Author Topic: M32 Engine Lubrication questions  (Read 229 times)

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Offline Hamwic

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M32 Engine Lubrication questions
« on: 23 Jul 2020 at 21:34 »
Hi Chaps,

Well the M32 engine is all in pieces now, and a number of interesting anomalies have emerged.

1)  The crank is drilled for lubrication down the timing side mainshaft, but no feed is provided and it relies on the spray bar. The orientation of the holes in the spray bar are predominantly toward the front cylinder, and not down onto the crank as I would expect - any views on this please?

2)  The oil union to the top of the front cylinder has been cut short, and has been internally blanked off by a cylinder re-sleeve. I don't have a lubrication diagram for this particular machine, so is it a dribbler and supposed to be connected to a feed in, or is it a timed breather?

3)  Not surprisingly the big ends are tired but probably recoverable. However some stamping flash on the rear cylinder big end has been happily tapping away at the top rear crankcase mounting stud, and two of the studs are slightly bent. I can tidy up the rod, but did Douglas really do this?

4)  Taking off the oil regulator revealed a ball bearing apparently blocking off the drain outlet from the bowl, with a miserable and probably home-made spring beneath it in the timing chest. I'm guessing that the ball and spring should be on the entry side to the beak, and would the proper spring be a fairly light thing on the beak side to stop oil syphoning over the top?

5)  The crankcase cam followers are showing a bit of wear on the sliding faces. Is there any real depth to the hardening, or are they best left? The cams look fine.

6) One of the adjusters was such a tight fit that the follower body had cracked through - seemingly just too tight, but also forms an hydraulic lock. Flea Bay has provided another one, but is grinding a small relief flat on the adjusters a good thing?

Thanks for reading this far, and I look forward to your replies.

Doug
« Last Edit: 23 Jul 2020 at 21:40 by Hamwic »

Offline Doug

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Re: M32 Engine Lubrication questions
« Reply #1 on: 24 Jul 2020 at 03:52 »
Doug,

(1 & 2) All the lubrication into the engine is via the spray bar, and the holes are aimed downward. By 1932 they had stopped feeding oil to the base of the front cylinder. It sounds like you may have a mix (or complete crank) from and earlier model where they were feeding the oil via a quill and internal drilling in the crankshaft. Another subtle difference between the side valve and the ohv crank (as used in the K/M32) was the drive side main shaft was not drilled to save weight. If so, it may be missing the shallow grooves in the center web that allow oil to get past the side of the rod and to the big end rollers. The bores are lubricated by splash from residual oil pooling in the bottom of the crankcase.

(3) Clearance should not be that close! Again there are early and late rods (see comparison here: https://www.douglasmotorcycles.net/index.php?topic=109.msg259#msg259 ) but I do not know when they switched from a removable race to direct case hardening of the rod; but I suspect it was later during the 250/350cc Aero models. As such, the big end o.d. got smaller so I do not see how it could be a problem. Maybe a picture would help.

(4) The is a ball and light spring between the oil sight/regulator and the timing cover to prevent oil from draining down through and into the engine when the engine is not running. I think the ball and spring are usually on the oil bib side, with the spring in teh regulator body up into the drilled cavity leading to the needle valve and the ball sitting on the timing cover joint face.

(5) Case hardness depth on the very similar design 500/600cc Aero model tappets four years later was specified as 0.020 to 0.030", and I would expect that was a typical value for earlier models. So not an abundance of case depth to work with.

(6) Probably a tight thread or bad heat treatment; I doubt it split due to hydraulic lock. I have never experienced a need to cut a relief flat on the threads of the tappet adjusters. There is plenty of time for the air to work its way out as you do them up.

-Doug


Offline Hamwic

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Re: M32 Engine Lubrication questions
« Reply #2 on: 24 Jul 2020 at 13:06 »
Thanks for getting back to me re the M32 questions. It seems that the rod has actually been wearing away at the crankcase boss, so I suspect a little bit of tidying up to provide more clearance will remedy this,along with rectification of the big ends. I have seen the excellent information on this subject in these pages, and will take appropriate action. The crankshaft is fully drilled, including the drive side mainshaft.

I have also now noticed a witness on the front conrod big end and a bruise on the crankcase showing where that rod has been a-tapping away too, so things are pretty tight in there! Is the double-row self aligning bearing here really a good idea, and would a double row roller be a better bet for more support?

