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Old 04-28-2018, 07:08 AM   #1
BobGibson
 
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Default Need help identifying these propellers

I am trying to identify these two propellers that I have been offered, and establish their value.
Detail on the hubs as follows

DRG 2502 D2550 INSHAW 100 HP 2570mm length

TYPE A4 NO 7 D2400 P1350 2400mm length

Thanks if you can help

Bob
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Old 04-28-2018, 08:17 AM   #2
Dbahnson
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I won't have access to my data files for a few days, and I'm not sure what numbers go with which propeller but the one with the decal is almost certainly more valuable than the one next to it, which looks like it has been altered at the hub to accommodate a clock. It may also have been refinished.

I'm guessing that that the GAC prop will have a number that matches a Regy prop. PMdec or Bob Gardner might join in before I'm home, and may be able to provide more information, but I'll try to look it up when I get back to my files.
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Old 04-28-2018, 08:55 AM   #3
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Many thanks. I assumed the GAC was more valuable. Not sure about whether the other has been refinished. I'm going to have another look at them later this week
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Old 04-28-2018, 09:01 AM   #4
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I meant to add that the GAC propeller is the smaller of the two, marked A4
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Old 04-29-2018, 08:57 AM   #5
Bob Gardner
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Bob, what an excellent forename you have.

It is not often that I come across an atypical British WW1 propeller and now two arrive at the same time.

TYPE A4 NO 7 D2400 P1350

The General Aeronautical Co Ltd began life c1911 as agents who stocked aeronautical items mostly imported from France. By the end of WW1 they manufactured many of the items they sold, including propellers.

The letter A in the drawing number A4 indicates a propeller of Vickers design but I have no details of such a prop.

The diameter of 2400mm and pitch of 1350mm similarly do not occur in any of the 24 Vickers props in the A series, nor in any of the V and VC series. The pitch of 1350mm is unusual. This tiny pitch is at the extreme edge of the design envelope of British WW1 props and suggests an engine of low power and a slow moving airframe.

Fortunately this combination of diameter and pitch was used by other makers at this time. The Air Department of the Admiralty drawing number AD561 had dimensions of D2390mm and P1350mm for a propeller for the 75hp Rolls-Royce Hawk engine used in the SSZ airship. This propeller was also made by Ebora with the nomenclature of Ebora Type 90.

The British Integral Propeller Company also made a prop of dimensions D2450mm and P1350mm, its use unrecorded.

DRG 2502 D2550 INSHAW 100 HP

Similarly, the drawing number 2502 does not occur in the 4000 or so drg nos I have recorded.

An engine of 100hp suggests both the RAF1A and the Gnome Monosoupape. Only the latter fits. Bristol made a propeller with the drawing number P3012 with dimensions D2550 P1800 for the 100hp Monosoupape in a BAT Bantam and Bristol Scout D. But I don't think this is the answer. The hub centre on this prop has been considerably opened. I have seen this only once before on a propeller owned by the Museum of Flight in East Fortune in Scotland made for the Bristol Boxkite c1911 powered in a pusher configuration by a 50hp Gnome engine.

Both these props are exceedingly rare and might be in the category of sole survivors of the type and attributing a value to them is not feasible.

This research has taken five hours. Did I mention that I have decided to charge for my research? About £50.00 per hour seems reasonable!

With kind regards,

Bob
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Old 04-29-2018, 12:01 PM   #6
Dbahnson
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Bob, we are ALL grateful for your research and your books!

As I look back on my own 40 years of this hobby as a collector I'm struck by my own ignorance at first about how much more complicated this identification challenge really is. Like many others, I thought that someone could identify a propeller by simply looking at a photo, and also like many others I submitted photos to museums hoping that they would have a quick answer. They never did.

What many people don't realize is that the reference material needed for this process is either non-existent or very, very difficult to retrieve, and while "drawing numbers" are the key, the "drawings" themselves are largely discarded in their obsolescence.

I'm honored to join both you and Pierre-Michel in a collective enthusiasm and appreciation for these early propellers, which I view as a rare combination of historical value, craftsmanship, and elegance all encompassed in one single item.

I'm hopeful that all of this effort helps to preserve all of these propellers that remain in original condition to continue to remain that way. Perhaps 50 or 100 years from now, it will be even more appreciated that they all represent a narrow band of time around the dawn of aviation.
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Old 04-29-2018, 12:28 PM   #7
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As a non collector, new member, who just joined the club to get a "valuation" of a propeller my father acquired.......I do enjoy the referencing and reading all the posts. I thank all involved in this forum. I am acquiring a taste for props. An insight I acquired in regards for valuations (and finding out museums beat to their own drum) is that the propeller is worth what a fellow member would want to pay (or shoot from the hip for value) after identifying. To me, the preservation of history. Personally, I would love to see a picture of a WWI propeller with the metal bullet deflector plates before the synchronized machine gun. I have always been intrigued with the early era of aviation. Thanks all.
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Old 05-04-2018, 03:50 AM   #8
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Here are a couple more pictures of the propeller stamped
DRG 2502 INSHAW 100HP

It has 9 holes which I understand is unusual. Looking at engine images on the web, the only engine i found with 9 bolt hub is a le Rhône

Hub diameter is 8 inches and bolt circle 6 1/2 inches

The brother of the deceased owner says that he was told at some time it was ‘off a Sopwith’

Hope this adds some useful information to aid identifying this propeller for him

Many thanks, Bob
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Old 05-04-2018, 03:57 AM   #9
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Here are pictures of the hub and blade shape

Bob
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File Type: jpg DE20D189-3A4F-4FEE-B822-EAA8B8FE1573.jpg (90.3 KB, 2 views)
File Type: jpg 788FD5B0-1686-4417-957C-19C9EED4CF45.jpg (87.8 KB, 3 views)
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Old 05-04-2018, 07:05 AM   #10
pmdec
 
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Hi,

Thank you for posting the picture of the "Licence Régy" decal : it is the first time I see one from "abroad".

The shape of the prop is the same that Régy propellers.There is no Régy prop with the same diameter and pitch in France but there are quite the same propeller from other makers: Ratier serial 15 was 2.30 meters long with a 1.35 pitch and Ratmanoff serial L was the same. Both were used on low powered a/c (45-60 HP) during WW1.

Régy factory practices were to produce few propellers by themseves and to sell licences: it is the French constructor with the greater number of known licencees. I join some examples.

A very interesting propeller you have!

Regards,
PM
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