#1
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Sick hub gear
This last week my chain started skipping (at least I thought the chain
was skipping) so I thought it was time to replace the rear cog and chains on my Brompton. I'd sort of expected this because in year 1 I got through 1 chain and 1 rear cog. I've now been alternating two chains and it's been two years. However, on comparing the old chain with the new chain it hasn't stretched much (ISTR that last time I did this the chain had stretched by over half an inch) and on reassembling everything the bike still isn't running right. I haven't actually taken it out on the road because it's now dark but the pedalling is not smooth and sticks when I put the bike on the stand. Also I can see the little chain going into the hub moving backwards and forwards while I turn the pedals when in 2nd gear - which is the gear I use almost all of the time except for starting off and a few downhills where I'm doing over 40kph. I've opened up the hub and cleaned up as best I can (without actually disassembling the gear, just removing it from the shell) but that doesn't seem to have helped either. Is this the end of the line for this hub? I've had the bike for three years and probably done about 6000 miles but those have been riden hard and fast (but not up and down kerbs or things like that, just potholes etc) The hub has never been serviced except a bit of grease when there was some play needing tightening up and some oil into the hole with the chain going into it. Or if I strip down the hub completely will it start working again. This could, of course, be the perfect excuse to get a titanium Brompton :-) Incidentally, it looks like the bearing race was installed upside down on the side without the cog. It was the other way up to the one on the cog side and the bearings are falling out of the race which made it slightly interesting to reassemble it all. Opinions? Tim. p.s. Replacing the 2W4 bulb with a 3W seems to have fixed my bulb blowing problems. -- God said, "div D = rho, div B = 0, curl E = - @B/@t, curl H = J + @D/@t," and there was light. http://tjw.hn.org/ http://www.locofungus.btinternet.co.uk/ |
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#2
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Sick hub gear
On Feb 3, 6:27 pm, Tim Woodall wrote:
This last week my chain started skipping (at least I thought the chain was skipping) so I thought it was time to replace the rear cog and chains on my Brompton. I'd sort of expected this because in year 1 I got through 1 chain and 1 rear cog. I've now been alternating two chains and it's been two years. Someone I ride a tandem with has hub gears and we were having problems with the chain skipping when in 3rd gear (5 speed hub). The problem was that the rear wheel wasn't quite straight between the forks due to two large cyclists pedalling hard up hills. Once it was straightened and done up really tight it worked fine again, although a year later it's starting to suffer the same problem again! peter |
#3
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Sick hub gear
On Sat, 3 Feb 2007 18:27:52 +0000 (UTC), Tim Woodall
wrote: This last week my chain started skipping (at least I thought the chain was skipping) so I thought it was time to replace the rear cog and chains on my Brompton. I'd sort of expected this because in year 1 I got through 1 chain and 1 rear cog. I've now been alternating two chains and it's been two years. However, on comparing the old chain with the new chain it hasn't stretched much (ISTR that last time I did this the chain had stretched by over half an inch) and on reassembling everything the bike still isn't running right. I haven't actually taken it out on the road because it's now dark but the pedalling is not smooth and sticks when I put the bike on the stand. Also I can see the little chain going into the hub moving backwards and forwards while I turn the pedals when in 2nd gear - which is the gear I use almost all of the time except for starting off and a few downhills where I'm doing over 40kph. AIUI 2nd gear is "direct drive". The movement of the toggle chain and the skipping suggest that the changer cable tension is slightly out, such that the clutch doesn't engage properly. Tighten it slightly. You might have to move the lock nut a bit to do this - although I'm not familiar with the Brompton hub gear, so I could be talkking rubbish. This could, of course, be the perfect excuse to get a titanium Brompton :-) This can only be a Good Thing. Tim |
#4
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Sick hub gear
On Sat, 3 Feb 2007 18:27:52 +0000 (UTC),
