Mystery Prop ID Help

[v8sharkie]

Hello there,

Hoping to help a friend ID this prop. Any info would be appreciated.

The prop is 7' long and 4" thick at the hub. Hub Diameter is 8" and hub plate is 7" diameter

See attached photos.

Thank you in advance for any help.

[Bob Gardner]

Magnificent Prop!

The letters SC indicate that it is an aircraft prop from a US Navy aircraft c1918.

Is there any more data stamped anywhere on the prop, which would give the diameter (D) and the Pitch (P)?

Dave Bahnson is the forum expert on USN and USAAF early propellers and will be in touch soon.

With kind regards,

Bob

[Dbahnson]

It's a very high Signal Corps number, so I suspect that it's a post-WW1 manufacture. (The Aviation Signal Corps was a division on the U.S. Army.)

The short metal sheathing on the tips is unusual, as usually the sheathing runs further back along the leading edge.

I think the best you are likely to find is a possible engine based on its hub dimensions, and I'm just guessing that it's probably an OX5 engine.

[v8sharkie]

Bob & Dave - Thank you very much for your responses and information! It appears I did forget to include the other stamping. I will attach below. Maybe this will help further ID the prop.

Additional stamping appears to read
0434500 ( but is hard to make out )
RIGHT HAND stamped below

[Dbahnson]

Bob & Dave - Thank you very much for your responses and information! It appears I did forget to include the other stamping. I will attach below. Maybe this will help further ID the prop.

Additional stamping appears to read
0434500 ( but is hard to make out )
RIGHT HAND stamped below

0434500

I think that "0434500" is actually "D- 8'3" x 5.00" which would represent a diameter of 8 feet, 3 inches and a pitch of 5.00 feet, or whatever those actual digits are. But that size is quite consistent with many aircraft in the twenties.

Did you check the hub measurements

Measure the prop from tip to tip and that will be the diameter. If it's not 8' 3" then the stampings would be the same as the actual measurement in feet and inches.

"Right hand" is obvious by its appearance, but it's stamped there because it isn't obvious to every mechanic, and using the wrong rotation would make the plane go backwards on its first take off attempt.

[v8sharkie]

Dave - thanks for the info. Unfortunately, I'm not where I can measure the prop accurately, but simply going off my friend's provided dimensions.

I was told the prop is 7' from tip to tip. So I guess that means the first two numbers in the stamp are actually 84 (as in 84").

The hub is supposedly 4" thick (front to back) and 8" in diameter top to bottom. The hub plate (Metal) is 7"

[v8sharkie]

Oh, and any idea on maker? Also, Ive seen the cross shape with round ends stamp before but have forgotten who/what it represents.

[Dbahnson]

So, things aren't adding up. Most Signal Corps props had diameter in feet and inches and pitch in feet and decimal.

If it's actually 7 feet long and actually stamped with an "8" then one possible explanation is that it was damaged and the tips shortened and trimmed to make equal length blades. That might also explain the unusual sheathing - done simply to cover the altered tips.

You need to determine the bolt hole circle diameter. There was flexibility in the width and even the thickness of the wood, but the bolt hole circle diameter is a fixed dimension that corresponds to the size of the metal hub assembly.

[v8sharkie]

Ok - I've asked my friend to measure the bolt hole circle diameter. I am told it is 5.25" and according to the chart that's for an OX5 as you had previously mentioned.

[Dbahnson]

It's most likely that it's for an OX5.

It's nearly certain that it's not for one of the other common engines.

[v8sharkie]

Understood.

Also, I was reading somewhere else that the SC prefix was used through 1918. Or did they use this stamping after 1918?

I had also read that the clover stamping is another indication of Signal Corps. Is that accurate?

[Dbahnson]

I don't know the answer to how long SC numbers may have been used, but I've seen some props that certainly suggest that it may have been considerably past the 1918 dates.

Might be a good research project.

[v8sharkie]

No problem. Yes, that would be interesting to know more about.

Also, curious if you have any knowledge on the Signal Corps clover shaped stamp? It reads USA 76 inside each of the legs (U) (S) (A) (76)

[Dbahnson]

I suspect that it's an inspector's stamp, and 76 identifies the inspector. That's often the format in other countries.