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Old 10-29-2018, 09:12 PM   #11
pmdec
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Hi Viper,

Thanks for the pics. I think the markings read:
DE LA GRANVILLE - SHAM PROPELLER: name of the maker and of the brand
TYPE 11(?) N°8: propeller serial (11?) and propeller number
O-112: don't know!

On the other side -

DH-4 LIBERTY 12
: aircraft and engine
430 HP: engine power
1750 RPM: rotation speed

See https://en.wikipedia.org/wiki/Liberty_L-12 where "The primary use of the Liberty was in aircraft. American-built versions of the Airco DH.4"
Power on the prop seems a little optimistic...

SHAM props where made by Mr Louis Paulhan (a well known pilot) and Mr Henri Joseph Léon Marie de la Chevardière de la Granville (*) from 1916 to the end of 1918. Probably they try to sell props in USA when the European market ends with the 11th november 1918 armistice.

Your prop has hub mounting marks (the circles around the central hole) but it is not sure it flew, perhaps only for a static show on a plane or on an engine.

I join a patent for this kind of prop. If you can try a metal detector on the prop, I would be very interested in the result. You can also take the prop through a security gate in an airport but I dont want to be responsible if TSA jails you...
In France, even with what is written in the patent, all SHAM props I saw were reinforced with fabric between the lamination and not metal sheet.

Regards,
PM

* In France, when some people have a so long name and somebody say it all, there is an habit to answer "que le dernier ferme la porte" (have the last one closing the door)!!!

EDIT: Added a pic to explain how the prop is built.
Attached Images
File Type: jpg IMG_20181029_163103662-txt.jpg (84.2 KB, 9 views)
Attached Files
File Type: pdf GB127019A.pdf (115.2 KB, 2 views)

Last edited by pmdec; 10-29-2018 at 09:29 PM.
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Old 10-30-2018, 07:04 AM   #12
Bob Gardner
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Pierre-Michel,

What an excellent reply. Thank you. I had heard of SHAM but only with a note that they were armoured propellers. This is a fascinating account.

With kind regards,

Bob
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Old 10-30-2018, 10:12 AM   #13
Viper
 
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Thank you Pierre-Michel! Your insights are very helpful to me and I appreciated the other comments as well. I just learned about the restoration of a DH-4 Liberty in Bowling Green, Kentucky which is not far from my home. I look forward to visiting and perhaps volunteering some time to help restore the only flying DH-4 in North America. I understand there are some still flying in France?
Here is a link: http://www.savinglibertydh4.org/blog/

I accomplished a metal detection survey of the propeller. The only metal I discovered was on both blades where the pigskin cover begins. There is no metal between this spot and the tips and no metal discovered going back to the hub. I can see the thin lamination between the wood layers that appears to be metal near the hub but it must be a fabric layer (I assume).

Last edited by Viper; 10-30-2018 at 11:41 AM.
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Old 10-30-2018, 10:25 AM   #14
Dbahnson
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Ditto to Bob's reply above - lots of good information there, as usual from pmdec and Bob.

And Viper, thanks for posting the photos and text with the critical stamped information. You can see how quickly it leads to a definitive answer to the question of aircraft usage.
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Old 10-31-2018, 09:02 PM   #15
pmdec
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Hi ,
Quote:
Originally Posted by Viper View Post
.../... I understand there are some still flying in France?.../...
Sorry but I know nothing about aircraft and I have not heard of a surviving flying DH-4 in France.

Quote:
Originally Posted by Viper View Post
.../... I accomplished a metal detection survey of the propeller. The only metal I discovered was on both blades where the pigskin cover begins. There is no metal between this spot and the tips and no metal discovered going back to the hub. I can see the thin lamination between the wood layers that appears to be metal near the hub but it must be a fabric layer (I assume).
Many thanks for that. I think there could be some small nails at the beginning of the pigskin.
Anyway, one more SHAM with fabric "armoured". So I attach another patent more in adequation with yours.

The very specificity of SHAM propellers is to be bent, almost not carved (just a little to remove the small "steps" of wood). After all the layers of wood and fabric are piled up with casein glue between each layer, the whole thing is pressed in a mold which give the pitch to the prop. Then, you have to wait 24 to 48 hours for the glue becoming hard. The productivity is, therefore, limited, and the price high. Another fact make the price higher: to have a lamination flat and straight enough, you have to remove about 3 mm on each side. With 21 mm thick classical laminations (cut in 27 mm thick planks), that is 6/27th of the wood to be lost, and if you add the loss when sawing the plank, it is around 8/29th. With 5 mm thick lamination, the wood lost become around 9/14th, more than double!

At the end of the war, Mr Valeri patented a "molded" propeller using very thin layers of wood: 1 to 2 mm thick. But Valeri used peeling wood (not sure 'peeling' is the right word), so there was no wood lost. I don't know if any of these Valeri prop came in use but I found one picture (only one!) of this kind of propeller. Sorry for not have the right to post it. And no decal is known.

PM
Attached Files
File Type: pdf GB127020A.pdf (61.8 KB, 2 views)
File Type: pdf GB131951A.pdf (399.8 KB, 2 views)
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Old 11-01-2018, 02:01 PM   #16
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Thank you PM! Very interesting information about the manufacturing process for these types of propellers.
Kindest regards, Viper
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