General => Douglas Motorcycles - General Discussion => Topic started by: Brian on 07 Feb 2007 at 18:06

Title: Douglas Aero Engines
Post by: Brian on 07 Feb 2007 at 18:06
Can anyone suggest a source of info on the applications of redundant DT engines ,and later the specially-designed engines up to 10,645cc ,for light aircraft ?
I have read the relevant chapter in "The Best Twin" and have some refs to various AERO ENGINES LTD products of mid thirties,but i would like to see more pictures and drawings of
these motors so i can collate everything into a small book.

Title: Re: Douglas Aero Engines
Post by: Doug on 14 Feb 2007 at 04:36
Well that is a pretty tall order! Original source information on the Douglas aero engines is pretty scattered. What you see in The Best Twin is by far the best compilation available on the subject in one spot. Since you have undoubtedly read that, you will know their aeronautical aspirations long proceeded the DT era.

It seems the first factory involvement (verses amateurs converting a second-hand motorcycle engine) centered on the 1923 OHV engine from an S2 model of 733cc (though often classified as a 750.) These were used direct drive and through a chain drive reduction unit bolted to the top of the engine via a very long extended set of crankcase bolts (the S1 and S2 was like the 4hp side-valve in that the crankcase was split horizontally.)

Pictures of the reduction drive:

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Mention is made of a program printed of the 1923 Lympne competition sponsored by the Daily Mail. I have only seen portions of this program, which primarily seem to be little more than just a list of entrants, eleven of the twenty-eight having Douglas engines. I have heard the whole competition was written up in a book The British Light Aircraft circa 1965, unseen.

Clew then says the next application of a Douglas engine for light aviation was 1932, but this is not quite correct as in the engine prefix appendices of his book there is mention of GE/1A 4hp. Aero engine (for Royal Aircraft Establishment glider) 1st stamped GE/6 No date, but engine prefix GE/ is assigned to 1923 68x82 engine. This must have been a very early appearance of the OB engine, as the S1/S2 and the RA models had 68mm stroke crankshafts. In any event, I quite by accident ended up with the remains of engine GE/6 with some DT spares, and it is essentially an OB motorcycle engine with aluminized (clad) cylinder barrels and heads. Nothing remains to indicate it was used for aviation.

Publications of the time tend to focus more on the airframes rather than the engine, so anything you cull will be of derivative nature. Publications to look up are Aeronautical Engineering, Supplement to The Aeroplane. The September 19, 1923 issue on page 296 has a nice line drawing of Mr. Raynham's Douglas power plant installation.

Then moving on to 1932 we have the well known Sprite, based on the F/G31 motorcycle engine. There seem to have been two versions of these. The first used the cycle barrels. Then a version was made with circular fins on the barrels and horizontal fins on the cylinder heads, better suited to cooling in the aviation application. This latter was 79x82 for 803cc. Both are commonly (miss?) stated as 750cc models, though I wonder if the earlier one was not really a 600cc displacment. I have not seen a publication for the Sprites but I suspect Douglas probably did make a pamphlet. I have also seen a one page of a crudely typewritten data sheet, much like the factory issued for the DT. It references additional sketches for the petrol and oiling systems not seen. They did pass off a Sprite engine as an OW/OW1 engine on the cover of that model's 1934 brochure, the back prop flange is prominently in view, as well as a corner of the AC fuel pump can be seen on the far side! However the crankcase and timing cover joint for the 1934/35 models was completely redesigned from the 1931-33 models, and as shared by the Sprite. The only thing they had in common was the upper end. So to pass it off as an OW/OW1 engine was a bit cheeky.

The F/G31 based Douglas Sprite:
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The 79x82mm engine with new cylinders, heads, and timing cover:
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These Sprites powered various Planette, Tipsy, Gordon Dove, and B.A.C. Drone designs. It is write-ups on these that are more numerous than information on the engine(s) themselves. Some places to look is a book called Ultralights (no further information); Aero and Airways Oct 1935, test report #8, The B.A.C. Super Drone; Seventy Hours of Dronish Delight in Aeroplane Montlhy November 1974; and Vintage Ultralights, B.A.C (Kronfeild) Drone, Popular Flying Jul-Aug 1983.

Henri Mignet and his Flying Fleas 1990, ISBN i085429-765-0, has some information re- Flea powerplants, Douglas included. It lists a Douglas Sprite of 500cc, 17hp. This is probably meant to be the cycle barrel engine. Then it lists an Aero Engines Sprite, of 803cc displacement, and 25hp. This is the 79x82 engine. There are a number of pictures of Douglas powered Fleas, perhaps the most terrifying using a 4hp side valve engine!

Then then the crankcase was redesigned specifically to suit airframe mounting. The mounting saddles run across the case rather than longitudinal as in the case of the cycles. Also the timing chest was far more elaborate, incorperating dual magneto drive. There is one shown in Clew's book, as well as there being a sectioned engine on display in the Bristol Industrial Museum. The rules requiring dual ignition apparently came out just about this time, catching Douglas by surprise and requiring a redesign. Clew captions this as engine 1800cc, but it shares the same barrels and heads (now with twin spark plugs) as the previous 803cc Sprite. Whether these were intended to also be marketed as the Sprite is unknown. They have been seen with the same brass plate affixed to the rocker perches, but the perches are interchangeable with the smaller engine, so it might be a case of mistaken identity.

