Propeller detail for the Alfa-Romeo RA1000 RC41 "Monsone" (1 Viewer)

[Engineman]

Hi all!

I am gently examining the details of the Italian propellers used on the Macchi C.200, C.202 and also the C.205.
So far, it is not a simple task, as there seems to be relatively little detail, although my task is not easy due to my lack of Italian language skill!
Very simply, the propellers used are, when rarely mentioned, referred to as the "Piaggio P.1001" which seems to be an Italian design that incorporates some common features with the German VDM types, although with considerable differences.
The information trail starts with the C.200 and this is slightly more fruitful. With the radial FIAT engine and no spinner, it can be seen that the prop Hub assembly and the operating pitch-change gear mechanism behind have some similarity to the VDM, but they are different. This "P.1001" propeller system seems to be covered in a Piaggio P.1001 manual. However, the description of the operating system is complicated and does not match the cockpit equipment to be seen in the aircraft, C.200, C.202 or C.205 as far as I can tell!
Unfortunately, pictures of the propeller hubs and prop equipment of the C.202 and C.205 seem to be very rare and definitive detail of the propeller type on the later aircraft is elusive.
So, does anyone have some better detail on these propellers?
To start with I can show a little info that I have defined.
The Italian propellers on the Alfa Romeo RA 1000 RC.41 licence built DB 601A engine were fitted onto an extended stub shaft with x36 fine splines, rather than the German DB 601A engine that used a radial splined coupling on the prop shaft extension with x16 coarse splines. The plot thickens, when I look at the Piaggio P.1001 prop manual and that seems to show x16 coarse splines in the Hub.

DB 601A

Alfa Romeo RA 1000 "Monsone". Pic from Milan Museum. Note the fine splines on the extended stub shaft.

A screen grab of the Piaggio P.1001 Prop hub, visible in the centre is the coarse spline shaft feature.


Cheers

Eng

 

[Engineman]

Hi All!

Well, I have achieved some progress! I have found several manuals that can be viewed on this site! The member who posted them has not been logged on the site since 2014 and only has 7 posts! However, he posted several Macchi manuals! These are a good mixture that cover the C200, C202 and C205. To find them, search member Alexxtres and look on his posts. The downloads work today for me, they are great. The only issue is that only the first will download as saved file, the others seem to be locked so I cannot print them.
Anyway, they have some great information! Thanks Alexxtres!

Looking through these downloads, I have found primary detail on the propeller types for the Macchi C200, C202 and C205. The original manuals show the following written details:

C 200 . The first 24 aircraft were fitted with a tipo "FIAT" prop. After that, this type was fitted with the Piaggio tipo P.1001 propeller. This version is described as being able to hold an rpm when selected on an unusual selector/indicator instrument that was fitted on the LHS of the cockpit. The indiicator instrument did include a blade pitch reading scale, but the instructions say that it was inaccurate (translation "crazy"!).
At the moment, I understand this system could HOLD a set pitch OR maintain an rpm (constant speed) when selected on the selector/indicator. I also think it could select minimum pitch and step down to that in stages by selecting with timed adjustments or 2 or 3 seconds at a time.

C 202 . This is the first with the DB 601 V12 engine. The partslist/instructions list a different propeller/control, the Piaggio tipo P 1001A propeller. This is a different unit without the indicator/selector. Instead it seems to have simple selections between automatic constant speed or adjustable fixed pitch.

C 205 . This is with the DB 605. The manual/partslist shows these aircraft to have been fitted with another type of propeller, the Piaggio tipo P 2001. This is similar looking to the earlier
ones, but looks a bit stronger/chunkier. Again no indicator.


So, some great detail, if you are interested, have a look at those manuals!
At the moment I am having difficulty with the translation of the operation of the units, the translations seem to be very poor. However, I know more than I did this morning!

Hope that is interesting.

Eng

 

[MiTasol]

A great project and I wish you well with it.

It is a pity that covid killed the avia.it web site as that had hundreds of Italian manuals. Maybe try the wayback machine to see if any were captured.

 

[Engineman]

I thought you all might like a screenshot of the Propeller controller/indicator/selector that is listed on the description of the Macchi C.200 Saetta using the Piaggio P.1001 Propeller and control units. This drawing shows two types of the unit, the one on the left was used on the C.200.

