Need help identifying propeller blade

[hawkeyepoole]

Doc Hospers at the Vintage Flying Museum in Fort Worth asked me to work on a display of prop blades to go with some of the engines in our engine display room. He sent me into the abyss to pull what I initially thought was a blade from a B-17, but upon closer examination it's either 1) not from a B-17 or 2) maybe an alternate blade style or 3) from something else entirely.

Here's what I know:
Our B-17 has the paddle style blades that have a fairly constant chord until almost at the root. This blade has what I would call a more common style of tapering chord down to the root. I'll get a picture.

Here's what is written on the blade:
SER NKSR-140
DWG 6359-18
LOW 24 AT 42
HIGH 90 AT 42 ('90' not clearly legible could be another number)

Stamped at the base: AMS 4130 CONT NOW 535 AC 25049 SHANK 56155 CHG-L

The blade is approximately 72" long and almost exactly 12" at the widest.
Any clues?

[51fixer]

Doc Hospers at the Vintage Flying Museum in Fort Worth asked me to work on a display of prop blades to go with some of the engines in our engine display room. He sent me into the abyss to pull what I initially thought was a blade from a B-17, but upon closer examination it's either 1) not from a B-17 or 2) maybe an alternate blade style or 3) from something else entirely.

Here's what I know:
Our B-17 has the paddle style blades that have a fairly constant chord until almost at the root. This blade has what I would call a more common style of tapering chord down to the root. I'll get a picture.

Here's what is written on the blade:
SER NKSR-140
DWG 6359-18
LOW 24 AT 42
HIGH 90 AT 42 ('90' not clearly legible could be another number)

Stamped at the base: AMS 4130 CONT NOW 535 AC 25049 SHANK 56155 CHG-L

The blade is approximately 72" long and almost exactly 12" at the widest.
Any clues?

Possibly A-26, B-25 and/or Avenger

Rich

[Taigh Ramey]

Rich is correct. The blade designation 6539A-18 is used on the B-25 and the A-26 but the TBM used the 6539A-12 so it would be too short for the TBM.

The NK in the serial number means it was made by Nash Kelvinator and the contract being AC (Air Corps) 535...is a typical WWII contract so I would easily bet it was made during the war.

B-25 blades are quite desirable these days. Ask Jaybo he will certainly give you the straight poop on its value.

[B25PBYGUY]

B-25 blade for the 23E50 hub
Most of the TBM's (and DC-4's) I've flown, had 6507's.

[hawkeyepoole]

Thankx guys! I'll ID it as a 'likely' B-25 blade. This one is a non-serviceable unit. It'll just be a display piece. I may polish it up to make it pretty, and then re-stencil the data on the front surface. This particular blade, and its two sisters had most likely been on static display somewhere for years. Last night I stripped off: Clear, Black, Teal Blue, Red, Pale Green paint. Even the rubber boot had several coats of paint on it. The blade tip on this particular one looks like it was dipped into sand while running. The black paint appears to have been put on with a paint brush.

Can someone explain the "24 AT 42" and "90 AT 42" on the stencil? Reads like a tolerance, but of what?

[DryMartini]

Can someone explain the "24 AT 42" and "90 AT 42" on the stencil? Reads like a tolerance, but of what?

Those are the pitch angles - 24 degrees min - 90 degrees max (feathered).
However, I cannot remember what 42 means...

[TEN]

Probably measured at 42" radius from the center.

[hawkeyepoole]

It's not likely a radius measurement. Each blade is 72" long for a radius of somewhere in the 75-78" range.

[DryMartini]

It's not likely a radius measurement. Each blade is 72" long for a radius of somewhere in the 75-78" range.

I believe TEN is right.
The blade pitch would be 90 degrees as measured 42" from the
centerline of the hub. It is not the blade length (prop radius),
which is what I believe you are suggesting.

[hawkeyepoole]

DOH! I misread the post the part "measured AT 42 inches". I just took a tape measure to the blade. 42" isn't quite at the widest part of the blade, but just shy, so that sounds reasonable to me. I learn something every day here!