The display engine from the Bristol Industrial Museum, at the Bristol Cavalcade 1988:

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Then there was the Dryad which was written up and illustrated in Flight of May 18, 1933. This was stated as a 92x92 engine for a capacity of 1.2 liter. This looks to have been designed from the ground up as an aviation engine, rather than an evolution of a motorcycle engine.

The "Dryad":

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It never seems to have gone into production. It had a shaft driven novel cam in head design, almost but not quite OHC, subject of a British Patent 405304, applied Sep. 16, 1932, and accepted Feb 8, 1934. The illustration accompanying the patent shows a conceptual single cylinder test engine.


[odd formating characters removed. -Doug 19sep07]
Title: Re: Douglas Aero Engines
Post by: Brian on 08 Mar 2007 at 19:19
I continue my researches into "Aviation Applications of Douglas Engines 1923-1939",and the file grows steadily.What a mine of gen Doug is,and how willing to share.I had most of the facts in his post, but what super pictures of such rare bits as the reduction unit! Thanks a lot Doug.
I have found that the Dryad did get into the air,and how about a Trimotor Aircraft with Three Sprites that did 160mph with 4 people on board ? I am going to include the Pullin-designed twins,plus the fours(flat and inverted in-line), the V-6 and V-8 projects that followed the Douglas and Aero Engines Ltd motors.
My"Aircraft using Douglas/AE Engines" page now lists 19 types.
More anon,as they say.
Title: Re: Douglas Aero Engines
Post by: Doug on 13 Mar 2007 at 14:42
You may also then want to check out (if you have not already) these patents by C.G. Pullin after he left Douglas, taken out in conjunction with G&J Weir Ltd circa 1935, who were into helicopters and autogyros. They show various features and aspects of engines.


Title: Re: Douglas Aero Engines
Post by: Brian on 15 Mar 2007 at 13:28
Many thanks ,yet again Doug,for the Patent Number info. I am currently focussed on the doings of Cyril.G.Pullin and another ex-Douglas emplyee when they joined Weirs.
Pullin became a Director of Weirs at Cathcart Works, Glasgow, in 1940.
He was responsible for the design of the1500cc Flat Twin and the 4 cylinder ohc engine
which followed it,for use in the W-2/W-3/W-4 Autogiros.The W-1 was fitted with the
Dryad, designed and built at Kingswood before Douglas went down.
I am about to view the W-2 Autogiro which survives here in Scotland,to check whether it has
the "Dryad II" ,as advertised by the Museum ,or the Weir(Pullin)1504cc Flat Twin
which followed the Dryad.I cant imagine that they would have used the same Dryad
 name for two such  different engines,from two different manufacturers.In fact it was only known as"the Flat Twin" engine at Weir.
Ive just discovered some good pictures of the Douglas Sprite fitted to the
smallest Tri-Motor Aircraft, at 26feet 4 inches span and 19feet long,and 4 seats for
a max all-up weight of 2,400lb.Those motors must have been working hard for a
 climb-rate of 600feet/min.The Helmy Aerogypt (honestly,that was its name) had a max speed of 160mph.

Much more anon(when Ive climbed up to see the W-2 Autogiro*,which hangs from
the ceiling in the Museum of Scotland!)   * spelt with and "i" not a "y", only at Cierva /Weir.
Brian Thorby
Title: Re: Douglas Aero Engines
Post by: Brian on 19 Mar 2007 at 18:46
Has anyone (besides Doug, I expect!) heard of a Dryad II ? The motor that I have yet to see close up,but have a recent indistinct photo of in the Autogyro,is described as a Dryad II.
It looks very "technical",where its cylinders protrude from a conical fairing .It fairly
bristles with bits.I look forward to a closer view.
I found the smallest UK-built Ultra Light Aircraft(Ward Gnome) with a curiously described
"Douglas Engine" hanging from a Hangar roof.It has a Side-Valve H.O Twin Engine with
a tall crankcase, looking very Industrial Engine-like.Radial fins on cyl-heads.
What a strange combination for use in a plane built in 1966.
It was registered and flew.I have asked the guardians of this midget, at the Museum
in England, to get a ladder and geet some close-ups and numbers of the
mystery motor.So far we have 5 existing Flying Fleas(Henri Mignet HM14) with Douglas
engines(none flying) plus a 350-powered modern-built example which ground runs(very wise)

More anon.
Come on Doug,I bet you have one of these Dryad II's in the shed
Title: Re: Douglas Aero Engines
Post by: Doug on 20 Mar 2007 at 18:17

No, actually I had not heard of a Dryad II, and no I do not have one out in the shed!  :P I do have a loft out there with some Dougie bits stored, but that is as far off the ground they have ever gotten. Of course, the same probably could be said of most of Douglas’ aeronautical efforts!

