ID Please?

[ahranis]

the third stamp is also visible in dsc09725 and dsc09727.
Is that an R. and a B or 8?

There is no other rectangular stamp on the flat parts of the hub

[pmdec]

Hi ahranis,

I can't read the sign beside the SFA stamps which is on the right of M1...

The three others (2 on the flat side and 1 under Cu 260) could have the same sign, which is the greek letter beta. It has nothing to do with your country or the place the prop was found. It is there because the workshop where the prop was repaired or modified was the Chauvière workshop and one of the militaries who controlled the prop in the late WW1 used this beta sign to show who has the prop controlled. I join a pic of a Ratier serial 15 which was repaired and controlled in what I guess was the same workshop.

I am still looking at pictures of Salmson aircraft of the 1917-1920 era but all where it is possible to know which way the prop was rotating show left handed prop... The only right handed are on Salmsom-Moineau where there was one right handed and one left handed on the same aircraft, but they used Salmson 230HP engine...

Just an idea: are you sure your pics #9730 and 9746b are not flipped?

Regards,
PM

EDIT: Removed one question about font.

[pmdec]

Hi,

I am trying to have some answers to which Salmson aircraft could use a 260 HP Canton-Unné with a right handed prop.
I have posted a question on a French forum where there are very knowledgeable people about aircraft :
https://forum.pages14-18.com/viewtop...521329#p521329

To go forward on this thread, I have to wait for possible answers... excepted if the 9730 pic was flipped!

Regards,
PM

[Dbahnson]

Pierre-Michel, with digital files it takes some effort to "flip" photos, but it can be done. (It's not like the old photo negatives that could be inserted backwards.)

I did use some "mirror image" software to digitally flip the original prop photo, but I doubt that it would happen accidentally, and if it did I would expect to see the letters on the other photos also appear as mirror images. If that is done, however, it creates a digital appearance of a left hand thread.

I'll wait for ahranis to confirm or deny if the photo has been "flipped".

[ahranis]

The pics are not flipped (mirrored)

(My apologies, I thought I sent the message last night. Fell asleep trying to text 😂 )

There was no reason for doing this

The sign is quite unreadable because of the varnish there.
It seems to be that beta symbol again but I
cant be sure .

If thers is a gentle way of removing that varnish I
could proceed

[ahranis]

Does this help?

It is a short reference to the planes used near my area during the war. It mentions the collaboration- assistance between National air forces.

https://www.haf.gr/history/haf-history/1914-1918/

[ahranis]

I had a talk with my mother last night about the propeller.
She rememberd that my father tried to make a windmill out of it. Maybe that explains the hub's condition ?

[pmdec]

Hi,

Ok, so the prop is a right handed one (with some softwares, it is very "easy" to flip a pic if you crop it and reduce its size at the same time).

About the sign on the right of the SFA stamp on the side with serial and prop number: it would be extremely stange that if it is also a beta letter: the prop was made and repaired (or modified) in two different workshops so it would be very amazing that the prop has been controlled by the same person.

About the hub: it seems to have been made as a tractive prop.

I don't know if geared Z9 engine existed, but it would explain the right handed prop. But then, the pitch had to be very high. Do you know how to measure it?
The Régy 804 for the 260 HP was 2.75m long and had a 2.10m pitch.

Regards,
PM

[ahranis]

is it me the one that has to measure it?

[pmdec]

is it me the one that has to measure it?

Hi,

You have to have the prop to measure the pitch, so...

An estimate would be enough. Have you something to measure angles? Some phones do it. In this case I could try to write how to do excepted if Dave or Bob can explain...

I don't be logged again before this evening (in France, where it is half past one PM).
Regards,
PM

[ahranis]

I now can measure angles.
When ever you are ready.
😂

[pmdec]

OK,

What have you? A protractor? Or a clinometer (phone, ...)?
A graduated ruler may be used but it is more difficult and less accurate.

With a protractor or a clinometer you need also a measuring tape,
With a protractor you need also a ruler (or anything straight larger than the blade width).
With a ruler you need also a bracket. A graduated one is better.

In both cases, adhesive tape could help.

PM

[ahranis]

it is a phone clinometer
and all other tools
meaning tapes rulers etc...

[pmdec]

OK, a clinometer is the easier way!

You have to measure the angle between the flat side of the blade and the rotation plane of the prop, and this in different places.

First, have the prop on a table with the flat side of the blades upward.
Verify that the table is horizontal, placing the clinometer on the hub: it has to show "0" when the phone is paralelle to the blade width (= perpendicular to the length of the prop). If not, have something under the feet of the table until the clinometer show "0".

Now, measure the angle of the blade at three distances from the prop center: 93, 100 and 120 centimeters. For each, take note of the angle (A1, A2 and A3). For each measure, be sure the phone is exactly perpendicular to the prop length.

That's it!

In each place, the pitch (in centimeters) is:
- at 93cm : 186 x pi x tg(A1) : it is the "Régy pitch", measured at 2/3 of the blade,
- at 100cm : 200 x pi x tg(A2) : it is just for a control...,
- at 120cm : 240 x pi x tg(A3) : it is the "(French) military pitch" for props between 2.70 and 3.10 meters long.

OK?

Regards,
PM

PS: If the prop was exactly helicoidal, the three pitches would be the same. But the prop makers didn't make their props exactly helicoidal to compensate the distorsion of the wood when the prop was in use. Generally, the pitch was higher towards the tip, because the centrifugal forces "try" to flat the blades when the shape of the blades is "traditional".

[Dbahnson]

And here's a general schematic illustration of pitch along the length of the blade, as PM describes above.