Expert help required

[Vulcanworks]

Hello all,
I have unexpectedly unearthed a prop on the other side of the globe during my biographical research into a Tasmanian aviator.
The chap who has been helping me out sent me the following;
"The prop is 100 " in diam with the following markings on the hub: AD 543 LH - 90HP Curtiss D2520 - P1580 and on the other side: b 7 - N - 1208. It appears to have been originally painted battleship grey and then sanded back to bare wood."
From my previous dabblings with a prop I would suspect this is from a Curtiss Jenny but would be grateful if someone could confirm this.
The owner has asked if it should be left as is or reprotected. From my limited knowledge I would suspect it just needs a good quality wax polish prior to being put on display.
Regards,
Mike

[Dave]

I don't have that drawing number listed, but at first glance the use on a Jenny seems unlikely based on the "LH" (left hand) notation, which on an OX5 engine would make it a pusher application rather than a tractor like the JN4. Perhaps Bob will chime in with more info on the drawing number, or maybe it will be listed in one of his books, the entire set of which I have recently ordered.

Unfortunately, the previous sanding of the finish has rendered it "non-original" and the best you would ever end up with is a "restored" propeller. Having said that, I've recently come around to suggest the use of shellac, as advocated by Adrian and Pierre Michel in previous threads, including this one.

[Bob Gardner]

Hello Mike,

The data on this prop translates as;

AD543 A prop designed or made under licence by the Air Department of the British Admiralty for the Curtiss 90hp engine for use on the American Curtiss JN3, JN4, JN4A and the British AIRCO DH6. It was the standard prop from 1916 until after WW1.
D2520 Diameter in mm
P1580 Pitch in mm
B7 N 1208 A similar prop made for the DH6 by the firm of Betjemann carries the company data B8 358, which is close enough to suggest that this prop was also made by Betjemann.

The use of the AD drawing number indicates the prop was certainly made before the RNAS was merged with the RFC to form the RAF in April 1918 and was probably made before September 1917 when the Air Board started to control the manufacture and procurement of all aircraft props. Theoretically the drg no. AD543 became AB543 from then onwards.

[Dave]

Bob, the JN4 used a right hand prop with the OX5 (and other) engines. Do you show this one as actually right hand rotation, or is the stamping noted in the OP correct as "LH".

[Bob Gardner]

Greetings Dave,

All the props for this range of Curtiss aircraft and the DH6 are listed in both LH and RH form. Is that unusual?

Bob

[Dave]

Greetings Dave,

All the props for this range of Curtiss aircraft and the DH6 are listed in both LH and RH form. Is that unusual?

Bob

It seems unusual to me, only in that the OX5 was built in the U.S. as a right hand rotation engine. I suppose it's not that hard to reverse the components to make it left hand rotation, but I wasn't aware that this was actually done. The existence of a propeller actually built to be left hand sort of implies that it was done. I can't imagine any other reason to have the rotation reversed on a propeller for that engine.

[Bob Gardner]

Dave,

Also the prop is listed with the Curtiss OX2 engine for all these Curtiss aircraft, not the OX5, but I note that the DH6 (which primarily used the 90hp RAF 1a engine in RFC use) did use the OX5 90hp engine in Navy use.

Bob

[Dave]

Was the OX2 itself a left hand engine? I'm not familiar with that model.

[Vulcanworks]

Hello Bob, Dave,
Thanks for the information provided so far. It seems there is always more to these things than first meets the eye. The other propeller I was interested in last year had the DH6 as one of the aircraft it could be installed on, but this was for the RAF1a and was four bladed.
I had wondered about the grey paint. Was it common practice to paint propellers? If this was once fitted to a naval DH6 then I suppose it would make sense to apply some additional protection. It would also make sense that if someone once intended to display it they would probably not want to do so with a tatty grey paint finish.
Regards,
Mike

[Dave]

I think that painted props were more common than it seems, since many of them have since been refinished to "show off" the wood. Many of the original French props were painted, although many were not as well.

[Bob Gardner]

Mike,

The fabric on props was always painted with aircraft dope, almost always an olive green. Late in WW1 I recall that one of the cellulose companies developed a grey enamel-like paint which was used by the Oddy Company of Leeds.

With kind regards,

Bob