Until you mentioned a Dryad installed in an airframe in a Weir W2, I was not aware any survived beyond a prototype stage. But then I have been more preoccupied on the motorcycle side than with Douglas’ aeronautical ambitions. All I have ever seen on the Dryad was the brief articles in Flight, from where the earlier image in this post was copied from. Possibly some of the patent illustrations that I mentioned are for the Dryad II, without being credited as such?

And of course this ignores the HO twin cylinder pony engines (in air and water cooled variants) that were prototyped to start larger piston aircraft engines. I think one of those might be a Douglas installation that I could feel reasonably safe flying behind!

Title: Re: Douglas Aero Engines
Post by: Brian on 21 Mar 2007 at 12:02
Hi Doug,
Thanks for owning up that there is nothing "funny" in the woodshed.

So far,the Dryad II (which exists ,in the Prototype W-2 Autogiro) has an angled
drive to clutch-in the rotor,in a reareward compartment of the Crankcase,as per GB 433340.
So you could be right about the Patent ref.The first flight of the W-2 was in 1933,so the mills of the Patent Office would have ground exceeding small for the 2 things to be connected. The W-1
prototype had the one and only Dryad(as far as I can see).This engine was Cyril Pullin and George Walker's last project before moving off to Weir, as the Douglas-ship went down.
Power went up from "40bhp" to "50bhp",between Dryad 1 and Dryad II it is said. The proof of 2 different models I hope to find, when I get up close to the W-2 Autogiro.

I'll send some pictures soon I hope.
Title: Re: Douglas Aero Engines
Post by: Brian on 26 Mar 2007 at 16:12
News from the Douglas Hangar:  As rare as a Unicorn! A Three-engined (Douglas Sprites)
4 Passenger Aircraft,built in 1939 with a 26ft 4 inch wingspan;19ft long;gross weight of 2,400lb; and a top speed of 160mph (dont tell Henry Body) .Its name "Helmy Aerogpyt" is not a weird acronym,but derives from the designer/builder Saleh Helmy an Egyptian student in London before WW2. Helmy got support from the Egyptian Goverment to finish his project,and it all worked.The novel fuselage shape is designed as a "lifting-body" and a raisable module on the cabin roof acts as a flap.The aircraft flew as a development during the War and was taken out of service in 1946.the design premise was a quarter-scale model of an aircraft to be built in Helmy's native land.although it survived the war,the Aerogypt became a chicken shed near Denham ,west of London.Helmy went on to other brainstorms.In its latter months the aircraft was re-engined with 2 Continental Flat Fours. (probably why it became a chichen-shed)
There are even more exotic delights with Douglas Power awaiting the interested reader.



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Title: Douglas Dryad 2 Engine
Post by: Dave on 18 Sep 2007 at 23:14
Brian kindly sent in this note and photo.

Quote from: Brian
DOUGLAS AERO ENGINES.. another snippet from the Douglas Hangar. At last i made the trip to photograph the Cyril Pullin designed Dryad 2 Engine,
for the Book I am getting together on Douglas engines in aviation. 50bhp 1504cc OHC (Face Cam). This view shows Oil Cooler and Fuel Pump driven off centre of shafts operating face-cams in heads.

Title: Re: Douglas Dryad 2 Engine
Post by: Brian on 19 Sep 2007 at 10:11
Thanks for "sticking" the photo on the board Dave.I should have clarified the "Pullin-designed" reference ,with
"when he had moved from Douglas to G & J Weir of Cathcart,Glasgow in 1933".He needed a move powerful engine than the Dryad 1,designed and built at Kingswood just as the company collapsed, to power the second Weir Autogiro (W-2)..hence this beastie.It is amazing that Pullin produced 2 such progressive and complex designs just for prototype aircraft,but they both worked.I haven't confimed yet(but I will) whether this engine was licenced back to Kingswood in 1938 along with "others",such as the 4 cylinder Pixie.More gen when /if I finish the book!
This engine was only referred to as "The Flat Twin" at Weir.
It might be more appropriate to shift this pic etc to "Douglas Aero Engines" topic,if possible.

Title: Re: Douglas Aero Engines
Post by: Brian on 27 Sep 2007 at 09:36
Yet another morsel from the Douglas Hangar.
Does anyone know whether the 9.15litre ,SOHC,Air-cooled, inverted V8 ,Supercharged Aero Engine ,designed by Aero Engines Ltd ,was built and run, just before WW2 ? I have just been perusing the drawings of this handsome
motor and it looks very fine.Quite which market A.E.Ltd had in mind for this engine is not yet clear.
The inverted V4, 4 litre, was built, and flown in a DH60 Moth.

More anon.

