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General => Douglas Racers and Racing History => Topic started by: pvn06 on 03 Mar 2019 at 13:05

Title: Still looking for 1914 OHV Heads?
Post by: pvn06 on 03 Mar 2019 at 13:05
Hi All,
I haven't had chance to post many updates recently, but am now back working on my Douglas 2 3/4hp project bike, which I am hoping I might have back on its (now restored) wheels later in 2019.

However, as a future project, I still have in the back of my mind it would be nice to build a recreation of the first OHV racing bike - of the type used by Douglas in the 1914 TT.  With this in mind I have been slowly acquiring possible donor parts - a very rough 1917 2 3/4hp frame and forks (would really appreciate if anyone has a gaff 4 hp frame for sale though - with duplex front tubes) or reasonable fork blades as mine will need retubing) or any other period parts.

Particularly though .. . I would love to hear if any of the original OHV engine parts have survived, particularly cylinder heads (which I would really like to acquire).  As far as I can tell from the few photographs of these engines available - they look to use the 2 3/4hp crankcases, but special barrels and heads made only for this model.  As far as I can tell there was a second hand oil pump fitted (built into the oil/petrol tank behind the normal one) - which looks to be feeding oil directly to the bigend. 
I have seen one photograph of what I assume was a prototype engine with barrel/head combined (as per SV 2 3/4hp models), but all other photos look to show seperate head/barrels.


I thought that if I was to make a recreation of this engine I would need to have patterns made for both barrels and heads - but fortunately, I recently acquired a set of early 350 barrels which with some machining look like they will be suitable.  I am assuming these are from the first production OHV models of 1920/21, but luckily these are correct 350 bore (others I have seen have been 500), and have correct '2 stud' type mounting points to the crankcases.  They are actually '3 point', but from the look of it the 3rd casting mount can be removed without issue.  They will also need the base flange machining as it is much 'beefier' than the original SV barrel flange on 2 3/4hp models.  However, very close and looks like it will save me having to have these cast.

It would be great if a set of heads were to turn up in the same fashion - and save a lot of grief.  This is a (very) long term project bike anyway, but any parts or information anyone has about this model would be greatly appreciated - and obvioiusly if you have any old head parts propping open a shed door, then please let me know!

Best wishes
Paul
www.RacingVincent.co.uk
Title: Re: Still looking for 1914 OHV Heads?
Post by: cardan on 17 Sep 2019 at 08:32
... I recently acquired a set of early 350 barrels which with some machining look like they will be suitable.  I am assuming these are from the first production OHV models of 1920/21, but luckily these are correct 350 bore (others I have seen have been 500), and have correct '2 stud' type mounting points to the crankcases.  They are actually '3 point', but from the look of it the 3rd casting mount can be removed without issue.

Hi Paul,

I think you'll find the "3-point" 350 barrels date from the late 1920s or early 1930s. Yours look to be possibly the ohv D28:

https://www.douglasmotorcycles.net/index.php?topic=2161

The side-valve cylinders from bikes like the "EW sports" and the A31 are similar, but have fins cut away to clear the valve chests which were part of the detachable head:

https://www.douglasmotorcycles.net/index.php?topic=3407

You might be interested in the early ohv chronology in this thread on Les Bailey:

https://www.douglasmotorcycles.net/index.php?topic=7014.0

Cheers

Leon