Author Topic: Oiling on an EW 350  (Read 9749 times)

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Offline Ian

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Oiling on an EW 350
« on: 12 Nov 2005 at 07:48 »
Could someone please explain the oiling system on the 350 EW. We were having a discussion about oiling problems on the EW on the VMC rally. Does the drip feed to the motor route through a quill into a hollow crank ? The bike on the rally was using heaps of oil - I suspect that there may have been an internal leak in the mechanical pump allowing oil access to the motor directly. Is that possible ?

Offline Doug

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Re: Oiling on an EW 350
« Reply #1 on: 13 Nov 2005 at 02:45 »
Ian,

The early style with one oil pipe entering the timing chest or the later style with two pipes?

-Doug

Offline Ian

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Re: Oiling on an EW 350
« Reply #2 on: 13 Nov 2005 at 05:25 »
Doug, didn't realise there were two types. I think this is a 27 model. I suspect it is supposed to have two pipes but only has one from the drip feed at the moment.

Offline Doug

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Re: Oiling on an EW 350
« Reply #3 on: 13 Nov 2005 at 07:11 »
Right, two pipes it is.  From about engine YE6500 and onwards they used a different pump and had two pipes into the timing chest.  The oil pump is a duplex plunger, where as the original was a gear type.  So probably a 1927 EW has the duplex type. 

In this duplex system the oil circuit is as follows:  The oil flows from the oil tank through the oil tap, and on down the fitting on the timing chest.  This is the inlet for the pump.  The pump returns this up to the sight glass via the other pipe.  On its way it is joined (via a t-junction) by the hand pump output, which can be used to add additional oil or if the mechanical pump fails.  The oil travels up and through the sight glass on the top of the petrol tank.  The oil then drains down to the engine by gravity, entering via a one-way check valve screwed into the base of the front cylinder.  Crankcase depression when the pistons ascend draw in the oil through the check.  Note then all the oil enters the engine through the front cylinder and has to pass through the sight glass.  After the oil has splashed and frolicked about the bottom end a bit, it eventually finds its way over to the timing chest cavity.  There it accumulates and the level rises till the lower run of the timing gears just dips into the surface, thus lubricating the timing gear train, cams, and tappets.  There is an overflow pipe that leads excess oil away to pee on the primary chain. 

Also dipping into this pool of oil is a siphon screwed onto the bottom of the oil pump.  This is connected to the lower portion of the duplex pump, and it is that portion that pumps oil via a quill, into the end of the crankshaft, and thence via galleries through the crankshaft to the connecting rod big end bearings.  This quickly escapes the usually very loose big end bearings, joins the rest of the oil in the crankcase, and eventually finds its way back over to the timing chest.  Often via the hollow cam spindles and the whole process repeats itself over and over.  The oil pump does not return oil to the oil tank; it only pumps it up to the top of the tank to run through the sight glass.  It is not a scavenging system; rather it is a total loss system.  The only way for oil to escape this cycle of abuse is to leak out every orifice and joint, or work up past the piston rings, and out to freedom via the exhaust pipe.  This is because oil has an affinity to return to the ground, whence it came. 

Because oil for the crankshaft is picked up from the level in the timing chest, it is important before starting these engines after a rebuild to fill the timing chest with some oil, as it may be a while in the normal course of 'running' before enough oil accumulates to submerge the end of the oil pump siphon.  Meanwhile the crank has to survive on oil mist being thrashed around the crankcase.  If the mechanical pump fails and you are operating the machine solely on the hand pump (like it were a 2-3/4hp model) the crank shaft is not being feed oil via the internal galleries.  Also if the engine has set for a while, some priming with the hand pump will help fill the oil lines before starting. 

So if the engine is using too much oil, one is letting too much in for a start.  But maybe it is just burning too much oil.  Beyond the obvious worn bores and rings, there are other situations that can make smoke.  If the oil level in the crank case is too high, even the best cylinder and piston will be unable to cope.  Often this occurs because the oil in the lines leaks down while the bike stands unused, and ends up in the crankcase.  But this should eventually burn off and equilibrium be restored.  Also make sure the overflow standpipe pipe passing up through the bottom of the timing chest is not blocked or intentionally sealed off.  If it continues to use too much oil, the drip rate is set too high.  Otherwise it may be the plumbing is not routed as the makers originally intended.  If the oil line were to run from the tap on the oil tank directly to the non-return valve, the engine is going to suck in as much oil as it can on each stroke, like a greedy puppy.  It would not pass through the sight glass, and therefore there would be no metering or regulation of the amount of oil entering the engine.  It should only be sucking in the tiniest amount of oil each stroke, not a whole teaspoon full. 

So that is the ‘improved’ system, and you may be wondering how the earlier system worked.  Well it didn’t, or not very well anyway, which is why Douglas changed it.  It relied on suction to draw oil up through the sight glass and then it could flow down in to the pump via gravity.  Problem was it passed through four fittings and the sight glass itself, all of which had to be vacuum tight.  The system sucked alright, but not oil. 