Title: Re: Douglas Aero Engines
Post by: Brian on 07 Oct 2007 at 15:58
In the March/April 2007 edition of "The New Conrod" journal of the LDMCC, a photo appeared
of a "Sprite Aero Engine serial No 75E 112 owned by Doug McLaclan in Australia"'It was pictured
mounted on acrude frame with a large drive sprocket (sawbench power ?) Was this an old pic
 or is Doug and/or the engine still around ??
Im trying to list "extant engines and airframes" for my dreaded book.


Title: Re: Douglas Aero Engines
Post by: Doug on 07 Oct 2007 at 20:28

Yes it is an old picture. I'll try to find the original date of publication and re-post. There was an attached article mentioning essentially that Doug McLean had just acquired it.

Title: Re: Douglas Aero Engines
Post by: Doug on 08 Oct 2007 at 13:28
The picture first appeared in the 1986 May/Jun issue. It mentions in the text it was engine 75/E112. I'll get you a copy of the article.

Title: Re: Douglas Aero Engines
Post by: Brian on 07 Nov 2007 at 17:54
Still no news about Doug McLachlan's Aussie Sprite Engine ( No.75/E112) .Surely someone knows where it lies?
Doug K kindly sent me a copy of the old NCR article,and I would like to find out whether it still exists for
"Chapter 99- Extant Engines/Aircraft" of "Mein Crunch" ,as a certain DK has christened by humble scribblings.
 I have pretty much drawn a line under the number of airframe-types that fitted Douglas /Aero Engines Ltd,
 or Weir (Pullin) engines,at 30.There may have been more, but Ive done my best to find them all.

I'm including details of the Aircraft-Engine Starter Engines ,as well as APU's (Auxilliary Power Units).A certain
LDMCC and Forum Member has several of these remarkably compact units(but that's his project,so I'll confine my book's mention to the spec's and their purposes.

The air-cooled V-4 & V-6 units of 1935 have absorbed a bit of time lately.At least AE Ltd did soemthing with these G.A.Ltd designs,instead of sitting on their licence (as they did with the one for Hispano Suiza units).
The daddy of them all at this period in Kingswood was the 9.15 litre Inverted ,air-cooled , supercharged,OHC, V-8.

A long way from the 1923 494cc ohv twin where I start. I'd better get on with it.

Best wishes to all,

Title: Re: Douglas Aero Engines
Post by: Brian on 11 Nov 2007 at 16:14
Hi all you avid Aviation Enthusiasts,especially in Australia,
As part of my examination of "the competition for Douglas Engines in light aircraft pre-ww2",
I have come across a flat twin made in Australia (Randwick NSW) by Squad Ldr L.J.Wackett
for use in his Wackett Warbler (honestly) in Dec 1924.1490cc 40bhp wt 88.5lb.Does anyone
know any more about this motor(apart from DK probably having one in his shed with a
 broken rocker-arm,and some singeing under the sump)
My last inquiry for info from Oz (re Doug McLachlan's Sprite) has brought no response so far.
Maybe I should just close the Hangar doors quietly and just get on with the Book.
Best Wishes

p.s. I have included details of the Wackett Wizard engine in Chapter 7 (Competition)of the book, just
 for my friends in  Oz.
Title: Re: Douglas Aero Engines
Post by: Brian on 20 Nov 2007 at 20:56
Hi All,
Just a  whimper from the Hangar Doors,as an update on Book-research progress.
Latest(and hopefully final) count of Aircraft fitted with Douglas or Douglas-derived motors.

U.K.         21
France       2
Belgium     2
Germany 10
Austria       1
Total 36 different types (of which 35 actually flew)
Remember.despite what Doug might advise, "FLY DOUGLAS"

Title: Re: Douglas Aero Engines
Post by: Doug on 20 Nov 2007 at 22:09
Quote from: Brian
Remember.despite what Doug might advise, "FLY DOUGLAS"

If flying behind a Douglas engine is so safe, why are all the Douglas aero engines one comes across low hours?

advert, estate sale- Douglas aero engine, only used once...  :o

But the Mark 1 Sprites are a good source of spares for the DT/SW models.

If you fly Douglas, make sure it is a DC3! But a Kingswood powered plane? It would take a braver man than me!  :)


Title: Re: Douglas Aero Engines
Post by: Brian on 26 Nov 2007 at 18:04
Calling all Codgers,

Is there anybody out there who knows of anybody ,still alive ,who worked
at Kingswood in the 1935 to 1939 ( Aero Engines Ltd ) period ?
Im trying to knock on the head ,the questions.....
1/  "was the Inverted V6 Monarch Aero Engine flight-tested ,like the V-4 ?"
2/  "were the 9.15litre and 10,5 litre  V-8's built ?" I have the drawings but nothing else.
3/  " was the 1.5 litre side valve twin aero engine flight tested ?"

Lastly,has anyone found Doug's missing Rocker Arm ?


Title: Re: Douglas Aero Engines
Post by: Brian on 28 Nov 2007 at 09:26
Does anyone have a copy of the Douglas Publication 
"Douglas Vibrationless Twin Cylinder Engines for Light Aircraft".I have a fuzzy image of a couple of pages only.
Page 8 is referred to as ..."For detail Dimensions see page 8" .That page would be very helpful.


