Author Topic: Anyone else had a problem with the new sprocket?  (Read 564 times)

geocycle

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Re: Anyone else had a problem with the new sprocket?
« Reply #15 on: August 24, 2017, 01:31:07 PM »
I think I need a a diagram to understand how a loose chain could cause the sprocket to flip off.  What happened to the bit of metal wire we saw in the early photos?  I could just about imagine a freak accident where the wire got tangles between sprocket and frame and dislodged the circlip.  Anyway, great to know Thorn are helping to keep you on the road and I hope the rest of the tour goes smoothly!
 

onebikeoneworld

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Re: Anyone else had a problem with the new sprocket?
« Reply #16 on: August 24, 2017, 02:16:26 PM »
I think I need a a diagram to understand how a loose chain could cause the sprocket to flip off.  What happened to the bit of metal wire we saw in the early photos?  I could just about imagine a freak accident where the wire got tangles between sprocket and frame and dislodged the circlip.  Anyway, great to know Thorn are helping to keep you on the road and I hope the rest of the tour goes smoothly!

That was Rohloff's official explanation. Apparently, during development, they tested the design and the only time a sprocket ever came off they put it down to a chain being loose.

Tigerbiten

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Re: Anyone else had a problem with the new sprocket?
« Reply #17 on: August 24, 2017, 03:47:38 PM »
I think I need a a diagram to understand how a loose chain could cause the sprocket to flip off.  What happened to the bit of metal wire we saw in the early photos?  I could just about imagine a freak accident where the wire got tangles between sprocket and frame and dislodged the circlip.  Anyway, great to know Thorn are helping to keep you on the road and I hope the rest of the tour goes smoothly!
The spider on my Schlumpf HSD is held in place by a circlip and I run twin chainrings.
If I get the change between ring wrong under load, when the chain is quarter shifted there is enough twisting force on the chainrings to pop the circlip.
It was mainly on the upshift but I have popped it on the downshift as well.
I've now learnt to treat the shift more like hub gear shift and have gone well over a year without this happening.
The main difference is the HSD has a round circlip in a round groove while the Rohloff has a square clip in a slot, so the Rohloff will need a lot more force to pop it.
But if something does jam in the chain and it starts to unship under load, if you're very unlucky and everything lines up right, then I can see the sprocket getting forced off.

David Simpson

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Re: Anyone else had a problem with the new sprocket?
« Reply #18 on: August 24, 2017, 05:04:11 PM »
That was Rohloff's official explanation. Apparently, during development, they tested the design and the only time a sprocket ever came off they put it down to a chain being loose.

Chain being loose, or chain coming off the sprocket (as a result of being loose)?

Also, did Rohloff test the case where a small wire is caught in the chain? Probably not. I'm just saying the Rohloff's explanation may not be the true one. Sometimes it is very difficult to determine the true cause of a problem.

As for Thorn's handling of this problem:  ;D ;D ;D   Good job, Thorn!

- DaveS
« Last Edit: August 24, 2017, 05:06:29 PM by David Simpson »

onebikeoneworld

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Re: Anyone else had a problem with the new sprocket?
« Reply #19 on: September 05, 2017, 05:24:25 PM »
That was Rohloff's official explanation. Apparently, during development, they tested the design and the only time a sprocket ever came off they put it down to a chain being loose.

Chain being loose, or chain coming off the sprocket (as a result of being loose)?

Also, did Rohloff test the case where a small wire is caught in the chain? Probably not. I'm just saying the Rohloff's explanation may not be the true one. Sometimes it is very difficult to determine the true cause of a problem.

As for Thorn's handling of this problem:  ;D ;D ;D   Good job, Thorn!

- DaveS

Chain being loose and pulling the sprocket off.


To update, the parcel was sent as soon as I gave Thorn an address and arrived with my contact here in Cape Town 3 business days later. It took me a while to eventually get over here, but I went to a bike shop and armed with the PDF, a couple of Rohloff bike tools, a helpful bike shop called Williams and a couple of phone calls to Dave at Thorn the seal was changed. The flange around where the seal sits had got knocked out of alignment and so wasn't a perfect circle anymore (look on the right-hand side of the first pic), so William pushed it out towards what it should look like and got the seal in. I did the oil change a few hours ago and it's not leaked yet. Fingers crossed it is fixed thanks to the wonder of Dave and the people at Thorn.

Old seal


Bashed


Bent back a bit