B-17 Flying Fortress part (s)

[BFreer]

I picked up these two parts a few months ago The box like part has a B17 part number and Boeing stamp and is from the air filter for the supercharger and was situated in the nacelle.
Still a bit dented but a lot more 3D than when it arrived.

The other part is the enigma - it is ca. 1m long - it has no part numbers. It is stainless steel - heavy grade which in my experience means US built.

It has remains of a grey paint at one end. There are 4 angled brackets which are spot welded and held steel bolt and the lower edge curves in and out - two outward curves and one inner curve with shaped depression. I am not yet sure if it was straight or curved as the stainless is thick and not easily adjusted.

I assume as it was stainless and from th shape - it was form a cowl ring of a radial engine or perhaps an exhaust shroud from an inline. I can't work out which aircraft it is from.

Any ideas welcome.

 

[bse7entn]

That looks like Fire Cut-Off Cam for a ball turret. Could be from a B-17 or B-24.

 

[BFreer]

Thank you - looks like the same function and design parts.

 

[BFreer]

I have been looking through Sperry A2 Ball turret manuals and can confirm 100% that you are correct and this is the fire cut off cam for a B-17 Ball Turret..

The B-24 had a different shaped cam.

The cam shape matches with the propellers of the B-17 and stopped unintentional self harm. The B24 had a more bulbous lower fuselage and did not need the same profile.

http://hangarthirteen.org/wp-content/uploads/2020/08/11-45G-1-Handbook-for-Sperry-Lower-Ball-Turrets-A-2-A-2A-A-13.pdf

Thank you.