Selling WW1 Sunbeam Arab 1

[Ebelgrahc]

Looking to sell offers welcome! WW1 Sunbeam Arab 1 in very good condition with a few minor marks 9ft 7” long

[Dbahnson]

What's going on with the hub? It looks like holes are partially drilled in between fully drilled holes. Can you post a photo of the opposite side of the hub?

[Ebelgrahc]

Hi there thanks for your question! I don’t know to be sure, I can only speculate some theories! All looks to be factory done! Possibly trying to make it fit other engines?

[Mtskull]

That’s a nice propeller, although likely to be outside my price range.

I can’t see any inspection stamps, so maybe this propeller was rejected (or the contract cancelled) before it was drilled?
For what it’s worth, the left hand thread confirms it as a tractor propeller with this engine.

Rare indeed: As far as I can ascertain, the Sunbeam Arab engine was troublesome and only in production for a couple of years (1916-c. 1918
It was used experimentally (and unsuccessfully) in a variety of aircraft but only the Sopwith Cuckoo used it in any numbers and many of them were subsequently re-engined.

*EDIT* I wrote the afore going before the second batch of photos was posted.
To my eye, (judging by the interruption to the pattern of concentric circles), the bolt holes are indeed present but have been carefully plugged.
Certainly the larger round marks are of the number, size and in the position where would expect to see the bolt holes for a Sunbeam engine of this era.

[Ebelgrahc]

Hi there thanks for the info! I can confirm this propeller has been stamped 4 times (AID) see pic. Also what I’ve found out by my research the the N515 is the only plane with the arab 1 engine that ever flew so google tells me! I’m not quite sure. Also I’ve researched that there are only 20 world wide sunbeam Arab 1 engines in existence. So if this propeller is stamped it obviously must be one of the prototypes that were bench tested & possibly flown. What’s your thoughts

[Mtskull]

The Sopwith Cuckoo Mk1 definitely went into production and service with the Sunbeam Arab engine, although I can’t find any definitive information as to exact numbers before later marks with other engines were introduced.

As I understand it, the figure of 20 surviving engines refers to Sunbeam aero engines of all types, only two or three Arabs are known to survive.

I’m intrigued by the bolt holes (or lack of them). I would have expected to see 10 holes as marked by the red circle but I have found this photo which shows the hub on a Sopwith Cuckoo reasonably clearly (this isn’t to say that yours is from a Cuckoo, just to illustrate the installation).
It appears that the bolts are further out from the hub centre than this, which suggests that the other circular marks may just be witness marks from the attachment plate. Do any of the holes in your propeller go all the way through the hub and can you tell if any have been plugged?

[Ebelgrahc]

Hi your circle mark around the hub do look to me to be plugs 10 plugs which go all the way through see pic, the other plugs on there another 10, do not go all the way through but do look like plugs! So 20 plugs in total! Plus the aborted drill holes looking at the hub of the sopwith cuckoo zooming in I can make out there are 3 rows of 10 holes, the outer ring look bolted, which the holes actually are very similar to my hub with my 10 holes all the way through and the 20 plugs in mine , although I have no idea about the other 10 slightly drilled holes I have! Just speculating with the milliatary order of the Arab engines all being cancelled 2000+ all the problems with the Arab engine had,they must have had a surplus of propellers which possibly would be adapted to fit other engines! Have you ever heard of any propellers being adapted to fit other engines?

[Dbahnson]

Here's my opinion. Excluding the large circle (s) that make up the hub itself, there are a total of 40 circles visible on the hub face. Ten of them are bolt holes (the smallest circles drilled through the hub), 20 of them are witness marks from mounting on the metal hub, and ten of them are mysterious partially drilled holes on the face of the hub. Except for the partially drilled holes, the rest of them are what you would normally expect on a 10 bolt hole mounting system. To me, the only mystery is the 10 partially drilled holes. Could the front hub plate have had a row of 10 studs that protruded about 1/2 inch into the wood to provide additional resistance to engine torque? I've not seen such an arrangement, but I've never seen this particular pattern before.

With a history of engine model replacement, you would expect engines that were removed would have had intact propellers removed with them, even after having been in service, which would account for witness marks on the hub as opposed to a fully surplus propeller that was never mounted. ("Witness marks" refer to the indentation in the wood that comes from compression of the metal hub, particularly as the would expands and contracts with changes in moisture.) I can't imagine a reason to drill large holes then plug them with dowels.

