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Old 04-23-2019, 01:00 AM   #21
ahranis
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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/
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Old 04-23-2019, 01:08 AM   #22
ahranis
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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 ?
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Old 04-23-2019, 06:31 AM   #23
pmdec
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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
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Old 04-23-2019, 06:48 AM   #24
ahranis
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is it me the one that has to measure it?
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Old 04-23-2019, 07:28 AM   #25
pmdec
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Quote:
Originally Posted by ahranis View Post
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
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Old 04-23-2019, 08:14 AM   #26
ahranis
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I now can measure angles.
When ever you are ready.
😂
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Old 04-23-2019, 02:18 PM   #27
pmdec
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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
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Old 04-23-2019, 02:44 PM   #28
ahranis
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it is a phone clinometer
and all other tools
meaning tapes rulers etc...

Last edited by ahranis; 04-23-2019 at 02:54 PM.
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Old 04-23-2019, 03:57 PM   #29
pmdec
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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".
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Old 04-23-2019, 05:22 PM   #30
Dbahnson
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And here's a general schematic illustration of pitch along the length of the blade, as PM describes above.


Attached Images
File Type: jpg airscrew.jpg (52.1 KB, 12 views)
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