Author Topic: Six spring plunger clutch (duplex chain)  (Read 523 times)

Offline jimbo

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Six spring plunger clutch (duplex chain)
« on: 08.08. 2017 11:40 »
I am getting a lot of slip and chatter from the clutch now that I have replaced the springs and friction plates. Having stripped it the roller bearings are all the same diameter (0.250"), but 14 of the 18 are 0.250" long, whilst 4 of them are about 0.015 short. I intend to replace these as a set. The next thing I noticed is that when the clutch centre and chainwheel are secured with the centre nut, there is a bit of movement in and out on the chainwheel, whilst there is no back and forth movement on it. This is the same whether or not the bearings are in place. Having removed the parts again and put them face down on the bench, and put a flat edge across the two parts, there is a gap of about 0.020" between the flat edge and the back of the chainwheel.
Here's the question; do I need to make up a shim, or is there an available part?

Any help would be very, very welcome.
Regards
Jimbo

Offline Sluggo

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Re: Six spring plunger clutch (duplex chain)
« Reply #1 on: 08.08. 2017 20:17 »
I would have to carefully look at the parts book to say for sure, But I am sorting out clutch bits for a few projects at the moment but in the past, It seems to me certain BSAs and some Triumphs used a brass thrust washer on the back of the clutch baskets. 
I have little experience on a plunger style clutch but trying to assemble one from parts for  a project so will be working on that tonight in the shop, But in the past I had similar issues with Unit style clutches (BSA & Triumph) and took some fettling to get a good assy that did not wobble and have excess play, as well as line up the chain run also. If you shim or run too thick a thrust washer, or dont get the parts set up just right it can misalign with bad results,  Too loose on the clutch center and main shaft is disconcerting as well, But it just seemed to be a lot of work to get right.  Once you do, it pays to take a photo of the parts used as well as measurements so its repeatable,
It would be nice if we could just order new parts and it all fits perfectly, but hahaha! Not on a old British bike.   Parts should come with  a label  "Some fettling required"
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Offline morris

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Re: Six spring plunger clutch (duplex chain)
« Reply #2 on: 08.08. 2017 20:50 »
Skimming the clutch centre on a lathe worked out very well for me.
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Offline jimbo

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Re: Six spring plunger clutch (duplex chain)
« Reply #3 on: 09.08. 2017 06:06 »
Skimming the centre seems easiest, so I'll see how much meat there is on it. Also, will that then mean that the bearings will not have the necessary height to fit in? Maybe a copper shim of about 0.020 would be less likely to adjust the space for the bearings, although smaller bearings could be used. Hmmmm

Offline duTch

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Re: Six spring plunger clutch (duplex chain)
« Reply #4 on: 09.08. 2017 10:16 »

 Jimbo, I may have read some of this wrong, but think I know and have the same issue, I've debated the same and morris's idea may be a good option (with stated reservations)...I don't like the idea of thin shims where I *think* is suggested (against moving parts) as too thin and could cause grief;

 
Quote
Here's the question; do I need to make up a shim, or is there an available part?

 The parts list has three different thickness 'Thrust Washers' ;see attachment, but not sure where the measurements are done, and so far as I can tell are rare as RHS (in different sizes)

  Having said all that, I just slapped it together and ride it (well I will again when things are straightened out)
 
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Offline jimbo

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Re: Six spring plunger clutch (duplex chain)
« Reply #5 on: 09.08. 2017 16:20 »
Yes, duTch, there is a thrust washer behind the basket, but this is in contact with both the basket and the centre, so it won't make any difference to the relationship between the two. Morris's idea is currently the fave.

Offline bikerboy

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Re: Six spring plunger clutch (duplex chain)
« Reply #6 on: 15.08. 2017 00:50 »
I may be misreading this but how can anything be in contact with the centre and the chainwheel? Thats really not right?

The chainwheel always moves a fraction anyway because it only sits on the bearings which if I remember rightly are marginally longer than the chainwheel so it can free spin when you disengage the clutch.

At least thats my interpretation of things

Offline jimbo

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Re: Six spring plunger clutch (duplex chain)
« Reply #7 on: 15.08. 2017 17:23 »
Thanks, bikerboy. That clears up that one. There is about a 0.020 difference between the two, which allows the chainwheel a little slack.

Offline morris

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Re: Six spring plunger clutch (duplex chain)
« Reply #8 on: 15.08. 2017 22:24 »
Thanks, bikerboy. That clears up that one. There is about a 0.020 difference between the two, which allows the chainwheel a little slack.
There has to be some clearance but .02", which is over .5 mm sounds like a bit to much. I would aim for a maximum of .005"
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