Title: Re: Douglas Aero Engines
Post by: Brian on 29 Dec 2007 at 10:20
Latest News

First of all: you Aussie Aero Enthusiasts can cease your search for details of the Wackett Warbler,powered by
 Squ Ldr Wackett's own 40bhp Flat twin.  Problem solved.

Second:I now have 39 different aircraft-types that used Dougie-power (contradiction in terms, according to DK)

Third: I have concluded a different definition, to previous documenters of Douglas Aero Engines, of "Sprite".
          Most references in Aircraft Magazines and Books,about Douglas Flat Twins since 1937 are just wrong.
          Basically they say,anything from 1932 to 1939 with a prop on it was a Sprite.The Sprite was only made for
          a short time in 1936-1937.Mk I & II (803cc).Previous to that we have the "Aero Douglas 750"(744cc)which is
          most numerous, in Mk I & Mk II forms.Before the "Aero Douglas" we had the 6/D 596 cc motor (derived from
          G31 motorcycle unit ) in 1932.I have many refs from learned journals and books which picture all of these
          engines as "Douglas Sprites".There was only one series of Sprite, in 2 Marks, and they were made by
           Aero Engines Ltd,all prefix SP or SPR engine numbers.

Fourth:Re my post on "Calling all Old Codgers "(past employees at Kingswood pre-war). I've got 2 live ones.
More anon.

Title: Re: Douglas Aero Engines
Post by: Brian on 01 Jan 2008 at 12:16
Happy New Year Everyone.

For the New Year,I have some puzzles for you avid enthusiasts.

After the Pixie ,in 1938,there were 5 more names allotted for future engine projects.


Any info on what they were to be (i.e. was one of these names for the 1.5litre 1937 twin ? )
would be gratefully received.

Lastl,but by no means least, has anyone got page 8 of the 1923 Aero Engines pamphlet ?
I could do with a copy of this please.

Best wishes.

Title: Re: Douglas Aero Engines
Post by: Brian on 27 Jan 2008 at 18:17
For the benefit of any interested parties, who read my last post on 26th November 2007, I can
answer some of my own questions now.
1/ Yes,in October 1935
2/ Don't know yet
3/ Don't know yet (drawings are coming together though.)

Lastly ,Doug isn't looking for his missing Rocker Arm,any more.

Body (aircraft) count for "Mien Crunch" ("From Kingswood to Cathcart")
is now 45 fliers,plus several Groundhogs.

Best Wishes
Title: Re: Douglas Aero Engines
Post by: Brian on 04 May 2008 at 14:50
Hi Everybody,
The latest discovery (if I can get some pictorial or drawing info) is an amazing "oddity" from bygone Australia.
A certain Bill Heinz of Carnamah W.A. apparently "commenced building a Helicopter in his back yard in October 1947 ,using parts from an Avro Anson and a  modified 1925 DOUGLAS motorcycle engine." The first Autralian-built helicopter.
If anyone can throw more light on this one I would be delighted. Im working on Chapter 6 of "Kingswood to Cathcart" and in parallel scribing the Aircraft 3-view drawings..only 13 to do !

Title: Re: Douglas Aero Engines
Post by: Brian on 26 Oct 2008 at 11:32

I thought I would send an update on where my Book project had got to.

After nearly two years of research I am nearing the completion of the proposed Book.It started out
purely as a  private project, of information gathering, as I am interested in both aviation and Douglas motorcycles.
I soon became caught up in so many side-issues where available "literature" was very conflicting ,or just plain wrong, that I set to in a more serious attempt to find the truth about an ever increasing file of airframes that were powered by Douglas (and their successors) In addition there were of course the Generator and Starter Engines;the power units for Film Replicas;the Ground Trainers;the home-built novelties.It went on until I had 50
machines that had a Douglas or Douglas-derived design of engine. then there came the discovery of pre-war works drawings from the Aero Engines Ltd era,and a whole story in itself of Cyril Pullin's time at weir on Autogiros and Helicopters,all with special engines. So a Book it seemed to me, was there to be put together.
   Now I have reached the time to find a publisher,although there is still work to be completed, the most likely victim for this work is not optimistic;"too much of a niche market,who would buy such a thing?". They may be right,but I have resubmitted the synopsis and their "aquisitions questionnaire" for them to reassess it."They are a publisher of local history (Gloucestershire,as Bristol) and transport, and certainly have published such stunners
as fully illustrated works on Tram Tokens. My title is "Kingswood to Cathcart".You will all know the former but
perhaps not the latter. Cyril Pullin left Douglas to join G & J Weir in Cathcart ,Glasgow, as the Kingswood Works
went bust in 1933. One of his designs was licensed back to Kingswood in 1938,so that's the link. I claimed that teh interst groups(potential buyers) would be enthusiasts for Vintage Motorcycles ;Light Aircraft and Aero Engines; Douglas products and Bristol local history;Helicopters and Autogiros;Dentists Surgeries etc.
If it doesn't fly as a 200page book, then I may do it myself as a "knife and fork" A4 comb-bound version for anyone who is interested. As a 9" x 6" bound edition, it would run to 200-230 pages with 84of them photos and drawings. If nobody reads, it in any form, I will still be well satisfied with the fascinating things I have uncovered and the people I have come to know in gathering in the data. If you have a view as to its appeal then please let's hear from you, and I could perhaps  use it as ammunition if any Publisher is unsure ,or just file it and get on with something else.

