Sperry A2-A Lower Turret
From the AN-11-45G-1, Handbook of Instructions, For Lower Ball Turrets, A2, A2-A, and A13, 25 April 1944.
1. GENERAL DESCRIPTION.
a. The lower ball turret is a spherical metal structure
mounting two caliber .50 machine guns, and containing
equipment needed by a gunner to accurately direct the fire of the guns.
(2) The ball is 44 inches in diameter, being an assembly of aluminum alloy castings and armor plate with transparent Plexiglas windows, giving the gunner a wide field of vision. The circular sighting window is made of laminated safety glass.
b. The turret is designed for mounting in the lower part of the fuselage on an airplane. The opening required is a circular hole 46 ¾ inches in diameter, through which the ball extends approximately 24 inches beyond the skin line of the airplane.
The turret may be moved in elevation from zero degrees (horizontal) to – 90 degrees (straight downward). It may be rotated 360 degrees in azimuth. The guns may be fired in any direction in a hemisphere below the airplane fuselage, except where the firing is automatically interrupted according to the fuselage and propeller contour.
TRUNNION RING SUPPORT ASSEMBLY
The supporting structure of the turret rotates in azimuth.
The trunnion ring support assembly is bolted to the hanger
and collector brackets which carry the turret ball by means
of elevation trunnion bearings permitting rotation of the ball
TOP MOUNTING SWIVEL – TYPE A-2A
(1) The type A2-A turret is suspended in the
aircraft by means of a top-mounting swivel assembly
which includes a flanged retainer bolted to a supporting
beam in the airplane fuselage.
(2) HANGER AND COLLECTOR RING ASSEMBLY
(a) The hanger and collector ring assembly includes a
tubular supporting framework bolted to the collector ring
housing assembly. The framework and the collector ring
housing rotate in azimuth with the turret.
(b) A flexible cable carries the electrical circuits from the
collector ring housing to the turret ball.
HANGER TUBE STRUCTURE – TYPE A-2A
The hanger tube structure suspended from the collector ring
housing is bolted at four flanges to the trunnion ring support
assembly which carries the turret ball.
From The Field To Restoration
A Pictorial Summary
There were over 150 pieces of turret shell found, along with that were the more familiar main pieces that formed the circular shape and support. The primary hanger assembly was pretty much complete with little damage. Most damages occurred to the support legs being bent. These were to be cut off and replaced to stabilize the exhibit and be true to its original form. Several artifacts representing the inner assembly of the turret were also recovered but suffered much damage from the impact. Some of the fragments were also found in the surface finds of the fields in addition to the parts recovered from the deposited craters.
The process of cleaning each and every piece takes some time. After all the parts are cleaned each is identified, cataloged, and numbered with a tag and index card for description as to the part number, where found, parts catalog it is found in, geo-data, and site location. Then begins the fun part of fitting the jigsaw of parts back together.