Sturmey Archer BWR slipping in 3rd gear

Discussion in 'Folding Bikes' started by berylthebrompton, 19 Nov 2017.

  1. berylthebrompton

    berylthebrompton Active Member

    Location:
    Bristol
    Hello

    I am having an issue with my 6 speed Brompton. The hub keeps slipping when in the 3rd hub gear (hardest gear, when the indicator chain is loosest), or 5th and 6th gear overall. I opened the hub initially to re grease the bearings, but afterwards the gear started slipping. Both 2nd and 1st are fine. I adjusted the indicator chain, but the issue carried on. So I opened the hub again and found the actuator plate had broken! So I cleaned up the grease I had added and got a replacement actuator plate (https://www.sjscycles.co.uk/hub-spares/sturmey-archer-actuator-plate-for-driver-hsa470/), but this issue has carried on. I can’t figure out what I have done or how to solve it! Can anyone offer any advice?

    Cheers,

    James
     
  2. Kell

    Kell Senior Member

    Way too scared to peek inside the hub, so I’m no help at all.

    Good luck with the solution.
     
  3. XC26

    XC26 Senior Member

    Can you provide a little more information, such as:
    1. Does it slip continuously in 3rd gear or intermittently and, if so, how frequently?
    2. Does it slip only under heavy load?
    3. Did you only grease the bearings?
    4. What kind of grease did you use?
    5. Did you reassemble the hub correctly, particularly regarding the right side cone adjustment?

    Without being able to get my hands (or at least eyes) on the hub, it’s difficult to diagnose the problem. To my knowledge, the hub should work without the actuator plate (not so for coaster brake hubs). One hunch is that the 3rd gear pawls are not engaging correctly. These pawls are situated on the gear ring and engage with detents on the ball ring which, in turn, is screwed into the hub shell. The pawls are pushed outward and into place by those very delicate R-shaped springs, which can sometimes struggle to overcome the resistance from grease that is too thick and sticky. When in 1st or 2nd gear, these pawls are retracted so as not to engage with the ball ring, thus switching off 3rd gear and allowing the other gears to operate. The fact that the other gears function OK also points towards these 3rd gear pawls. So, perhaps ensure these pawls are correctly installed and very free to move in and out. You only need to take the main internal unit out of the hub shell and observe it while rotating the driver, holding the axle still, to see if everything is working correctly. If not, squirt some oil on them. Apart that, I can’t see what else it could be unless something is worn out.
     
  4. OP
    OP
    berylthebrompton

    berylthebrompton Active Member

    Location:
    Bristol
    Hello, thanks for replying.

    1. Every 1-2 pedal rotations.
    2. No, it will slip whilst in a stand.
    3. Only the bearings, but on both sides.
    4. Lithium.
    5. I followed Sheldon Browns website, but I am a novice.

    I tried to test the pawls you are talking about (I think) by pressing them in and they seemed to spring back - but I don’t have a reference to gauge them against. Likewise the grease is white, and was only applied the other day, and I can’t see any on or near pawls. I don’t have the tools to remove the internal unit, so would want to try oiling them first. Can a small amount of chain oil be used? Also I can take a picture of the pawls if you think it would help.

    Thanks again,

    James
     
  5. YukonBoy

    YukonBoy Guru

    Location:
    Mars
    Is the shift cable correctly adjusted?
     
    mjr likes this.
  6. XC26

    XC26 Senior Member

    The 3rd gear pawls are sort of covered/concealed by the ball ring when the hub internal unit is fully assembled. Though you can not touch them, you can observe them in action when you rotate the ball ring wrt to the gear ring.

    However, I am a bit confused as to how you replaced the actuator plate without removing the internal unit. Did you just undo the right side cone to remove the driver assembly without firstly undoing the left side cone nuts and unscrewing the internal unit from the shell? The usual stratgey to work on most Sturmey Archer hubs is to undo the left side cones and then unscrew the internal unit from the hub shell on the right, using the special C-spanner or a hammer and punch applied to the notches on the ball ring. This allows for the removal of the complete internal unit with the right side cones completely untouched. One would then undo the right side cones to dismantle the internal unit into its many components. When reassembling the internal unit it is very important not to tighten the right side cones onto the bearings but to leave them slack/loose by a quarter/half turn and locked into this position. When the internal unit is screwed back into the hub shell, final bearing adjustment can be made by tightening the left side cones so that there is free rotaion but no lateral play on the axle wrt the hub.

    If you only undo the right side cones to access the right side bearings and driver, you will not really be able to correctly set the bearing adjustment, as described above, on reassembly. The unit relies on correctly adjusted right side bearings so that the internal mechanisms are free to move and are lined up correctly. If the right side cones are too tight, I think this would compromise the operation of the internals.

    Following Sheldon’s website is excellent as it will detail absolutely everything you need to know. Post some photos as they might help.
     
  7. OP
    OP
    berylthebrompton

    berylthebrompton Active Member

    Location:
    Bristol
    Yes I removed the right side cone and the driver. I then loosened the left side cone, tightened the right cone finger tight + back half a turn (as per Sheldon Brown), replaced the lock nut, and then adjusted the left cone back again. I have done it this way in the past without issue - but maybe my luck has run out! Would misaligned cone only affect 3rd thought, surely its would affect all of them?