Best Wishes to all ,

Brian Thorby
Title: Re: Douglas Aero Engines
Post by: Reg on 26 Oct 2008 at 20:53
          If you are having difficulty in finding a suitable publisher try the following;
Redcliffe Press Ltd, 81g Pembroke Road, Clifton, Bristol. Tel No. 0117 973 7207 (
Title: Re: Douglas Aero Engines
Post by: richson on 26 Oct 2008 at 22:38
Hi Brian,

I hope you can find a publisher, I'm looking forward to getting a copy. Reg's suggestion sounds good - being a local publisher they will  know all the best outlets in the Bristol area which one would hope will help to get it off the ground (no pun intended!). Perhaps the LDMCC could lend some support in some way? . . .


Title: Re: Douglas Aero Engines
Post by: Dirt Track on 31 Oct 2008 at 23:39
G'day Brian
Sounds fascinating and no doubt a hell of a lot of work!
Would be great if you could include some info about Douglas personallities the likes of Cyril Pullin and Freddie Dixon, Les Bailey.....this is an area always missed by authors of marque histories.
Title: Re: Douglas Aero Engines
Post by: Brian on 01 Nov 2008 at 09:09
G'day Howard,

Thanks for your response.

Yes ,a hell of a lot of work but enjoyable none the less for all the new info Ive found and wrongs to right.
Also the contacts made (like yourself ) who have an interest in these things. I'm glad you raised the subject of "personalities".Too true,the main connective thread through my work is Cyril Pullin, with all his different hats on.
There were more talents in his box than even Freddie Dixon had I think.. I am truly amazed that nobody appears to have written Pullin's biography.My provisional (a possible Publisher wants to change it) Title for the Book is "Kingswood to Cathcart" which signifies Pullin taking his design genius from Bristol to Glasgow.This is too obscure for these blokes,although there is "Douglas" in the sub-title ,as they reckon Internet search would not find the thing.
Anyway,thanks again for the encouragement. If nobody wants to print it I may just self -publish it in a less posh form and also write up some of the other stuff,like the rotary valve designs including the motorcycle type air/watercooled 500 twin. As they say Howard,more anon.

Best wishes

Title: Re: Douglas Aero Engines
Post by: Brian on 09 Nov 2008 at 17:21
Here's another little story, about just one of the 50 aircraft types which "used" Douglas power;too much to incorporate in "the Book", where only technical details will appear.

" To the stars on 30bob and 4hp (well nearly) "

As an aviation enthusiast, as well as Douglas owner, I have developed a consuming interest in the applications of Douglas engines to light aircraft.About two years ago I decided to gather together any data I could find on the pre-war involvements of our beloved flat twins in any airborne uses,just for my own interest you understand.Because of the growth rate of this "file" it became a book in-progress.During my research I found some very strange combinations of engine and airframe. The most recent of these, built in 1966, was the Ward Gnome,
which incorporated a 1915 4hp  Douglas motor in a home built low wing monoplane !!  How did this anachronism come to pass ? Well, there were three blokes sitting in a Nottinghamshire (U.K.) pub, enjoying their beer and discussing a mutual interest in aircraft ; radio-controlled models, and the real thing. Two of these forty-somethings had been RAF stalwarts; Mick Ward had been a Tail Gunner in Bomber Command and George Clover a Ground Engineer. The third member of the "crew" , Peter Anderson, just happened to be a private pilot.  The bar-banter progressed to "what model project shall we tackle next?"  "Why not a much bigger model;one big enough to sit in ?" Mick Ward,a skilled woodworker as well as a model-maker of renown, offered to design and build the airframe, if George could furnish a suitable engine. Peter just smiled, thinking their was no job for him as this was to be just a much larger radio-controlled project. More pints, and then bets were bandied about to the tune of Ł20 to achieve a completed and running machine. George Clover was a canny spanner-man.He knew of a motor when he took the bet,although it had still to be prised away from local village lads who played about with an "old engine" in idle moments. The boys had never managed to get the ancient Douglas twin to fire, but still relieved George of 30 shillings for "taking the engine of their hands". George mused he would have to tune the motor a bit if it were ever to turn a propellor. He viewed such heavy parts like cast-iron pistons as inappropriate to aerospace engineering and resolved to lighten them. His power-drill's bit grabbed at one of the piston's skirts,and it flew asunder. Undaunted, George pedalled off into town with the bits and engaged a welder friend to make do and mend. Having "filed off the high spots" and "carefully reassembled" the powerplant, George went to check on his comrade's progress with the airscrew. They had reasoned that unless enough draught could be developed there was little point in pursuing the airframe, and Mick would win the bet.
Now the fun really started.Mick had carved a 46"  mahogany propellor ( a bit larger than his normal practice).
They bolted the trusty Douglas to a railway sleeper in Mick's garden and gave the prop a swing. At least it started and straightened Mick's hair a bit. George hollered ,from a safe distance down the garden,"do you think there's enough power?"  Mick said seriously "yes".  At this point, George could just make out that the prop was beginning to wobble on its shaft-adapter. Although hand-made by an amateur, the tractor-prop showed its efficiency when it came free and flew forward,and although he didn't see it, George heard the thing whistle past his head and hit the garden fence. This escape from decapitation was regarded as a good omen for the project and construction of the airframe was started in Mick's "workshop". Although the aircraft was tiny,with a wingspan of less than 16 feet, it was necessary to cut a hole in the wall of Mick's 8 foot shed. A flap was made to allow work on the wings,and before very long the "Ward Gnome" emerged and was bolted together.The cockpit was simply appointed . Stick;Rudder Bar; Petrol Tap; Ignition Cut-out Switch. That was it.
The 4hp Douglas engine, serial number 216(1/4 BSF), had been fitted with a more modern Amal 276 carb and given a clean. The little prototype low-wing monoplane looked quite plausible (as a garden weathervane?)
and fairly sleek with its 1.5mm plywood covered structure. The engine looked a bit "different", but with a name like Douglas shining on the crankcase, why not head for the nearest runway ?..............

