Author Topic: S6 Clutch  (Read 7222 times)

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Offline Austinpike

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S6 Clutch
« on: 11 Feb 2008 at 09:30 »
On my S6 there is side ways movement (whole crank) when the clutch is engaged causing drag and crunching of gears. Is this the norm or should I be looking to shim up crank, and if so from inside the crank case or on the timing main gear ?

Offline Alan Cun

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Re: S6 Clutch
« Reply #1 on: 12 Feb 2008 at 00:07 »
Hello All, Guess I should throw in a few cents worth on this one firstly on the vast improvement of the S6/ T6 motor however on the new type of clutch I would only give it about 3 out of 10. Although it is much more robust if you can get it to operate without slipping you are a winner. I have known at least 2 friends with S6 that have had large size check books that have sold their machines in frustration at not overcoming the clutch slip problem. I too decided to put the fly wheel clutch and gearbox from my SW600 in to moth balls and fit a Norton box with Jawa plates. Result from the start line, rear wheel spinning front wheel 6 inches off the ground. Now getting back to your problem it certainly sounds like a spacer washer is missing and too much crank end float. Douglas decided that a bearing diameter washer with a small hole was required between the double row bearing and the throw to prevent the compression stroke sucking and running dry the outer race. Also many douglas owners will know that  to much end float will cause the half time gear to grind away the ally on the timing chest. And dont forget my thoughts on too tight a primary chain. Hope my ramblings are of use regards Alan.

Offline Doug

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Re: S6 Clutch
« Reply #2 on: 12 Feb 2008 at 01:43 »
The S6 spares list, besides an "oil-thrower between spring and flywheel" (?), mentions a "spring location washer" and an additional "washer for bearing" in the drive side. So there are bits in there that could have been omitted during the last rebuild. The timing side is just a plain bronze sleeve on these engines, and does not contribute much to axial location, or is not intended to I think!  :)

Also, I do not know if it is the practice with the S6 types, but certainly on other Douglas engines Kingswood was not very precise about machining crankcases, particularly on the side valve models. It is not uncommon to remove what appear to be original bearing races, and to find neatly made shims behind the outer race. The practice seemed to err on the deep side and shim out extra play behind the outer race, rather than between the inner race and the crankshaft.

Now I probably could check all this as there is an S6 engine in bits out in the shed packed away. But as it is also about -12 Celsius out in the shed at the moment, and I am not that dedicated, sorry! Perhaps someone presently enjoying a warmer climate would oblige?

-Doug

Offline eddie

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Re: S6 Clutch
« Reply #3 on: 12 Feb 2008 at 06:20 »
Hi All,
           Something else which may need to be taken into consideration is that some Douglas engines around the late twenties had a drive side main bearing that was 62 x 30 x21. Nowadays, the bearings have been standardised to just 20mm wide, so an extra 1mm shim may be needed between the bearing and it's housing.
                                        Regards,
                                                 Eddie.

Offline ChrisS

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Re: S6 Clutch
« Reply #4 on: 14 Feb 2008 at 21:31 »
Gents,
My E32 (T6) had the same problem when I bought it. As you pulled in the clutch the crank moved over bodily towards the clutch side.. It was in fact the shaft moving through the bearing because the clutch side had not been assembled correctly. Also the bearing was a self aligning type!! I've no idea how the crank survived. The parts book details 3 parts as being between the bearing and the flywheel. 11195 is an oil thrower, 11196-1 is a wave type spring washer and 11678-1 is a spacer washer. Correctly fitted this assembly and bearing are nipped by the flywheel, which locates the crankshaft but will still allow the flywheel to seat on the taper. The oil thrower was there because at that time they had no lipped oil seals and that's how they stopped the oil leaking out of the crankcase.  When I rebuilt my engine I fitted the bearing on the crankshaft using high temperature loctite then followed this with a sleeve which buts up to the bearing but is clear of the flywheel so allowing the flywheel, when fitted, to seat on the taper. This sleeve with a slight tapered leading edge is also fixed using ht loctite. The crank and bearing are now securely locked together. The OD of the sleeve is sized to suit the new lipped oil seal fitted into the crankcase half.
Before I assembled everything I had a dry run and checked that the con rods were centered in the cylinder apertures. In my case they were, but its at this point you can determine if shims are required to get the crank central (not forgetting you do need some clearance at the timing side).
When fitting the crank assembly into the crancase half, the tapered leading edge of the sleeve  helps to enter the sleeve into the oil seal. I now have a ridgid assembly which helps the clutch to work well and keeps the oil in the crankcase.
Hope this helps 
ChrisS

Offline Doug

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Re: S6 Clutch
« Reply #5 on: 15 Feb 2008 at 00:56 »
The double row self-aligning bearing is actually the original fitment for many Douglas models. It allowed Douglas to not be very fussy in getting the bearing bores directly in line, without putting undue stress on the crankshaft or cases. Originally double row self-aligning ball, they can be replaced with advantage by the higher capacity double row self-aligning roller bearings now available. 

-Doug

Offline ChrisS

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Re: S6 Clutch
« Reply #6 on: 15 Feb 2008 at 21:04 »
Interesting that Doug, I am surprised at that.   As there will be a reasonably large moment from the primary gear/chain the self aligning bearing would allow the crank to more easily deform under load. I suppose because the timing side bearing is a bush and the clutch side is small diameter facing out, they couldn't line bore. My crank appears free enough so I must be lucky and have one where the bores are ok.
Anyway one of the nice things about working with old bikes is that you can learn something new every day.

ChrisS

Offline Doug

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Re: S6 Clutch
« Reply #7 on: 16 Feb 2008 at 00:32 »
I doubt that Douglas line bored, ever! There is a shop picture circa 1915 showing the 2-3/4hp crankcase half in a box chuck type fixture in a #6 Warner & Swasey turret lathe, wherein all the turning and boring operations were carried out. Final sizing of the bearing bore and shaft hole was by a combination (step) reamer.

Usually the timing side consisted of a single row radial ball bearing, which had a little bit of angular 'give'. So you only had a slightly large than 1" hole clear though for the main shafts with 52 or 62mm bore (depending on model) inside that for the ball bearing. The bronze timing side bush of the S6 series was a rare exception during that time period for Douglas, and a bit of a technological step backwards. 

Beside allowing a greater manufacturing tolerance, having some angular freedom in the bearing took some of the moment stress off the drive side crankcase wall. Particularly on the OHV machines with there greater power output, the crankcase wall was a bit fragile and did not like being flexed in and out. The crankshaft was more resilient and likely to spring back into its original shape; the thought might have been let the crank take the beating. Less so on the low strength porous aluminum castings that Douglas sometimes turned out. And the crankshafts do flex as anyone who has taken apart a well used late twenties through thirties 350cc, the conrod rollers track sideways and chew into the center web. The larger twins had more room inside to be a little more robust (and later on a bearing cage.)

-Doug

P.S. Usually most of the chain snatch from the primary was accommodated by the frame bending!

Offline Austinpike

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Re: S6 Clutch
« Reply #8 on: 16 Feb 2008 at 12:30 »
Thanks gents
I was hoping to go on a run to the London Douglas M.C.C AGM tomorrow, but seems like a quick fix is not on the cards, shame because the weather is good for a ride out.