The 0-30 numbered scale is, I believe, indicating the prop pitch. This function seems to be discounted for use, because of inaccuracy, in the description. However, the 0-30 range shown is very limited, unless it shows a range above the Fine pitch stop or, if the scale is not simple degrees of blade pitch.
The rotary selector knob is used to select the mode, in conjunction with the two "Max" and "Norm" pushbuttons (with indicator lights).
The rotary selector is headed, "Commanded Pitch" and has four positions, 0, MIN (Finer pitch), Arresto (Hold) and Max (Coarser pitch).
The lower two pushbuttons are RPM range selectors. You are either in the Norm rpm range, or the Max rpm range.
This is quite a busy instrument/selector. The functionality is complicated and I will try to decipher it for us later. The descriptions of function are very confusing when translated!
At the moment, I think for adjustable manual pitch control, you have the rotary selector at ARRESTO with NORM selected. Then, to coarsen the Pitch you select the rotary selector to MAX for a few seconds then back to ARRESTO. Or, to fine-off the Pitch you select MIN for a few seconds then back to ARRESTO to hold the Pitch.


Cheers

Eng

 

[Engineman]

Hi everyone,

Not much progress today. I am having difficulty with the poor translation tool that I have (phone photo translate). The basic manual prop pitch control seems to be as I described previously, and the "0" lever position seems to just be "Off", in effect. The other selections of more automated operation translate into unreadable nonsense.
I am hoping that someone has either a good understanding of technical Italian or, a good text translation tool and can make some better translation for this?
So, sticking with the C.200 Seatta for now, I have copied the manual cover and 11 other pages that describe the operation of the Piaggio P.1001 propeller system. Included is the illustration of the control/selector instrument in simplified form and a table of selections to use the system. From the table, I have so far deduced the OFF position (yes, WOW!) and the manual adjustable pitch mode. That leaves what should be cruising and max performance constant speed modes.
TBH, even the Italian titles for these modes seem complicated.
So, here are the cleanest copies of these pages. If anyone is able to OCR these I would be very grateful and/or if anyone feels able to offer any insight by reading them, please post your interpretation.

Cheers

Eng

 

[Engineman]

Hi everyone,

I thought that some might be interested in the basic information that I have found, so far, about the type of propeller construction and operation that the Piaggio Tipo P.1001 and its developments the P.1001 A and the P.2001 had.
These Italian propellers have similar design features to the German VDM propellers. They have a basic strong steel "shell" hub that mounts the 3 blades into hollow stub mouths, each blade base free to move in bearings that allow pitch change from a worm gear running onto a circumferential gear on each blade root. The 3 worm gears are interlocked onto a common pitch changing gear that is operated by an electric pitch change motor working through an annular gear train that transmits the pitch changing relative movements while rotating with the propshaft. The structure of the hollow shell hub carries all the forces that act on the blades, the twisting torque of the power from the propshaft and the thrust from the propeller.
This shell structure is very distinct from the more common "Spider" arrangement type hub in many Allied propellers where the blades sit on stub shafts radiating out from a strong central structure that also transmits the turning torque from the propshaft.
In the VDM system, most of their propellers were able to accept a motor cannon, with a hollow blast tube through the centre of the hub. Although the Piaggio hub has the architecture of the VDM, it does not appear to be detail designed to use this feature, and the hub centre dimensions look to have been reduced to minimise the effective diameter of the hub and blade roots.
Although using a similar pitch changing gear-train, the Piaggio electro-mechanical system differs considerably in the pilots control method and the automation of the pitch control functions. Nonetheless, the P.1001 has some selectable Automatic pitch control functions.
The early P.1001 pitch control/selector/indicator unit does appear to have initially had a display of blade pitch. However, this is described as unreliable in function by the 1940 dated manual and the pitch control/selector/indicator unit seems to have been deleted from the later P.1001 A and the P. 2001 types. The VDM propellers continued to use an accurate pitch indicator "clock" with their propellers throughout WW2.

Here are some comparative illustrations.

Here is a side section of the P.1001 Hub, pitch gear train and at the top rear, the electric motor/control.

Here is the approx 1937 VDM system. The layout is similar, but the detail design is very different.

Here is the P.1001 Hub from the front.

Here is the 1937 VDM system from the front, as used on the DB601 A engine. Note the VDM type propshaft extension. This was not used on the
Italian Licence-built DB 601 A, but instead had a longer propshaft, as used with the Piaggio P.1001 A type propeller.

