prop ID

[dfletch.1]

I have recently acquired a wooden prop that is 100" long.
It has Signal Corp markings of SC9668 and underneath that number is a square with an arrow in side and the numbers 113 beneath the arrow.
90 Degrees clockwise from this set of markings is the number 1506 followed by a clover leaf symbol with the letters U S A inside the leaves.
The propeller has copper protection flashing on the tips.
There are 8 holes in the hub which is also notched.
Can anyone identify the age of this propeller and perhaps what airplane it was used on.
Any information will be greatly appreciated.
Thanks.

[Dave]

There's not enough information (as near as I can tell) to identify it just from those stampings. It's a low Signal Corps number, but I don't know how to correlate that to a specific year. I suspect it's from the mid teens. The inpection stampings are non specific and don't really help with the information you're looking to find.

If the notch is large, it's probably part of a 4 blade combination, with another notch interlocking with it. Those were most commonly seen on Liberty engines, which of course were used on a variety of aircraft.

I would start by reading this page and then checking the hub dimensions compared to those on the linked chart. A photo may also help narrow it down.

[dfletch.1]

Prop ID

Hub thickness is 4"
Center bore is 2.66"
Bolt Size is 3/8
Bolt circle is 5.25
As you can see there are notches in the hub. If this is off a Curtis OX-5, why are their notches? Do you think someone cut those?
Thanks.

[Dave]

Yes, I think it was cut to fit a clock or barometer or similar device. It's certainly not part of the hub installation.