The orientation of the spray bar holes is actually horizontal. Is the spray bar cast in, threaded in or pressed in, and what is the likely success - or otherwise of trying to move it? Would it be better to blank off and re-drill as required?

A spring has now appeared from the darkest recesses of the oil sight glass, kept in place by a piece of what was probably a bit of leather wallet or similar used as a gasket.

As for the slightly bent crankcase bolts, seeing what they are being asked to do, I'm not surprised that have taken a set, so probably best left.

Between the crankcase halves there was a gasket of indeterminate thickness. Is there any indication of what thickness material was originally used please? It obviously affects the crank position and the fit of the cylinders, so a likely starting point would be good to know.

Similarly the cylinder base gaskets, which are pretty thick but actually in good condition might be a bit tired after getting on for 90 years, so I will be seeing about those too.

The cylinder head registers are plain, and have been fitted with thin copper gaskets that look to be home made. Should I expect to find any gaskets at this joint please?

Many thanks
Doug
« Last Edit: 24 Jul 2020 at 15:20 by Hamwic »

Offline Doug

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Re: M32 Engine Lubrication questions
« Reply #3 on: 25 Jul 2020 at 05:10 »
Doug,

As Ii said, sounds like it might be a earlier crankshaft. If so, the main worry is it might lack the grooves to introduce oil to the rod bearings from the spray bar, as seen here:



The theory of the use of a double-row, self-aligning bearing is Douglas did not trust their bearing bore alignment and it prevented crankshaft whip from stressing the drive side crankcase and cracking around the bearing boss. The later has happen on the more powerful engines, like the DT. The common practice now is to use a double row spherical self-aligning roller bearing. I don't know if there a a lot of folk out there that have upgraded to a cylindrical roller bearing.

The spray bars that I have seen have been threaded into the pump body. They have a thin jam nut to lock them in the proper orientation. Like seen here:



Not sure why the crankcase bolts would be bent due to the crankshaft/rods. Does the K/M32 retain the practice of the 350EW and A31 of using eye bolts anchored on the crankcase bolts to serve as cylinder base studs? If so, I an not surprised as that was not one of their better weight/cost saving practices!

Some engineering data for the DT engines survive where the crankcase gasket allowance can be calculated as 0.006". I have some NOS gasket sets for the Aero models where the paper for the crankcase joints is also 0.006". I don't who the supplier or brand is, but six thou of an inch seems to have been the original intention.

The cylinder base gaskets in the same set is slightly thicker at 0.008" thick for the 250/350cc models. But in the 500/600cc sets they are twice that thickness. Both are some sort of branded gasket material, though not enough of the text is visible to read it. The timing cover and oil pump gaskets are just plain looking brown paper, and those are fairly thick at eighteen to twenty thou.

I would expect the K/M32 to use the same cylinder head gasket as the detachable head EW or the A31. The parts list for those just call it a joint washer, without saying if it is solid copper of a copper sheet and composite sandwich. Given that it is just a narrow ring, probably solid. In any event I imagine solid copper would work fine.

-Doug






Offline Hamwic

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Re: M32 Engine Lubrication questions
« Reply #4 on: 25 Jul 2020 at 11:53 »
Thanks Doug,

Thanks for the excellent information. I will have to contrive a lead-in groove for the oil as my webs are plain. My crank was plainly intended for an oil quill set-up originally. Given the evidence of some kind of previous disaster, I suspect it is a replacement.
 
My spray bar seemed solidly fixed in position, and the holes are nowhere near the crank centreline. It is of course threaded in, but with no lock nut. I suspect it has in the past been snapped off, and re-threaded with little account being taken of where the holes ended up. I shall have to make another one.

My existing cylinder base gaskets are a mighty 0.064", or about 1.6mm thick, so I suspect there has had to be a degree of adjustment to compensate for something in the past, possibly the crank change? It may be a clearance issue between the rod and the cylinder base - this has yet to be established after the crank is reassembled.

The bore and stroke would appear to be 69.4 x 66. This works out at about 249cc a pot, so a full 500. The pistons are marked as STD, and probably new after the cylinder liners were fitted.

On we go!

Thanks once again
Doug

« Last Edit: 25 Jul 2020 at 12:16 by Hamwic »

 

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