US Navy prop ID help

[BT13guy]

Hi folks,

Any idea what engine/aircraft this came off of:









Thanks for any help,

BT13guy
Daniel Hammer
USMC Ret
1985-2007

[Dave]

I think it's almost certainly part of a 4-bladed propeller for a LIberty engine used by the Navy for one of its many flying boats in the late teens and early 20's. I'm not sure of the meaning of the "FCR" stamping, but it's on many props from that era. The notching on the hub is designed to fit into a corresponding notch on another 2 blade to make the 4 bladed combination.

I think you'll find the hub dimensions match that of the Liberty 12 cylinder engine seen listed on this chart.

[BT13guy]

THANKS! thought it came off a Curtis Flying Boat.

US Navy HS-2L, but was not positive.

Thanks again.

Great forum!

r/Dan

[Dave]

It could be something like the HS 2L. It looks like a left hand thread, and the HS2L was a pusher so would use a left hand rotation with a normal Liberty engine.

[Bob Gardner]

Hi Dan,

Welcome aboard!

I was in the British Army for thirty years until 1993 and worked occasionally with both the USMC and the British RM.

Your prop is almost certainly from the HS2L. The pusher location of the prop was constricted on this aircraft and so had to be a four-bladed prop to transmit the power of the Liberty engine.

Storing four-bladed props on USN ships took up a huge amount of space so they were made as a pair of two bladed props. Yours is a very early example and the hub is described as a mortised joint. It worked but cracks formed at the joint. Are there any visible on yours? So it was quickly redesigned with each half-prop having a slightly thinner boss so that they could be bolted onto the existing engine hub.

I describe this in a book I'm writing but I don't have a photo. Might I use yours? And if so could you e-mail me high-resolution copies to aeroclocks at btinternet dot com (written in this form because I get enough spam as it is!)

With kind regards,

Bob

[Steve 2862]

Photos

Hello Bob, my name is Steve from New York. I am the owner of this propeller. I purchased it on a hunch from a contact I made at a yardsale. I posted it on the US Militaria Forum to see if I could receive some assistance due to the fact that I had no idea which Navy plane it was for.

I will contact you via the email you posted and send you full sized JPEG files. I am having a devil of a time taking good photos with the new cameras in the household. Crunching them to postable size is not working out very well for me either!

One cannot observe in the photos the following items.

The 975 is on the "flat" side, but is also on the (bottom) outside rounded portion. Next to the additional 975 is what I think is a 5 digit serial number. Several numbers are damaged (so I will show them as an "X") 08XX8. They would read like this if the 975 on the outside is read right side up. If not, they could be 8XX80. I suspect the 975 is a factory serial number as it could be read whether the propeller is mounted or not.

On the notched side is a stamp with the number 375.

Steve NY

[Dave]

Many of the HS2L propellers were stamped with "SE 50"x"0 , where "x" designated a pitch. I believe the "SE" was for "Steam Engineering", which was the Navy department that procured propellers in the late teens. See this page for one example.

[Bob Gardner]

Thanks Steve,

I look forward to seeing your photographs and I'm grateful for your help. I enclose below details of the USN report written about its experiences in making propellers.

The following information comes from the History of the Bureau of Engineering, Navy Department published by the Secretary of the US Navy in 1922.

The propeller problem on the HS seaplanes was difficult but was solved quickly. This seaplane required a pusher propeller but on account of the limited distance between the boat hull and the crankshaft it was necessary to use the 4-bladed form. The small diameter to which it was limited, and the many interferences on the plane to a free flow of air to it, made the design of an efficient propeller difficult. Fortunately, the first design gave a very good performance and was at once put into production.

A second question that had to be met was the difficulty of handling, transporting, and storing the 4-bladed propeller. It was imperative that this propeller should be made in two parts, if only to meet the demands of limited transportation space for overseas shipment.

After a certain amount of investigation, a 4-bladed propeller was devised by taking two 2-bladers and making a mortised joint at the hub by cutting partly through the first lamination on each blade.

This propeller gave good service, but a tendency was found to split at the joint, and the design was abandoned in favor of two blades without the mortise, but with a slightly thinner hub so that they would fit the engine hub.


With kind regards,

Bob