 Well , so as not to bore you all in one go, more of this bedtime story, in a day or so.

 Goodnight children, everywhere, goodnight .

Title: Re: Douglas Aero Engines
Post by: Brian on 10 Nov 2008 at 20:09
"To the stars on 30bob and 4hp,well nearly" ......part 2

If you are sitting comfortably I will continue..

The logistics of transporting even such a small aircraft to trials were solved by having quickly detachable wings and hitching the Gnome's tail to a Lambretta Scooter Combination (a shame no Douglas Vespa was available)
At 6 o'clock one chilly Sunday morning in 1967, on the disused wartime airfield at Wigsley, near Newark Nottinghamshire, taxying trials commenced (with a sharp lookout for the local cops) . Even at the heady groundspeed of 50mph,measured by the chasing Ford Anglia, the Gnome remained a groundhog. The "pilot" Peter Anderson, told his ground crew that their experience in varying the incidence of the prop-shaft's downthrust, on true model aircraft, should be tried  on the Gnome. Packing was inserted under the Dougie's crankcase and away trundled Peter, until he found he lifted off the perimeter track and was drifting over the grass.There was insufficient urge to gain altitude and the approaching treeline obliged him set the tiny 'craft down again. At this juncture a small design omission showed itself as the Gnome would not turn using just power and rudder.As the tailwheel was fixed, and unable to castor, an undesirable straight line was maintained. Assistance was summoned from a perplexed ground-crew. George produced a length of rope which was tied to the tailwheel strut. At the Pilot's command "left" George (rope anchor-man) would run right , causing the aircraft to veer enough to turn for home. these manoeuvres resulted in more than a few laughing fits, and mild exhaustion. Modifications ensued and further frosty morning sorties were made to test the craft.. During one of these missions, a local bobby on his BSA C15 arrived unexpectedly to inspect the unauthorised activity.On viewing the diminutive aeroplane,along with the trio's transport and technical equipe , it was agreed that it was unlikely to be more than just a large model, so they were left alone to play. The next unscheduled visitor to the test centre was a certain Ray Fixter,resplendent in Captain Pilot's Cap and Jacket,plus trainers. Ray had heard rumours of the midget plane,and after some camel trading and pocket-emptying the Gnome was his.  Bereft of their Sunday Morning fun, Mick and his pals set to designing and building their next machine. There were no more surplus Douglas twins in the stores,so a Citroen Ami twin
just had to do for the Elf...a tiny biplane. Endowed with probably three times the power and twice the wing area the Elf really took off,rather than the just super-ground-effect antics of the Gnome.

Ray Fixter flew the Gnome for a year or so, and then it passed through various museums,until coming to rest high in the rafters of a hangar at Breighton in Yorkshire,where The Real Aeroplane Company watch over it(or under it)  to this day. I climbed a very long ladder recently, to find the engine number and date the power-house. In 1968, the Ward Gnome was listed in two well known publications. The Guiness Book of Aviation Records showed it as the "Lightest Monoplane", at 95kg dry,and Janes All the World Aircraft thought it worthy of an entry, as an "Ultralight Monoplane".

Good night Children, everywhere.

P.S. If you are all very good,I might just send you off to sleep with the story of the passenger plane with three Douglas engines which became a chicken shed(because someone dropped it).No scary giants in this one I promise.