The duplex pump used on the EW was not much better.  The biggest problems is the drive gear tends to strip.  This is driven by a worm on the end of the crankshaft.  I suppose in order to save money; Douglas did not cut the drive gear to a corresponding helix to match the worm.  The gear is straight cut, which normally would bind as the tooth of the worm passed by on its oblique path.  Douglas solved this by cutting the tooth space much wider than the thickness of the remaining tooth, giving the worm some extra space.  But it made the tooth weaker.  Also all the wear (and load) is at each end of the gear tooth on opposite flanks, as they are the only places the gear actually touches the worm.  The oil pumps used on the big twins had the gears cut on an angle to match the worm helix. 

By 1931, they changed it again to a much more robust multi-stage rotary-plunger pump (similar to that used on the DT/SW) that they kept right up to the end of pre-war 250/350cc sv engine production.  Also gone were the oil galleries in the crankshaft.  The crankshaft is rather weak as it is, having holes drilled in it just made the center crankshaft web that much more prone to break.  Instead the pump had a spray bar passing over the crankshaft dripping oil into the path of the big end bearings.  These had special grooves to lead the oil into the rollers where it was alleged to have done some good. 

-Doug
« Last Edit: 14 Nov 2005 at 00:11 by Doug »

Offline Ian

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Re: Oiling on an EW 350
« Reply #4 on: 13 Nov 2005 at 20:26 »
Thanks Doug - makes sense now. I was wondering how thye crank feed worked and did not realise it was a duplex pump ! Quite different to my OC !! Assuming the drip is operating at the right speed then the only way bulk oil could get into the motor is through a fault in the oil pump where maybe a gasket is missing or something like that ?

Offline Doug

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Re: Oiling on an EW 350
« Reply #5 on: 14 Nov 2005 at 00:10 »
I just discovered that there may be two variations of the duplex pump style.  Looking through some EW handbooks, I see one illustration shows the lower of the two fittings as the oil inlet and the upper fitting goes to the sight glass.  In another handbook the upper fitting is shown as the feed to the oil pump and the lower goes to the sight-glass.  I am not entirely sure if this is not an error in the handbook, further investigation is required.  Meanwhile I have removed the specific reference in the previous post as to which fitting is the inlet and which the outlet.  Will post a picture of the pump in a few days, when hopefully I will have a timing cover to also photograph. 

-Doug

Offline Derek

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Re: Oiling on an EW 350
« Reply #6 on: 14 Nov 2005 at 06:45 »
I just discovered that there may be two variations of the duplex pump style.  Looking through some EW handbooks, I see one illustration shows the lower of the two fittings as the oil inlet and the upper fitting goes to the sight glass.  In another handbook the upper fitting is shown as the feed to the oil pump and the lower goes to the sight-glass.  I am not entirely sure if this is not an error in the handbook, further investigation is required.  Meanwhile I have removed the specific reference in the previous post as to which fitting is the inlet and which the outlet.  Will post a picture of the pump in a few days, when hopefully I will have a timing cover to also photograph. -Doug

Dear Ian & Doug
Thanks for all the information, Ian was kind enough not to mention that it was my EW at the rally which experienced thew problem of excess lubrication evident from the copious amounts of smoke each morning (cleared later) and the rustproofing of all external surfaces below the level of the seat springs.
From the information to date it seems I have read (or misread) a very unclear oil diagram I had available. During the rally the oil line from the tank was connected to the upper fitting of the pump another, I had actually changed it from the other way around after reading the diagram referenced above. The change was re-inforced by the fact that we attained an oil flow through the sight-glass.

Prior to the rally the bike had only been finally asssembled and ridden in the previous week (about 25 kms). It had been very smokey at the start (due to what I had thought was a build-up while standing a few days with oil in the tank) however this cleared shortly after sufficiently amusing all my employees and gave a trouble free 25 kms of riding at 40 to 65 kms.

However, at the rally a week later about 2 inches of oil drained into the timing case over-night (because I thought I would do the right thing and prepare everything the night before). The result was not that much smoke but a fairly dramatic distribution of oil from the joint between the timing case and the magneto, basically covering the full length of the bike (and me), fore and aft, to the level of the seat springs. Immediately after starting their was a very strong flow through the sight-glass, half filling it. After that it settled down a bit but continued to drip at a fairly strong rate even when adjuster screwed down. The interesting thing was that the oil continued to drip though the sight-glass for some considerable time after the engine was stopped.

The earlier discussion points have certainly shed a higher level of understanding on the oiling system of my EW.  I can see how I got somewhat confused with the different system information around. I look forward to further information - thanks for the assistance.

As far as the VMC rally was concerned, it was great, great bikes (including four Douglas) and good friendly company.

