Odd 7-bolt Chauviere Prop

[Dave Burnett]

I have an old propeller which has been in my family for more than 60 years. The story was that it was plucked from the North Sea by Norwegian fishermen during World War One. It was believed to be from a German aircraft which was seen to crash. It is quite similar in overall shape and size to the "Early Chauviere" propeller in the forum photo gallery, however it has a 7-bolt pattern which is puzzling. From this site and others I have found reference to the early Farman and Voisin pushers with seven cylinder Gnome radial engines. Perhaps the propeller is really French and simple symmetry might be the explanation for the seven studs. Can forum members shed any light on this configuration or suggest a matching aircraft.
Dave in Alberta, Canada
Specifications
Prop is left hand thread and 260 centimetres long
Pitch is quite flat so that centre portion is only about 7.5 cm thick
Center portion has a rather large 27.5 centemetre total diametre
Seven holes are in a 16 centimetre circle and each about 6mm dia.
Shaft hole is 14 cm
Leading side is counter bored 19 cm diameter and 2 cm. deep
Trailing side is counter bored 18 cm diameter and 1 cm. deep
Blades are 25.5 centimetres wide at the widest point
The only marking is hand engraved on side of hub portion 260 X 7.40
The wood is laminated in four pieces and has dark grain similar to walnut
Blades are painted orange extending 85 centimetre from the tip
There are pry marks on the back suggesting a rather rude hub separation

[pmdec]

Hi,

The large center hole (14cm) is probably for a direct mounting on a rotary engine crankcase.
Could you post pictures of the whole prop (front and side views) and clear close-ups of the 4 side of the hub?
And please, look for possible stamps like those: http://woodenpropeller.com/Chauviere.html
Could "260 x 7.40" be 260 - 140 (diameter and pitch in centimeters)?

Regards,
PM

[Dave Burnett]

Odd 7-bolt Chauvier Prop

Wow! Thanks PM. If I understand correctly the whole engine rotated with the prop. It is starting to make more sense to me now. There is a fantastic printable image of the 7-cylinder Gnome engine at www.griffwason.com/gnome1.htm. I am sorry to report that in spite of apparently original paint there are no markings. I can confirm 7.40. If there is interest I can take the darn thing down again for detailed pictures. The one I am trying to post now is taken at a slight angle which makes it look a bit longer and more narrow than it is.

[Dave Burnett]

Odd 7-bolt Chauviere Prop

OK! New clues. I spent the last day of 2012 in a long internet search. I could not find a matching 7-bolt hub but I did find a likely solution to some of the other odd features of my prop. The first page at WWIAVIATION.COM shows the 1913 Henri Farman Biplane. This design is unusual because the propeller is sandwitched between the cylinders and the airframe. I will call it a prop forward rotary pusher. In this arrangement the width of the prop would dictate a longer crankshaft. Henri and his engineers would certainly have needed to counter-bore the propeller to the maximum possible amount to reduce its effective width. My prop matches this requirement and a new clue is that the trailing side paint shows heat and oil distress which you would expect from being next to the cylinders. The 1913 Henri Farman aircraft was apparently sold to many countries for testing and evaluation but did any of them make operational use of the prop forward rotary pusher design? I sure would appreciate help or comment from forum members.

[Dave]

Let's go back to some of the original post and consider a few issues. One, the 7 bolt hole pattern is EXTREMELY unusual, so finding any engine/hub that used one would likely narrow your field down to almost nothing. I doubt very much that it has anything to do with Chauviere, if you're basing that on its design features. Second, I am very skeptical of the story (as I am with most stories accompnying these items) which implies that the propeller survived a crash into the sea, which seems implausible (although possible). Most landplanes will nose over when they hit the water and the force would likely break the blades. That might be different with a pusher configuration, but I'm having trouble getting a clear picture of what you're describing with "prop forward rotary pusher", or what the need for the sandwich concept would be.

Can you pull up the link to the Farman aircraft? I can't find it on the wwiaviation.com website.

[Dave Burnett]

Hi Dave. I too am skeptical of the crash at sea story. I will try again to describe the Henri Farman pusher design. The rotating cylinders are behind the prop as the aircraft flys. This less common configuration was a rather unique feature of early Henri Farman designs between 1907 and 1913. I find that it was copied by several counties but ultimately it gave way to the more common configuration which had the pusher prop trailing the cylinders.
Try this:
http://www.wwiaviation.com/development.html

[Dave]

Got it. Thanks for the clarification.

I can see why that design didn't catch on . . .

It would be interesting to see if there were some kind of coupling mechanism that used the standard 8 hole hub on the engine and had to use a 7 hole propeller hub to offset the components. (VERY speculative, but on the other hand I've never seen a 7 bolt hole hub on anything.)

