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Old 04-10-2018, 03:36 PM   #1
nick78
 
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Default Rupp propeller from Bulgaria - Identification

Hi!

Please help me in identification of this wooden propeller found in Bulgaria!

Overall length - 2.20 m
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Old 04-10-2018, 04:51 PM   #2
Dbahnson
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Interesting . . .

I'm not sure if Rupp actually made propellers. They made the Rupp Fastener for attaching a propeller to the engine, and that certainly looks like what I would expect one to look like. My understanding is that it was designed to allow the quick removal and installation of a propeller, and the ones that I've seen were drilled only from the rear face of the hub.

This propeller allegedly had a Rupp fastener, but there are only 4 holes for its attachment. I'm wondering if yours may be using a Rupp front plate as a decorative addition, as something doesn't look quite right to me on the opposite side.

Maybe Bob Gardner can shed some light on this, but my curiosity got triggered and I found this post on TheAerodrome from 2005.
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Old 04-10-2018, 05:00 PM   #3
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May be you are right, but the only clue is hub markings.
So the propeller is Bulgarian, and the hub is Rupp?
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Old 04-10-2018, 05:02 PM   #4
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The Rupp fastener is German. The propeller could be almost anything, and the design looks more typical of later propellers, i.e. some time after WW1.

Are there any markings on the wooden propeller hub itself? That would be your only clue to its origin.
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Old 04-10-2018, 05:14 PM   #5
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Unfortunately that's all I have for now.
I suppose the propeller is from Bulgarian plane, called DAR-3, designed in the second half of 30s.
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Old 04-11-2018, 03:52 PM   #6
Bob Gardner
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I agree with Dave. This propeller appears to be a mixture of parts. The Rupp hub secures the propeller with a single large nut, thus enabling a quick release and the quick fitting of a replacement prop. It was used by Germany in WW1 and by Germany and Swiss air forces in the 1920s and 30s, and by some civilian airlines.

The hub nut and cone on the front of this prop are genuine items (and extremely rare) but the back plate is of conventional form.

With a Rupp hub, a base plate is fastened to the end of the engine crankshaft. It has protruding four tapered studs which fit into four corresponding blind tapered holes in the hub of the prop. A shaft protrudes from this plate and has a thread at the end. The shaft fits through the hole in the centre of the hub.

Then the conical device is located and the nut tightened and its force delivered equally by the cone against which it tightens.

In twenty five years of research on WW1 propellers I doubt if I have seen more that twenty or so props fitted for Rupp hubs and I have only found one propeller with the apparatus attached. Two decades or so ago I flew from England to Germany to buy it and sold it to New Zealand a few weeks later, before I knew how rare they were.

Dave One of my books explains the Rupp hub in some detail. It extends to several pages. Does this website have sufficient capacity for such articles? Such an online library would transfer knowledge on our subject to a much wider audience.

With kind regards,

Bob
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Old 04-11-2018, 04:32 PM   #7
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Quote:
Originally Posted by Bob Gardner View Post
Dave One of my books explains the Rupp hub in some detail. It extends to several pages. Does this website have sufficient capacity for such articles? Such an online library would transfer knowledge on our subject to a much wider audience.

With kind regards,

Bob
I think it does have enough space. If you can scan it as a .pdf I can load it here or on my server and link to it.
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Old 04-11-2018, 04:36 PM   #8
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but...............a post-script.
Having looked in detail at the hub plate I think it might be a Rupp back plate. The five holes seem not to be for bolts but routine aeronautical lightening holes. There are three bolt heads which could be for the tapering studs which locate onto the corresponding holes in the wooden hub. (Three stud holes were used on smaller props such as this one.) But there is nothing to hold it all together. That back plate had to be firmly located on the end of the crankshaft. So perhaps this is the second complete Rupp hub fastner to come to light with the components perhaps glued together as there seems to be nothing else holding them together (?), the extension on the crank shaft being missing. If so I have now seen two complete assemblies in the last twenty five years. If I am correct, this should be on display in a museum.

Bob
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Old 04-12-2018, 11:24 AM   #9
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As a new member who just joined the club (wanting to find the value of my dad's old propeller) I would like to comment on the ethics of this club. Outstanding. Some fellow get's a find in Bulgaria and is told it is rare and museum quality. Much much better than a member saying they have an interest in buying and will take it off his hands. Kudos to all.
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Old 04-12-2018, 04:58 PM   #10
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Thank you. We do our best to help. We are aged aviators and have no mercenary interest, no ulterior motive. We hope to pass on our knowledge; Dave on American propellers; Pierre-Michel on French props; and me on British and German WW1 props. It's nice to be appreciated every now and then.

With kind regards,

Bob
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