Author Topic: Cam chest for early 1920s 4 hp Douglas [and 3 1/2 and OHV Sports]  (Read 5377 times)

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Offline cardan

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I came across this interesting Douglas part today. I assume it is a cam chest for a 4 h.p. Douglas.

I thought it would be worth posting for a couple of reasons. Many forum members have 2 3/4 Douglases of various types, and it's interesting that the construction of the bigger bike - first 3 1/2 hp then 4 hp - is so different from its smaller brother. The second interesting thing is that the engine number 8040 is stamped on this relatively small part of the motor - pretty silly when the part can be detached so easily! Is the number also stamped on the crank case?

Wouldn't it be great to re-unite the cam chest with its original crankcases. The gasket surface is stamped W66 which I take to be a matching number. Does anyone have a 4 hp crankcase with W66 stamped on the gasket face?

A final thought: how similar is this part to the equivalent part on the OHV Sports model S1/S2?

Leon
« Last Edit: 23 Jan 2014 at 06:42 by cardan »

Offline graeme

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Re: Cam chest for early 1920s 4 hp Douglas
« Reply #1 on: 19 Jan 2014 at 11:02 »
Hi Leon

On the 3 1/2 and 4hp engines I have seen, the engine number is only in this position. I guess there was no thought in the day of the possibility of such engines being stripped and subsequently being sought out for restoration decades later!

Cheers, Graeme

Offline oil baron

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Re: Cam chest for early 1920s 4 hp Douglas
« Reply #2 on: 22 Jan 2014 at 00:28 »
Hi Leon
I thought you might like be interested in to seeing my orphan, at least you have a machining number to try and possibly match your orphan with its other matching 2 parts of its crankcase.  I have photographed my orphan which is definitely a 3 1/2 hp, unfortunately there are no machining/assembly number to match it with its buddies.  I don't even know its engine number, it looks like a small 14 with larger 534, the larger numbers typical Douglas typeface.  As you can see quite a bit of development has taken place over the years between yours and mine, the casting is much more substantial especially on the mating faces, the cam followers are now roller, the camshaft is more substantial, putting one against the other would probably throw up a whole heap more differences.  Thought it might be of some interest to compare the two.
Keep up the good work, anything more in the wind on the R.A. saga, it has been really interesting up to now.
Best of Luck
Steve L

Steve L

Offline cardan

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Re: Cam chest for early 1920s 4 hp Douglas
« Reply #3 on: 22 Jan 2014 at 09:58 »

So everyone has one! I suppose 14 534 means engine number 534 from 1914?

Can anyone supply photos of the equivalent S1/S2 part? Then we'd have the the full set!

Lots of advancements on the RA front, so watch this space.

Cheers

Leon

Offline Doug

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Re: Cam chest for early 1920s 4 hp Douglas
« Reply #4 on: 23 Jan 2014 at 00:20 »
Leon,

Here is an illustration of the 3-1/2hp Sport cam 'box'.



There is a vertical 'tower' capped by a hex plug, tho hole for which can just be seen above the camshaft. Purpose unknown, but not present on the side-valve 3-1/2 and 4hp models. The engine number would also carry the prefix "CE" for the OHV Sports.

-Doug

Offline cardan

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Re: Cam chest for early 1920s 4 hp Douglas
« Reply #5 on: 23 Jan 2014 at 06:41 »
Thanks Doug. The man in your illustration is showing us that the flat-footed cam follower is stopped from rotating by a peg in its shaft and a corresponding groove in the guide that lives in the crankcase - very similar to the RA.

The valve lift detail is also interesting. On the 4 h.p. version (and possibly the others) the valve lift mechanism "hangs" on the rotating camshaft, and is operated by a cable that enters the cam box horizontally from the front. RA and later machines used a quite different arrangement, which did away with this pretty poor piece of engineering.

If anyone needs the 4 hp cam chest in the top post let me know.

Leon
« Last Edit: 23 Jan 2014 at 06:47 by cardan »

Offline TonyC

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Hi Leon,
Have taken some photos of the S2 engine I am stripping down and sent them to be attached to this topic.
All looks in good condition just needs a good clean.
What is the easiest way to remove the end caps on the gudgeon pins? Don't want to damage them!

Regards Tony












[Photos added. 31Jan21, Doug, Admin]
« Last Edit: 31 Jan 2021 at 15:28 by Doug »

Offline cardan

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Hi Tony,

Most 100-year-old motors have non-standard pistons.

That said, I'd expect that the gudgeon pins are parallel and hollow, and the brass end caps are just pushed in, usually interference fit inside the pin with the outer diameter smaller than the hole in the piston and little end. If so, the pins should just come out with the pads in situ. Your pistons seem to be aluminium, so some gentle warning before pushing out the pins will help.

Just beware the tapered or stepped gudgeon pin, usually reserved for two-strokes or weird early engines.

Have fun, and go carefully,

Leon

Offline Hutch

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Tony and Leon,

Attached is excerpt from The Handbook of the 3 1/2 H.P. Sports Model Douglas (i.e. S1). The disk type gudgeon pin fixing could be similar to what is on the S2 engine?



Hope this helps,

Cheers

Ian

[embed attached image. 01Feb21 -Doug, Admin]
« Last Edit: 02 Feb 2021 at 03:32 by Doug »

Offline BlueSilver

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Dear Leon,
I found the numbering of the 4 hp intresting you mentioned ,and now I have checked the crank case of the engine I am busy to restrore at the moment and found some more numbers.

Regards Leo.



[Image orientation/aspect ratio corrected.  05Mar21  -Doug, Admin]
« Last Edit: 05 Mar 2021 at 22:09 by Doug »

Offline cardan

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Hi Leo,

Good looking cases!

X38 is the matching number, stamped on all the three major castings of the motor. Matching numbers mean they started life together in the same engine.

9935 is the engine number: from the Dougs' dating info https://www.douglasmotorcycles.net/aa-files/html/identify-part1/veteran3.6.htm this would seem to be at the end 1919.

Cheers

Leon

Offline Doug

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They were very vigorous with the stamping, even including the patent numbers and dates on the top!

-Doug

 

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