Best Regards
Derek Firman

     

« Last Edit: 14 Nov 2005 at 09:43 by alwyn »

Offline Doug

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Re: Oiling on an EW 350
« Reply #7 on: 26 Nov 2005 at 04:55 »
I have been doing a little more investigation, and have come up with the following.  The illustration of the oiling circuit for the duplex pump as shown in the “Running Instructions for E.W. Model Douglas Motor Cycles” contains an error.  This shows the fittings for oil-in and oil-out of the pump reversed.  This incorrect illustration can be further identified by the sub-description “As fitted to all Engines from No. YE 6418”.   What I gather to be a slightly later publication, “Care and Maintenance of the 350c.c. E.W. Douglas” shows a redrawn illustration of the duplex system that has the correct oil line connections.  The sub-heading on this illustration reads “As fitted to all Engines from No. YE 6450”, rounding up to leave eighty two owners misguided!  But at least they got the oil lines hooked up properly!  So unless someone comes up with an example to the contrary, it looks as if there is only one version of the duplex pump. 

The correct connections for the duplex pump, is the lower of the two fittings is the feed into the pump, and the upper is the oil out to the sight glass.  I think the error in the illustration came about due to the fact that when Douglas switched from the gear-type pump fitted to engines up to YE6417, they designed the duplex pump to utilize the existing timing cover with the minimum of alterations.  Originally the one and only fitting was the feed in to the top of the gear pump.  The oil then exited out the bottom of the gear pump and went to the crankshaft quill via drillings in the timing cover.  With the duplex pump an output to the sight glass had to be arranged.  The existing (now upper) fitting became the pump output, and a lower fitting added which became the feed in to the pump.  This role reversal made the circuits in the plunger pump somewhat simpler to arrange.  But is seems the illustrator got mixed up or miss-informed about the change. 

However, back to your original problem.  I am at a loss as to why your sight glass should drip for a substantial time after the engine stops.  True, the line between the pump and the sight glass is under pressure, but that should bleed-off fairly rapidly once the engine stops.  There is a one way plunger valve in the top of the pump that doubles as a pressure relief bypass feature, controlled by a coil spring.  The force of this spring seems like it can be quite critical.  This is just speculation, but if it is a bit on the stiff side, it could prevent the pump from bypassing (or the valve can be stuck) and so develop a higher pressure to the sight glass, forcing its way past the needle valve even when it is closed way down.  But this is limited as the pump stroke for this is a function of a return spring; it can not develop a pressure higher than the spring can create.  Also your needle valve in the sight glass might not be restricting the flow as much as it might when screwed home. 

Also the sight glass filling up initially then settling down is puzzling but may be normal behavior with this system.  When the engine is cold either the pump is supplying more oil, or the engine is taking the oil more slowly (not fast enough to clear the sight glass.)  Of course both could be at play.  If the pump is worn, cold, thick oil will achieve a better seal and pump more effectively than in the normal course of operation (this of course can be over-done.)  The same cold thick oil may have trouble being sucked past the restriction in the non-return valve screwed into the base of the front cylinder, causing the oil to back up into the sight glass.  Though the oil is supplied to the sight glass under pressure, it still relies on gravity and vacuum to get out.  Even though a total loss system, engine heat does affect the oil flow as it passes through the pump in the engine on the way to the sight glass.  I think 40-50W oil is appropriate for this system. 

Ian brings up quite a good thought, and one I had not considered.  A bad gasket between the oil pump and the timing chest cover might cause it to deliver too much oil, if rather than pumping oil back up through the sight glass to be metered, it were to hemorrhage directly into the timing chest.  This should result in too much oil dripping onto the primary chain, if the overflow is doing its job.  But the additional details given by Derek tend to suggest the excess oil is entering via the sight glass. 

A technical article has been added given more detail and pictures of the duplex pump system that should expand and clarify the points just mentioned. 

The link to it is here:
https://www.douglasmotorcycles.net/index.php/topic,1002.0.html


-Doug

Offline Ian

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Re: Oiling on an EW 350
« Reply #8 on: 09 Dec 2005 at 05:18 »
Doug, all this discussion has made me understand how different the setup will be on my OC to what was implemented with the EW. My OC has a single oil pump driven off the magneto shaft. I had always assumed that it would get oil directly from the oil tank and then supply it under pressure to the sight feed on the tank - and that you could switch between that and the hand pump. After studying pictures and reading the brief description in the catalogue I have, I now think that the oil line comes from the sight feed to the mechanical pump and then directly to the motor. In which case the mechanical pump is using suction to draw the oil through the sight feed. I also assume that there must be a two way tap to switch between a direct oil pipe from the tank to the sight feed and the hand pump. Do you know anything about these systems ? If it does work this way it answers some questions I had about controlling the pressure the mechanical pump could produce !!

Offline Doug

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Re: Oiling on an EW 350
« Reply #9 on: 10 Dec 2005 at 04:15 »
Quote from: Ian
Do you know anything about these [OC] systems?

No, nothing beyond the same 1927 Brochure you likely have.  In there it states the pump sucks oil through the sight glass, so it sounds like the same system used on the early gear pump EW models.  I think the OC used a small gear pump very similar to the early EW, based on a photo of a partially sectioned engine I saw.  The handbook also mentions that a tap has to be turned 90 degrees to bring the hand pump into action.  Unfortunately there are no illustrations of the oiling system/circuit in this handbook, and I have not seen a good period photo showing the plumbing. 
-Doug