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Old 09-03-2019, 11:00 AM   #31
sanger22
 
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One other question Mtskull posted a photo of an Anzani engine with the same exact mark that’s on this prop.Would that mean that this prop was used on an Anzani engine?
Thanks John
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Old 09-03-2019, 12:10 PM   #32
sanger22
 
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I should say the witness mark on the propeller matches.
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Old 09-03-2019, 01:29 PM   #33
pmdec
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Hi,
Quote:
Originally Posted by sanger22 View Post
I should say the witness mark on the propeller matches.
I doubt it. Your prop has an exact 2 inches central hole, so the metallic hub (see http://ratier.org/zim/moyeux.jpg) was made with imperial measures and it certain the Blériot of the image posted by Mtskull has metric measures.

Another think about your prop + engine: The markings D9 P7 shows a probably 7 feet pitch. The Anzani of the Mtskull picture give 30 HP at 1250 rpm with 1300 rpm possible. A 7 feet pitch give a theoretical speed in the order of 100 mph... I doubt it is possible to reach such a speed before WW2 with a 30HP engine.

About brass and coper: Even if copper has to be used in France, I think both were used.
About counter-rotating: it could be a geared engine. It will also explain the high pitch of the prop.

Regards,
PM

@Bob: I have a prop with thin copper sheathing (LH for SPAD XIV canon seaplane). As the prop of this thread, the metal shows many cracks and some creases and there are witness marks on the hub. But I am sure the prop was never fitted to a plane (it is not finished and has not the third airworthy stamp). Perhaps it has been tried on a test bench at a too high speed? What do you think?
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Last edited by pmdec; 09-03-2019 at 01:42 PM.
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Old 09-03-2019, 04:56 PM   #34
Bob Gardner
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Pierre-Michel,

The Royal Aircraft Factory issued specifications for the material used in the manufacture of airscrews.

Specification Number 139 of 19 December 1916 stated that new brass should be 72% copper and 28% Zinc and free of any buckling, so it would seem that sheet brass could buckle long before it was added as sheathing.

Brass sheathing must have been stretched and then shrunk every time an aircraft in WW1 took off in warm conditions to climb to several thousand feet where the temperature could be below zero. I long ago concluded that the combination of large temperature variations and the flexing of wooden propellers, particularly in combat could cause wrinkles.

With kind regards,

Bob
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Last edited by Bob Gardner; 09-05-2019 at 06:30 AM.
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Old 09-03-2019, 05:50 PM   #35
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Quote:
Originally Posted by sanger22 View Post
One other question Mtskull posted a photo of an Anzani engine with the same exact mark that’s on this prop.Would that mean that this prop was used on an Anzani engine?
Thanks John
Sadly, as I mentioned before, the bolt circle diameter of your prop is larger than that of the Anzani hub that I thought might have been a match. Later, more powerful Anzani engines used 8-bolt hubs.
For other engines using 6-bolt hubs of a likely era to match your propellor, if anybody has the data to hand it might be worth checking the following manufacturers: Szekely, Lawrance and Continental.
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Old 09-04-2019, 09:05 AM   #36
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Thank you for all of your help
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