    The video attached - are the pawls your referring to the two you can hear and see on the inside of the rotating part?



    EDIT: Or is it the green on yellow ones in this picture?

    9F929A8F-A9E5-4516-96AD-BAF2B35A89C2.jpeg
     
    Last edited: 19 Nov 2017
  8. 12boy

    12boy Senior Member

    Location:
    Casper WY USA
    I had a lot of trouble with a standard SA 3 speed which wouldn't shift properly and had a mechanic disassemble it several times ( it was his first hub of this type) before he got it right as he applied the same heavy grease throughout. Since then I have simply added 5/25 synthetic motor oil and it shifts perfectly as long as the tension on the shift cable is good. I later got a 3 speed hub for my brompton and have used oil since the beginning. When either hub gets a little noisy, which usually occurs when coasting, I simply another cc or so of oil and it runs quiet, shifts smoothly and does not jump out of gear. The hub does allow some oil seepage which is why you need some more every once in a while.
     
  9. XC26

    XC26 Senior Member

    This got me thinking last night and I firstly need to correct my first post regarding 3rd gear pawls. After studying a diagram of the internals, I believe the mid set of pawls (that I previously referred to as 3rd gear pawls) as circled green in your photo, are also used for 2nd gear, which is direct drive as it bypasses the planet cage altogether. If I’ve got it right, this implies that if gears 1 and 2 operate OK, then all (3, I think) sets of pawls are functioning correctly.

    So, maybe we need to focus on the clutch mechanism - the lump of metal that is moved along the axle by the gear indicator/selector rod and chain. In third gear (i.e. gear cable slack or even disconnected), the clutch should be held down firmly onto the planet pinions by the large spring that slides onto the axle and is secured by the right side cone. Perhals you could disconnect the gear cable, unscrew and remove the indicator rod and then turn the pedals (forwards and backwards, just make sure everything is loosened up). If it slips in this situation, maybe the clutch is not fully located onto the planet pinions. This could be due to an obstruction, stiffness from over-tightening or undue wear, etc. If it does slip, try screwing in the gear selector indicator rod and then pull it in and out by hand and make sure it is pulled back in all the way by the spring when you let go of it. If you can hold it in the 2nd gear position, turn the pedals a few times, then release it, it should firmly snap into place with a good pull and travel of the selector rod. Back-pedalling should definitely ensure this happens. If it doesn’t, this could be the problem.

    I would recommend removing the entire internal unit, according to Sheldon’s instructions. Leave the right side cones in place and ‘play’ with the mechanism in your hands to check for any anomalies like stiffness or obstructions. Resetting the right side cone adjustment while the unit is out of the hub shell is a good idea. I must admit that I can’t really see what you are doing wrong with your method, it looks fine, I just wish I could be there.
     
  10. OP
    OP
    berylthebrompton

    berylthebrompton Active Member

    Location:
    Bristol
    That all makes sense. I will take a look after work tonight and report back!

    Thanks so much for your continued help.
     
  11. OP
    OP
    berylthebrompton

    berylthebrompton Active Member

    Location:
    Bristol
    Had a quick look before work, and your clutch theory was correct. The right cone was way too loose, so the spring couldn’t push the clutch plate all the way back and out of the way of engaging 2nd gear. Adjusting the cones appears to have resolved the issue.

    The only new thing I notice is you can hear a metal “tinkling sound” in 3rd gear. Sounds like the actuator plate is ratting. Not sure if this is something to be concerned about? Or whether it will quieten down when the oil in the hub gets on it.

    Thanks again.
     
  12. mjr

    mjr Comfy armchair to one person & a plank to the next

    According to https://forum.cyclinguk.org/viewtopic.php?p=1169332#p1169332 this hub may be missing a left-side cone lock washer which can make adjustment trickier.

    If this is like other recent SA 3-speed designs, it's best to avoid wheeling the bike backwards in top gear because IIRC it loads the actuator plate.
     
  13. XC26

    XC26 Senior Member

    Wonder if the tinkling sound is caused by a piece of the old broken actuator plate lodged somewhere inside the works? However, as it only occurs in 3rd gear, perhaps not. Otherwise, it could be the new actuator plate, or somewhere nearby/related, because, if I’m right, the pawls next to the actuator plate are not used in 3rd gear. This would mean that these pawls and the actuator plate are free to rattle/wobble/etc. as they are not held tight when out of use. In 3rd gear, these pawls are probably overridden by the faster rotating gear ring, which could, in turn, rattle the (loose?) actuator plate.

    Regarding lubrication, car gearbox oil is pretty good for the internals and marine grease for the bearings. Don’t get any grease near the pawls, unless it’s thin enough to allow proper movement.

    Glad you got somewhere with this.
     
    berylthebrompton likes this.
  14. chriscross1966

    chriscross1966 Senior Member

    Location:
    Swindon
    Are you sure the tinkling isn't just standard Sturmey clicking? None in bottom, little bit in middle, bit more in top?
     
  15. OP
    OP
    berylthebrompton

    berylthebrompton Active Member

    Location:
    Bristol
    No, it’s the not the rhythmic clicking of the pawls. It’s a new sound, more like a metallic rattle. Is it’s quietening down as I use it more and more.
     
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