Tim Woodall wrote: snip Well I tried adjusting things with no luck. So I've stripped the hub (almost) completely down. (I've left the planet carrier on the axle as that requires removing one of those clips that ping off never to be seen again) And the problem was obvious. The ball bearings on the cone on the driver side are completely shot to pieces. Pic he http://www.woodall.me.uk/hub/img_0110.jpg (about 2Mb) (For anyone with the 2003 sram gear hub manual, which is available on the web, this part is in part 17 in the diagram for the T3 hub and it's what part 18 runs against.) One of them (at the top in the picture) has broken in half. Another couple have also lost large chunks however, the missing bits were mixed up in the grease and ground up too small to recover and photograph. Almost all the bearing are visibly damaged somewhere or out of round although it's hard to position them to photograph so the ones that look ok probably have rolled so their damage is at the bottom. These broken bits then got tangled up with the inner compression spring which is slightly out of shape now: http://www.woodall.me.uk/hub/img_0111.jpg (RH end in the picture is the damaged end.) I've found some ball bearings of the correct size so now I'm going to try reassembling (I think I can manage with the damaged spring for now) which will hopefully get me to work until I can order some new parts to fix this lot properly. I just have to see if I can get the bearings to stay in place long enough for me to reassemble it. I've included some other pics of the removed parts incase anyone is interested. http://www.woodall.me.uk/hub/ The next (112) shows the damage to the driver where the rear cog sits and transfers the force. 113 shows the race where the damaged bearings run in the driver. 114 shows the ring gear from the driver side with the hole where the sliding key goes through visible at the bottom of the picture. 115 shows the ring gear from the other side and 116 from yet another angle. 117 shows the miscellaneous remaining parts, larger compression spring, fixed cone and sliding key. 118,119 and 120 are pictures of the planet carrier on the axle. 119 looks confusing because I've used the ring gear to hold it upright to photograph - I should have opened up the aperture a bit for this one so the ring gear was more out of focus which was my intention. Additionally, one of the spacers for the rear cog has broken so that it's now in one piece but has a break rather than being a solid ring. I suspect I did that today getting the clip off to get the cog off as I didn't notice that damage yesterday. :-( All the pictures were taken with a canon EOS 300D with a 80-210mm[1] zoom lens stopped down to it's smallest aperture and a No2 macro lens. All were manually focused. [1] IIRC this is really 135-300mm on the 300D. Tim. -- God said, "div D = rho, div B = 0, curl E = - @B/@t, curl H = J + @D/@t," and there was light. http://tjw.hn.org/ http://www.locofungus.btinternet.co.uk/ |
#5
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Sick hub gear
On Sun, 4 Feb 2007 15:10:29 +0000 (UTC), Tim Woodall
wrote: On Sat, 3 Feb 2007 18:27:52 +0000 (UTC), Tim Woodall wrote: snip Well I tried adjusting things with no luck. So I've stripped the hub (almost) completely down. (I've left the planet carrier on the axle as that requires removing one of those clips that ping off never to be seen again) And the problem was obvious. The ball bearings on the cone on the driver side are completely shot to pieces. snip I've found some ball bearings of the correct size so now I'm going to try reassembling (I think I can manage with the damaged spring for now) which will hopefully get me to work until I can order some new parts to fix this lot properly. When my Sachs 3 x 7 went ping (tooth broke off the sun gear) I ordered a new bit from an LBS. This took ages and when it came it was the wrong part. The problem seemed to be that Fisher (Sachs/Sram distributor) use their own part numbers rather than Sachs/Sram ones. *Really useful*. Tim |
#6
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Sick hub gear
On Sun, 04 Feb 2007 16:37:57 +0000,
Tim Hall wrote: On Sun, 4 Feb 2007 15:10:29 +0000 (UTC), Tim Woodall wrote: On Sat, 3 Feb 2007 18:27:52 +0000 (UTC), Tim Woodall wrote: snip Well I tried adjusting things with no luck. So I've stripped the hub (almost) completely down. (I've left the planet carrier on the axle as that requires removing one of those clips that ping off never to be seen again) And the problem was obvious. The ball bearings on the cone on the driver side are completely shot to pieces. snip I've found some ball bearings of the correct size so now I'm going to try reassembling (I think I can manage with the damaged spring for now) which will hopefully get me to work until I can order some new parts to fix this lot properly. When my Sachs 3 x 7 went ping (tooth broke off the sun gear) I ordered a new bit from an LBS. This took ages and when it came it was the wrong part. The problem seemed to be that Fisher (Sachs/Sram distributor) use their own part numbers rather than Sachs/Sram ones. *Really useful*. Thanks. I'll bear that in mind. All back together and running "ok". Not perfect, there's a bit more friction than there should be, especially noticable when letting it freewheel when the wheel stops in 3-4 revolutions. But it all feels smooth, there's no sticking turning the pedals. It might also be that I've done up the non drive side lock nuts fractionally too tight but it's dark now and it will have to do for now.. I also can't select 3rd gear properly but this looks like a sticking cable problem possibly combined with that slightly bent spring - if I pull on the cable so it's relaxed properly then the hub drops into 3rd gear ok. I've got new cables and outers but haven't had time to replace them :-( Tim. -- God said, "div D = rho, div B = 0, curl E = - @B/@t, curl H = J + @D/@t," and there was light. http://tjw.hn.org/ http://www.locofungus.btinternet.co.uk/ |
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