Cheers

Eng

 

[Simon Thomas]

Hi everyone,

Not much progress today. I am having difficulty with the poor translation tool that I have (phone photo translate). The basic manual prop pitch control seems to be as I described previously, and the "0" lever position seems to just be "Off", in effect. The other selections of more automated operation translate into unreadable nonsense.
I am hoping that someone has either a good understanding of technical Italian or, a good text translation tool and can make some better translation for this?
So, sticking with the C.200 Seatta for now, I have copied the manual cover and 11 other pages that describe the operation of the Piaggio P.1001 propeller system. Included is the illustration of the control/selector instrument in simplified form and a table of selections to use the system. From the table, I have so far deduced the OFF position (yes, WOW!) and the manual adjustable pitch mode. That leaves what should be cruising and max performance constant speed modes.
TBH, even the Italian titles for these modes seem complicated.
So, here are the cleanest copies of these pages. If anyone is able to OCR these I would be very grateful and/or if anyone feels able to offer any insight by reading them, please post your interpretation.

Cheers

Eng

This is Claude's attempt:

 

[MiTasol]

Can you provide the web link because I doubt those photographs of pages will OCR.

From a web link with my very large screen I should be able to get a decent screen print and get a reasonable result when I run that through ScanTailor.

Alternatively if you have a large screen do print screen for each page and save those and send them to me. For best results use fit to width (so two or three grabs per page). I can merge them easily before dropping in to ScanTailor.

 

[Simon Thomas]

If you didn't like Claude's version, here is the unlocked pdf for you to try.

 

[Engineman]

This is Claude's attempt:

Thank you very much Simon!

That is a very good translation IMO. The general structure of the original writing is somewhat idiosyncratic and this does not help with understanding. The translation does seem to be very true to the original.
There are a couple of points. The main point to remember is that this is the P.1001 system fitted to the FIAT A.74 RC.38 RADIAL Engine fitted to the Macchi C.200 .
I agree with the notes at the end, particularly the mixing of terminology in the original. For us today, it is worth noting that the original instrument/selector/control has two different selections termed "MAX" ! It is important to strictly recognise that the "MAX" on the rotary selector (or Lever) is related to Greater Pitch (Coarser). Whereas, the "MAX" on the Pushbutton is a selection of Maximum rpm. These identical terms with different meanings are extremely bad practice.

So, Thanks again for helping so much with this particular problem!

Eng

 

[ThomasP]

FWIW

In my notes I have the Fiat propeller used on the early C.200 and G.50 as a licensed Hamilton Standard 33D-1 model. The 33D-1 used a SAE No.50 shaft with 16 splines. Don't know what the -1 stands for unless it indicates left hand rotation?

 

[Engineman]

Can you provide the web link because I doubt those photographs of pages will OCR.

From a web link with my very large screen I should be able to get a decent screen print and get a reasonable result when I run that through ScanTailor.

Alternatively if you have a large screen do print screen for each page and save those and send them to me. For best results use fit to width (so two or three grabs per page). I can merge them easily before dropping in to ScanTailor.

Thank you!

If you go to the members list and find Alexxtres, then look on his postings, the second one down "Macchi MC 202 and MC 205 Flight Manuals" has the four downloadable manuals that he posted. Hopefully, they will download.
At the moment, I think Simon's Claude translation has made a good job!
I might have further requests with the C.202 and C.205 though!

Cheers

Eng

 

[Engineman]

FWIW

In my notes I have the Fiat propeller used on the early C.200 and G.50 as a licensed Hamilton Standard 33D-1 model. The 33D-1 used a SAE No.50 shaft with 16 splines. Don't know what the -1 stands for unless it indicates left hand rotation?

Thanks Thomas!

That HS prop sounds a likely fit on the first 24 C.200's and the 16 splines match the P.1001 Illustration. It also matches to words about starting with the prop selected to MAX to avoid oil pressure drop. That would not happen with the Electric operated P.1001 .

Eng

 

[Engineman]

Hi everyone!

I am now fairly happy with my understanding of the Piaggio P.1001 propeller and control system for the Macchi C.200 Saetta with the FIAT A.74 RC.38 Radial engine.
This last illustration is the diagramatic drawing of the propeller operating and control system. The quality is not good, but you can get a better one on Alexxtres post.

Here you can see the diagramatic prop and propshaft with the adjusting geartrains in the centre of the picture. To the right you can see the adjusting/control mechanism.
Arranged mostly below the centreline of the propeller shaft is the flyball governor for the Constant speed function, driven by part number 80 from the propshaft and gears.
The upper part of the control gear includes the adjusting drive to the pitch control gears and the adjusting drive bias for the manual propeller pitch control function, all of which
is combined to drive part 114 which is the drive gear for propeller pitch adjustment.
Later, I will write a short description of how the system was used.

Cheers

Eng