Author Topic: Douglas D28  (Read 5866 times)

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Offline MartW

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Douglas D28
« on: 13 Mar 2016 at 18:47 »
Wanted - Handbook for D28 or even or photocopy/information to enable me to to rebuild the engine.

Offline Alan Cun

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Re: Douglas D28
« Reply #1 on: 15 Mar 2016 at 09:51 »
Hello There,

The D28 and D 29 used most of which was used in the 27 and 28 EW with some exceptions.
Four studs secure the motor to the frame base. I dont think the shaft has the drilling of oil ways for lube of the big ends thus making a stronger shaft for the extra power. Therefore the big ends rely on splash. I believe the barrels with detachable heads are the same as EW and A29 models with detach heads. The sight glass is on the timing cover and without taking off my cover think the oil pump a bit different to early EW.

regards Alan

Offline cardan

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Re: Douglas D28
« Reply #2 on: 15 Mar 2016 at 12:16 »

Here's the extract from the 1928 Catalogue.

The age of the "workshop manual" had not yet arrived in the 1920s. There were sometimes rider's handbooks if you were lucky, but these were mostly pretty simplistic stuff. There were handbooks for the EW, but I don't have anything for the D28.

Cheers

Leon


Offline Doug

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Re: Douglas D28
« Reply #3 on: 15 Mar 2016 at 21:16 »
I have yet to see a handbook for the D28/D29 models. Just the catalog specifications, like Leon posted. As Alan said, the D28/D29 engine was based on the 350EW, with some changes to reflect the increased power.

On the EW the drive side main shaft is drilled hollow. On the K/M32 (the 1932 version of the D28) they certainly did not drill the main shaft, so that it was a little stronger. This practice may have started as early as D28 (and the colonial 350 version of the EW not built to a weight limit), but I am not certain.

Initially, judging by catalog images, they intended to feed oil into the end of the crankshaft via a timing cover mounted oil quill. But it may have been determined this weaken the crankshaft too much. Some machines still have the boss for this quill on the timing cover, un-drilled. Most have a smooth faced cover. The oil exited the timing cover and went to a one-way valve at the base of the front cylinder, and lubrication was solely by splash.

The oil pump mounting screws and oil ports are located a little differently on the timing cover of the D28 versus the EW350, so the pump must have been a little different too. However I have not seen a D28 oil pump, just the timing cover casting.

-Doug

Offline cardan

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Re: Douglas D28
« Reply #4 on: 15 Mar 2016 at 21:30 »

Interesting Doug. Here is some detail of the catalogue illustration, but remember that the artist has been at work so detail should not be taken as gospel.

Leon



Offline Doug

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Re: Douglas D28
« Reply #5 on: 15 Mar 2016 at 23:50 »
Leon,

I doubt that the artist added the fitting for the quill. It was probably present on the prototype, which the catalog illustration would have been based upon. But at some point, it was eliminated from the production machine.

Much the same situation exist with the OW/OB model. The initial catalog illustrations show it with the gearbox attached to the rear of the engine, like the RA. Yet all existing OW/OB models seen (so far!) have the gearbox mounted to the frame under the saddle. At some point between prototype and production Douglas changed the specifications, but it was too late (or not cost effective) to alter the advertising.

And there were some models of which there are photos or illustration of, which never made it to production.

-Doug

Offline cardan

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Re: Douglas D28
« Reply #6 on: 16 Mar 2016 at 00:25 »

Sorry Doug I don't know what the quill is?

Leon

Offline Doug

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Re: Douglas D28
« Reply #7 on: 16 Mar 2016 at 00:59 »
Leon,

Um, not sure what the Auzzie word would be. The spring loaded hollow tube that sticks in the hole in the end of the crankshaft to deliver oil. On the EW, the external manifestation of this was the hex head fitting/plug on the timing chest cover (threaded 9/16-20), aligned axial with the crankshaft. Just like the D28 catalog illustration.

-Doug

Offline Doug

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Re: Douglas D28
« Reply #8 on: 16 Mar 2016 at 02:04 »
Examples of D28 timing covers with the boss, but no fitting. There was also a timing cover option with the BTH pancake dynamo.





-Doug

Offline cardan

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Re: Douglas D28
« Reply #9 on: 16 Mar 2016 at 09:00 »
Um, not sure what the Auzzie word would be. The spring loaded hollow tube that sticks in the hole in the end of the crankshaft to deliver oil.

OK. Got it. I've got one of those on my Works Rudge, I just didn't know what it was called. Now I can tell people about my quill!

Leon

Offline MartW

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Re: Douglas D28
« Reply #10 on: 17 Mar 2016 at 21:42 »
Thanks everyone for your input. I was hoping to do some hkmework before starting this project. Specifically need info as to whether the magneto timing is the same as OHV engines. Also, how to adjust the tappets. I believe they are concentric cam in roller bearings. 

Offline oil baron

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Re: Douglas D28
« Reply #11 on: 18 Mar 2016 at 03:32 »
Hi There
 
 I have not seen any figures published for either magneto timing or tappet clearance for the D28 or the later K & M models. I used to time the magneto my M32 to full retard at TDC on the firing cylinder, there being enough advance on the handlebar lever to find the "sweet spot". 
As the D28 bottom half and the later K & M models and were all based on then current side valve engine.  The D28 certainly looks very EW-ish. The later K & M models differed in the crankcase, oil system and principally the cylinder heads, the rockers being mounted in split plain bronze bearings.
The cams timing gears etc were common to the side valves as far as I was aware.
To  adjust the tappets on the K & M models, and I imagine the D28 is similar, it is necessary to undo the castillated locknut on the pushrod tube. The pushrod tubes comprises of two halves that screw together, the smaller diameter screwing into the larger after undoing the lock nut fully,  this will then expose the ball ended adjusting screw  which is screwed into the cam follower and locked in place with a locknut.  From memory I think the clearance I ran was 6 thou. measured between the rocker and the end of the valve valve stem
Best of luck with you interesting machine, there are a few about but not many.

Regards  Steve.L.
Steve L

Offline cardan

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Re: Douglas D28
« Reply #12 on: 18 Mar 2016 at 07:58 »

We've discussed EW magneto timing before - it is a crazy (but necessary) 50 degrees BTDC. I'd guess 40 degrees BTDC with magneto fully advanced would be a good number for the D28. I don't like setting timing using a fully retarded magneto, because the range of advance varies from magneto to magneto. Also the outside flywheel makes it very easy to time the magneto: 36 degrees corresponds to one tenth of the flywheel circumference.

Leon

 

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