Rotol propeller; help please!

[dairwin]

Hello all,

New to this forum, but I have a specific request regarding a propeller hub I recently acquired. See photos.

A Rotol R5/3 hub, from a crashed Fulmar MkI aeroplane (crashed Dec 1940).

The hub has markings: RA926 4014

Can anyone help me identify what blade reference number this hub would have had (I assume it is not RA926 ?!). I have no reference books on Rotol props of this age.

Any technical info, and/or sources of Rotol specifics would be of great help.

Thanks, David.

[MWP_Lamar]

Yours is a hub for an adjustable prop. A gentleman by the name of Monte Chase specializes in this type. I would suggest contacting him through his website at www.notplanejane.com.

Lamar

[dairwin]

Hi Lamar,

Thanks for the reply. I have already contacted Mr. Chase, but his reply did not provide any further information.

I know what the propeller is and how it works (I have a few engines and propellers), however I do not have a blade reference for this specific propeller hub.

I have the 'Rotol series R4 and R5 installation, ops and maintenance manual' which provides one blade type for a Whitley MkIV and MkV as RA131 (they used R5/1 and R5/2 props), but does not specify for the R5/3 (which I believe was only used on the Fulmar MkI aeroplane).

I am hoping that if someone has a Rotol blade reference manual (or similar), then this will list a Rotol R5/3 blade reference.

Thanks,

DAI

[MWP_Lamar]

I don't have that reference but perhaps someone else does. Hope you find what you need.

Lamar

[dairwin]

Thanks Lamar.

DAI

[Bob Gardner]

David,

The following info describes three Rotal props for the Fairey Fulmar I and gives in turn prop type, blade type, Adaptor, spinner. All fitted the RR Merlin VIII

R5/3 DB191/A RA1269 ES/3
R5/3 RA1242 RA1269 ES/3
R5/3P DB191A RA1269 ES/3

Later Fulmar Mks I and II used the Merlin 30 engine where the data was;

R5/5 DB191A RA557 ES/3
R5/5 DB191A RA1269 ES/3
R5/5P DB191A RA557 ES/3
R5/5P DB191A RA1269 ES/3

I have kept to prop types R5/3 and R5/5. A further seventeen Mk II Fulmars had prop types RX5/7 and 7P with other blade types etc.

I can't find RA926 linked to a Fulmar prop. But RA9266 was an adaptor used on the Fairey Firefly, Barracuda, and the Fairey O.5 and about thirty other types of aircraft.

I hope this helps.

With kind regards,

Bob

[dairwin]

Hi Bob,

THANK you for the info! Exactly what I was hoping for. Fantastic detail.

Attached are two photos of the stamping data I quoted.

My focus is on the R5/3. My particular interest is because the prop hub I have is the very same prop that crashed with my Merlin VIII in early Dec 1940. The pilot bailed out of the aeroplane. The prop hub was recovered with the engine.

The engine has taken 10 yrs to rebuild to ground running condition and was test run in Dec 2010, 70 yrs after the crash.

One wonders whether the hub can be rebuilt as well to ground running condition. Hence my interest.

I assume that when I dismantle the hub and see the blade root, the exact blade spec will be printed on the base?

Kind regards and thanks,

David.

[Bob Gardner]

Delighted to help. Are you a David , Dai or Dafydd? I am in great awe of your success in getting this engine running. Particularly your bravery when you pressed the button for the first time! I have always wanted to have a running Merlin but I lack the expertise, devotion and money.

The metal sheathing at the blade root should carry the blade type. I still don't know what RA926 refers to. Perhaps my tables are not complete. Tell me what you find.

With kind regards and enormous respect,

Bob

[Bob Gardner]

Postscript; do those pairs of red holes above the plug leads indicate that you are running it without exhaust manifolds? Does the torque lift one side of the sub frame assembly off the ground?

Still in awe,

Bob

[dairwin]

Bob,

The exhausts stubs were not fitted in the test. I have the remains of the crashed stubs, but these are not recoverable. I am investigating where/how to get a set. I do have another set, but of a later type.

The torque (power at the propeller) is limited by the size of the trailer, typically to 900HP or so. The MkVIII engine developed 1080HP, but because of its 'experience' it will not be run often or at any power.

However, my other Merlin is a different matter. That has a metal prop, and therefore outside of remit of this forum

I need to clarify; that I did not restore the MkVIII; it was restored by a friend of mine in Carlisle. He is the genius behind the hard work. Thanks for the sunshine though!

DAI (my initials, or David for short!)

[dairwin]

... metal sheathing at the blade root should carry the blade type ... Tell me what you find.

Bob,

I have now had a good scratch around the metal sheathing at the base of the blade, and found a lot of information on each blade root, which I present as:

Blade position 1:
RA1269, 24.84 604, D3992, K2700, …D.B.191/A

Blade position 2:
RA1296, 24.84 605, D3980, K2701, ...191/A

Blade position 3:
RA1296, 24.84 616, D3986, K2793, DBL No. D.B.191/A

So I conclude the blade type is D.B.191/A, which ties in well with your first line of data.

I wonder whether any DB191/A blade profile data is available?

Kind regards,

DAI

[Bob Gardner]

'Morning David,

I'm delighted that the numbers match!

I'm not aware of any drgs available for WW2 blades, but this is outside my speciality which is WW1 props. Possible thoughts are trying some of the Merlin rebuilders, Retrotec etc. They might also have some time-expired hub and blade bits. Other thoughts are to ask the Rolls Royce heritage people and ditto the Bristol Aircraft trust. Don't think I've got the names quite right. Let me know if any come up trumps.

Bob

[dairwin]

Hello Bob,

Thanks for your reply. I shall contact the Bristol collection and see whether they have any information.

DAI

[Bob Gardner]

Tell me if you get any sense out of them.

Bob

[dairwin]

Bob,

I have made some progress regarding the R5/3. I contacted the Bristolaero group and the archivist there was helpful, although did not have the specific detail I was seeking. He advised contacting the RRHT Bristol, from which I have received a reply with more information, although not initially with blade profile detail. However, the information I have now is very specific and confirms your information and more; with:

"My list of Rotol props agrees that the Fulmar Mk.1 had the R5/3 prop fitted
with DB191A (Weybridge) blades with the 166mm root giving a diameter of 11ft 6in and weighing (with adaptor) 46lbs. The whole prop weighed 305 lbs
(approx). Its GA was drawing RA1571. It was controlled by a GR/2 governor
unit and covered by an ES/3 spinner."

I hope to receive more soon.

DAI