[Ebelgrahc]

Hi thanks for info, sounds very plausible! The partially drilled holes also have an indent in the centres. The witness marks your saying I’m still not quite sure about, as I’ve seen a picture that someone tells me is a sopwith cuckoo mk1 and that was known to have the Arab engine, this bi-plane has the same 30 pattern on the front side as mine that do look to be complete holes without the 10 partially drilled holes (see pic) do you see the similarities?

[Dbahnson]

Hi thanks for info, sounds very plausible! The partially drilled holes also have an indent in the centres. The witness marks your saying I’m still not quite sure about, as I’ve seen a picture that someone tells me is a sopwith cuckoo mk1 and that was known to have the Arab engine, this bi-plane has the same 30 pattern on the front side as mine that do look to be complete holes without the 10 partially drilled holes (see pic) do you see the similarities?

What you're seeing on that photo is a mounted propeller, so you see the metal face plate covering the wooden hub, and the nuts on the mounting bolts. The mounting bolts are on the very outside ring. The larger holes in the metal hub are for weight reduction, but they are what create the witness marks on the underlying wood, which you only see when the metal hub is removed. Here's an example of witness marks on the hub of an original German propeller.

LVG hubface.jpg

[Ebelgrahc]

Hi yes I fully see it now thank you! Would you know is it possible to connect a propeller to a specific engine or to the actual plane it was on? With the markings from said propeller? As I have numerous numbers etc around the hub! I have been searching your site for said information on the numbers I have on but to no avail! Thank you again for explaining the witness marks!

[Dbahnson]

Hi yes I fully see it now thank you! Would you know is it possible to connect a propeller to a specific engine or to the actual plane it was on? With the markings from said propeller? As I have numerous numbers etc around the hub! I have been searching your site for said information on the numbers I have on but to no avail! Thank you again for explaining the witness marks!

Short answer is no. Think of propellers being like tires. They are frequently replaced due to wear or damage and unless you have a logbook for an aircraft that specifies the serial number of a propeller you don't know the specific aircraft/engine, and in many cases don't even know the model of aircraft, as many props were used on multiple models.

I looked through some references I have, and although your drawing number (AB 8218 ) isn't listed, there are several listings in that number sequence that suggest your prop could have been fitted to a Bristol F2/b as well, although the Arab engine wasn't very successful on that aircraft.

[Dbahnson]

Here's a portion of the hundreds of drawing numbers. Notice the AB 82xx numbers, and the fact that yours is not included. Look for the same diameter and pitch as yours. It's likely that yours was just omitted or it was a minor modification of one of the others, but I think it's highly likely that yours was manufactured for one of the list aircraft, and not something entirely different.

AB 82xx.jpg

[Ebelgrahc]

Wow thank you again sir! My P&D match the cuckoo griffin Bristol f2b &cuckoo initially so directly between the two, could you tell me what the number 2 means? at the front of list please Does it mean 2 planes? If so that would be amazing news! Also what does cuckoo initially mean? The mk1?

[Dbahnson]

The number 2 simply refers to the number of blades. You'll see on that list there is a 4 blade listed at the bottom.

I don't know what the "initially" refers to, especially since it's a larger numerical drawing number.

My guess is that your propeller could have come from any of the three listed aircraft. They all have in common a transient use of the Sunbeam Arab engine with subsequent removal and replacement with a better engine. This would help explain the removal of an airworthy propeller (i.e. witness marks). The majority of WW1 propellers that have survived the century since their manufacture were either damaged and rendered unairworthy (which is why you see individual blades or hubs that have been saved) or more commonly were surplus propellers that were never actually mounted and used. Remember that propeller production during WW1 was in some respects "furious' in volume. Paragon, the U.S. manufacturer had produced 25,000 propellers by the end of WW1, and the U.S. had almost no involvement in the aircraft component of that war. At the same time aircraft engine development also accelerated and thousands of propellers were quickly sold off as surplus, most of them at a price of around $5 in the early twenties.

An astute purchaser back then would have left the surplus propeller intact, but sadly many of them modified the hub to insert a clock or barometer and many of them felt the need to strip off the varnish and decals and "refinish" the wood.