[pmdec]

Hi,

This is a very interesting propeller. I do know about left hand French propellers with a 2m60 diameter, 140mm central hole, 250 to 260mm blade width and very thin hub (46mm, which around what remains of yours when you substract 10 + 20mm from the 75 overall). They were made before 1912 for Sommer and Farman pushers, and perhaps others.
But to go forward, you have to post clear close-up pictures of all 4 sides of the hub and of the blade roots. If you can remove the barometer, it will be the best.
Are you sure of the 6mm dia bolts holes? It's makes me questioning, because it is very small.

Regards,
PM

[Dave Burnett]

Odd 7-bolt Chauvier Prop

Thanks for all your help PM. I promise that the pictures are coming as soon as I get the chance. The prop was not modified to fit the barometer and it comes off rather easily. I will take some photos with my basic camera and then perhaps I can get a more talented family member to take some better ones later. The man who had the prop shipped from Norway to Canada was a family friend so I have some trust in the basic story. I have no way of verifying the "crashed at sea" part though. It occurs to me that if this large propeller ever stopped turning the aircraft would likely come down like a stone.

[Dave Burnett]

Odd 7-bolt Chauviere Prop

Progress! I checked out the early Roger Sommer biplanes and they do have the prop-forward pusher configuration which matches my speculation. Yes, the bolt holes are small but not precisely measured at this point. I think that all we need now is to find the matching 7-bolt hub.

[pmdec]

Hi,

Sommer biplanes were derivated from Farman ones. And yes, they have "sandwich" propellers (I do like the word!). You can see a Farman with this kind of assembly there: http://www.flightglobal.com/pdfarchi...0-%200639.html and on the next page ( http://www.flightglobal.com/pdfarchi...0-%200640.html ), you have even the propeller diameter which is ... 2m60 (8'6")!!! That is the same the props I know about (dimensions given in my previous post) which are "Rapid" propellers Sommer used on his aircrafts along with Chauvière ones.

In an other Flight page: http://www.flightglobal.com/pdfarchi...0-%200785.html (bottom right) continued on http://www.flightglobal.com/pdfarchi...0-%200786.html there is some arguments about this kind of fitting.

So, if the prop is bolted on the crankcase, which has a x7 symetry, it could be logical this crankcase has 7 fitting devices for the prop. But... It seems very difficult to find a picture showing this because the hub his masked by the engine supports. The only way, except finding a propeller picture from this era, would be to find a blueprint of such an engine..

And there is ever the "problem" of your "7.40" marking: ??? I am curious to see it!

PM

Small bonus: http://www.flightglobal.com/pdfarchi...0-%200076.html (Sommer aircraft drawing with sandwiched propeller).

Poker bonus to come: found picture of a Rapid propeller with 7 (seven) bolt holes, 14cm center hole and 7cm thick hub prop for Farman or Sommer with 50HP Gnome!!! Will show my cards as soon as I see yours...

[Dave Burnett]

Odd 7-bolt Chauviere Prop

I am excited now. The teaser is fair enough so here is another. The photos are in the camera. I am not part of the electronics age so it will require a quiet time for me to transfer and edit them. The hand engraved marking turned out to be impossible to capture with an indoor flash but I did examine it very carefully. To me it best reads 2.60 X 7.40 but I could be convinced that it reads 2.60 X 1.40 if that makes more sense.

I did take out an atlas to see if I could find the fishing port of Arendal, Norway and there it is near the southern tip of that country. It is a long way from France and I don't believe that a French pilot would fly that far even with a lot of brandy beforehand. Germany and Denmark would be better candidates along with Norway itself. Do you think that the prop may be a German manufactured knock-off or copy for use on an aircraft of obvious French design?

Maybe if my luck continues some sharp eyed forum member might even be able to find a matching aviation death early in the war?

[pmdec]

Hi,

If you have difficulties to transfer the pictures, you can send them to my mailbox (pmdecombeix at yahoo dot com) and I will post them from a server. Don't use the flash. Light coming from the side is the better to capture the markings (try different placing relativly to light source).
Chauvière had a licensed maker in Germany before WW1. The Chauvière decal (see http://www.woodenpropeller.com/image...rtXXIVdec1.jpg ) read "INTÉGRALE- BSGDG - PATENT - DRP". BSGDG is for France patent (Breveté Sans Garantie Du Gouvernement), PATENT for England and DRP for Germany (Deutsch Reich Patentiert).

PM

[Dave Burnett]

Odd 7-bolt Chauviere Prop

Pictures are now transferred to my computer. I will send some full size ones to PM later. I will try to send some size reduced ones as samples.

[Dave]

Interesting . . .

(BTW, may I suggest taking a few moments to understand the rather straightforward method of processing photos to post on the internet using Irfanview, which is a free, very popular photo imaging software package. See this post for details. It can be very handy, not just here but in a variety of other circumstances as well.)