Best wishes


( Gnome-750.jpg)
Title: Re: Douglas Aero Engines
Post by: graeme on 10 Nov 2008 at 22:01
Great stuff Brian!
I look forward to the next instalment.
Cheers, Graeme
Title: Re: Douglas Aero Engines
Post by: Dave on 12 Nov 2008 at 03:48
Photo added above.
Title: Re: Douglas Aero Engines
Post by: Brian on 08 Dec 2008 at 13:30
News from the Douglas Hangar

Hi, All you aviators and critics of all things aero-Douglas. No more little stories about little aeroplanes
,for now. But I can announce that there will be a Book.A couple of publishers offered to do it,and I'm
pleased to say that the one Reg suggested is the one I have gone with, primarily as they are in Bristol.
The title I wanted is not to their taste, as it will not internet-search well,so we will argue about that.I want
to keep"Kingswood" and "Cathcart" in, at least in the sub-title,but clearly "Douglas" must be to the fore.
 My deadline to submit all the text/pictures/drawings is March  31,hopefully before. So,if anyone has any anecdotal or factual info on the Works ref.1935-39 to offer, or details of extant aero-engines before that
date it will be very handy.All this means that sometime in Autumn 2009 I will try to give J.K.Rowling
a run for her money.

Best Wishes to all for the festive season,

Brian Thorby
Title: Re: Douglas Aero Engines
Post by: Brian on 19 Jan 2009 at 09:58
S2 Engine cylinder bore

Gentlemen, I seek definitive proof of actual cylinder-bore on 1923  S2  6HP "750" , CE-prefix, engines.

All existing Douglas books , such as "The Best Twin", and Factory Catalogues show  " 83 mm x 68 mm, 733cc ". 
However, if you do the sums,this gives 735.938...736cc  unless that is, the bore is really less than 83mm !
It would have to be a very funny (odd) size to give 733cc ,metric or imperial, but as we know Douglas have
done this elsewhere on other motors. Does anyone in our fraternity have an S2 engine or a Piston Catalogue covering the S2 from which we can settle this ?
You might say  "who cares" ?  Well, I want to get things straight while I have the opportunity, in writing my book
on Douglas Light Aero Engines, the various engine specs and text-references could be contentious if I state something opposed to "the literature" that exists. So far I have consulted the obvious sages  in Doug and Eddie,
plus owners of S2 engines (who cant get at them) . I have e-mailed VMCC to investigate their Library Hepolite Catalogue covering  1923 Douglas pistons (if they have a copy !) Any ideas would be good,as the publishers
deadline spproaches.

Happy New Year to all

Title: Re: Douglas Aero Engines
Post by: Brian on 24 Jan 2009 at 09:50
A last call for info on extant Douglas engines with the following prefixes;

AE ; CE ; QE ;  6/D ; 75/ E ; 75 / J  ; SP or SPR
............some of these (or at least their crankcases) have found their way  into motorcycles, so they
 are now serving an active purpose, but were built originally for light-aero use.
I am compiling a list of remaining (or remains of ) engines for the Appendices of my book. Noowner's
 names,or locations will be stated; only that they exist.  I have some examples of nearly all the above,so far.

Finally, any evidence of the precise cylinder bore of the 1921 S2 "733cc" engine,quoted everywhere
as just 83 bore,(which should give 736cc) would be very welcome.

Thank you all, for your help and encouragement, I'm nearly there after 2 years of gathering shed-loads
 of info, and finishing up with a couple of hundred pages. At least I've learnt something along the way.


Title: Re: Douglas Aero Engines
Post by: Doug on 30 Jan 2009 at 00:35
I always thought that when Douglas said 68mm stroke, they meant 68mm stroke. After all they used the dimension on the 3-1/2 and 4hp, the 3-1/2hp Sports, the 6hp Sports, the RA, as well as the OW of 1924 (and a brief reappearance in the short-stroke DT.) After all 82mm OC, TT, and DT cranks are 82mm stroke. But apparently this was just marketing exaggeration for the earlier 68mm stroke OHV engines at least. I borrowed the crank shown below, which seems to match illustrations for the 3-1/2hp Sports and the RA. No idea which it belongs to; possibly they both shared the same item. It might even be for the '24 OW, since I have not seen on of those to exclude.


So I set it up on the surface plate nice and level and took a measurement to determine the stroke, and it came spot on 67.7mm. There is no sign that the crankpins have been reground eccentric, and the pins themselves measure 31mm diameter where they are not tracked by the rollers.

With a 67.7mm stroke, the displacement with 83mm bores works out to 732.60cc. So it seems Douglas rounded the stroke up to 68mm even, and the displacement up to 733cc.

Title: Re: Douglas Aero Engines
Post by: Brian on 06 Nov 2009 at 23:09
With the Book now finally typeset, I would like to thank all contributors to this topic, which may still attract new
information as new members might add to the thread. Readers will very shortly find evidence in the "Douglas Books and Manuals" section that the Book is just about here. The "Advance Information Sheet (" will be posted in the next day or so, describing the outline and Cover  of the publication. The delays since July at least allowed pictures of unexpected survivors to be added among the engines, as last-minute discoveries.

Thanks to all.


Link added - Dave, Nov 7, 2009