Metallurgists

[Nick_GParticipant @nick_g]

Posted by Brian Sweeting on 30/05/2017 15:37:54:

Doesn't a slipper clutch only slip on the over-run?

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I think you are right.

Nick

[JonParticipant @jon]

Bottom line it shouldn't have gone if a quality part.

Have had a couple of chain breaks where its tried to jump front sprocket. Ticking over when it broke, between sprockets there would have been play top and bottom coasting along. Combine that with possibly chain not adjusted 600 mile previous might find the problem, have a close look at front sprocket.

New chains stretch a lot when new

[Wayne WardParticipant @wayneward51978]

Let’s hope it didn’t happen again but, if it does, take some really high-resolution close-up pictures of the broken faces, straight into the face, so we can see what marks are there. Fatigue failures can have some very characteristic marks, which can be easy to identify if the faces agent too badly damaged.
Chains which are too loose can also lead to premature breakage through shock loading.

[Ian PParticipant @ianp]

I have little experience of knowledge of failure mode of a chain drive so have no idea what happened in this case, however I have a couple of comments hat might be relevant.

I can 'sort of' imagine how the bend in the pin might have been caused. At first it looked illogical in that it had bent the wrong way but I now presume that as the pin came out of the 'bush' that the roller runs on, the tension in the chain whilst the pin was part engaged would bend it as shown. However in order to bend it, the end of the pin still held in the one end plate would be subject to very high sideways force. It shows how well made that end of the assembly is for the pin not to be pulled out of the plate.

Also, for the inner link to slide off the pin after it has bent it, it has to make a gap for it to pass through. That gap has now closed. If the steel is as tough as I would expect it to be its amazingly springy!

Another observation (might be just an optical illusion) is that the break in the loop of metal that broke looks to be different different widths at each side, as if the hole had been punched off centre.

Just my 2p

Ian P

secure and

[WatfordParticipant @watford]

It would have been of interest to see the other end of the chain, the roller section, and any marks on that. Are there any such pics?

Mike

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