Sick hub gear

Tim Woodall said:

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

Tim Woodall said:

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.

Quoted message said:

This could, of course, be the perfect excuse to get a titanium Brompton
:-)

This can only be a Good Thing.

Tim

On Sat, 3 Feb 2007 18:27:52 +0000 (UTC),
Tim Woodall <[email hidden]> 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 here:
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/

Tim Woodall said:

On Sat, 3 Feb 2007 18:27:52 +0000 (UTC),
Tim Woodall <[email hidden]> 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>

Quoted message said:

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

On Sun, 04 Feb 2007 16:37:57 +0000,

Tim Hall said:

Tim Woodall said:

On Sat, 3 Feb 2007 18:27:52 +0000 (UTC),
Tim Woodall <[email hidden]> 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>

Quoted message said:

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/