I know we have not posted a true update in a while but that was on purpose. I have been steady working this whole time on the ball turret trunnion assembly and wanted to surprise everyone when it was finished.
And now it is. Hope everyone likes it!
The trunnion for Lucky Thirteen‘s Type A-2 Ball Turret is now restored.
The next step will be to restore the hanger assembly. The tube on the broken leg can be replaced with relative ease but the missing foot will be more problematic. That said, we have someone interested in recreating this piece so it may not be long yet! Other aspects of its restoration will include replacing the missing spare parts box and mounting the Type F-2 Oxygen Tank that we recently restored.
Check out the photo descriptions to learn more.
The newly restored trunnion.
While the ball turret was designed by Sperry Gyroscope, it was actually built under license. There were two manufacturers: Briggs Manufacturing, an autobody company from Detroit, Michigan, and Emerson Electric, an electrical appliance company from St. Louis, Missouri.
One of the easiest ways to differentiate the two were the paint colors: Briggs turrets had olive drab trunnions and hangers with gray interiors; Emerson turrets had dark bronze green trunnions and interiors.
There was little cooperation between the two companies. As such, the majority of ball turrets were produced by Briggs. This includes the one that was installed on Lucky Thirteen.
Photo taken 6 August 2025.
Briggs factory photo showing a Type A-2 Ball Turret in its fixture assembly.
We would like to replicate this fixture for Hangar Thirteen’s ball. If anyone would like to help in this effort, just let us know!
The turret’s trunnion and hanger assembly as it originally arrived.
The azimuth and elevation gears have been removed for restoration and an F-2 oxygen tank zip tied to the hanger for fun.
Note how the original olive drab paint has faded to an almost tan color from sitting in the sun.
Photo taken 8 January 2025.
The same angle as the previous photo, showing the now-restored A-2 ball turret trunnion assembly.
Special thanks is due to Eric Miller of Project Warbird, who provided the correct paint. This paint was color-matched to a piece of the trunnion that had not been exposed to sunlight.
Great care was taken to remove every trace of corrosion and ensure the best possible finish.
The missing leg is visible here. This will be the next step in the turret’s restoration.
Photo taken 6 August 2025.
The restored Type F-2 Oxygen Tank for the A-2 Ball Turret.
The oxygen line was recreated according to the original specs and donated by Custom Hose & Supplies of Cedar Rapids, Iowa
Photo taken 14 June 2025.
Factory photo of a Type A-2 Ball Turret. The spare parts box and Type F-2 Oxygen Tank are visible here.
The A-2 ball, which was used from B-17E 42-2505 through B-17G-20-BO, was the only ball variant to have an external oxygen tank. The others all had their oxygen plumbed directly through the aircraft’s main supply.
The same angle as the previous photo, showing the now-restored A-2 ball turret trunnion.
The trunnion is circled by a series of bearings. These keep the trunnion centered as it rotates inside its azimuth ring, which was bolted to the aircraft’s floor. We are in the process of casting anew the various brackets which attach said ring to the floor. The original were badly corroded.
Photo taken 6 August 2025.
Close-up of the azimuth pinion gear.
This is the gear which grabs the azimuth ring which, in turn, rotates the turret.
Photo taken 6 August 2025
Interior view of the trunnion, showing where the azimuth pinion gear attaches.
The pinion, visible here, feeds down through one of the two turret support brackets, on either side of the ball. Doing so, it connects with an internal gear attached to the motor and transmission assembly.
While work begins on the hanger assembly, I suppose I can start restoring the support brackets!
This photo was taken before restoration was complete. Not yet installed is the safety wire for the cap on the bottom of the gear box.
Photo taken 7 July 2025.
Close-up of the elevation hand crank.
The entry hatch into the ball was on close to the bottom, so the ball had to be hand cranked into position, with the guns facing down, to physically get in and out. The red handle on the brass assembly is the crank’s lock.
Photo taken 6 August 2025.
The interior of the elevation hand crank on the trunnion.
The smaller gear is the clutch for engaging this assembly.
Photo taken 6 August 2025.
Close-up of one of the placards near the elevation hand crank.
This placard is original, having been cleaned and refinished by hand.
Photo taken 6 August 2025.
The trunnion’s elevation gear quadrant, one of several pieces on the turret made of brass.
At this angle you can see the clutch handle on the elevation hand crank. This handle was present on the A-2 but not the A-2A. We are not sure why this change occurred, as the clutch was returned in the A-13A series. Both types appear to have been used on the A-13.
(A-2 and A-2As were for the B-17, A-13s for the B-24, and A-13As for late-B-24s and the B-32).
Photo taken 6 August 2025.
The maker’s mark on the ball turret’s trunnion assembly.
Photo taken 6 August 2025.
The brush assembly for the ball turret upon arrival.
Photo taken 11 June 2023.
The brush assembly stripped for restoration along with the cover plate, shortly after purchase.
The large brush housing was unique to the Type A-2 Ball Turrets found on E and F-model B-17s.
The next step will be to remove the dent from its midair collision.
Photo taken 17 July 2023.
The restored brush assembly cover plate for Lucky Thirteen‘s ball turret.
The turret’s dataplate is located at the top.
Photo taken 6 June 2025.
The wires needed to complete the wiring on the A-2 Ball Turret for Lucky Thirteen. Baseball for scale.
Special thanks to Thomas Schasney for this incredible donation!
Photo taken 1 August 2025.
The Hangar Thirteen Foundation is a 501c3 nonprofit charity and donations toward this project are tax deductible. If you can spare a little to help this project, you can guarantee that you will see the results on Facebook and here on our website.
You can contribute through the Donate page or, to avoid a PayPal fee, you can send something via the mail to:
Gerad Allen Blume
Hangar Thirteen Foundation
442 Old Chalk Bed Road
Batesburg, SC 29006
Volunteers are also always welcome. In fact, you need not be an Asheville resident – you can work from home! Persons skilled with metal fabrication, machining, CAD modeling, metal casting, 3D scanning, and laser/waterjet cutting, are particularly helpful. Just reach out to us to get started.
Keep the show on the road!