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Old 11-06-18, 12:05 PM   #1
Dan_pt
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Default Douglas Side Valve Flattie

I collected a nice little future project at the weekend that is a little bit unusual and (I think) quite interesting. It is a side valve Douglas flat twin that the previous owner had owned for 30 years without touching it. He rescued it off what he called a lift truck in a scrap yard.





The "wheel" on the front looks like a centrifugal clutch and has a sprocked behind it.



It is driven indirectly from the crank through three bevel gears so will run in the opposite direction to the engine, the insides look like a differential..
The centre gear is fitted to the starting shaft which runs alongside the RH cylinder.




The flywheel is machined to take a car type clutch, the spigot bearing is still fitted.



I wonder what those plugs will be like to get out?



Finally, the lack of an oil filler ir even a dipstick plus the presence of two oil line connections low down on the crankcase make me wonder if this engine is designed with a dry sump system.



Either that or there is a rather large bit missing!
The general condition appears good, there are a few chipped/broken fins and something is missing off the front gear casing but generally I am pleased with what I've got.

Dan.

Last edited by Dan_pt; 11-06-18 at 04:02 PM.
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Old 11-06-18, 07:22 PM   #2
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Kim Siddorn had something similar which he said was a pallet truck engine - apparently the hydraulics were driven by engine oil pressure.

See attached pic from Jeff Clew's 'The Best Twin' book which says that the engine was a variant of the 596cc EW motorcycle unit.


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Old 11-06-18, 08:15 PM   #3
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Thanks Nick. I found out a little snippet on Google where someone mentioned one having an oil tank for showing so it probably is a dry sump engine. At around 600cc it is a reasonable size then.... that said, it is quite heavy.

Dan.
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Old 11-06-18, 09:10 PM   #4
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The best way to get those brass valve caps is to get a really good fitting spanner or socket at least they haven't been butchered
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Old 11-06-18, 09:30 PM   #5
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Quote:
Originally Posted by oliver View Post
The best way to get those brass valve caps is to get a really good fitting spanner or socket at least they haven't been butchered
All being well they will stay that way......... Hopefully

Dan.
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Old 13-06-18, 10:36 PM   #6
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Well, I couldn't resist having a look at the internals of this engine so today I thought that I'd pull the heads off to check the bores. Another reason for this is that I jet washed it to remove years of filth and I wanted to assure that no water was left in the cylinders............

They were soon off.....





The bores are in superb condition and have been taken out to +30, water had made it into the cylinders too..





Me being me just pulling the heads was never going to be enough

The front gear housing was removed next...



Followed by the cylinders. The pistons look very clean and have surprisingly short skirts. Despite looking bright like aluminium they are quite heavy so are probably cast iron.



The governor is a neat little assembly with balls running in tracks inside the outer cover, the spring is rather heavy but the unit is run at at least double crank speed.



What was it I said about built up cranks on four strokes???...... This has just that. I wasn't expecting roller element big ends on this engine.



The flywheel simply bolts up to this plate and was easily removed.



Here is whats left of it tonight. I will be putting the crankcase assembly through the hot wash tomorrow to see how it comes up.



This seems to be a very well built engine, I wonder what speed it will want to run at once it is back together. the governor had been blocked by connecting its arm to a fixed anchor so it clearly has been run as a variable speed engine. I intend to try and reinstate the governor to control the speed once it is all back together.

Dan.
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Old 13-06-18, 11:01 PM   #7
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Quote:
that. I wasn't expecting roller element big ends on this engine.
Were you not? ABC were using rollers in 1915, Nick might be able to confirm whats used in the Marconi Douglas units.
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Old 13-06-18, 11:10 PM   #8
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I assumed that it would be like a Norman T300. The whole workings run on ball races, fortunately the bottom end rotates nice and smoothly.

Dan.
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Old 13-06-18, 11:42 PM   #9
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Quote:
Originally Posted by skankin_giant View Post
Were you not? ABC were using rollers in 1915, Nick might be able to confirm whats used in the Marconi Douglas units.
Plain bearings like its motorcycle counterpart but many subsequent models were rolling element - have to read up on EW.

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Old 18-06-18, 10:44 PM   #10
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This little engine has received a decent amount of attention this week and to be fair it has been pretty easy going as it is in such good condition...... not having to paint anything helps too!
The crankcase responded very well to the session in the hot wash...



The cylinders received a light hone and clean up before being refitted........ along with the pistons!



The engine immediately looked much better once the heads were back on.



The governor was next, I couldn't get the housing back on over the governor still fitted into the crankcase so I gently levered it out and assembled it off the engine. I heated the crankcase up with a hot air gun to ease the fit on the governors inner bearing, the assembly easily slotted back into place.



Next up was the inlet manifold..



Remember that I said the governor was blocked with a fixed anchor??



Well, it turned out that it wasn't a fixed anchor at all. It is actually a second throttle assembly. The engine is a variable speed unit but ultimately the governor has the final say in just how fast it will run.





The unit was seized solid but was pretty easy to free off. Initially, I had assumed that it was a simple adapter plate but as it turns out it is much more than that!

The carb was pretty clean inside but the flange was terribly distorted. There was around a millimeter of distortion in it that was removed with a file and then finished off with fine emery cloth on a flat surface. The flange is now perfectly flat and should seal perfectly.



The front housing and clutch assembly will be cleaned up tomorrow, the engine now has two good compressions and hopefuly will be running soon. I do still need to sort an oil tank out though.

Dan.
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