100" OAL Flottorp Chicago - Please help identify

[JeffL]

Hi, I have had this propeller for many years but I am wanting to identify so that I have a better idea of the application and year it was manufactured.

Approximate OAL is 100" tip to tip.

Marking is SC8704

Thank you for any help that you can provide!

Jeff

[Dbahnson]

It's hard to know a specific aircraft make and model without stamped design numbers. The numbers on the photos are Signal Corps numbers and inspection stamp, but they don't identify the engine and/or aircraft. The "611" is likely a production number. The prop is in nice original condition so be sure to avoid any attempts at "restoration".

The hub size looks consistent with an OX5 engine, but you should read this page and take careful measurements of the bolt hole circle, etc.

Is there anything else stamped on the hub area?

[JeffL]

Hi Dave, appreciate your quick reply. I have looked the prop over carefully and there are no other numbers or markings other than what are shown in my photos.

I did closely measure the hub dimensions and utilizing the chart on this website; have determined that the dimensions match that of the Curtis OX-5 engine.

I believe the wood to be either Walnut or Mahogany.

After reviewing the photo gallery on Wooden Propeller.com The overall scimitar (curved) blade shape of my propeller seems to match that of the Hartzell Liberty or Unico Liberty (450 HP) engine application rather than the Curtis JN-4 OX-5 that I have seen photos of except the length in that photo is much shorter (8'3") than my propeller?. I know that the Liberty is a 450 HP engine and the hub dimensions are all wrong so that can't be correct.

Do you know if the OX-5 could swing a longer (100") prop like what I have?

Lastly; since I have the Signal Corps marking, does that also mean that it had to be manufactured for a Curtiss JN-4 Jenny? I am not sure what airplanes the US Signal Corps used with an OX-5 engine other than the Curtiss JN4. Could it have been manufactured for a Curtis JN-1,2 or 3?

Jeff

[Dbahnson]

Jeff, I don't know the time sequence of the Signal Corps and which airplanes may have used the OX5. The JN4 is certainly one of the common applications, and may be the most likely just by sheer numbers, but you still can't exclude other aircraft that might have used it.

The hub on yours looks pristine and may indicate that it was kept as a spare and then sold as surplus (as many were). The comparative shape of the blade is nearly meaningless, as there were lots of similarities with completely different applications, but clearly the Liberty engine isn't one of them.

Most JN4 props I've seen were 8 feet 3 inches but there were variations. Either way, that's 99 inches and very close to yours. The length is certainly suitable for an OX5.