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Old 06-01-2017, 11:59 AM   #1
Mg Mark
 
Join Date: May 2017
Location: UK, Cambridgeshire
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Default A Long Shot Identification Question.....

Hi all,

What a great website (which I admit I've looked at numerous times before registering) for information and reference. Although my service in the RAF comes to a close soon after 40 years (so all in the jet age), I've always had a love of, and interest in, its history. Indeed, i remember seeing during my first tour, a stash in storage of about a dozen complete 2 and 4-bladed propellers from WW1 and the inter-war years - and wonder now where they all ended up!

I have just acquired a propeller hub (from ebay in UK) as a 50th birthday gift to my brother-in-law, together with a WW2 RAF P8 compass. I know he'll love them both and I am just trying now to see if I can ascertain anything about the propeller (whether definitive or not). The hub had a barometer in the centre hole, which I have removed.

It has no identifying numbers left - all of the original finish, except that left untouched in the centre hub mounting and bolt holes has been completely sanded off and the area where any markings might have been has been sanded down to create a flat spot so that it sits level. I've tried tracing/rubbing over that area and, while there are traces that there have deinitely been markings there, they are so faint and incomplete as to be of no use even with guesswork. Sad and a sacrilege that someone in the past has done that to it, however, I knew that was the case when I bought it, as it will still make a great gift and was within my budget!

It is an 8-bolt hole hub and the wood is definitely all good quality, old close-grained mahogany and the measurements are as follows:
Length between the blade cut offs - 17" / 432 mm
Overall hub diameter - 9 3/8" / 238 mm
Depth of hub front to back - 6 1/4" / 159 mm
Diameter of centre hub mounting hole - 3 1/2" / 89 mm
Pitch Circle Diameter of the hub bolt holes - 6 5/8" - 170mm
The pitch of the blades at the cut off roots is about 45 degrees
Pictures are at - http://s471.photobucket.com/user/mar...rary/Propeller

http://s471.photobucket.com/user/mar...rary/Propeller

You should be able to see that there are circular witness marks front and rear, not quite sanded away, which suggest that it may have been mounted on an aircraft at some point. The bolt mounting holes are slightly oval, varying from 1/32" - 1/16" or 0.5 to 1 mm out of round). The rear (I'm presuming it's the rear) infill of the hub mounting hole is of the same wood, a good fit, and is glued in place. As for the square infill pieces visible on the top and bottom of the hub (again, of the same wood), I have no idea how deep they are or, indeed, why they might be there. Looking from what I am presuming is the front of the hub, the blade pitch would suggest a RH rotation.

So, with all that in mind, with its size, wood type, 8 bolts etc, I'm thinking that it might be an old hub, possibly dating somewhere from WW1 though to late 1930s. Any ideas, thoughts or suggestions that would add to the story, whether definitive information or not, would be gratefully received. Many thanks,

Mark
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Old 06-01-2017, 03:01 PM   #2
Dbahnson
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It certainly looks consistent with WW1 era construction and material, although that can't be verified. It also looks like a LH thread, which usually (but not always) indicates a pusher application. I agree with the witness marks.

I think the best you can do is go to this page and see if the hub dimensions match closely to any of the known hub sizes of WW1 era props.

I don't know what's going on with that little rectangular inlay, but can only assume that it was an attempt to fill a defect of some kind.
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Old 06-01-2017, 06:40 PM   #3
Mg Mark
 
Join Date: May 2017
Location: UK, Cambridgeshire
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Thank you, that's helpful. I hadn't considered the possibilty of a pusher application with regard to rotation. I can't see a close match to data on the linked page, although I see that the engines listed are not British so, by exception, that might suggest that it was made to fit a British engine?

I've contacted the seller of the hub; he saw it at a local antiques fair (Swansea, UK) and knew it was unusual, even though it was painted white all over (except as I found on removing the barometer in the hub mounting hole). He hoped that on removing the paint that he would find an old laminated wooden propeller, which of couse he did, and knew enough about propellers that it might be from the WW1 or the years intervening until WW2, when metal hubs with separately attached individual blades became the norm.

So, it was he that sanded the paint off - I don't know whether a previous owner long ago had sanded the original finish to paint it and taken the ID marks with when creating the flat section for it to sit level, or if the finish and marks were sanded away by the seller in removing the paint - either way, it not worth pursuing as the odd trace left is not decipherable now.

I'm not familiar with the details of the hub mounting for wooden propellers. I'm presuming that the open face of the hub mounting with the pronounced chamfered edge is the outer face of the propeller - is that correct? The other infilled face that I am assuming is the side mounted to the engine does not seem to have any chamfer to its edge (although I have not yet attempted to remove the infill piece to check).

Mark
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Old 06-01-2017, 07:15 PM   #4
Dbahnson
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I think the rounded edge is typically the surface closest to the engine, so when the hub assembly with the propeller bolted on is placed over the crankshaft the wood contacts the shaft with an angled surface.
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Old 06-01-2017, 07:44 PM   #5
Mg Mark
 
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Ah - thank you, the possibility of a pusher application now makes sense to me!

Mark
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