Author Topic: EW Clutch Slip  (Read 7542 times)

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Offline Stuart Lister

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EW Clutch Slip
« on: 27 Jan 2007 at 16:32 »
Why does the clutch on my EW slip so much?

It's barely fit for the job at all. I have tried cleaning it, I've tried adjusting it, I've even tried a set of uprated springs. The lever is so hard to pull, now that it is hardly usable, and still the clutch slips.

I had it relined when I rebuilt the bike, perhaps the lining is made of a material that is too hard? It is a continuous circle of friction material, is that correct, or would a ring of disks be better? The pressure plate is pitted from having been subjected to such a hard life and the pitting is all on the same half; might that be the problem?

Any help gratefully received.

Stuart

Offline Chris

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Re: EW Clutch Slip
« Reply #1 on: 27 Jan 2007 at 21:51 »
I have never heard of this problem before. The Douglas flywheel clutch is normally extremely light to use and although the power of a CW is less than that of an EW I have never even bothered to put the full set of six springs in as the clutch is much lighter and works adequately without slipping with only four springs.
Are you sure that there is clearance on the cable and cam assembly? If there is not then pressure will be applied having the effect of releasing the clutch and no matter how much you tighten the springs or increase their strength, the clutch will slip.
The clutch discs have always been a full circle in all clutches I have seen.
 
« Last Edit: 27 Jan 2007 at 21:58 by Chris »

Offline Doug

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Re: EW Clutch Slip
« Reply #2 on: 28 Jan 2007 at 02:32 »
Not only should there be some slack in the cable, but just to be absolutely clear on what is meant you should also give the end of the clutch throw out cam arm a wiggle to make sure that when it is in the fully retracted position (clutch engaged), it is not being pinched. It could be that through repeated lapping and truing up of the flywheel and crankshaft taper, that the whole clutch assembly has moved in on the shaft such that there is no longer room for the thickness of the throw-out bearing no matter how much you back off the cam. It is not unknown for there to be variations in tolerances of the parts from the factory, so that if building up a machine from bits, you could end up with a smallish taper on the crank and a largish hole in the flywheel, causing the flywheel to sit too far onto the taper. The bearing is then holding the pressure plate slightly off the clutch disk. The quickest fix for this is to replace the ball thrust bearing with a sintered bronze thrust washer that you can machine to a thickness to restore some operating clearance when the clutch is engaged.

Some other thoughts in order of diminishing probability. The flywheel nut washer/drive dog is missing or replaced with a standard washer, so that the pressure plate is slipping round with the clutch disk and not contributing any to driving the clutch disk, relying solely on the friction against the backing plate. The flywheel nut washer/drive dog is non-standard and too thick, and the pressure plate spring cup ( the washer the spring press against) is bearing on the drive dog rather than the pressure plate. The pressure plate and or backing plate are cupped, and the lining is only touching around the edge rather than the whole face surface of the disk. The back lining is so worn the clutch disk is riding on the turned in lip of the backing plate; though I would expect it to make scraping noises when it slipped. The linings are worn down to the rivets. The clutch is not slipping; the whole flywheel is slipping on the crank taper.  :P

-Doug

Offline Stuart Lister

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Re: EW Clutch Slip
« Reply #3 on: 03 Feb 2007 at 22:21 »
Thanks for your help guys. It's good to hear that these clutches don't normally do this, it means that there is definitely something wrong and it's worth fixing.

I had a closer look today, and I think it is as you both suggest; the thrust bearing is constantly pressing on the pressure plate, and holding it off a little. I will replace it with a sintered bronze washer which I can make to a thickness that will give me plenty of clearance again. Once I am happy with it, I'll put the proper springs back in (four of them) and adjust it from scratch.

Thanks again for your help,

Stuart

Offline eddie

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Re: EW Clutch Slip
« Reply #4 on: 04 Feb 2007 at 08:35 »
Stuart,
           I dont know if the setup is the same on an EW, but on the S6 clutch mechanism, the depth of the release mechanism can be adjusted by rotating the collar that carries the three rollers for the cam. If you dismantle the unit and remove the collar, you will probably find three or four slots in the back of it and just one peg in the crankcase. Try refitting it using an alternative slot so that the overall height is reduced for a given position of the operating arm. This may give you that little bit of clearance you need. With the whole thing reassembled, there should be some free movement of the operating arm before the cable is attached.
                        Regards,
                                     Eddie.

Offline Stuart Lister

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Re: EW Clutch Slip
« Reply #5 on: 04 Feb 2007 at 11:16 »
Thanks for that Eddie. I'll certainly have a close look at that when I dismantle. I can't find any reference to the backplate being adjustable in the books, but then again, books were a bit minimalist weren't they?

Stuart

 

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