clutch), something in the hub will break. The actuator plate is meant to defeat the driver pawls when the clutch is driven backwards and this prevents any risk of the hub breaking when the bike is wheeled backwards. However more usually it falls off the driver or breaks up (through repeated backpedalling) and then bits of it fall off inside the hub and trash it. I think it is the single least reliable part in these hubs. However, you can usually hear the clutch riding up against its spring even if the actuator plate isn't working, so I have wondered if you really need it or not.

Stumbled on this thread whilst trying to work out why the used X-RD3 hub I've just stripped has completely eaten it's inners. As the driver and gear ring pawls along with the ears from the actuator plate and large chunks of the driver have been reduced to filings and debris I'm guessing the above quote nicely explains the failure.
My problem now is whether to try and salvage the hub shell or replace the hub completely. Searching for a complete internal assembly I find two two different reference numbers. HSX167 from the SA parts list or HSX120 from the likes of SJS.
If I replace the whole hub I was considering increasing the number of gears, reading through this thread the possibility of the C50 sounded interesting and I was wondering if since Brucey's first mention it has proved itself a better option than the X-RD5, although I haven't managed to find anywhere selling them ?

[Brucey]

you are unlucky that the driver is damaged. The pawls and the actuator plate are cheap enough, the driver is bit more money.

Still, I'd fix that hub rather than swap it out for another. The C50 uses sun pinion locking as per the 8s hubs which makes me worried, and the shifter internals are built like the previous thumbshifter for the W hub (which causes the hub to break) so I'm not confident that the C50 will be a really robust hub. It is a lot heavier than the X-RD5(W) though.

Not sure about the two different part numbers for an internal; are the axle lengths the same?

cheers

[Bsteel]

you are unlucky that the driver is damaged.

Yes, I think in this case it was definitely beyond all hope, further examination also shows damage and fractures to the ratchet surface of the ball ring. So before buying any parts I'll need to ensure there's no damage to the internal thread on the hub beyond it being a bit rough.

As far as I can see the HSX167 number only appears on the SA parts list so I shall ignore it and just ensure I find an assembly with a 165mm axle, although that is one part which was left undamaged.

thanks for the info.

[Brucey]

that hub was ridden on for some time after it because faulty. It annoys me when that happens, because the damage needn't have been so bad; chances are that it needed a few pound's worth of parts only when the fault first developed. A new actuator plate is £1.49 retail.

cheers

[Brucey]

according to this

http://www.sjscycles.com/Instructions/Sturmey_Archer/Sturmey_Archer_X_RD3_Hub_Instructions.pdf

HSX120 is an internal containing axle HSA440

https://www.sjscycles.co.uk/hub-spares/sturmey-archer-axle-nig-3-speed-1627mm-hsa440/

which is 162.7mm long. Earlier versions of the 3s NIG brake internal would have used a weaker axle design than this.

HSX167 internal contains axle HSA808 which is 177mm in length. I think the internals are otherwise similar.

cheers

[Bsteel]

Update:
Having cleaned out the thread on the hub shell the HSX120 was a good replacement, the only differences I could see without stripping the hub was the ball ring only having two notches rather than four and no sprocket dust cover being supplied.
Question:
Is there a special tool or technique required to adjusting the hub brake side bearing after assembly. The slots on the cone adjuster are tricky to grip when trying to tighten the cone locknut.

[mjr]

If you mean what I think, then I use a C spanner to hold a slot while tightening the nut.

[Bsteel]

Thanks mjr, I think we're talking about the same thing. I'll have a hunt around for a C spanner and give it a go. It just seemed odd it doesn't have flats for a normal cone spanner.

[Brucey]

the correct spanner is not easy to find. However you don't need a special spanner if you fit this



part HMW150 between the LH locknut and the cone adjuster. You can tighten the locknut and the cone will pretty much stay put.

cheers

[2Phat4Rapha]

Lost my pawls. Could've sworn they were in here somewhere.

[Brucey]

finely ground debris there, sir. Unusually the actuator plate appears to have survived the onslaught more or less unscathed.

I have seen this kind of damage in hubs where

a) the rider thinks they are riding trials (and slams the cranks down every time they resume pedalling) and/or
b) the gear adjustment is poor so that the high gear pawls are not fully retracted in first gear and/or
c) the hub has been used with too much slack in the bearings and/or bad RH cone adjustment.

The last of these conditions results in there being a higher than normal chance of just one of the high gear pawls engaged. This can cause the pawls to break. Even on good hubs about one time in ten or one time in twenty when shifting from 1 to 2 only one pawl engages (there is a reason why old SA hubs had 10T ratchets; the modern 20T ones may reduce backlash but they are otherwise not such a good idea..... ) . The normal result is that after about three turns of the pedals the drive slips slightly. The slippage will occur even under modest pedal loads.

It is therefore prudent with these hubs not to mash hard on the pedals hard having shifted from 1-2 or after any period of freewheeling in 2 or 3. If slippage occurs under high load this is what can easily break the pawls.

The chances of getting one-pawl only engaged are much reduced in hubs that are correctly adjusted and have been run-in well. But the chances are never zero, so it is best to assume that it might happen.

FWIW part of the problem appears to be that the newer hubs have slacker diametral tolerances than older ones, which lends itself to bad pawl engagement.

The other thing is that the designer of the NIG hubs appears not to have looked very closely at the way the old (pre NIG) AW actually drives the gear ring in gear 1 and gear 2. It looks as if the cruciform clutch drives the gear ring on four points, but in fact it is only ever two (because they are actually unevenly spaced inside the ring gear; check it out, I didn't notice this for years...); this (I think) helps to centre the ring gear as drive is taken up and this reduces the chances of one-pawl-engagement in gear 2.

cheers