Turret
Although the concept of a revolving gun turret was not novel
to armed forces of the mid-19th century, the USS
Monitor was the first vessel in history to incorporate
this engineering feature. The revolving gun turret allowed the
ship's crew to aim cannons without having to position the ship
to deliver a broadside.
The Monitor's gun turret consisted of an iron skeleton
covered with eight layers of one-inch-thick plates. Only 20
feet in diameter on the inside, the turret was a
claustrophobic place in combat. Inside were two 11-inch
Dahlgren smoothbore cannons, which were mounted on specially
designed "friction carriages" and operated around and under
the skeletal frame. On recoil, the cannons cleared the
diagonal braces with only about two inches to spare. After
workers assembled the turret, they drilled three
20-inch-diameter holes through the armor, one atop the other,
to make each gun port.
Thick iron pendulums (or port stoppers) that hung from the
overhead protected the gun-port openings. Crew swung the port
stoppers out of the way when they ran the cannon out for
firing and dropped them back into place on recoil to protect
themselves from enemy fire. The Monitor's cannons were
muzzle loaders, meaning that powder and shot were loaded into
the cannon from the business end. Because of the confined
space inside, each port stopper had a hole through its center
to allow the handles of the gun tools to pass through. During
loading, the handles protruded outside the turret; when not in
use, the loading implements hung from the overhead.
Crew members stored a limited number of non-exploding solid
shot along the base of the turret beside each of the guns. As
the turret slowly revolved, crew would pass powder and
exploding shells up from below. The turret floor had four
hatches (two beside each gun) for access down to the
berth deck.
The turret was controlled by linkage at the rear of the
starboard gun. Below deck, two donkey engines (small auxiliary
engines) connected to a crank—which, in turn, was
connected to four gears—put the turret in motion. Its
maximum speed was two revolutions per minute.
Before the turret could be revolved, it had to be "keyed up."
On the forward side of the midships bulkhead was a Y-shaped
structure called the turret support truss. This large mount
helped displace the weight of the turret resting on the deck
above. In the center of the truss stood the turret shaft,
which crew raised into position by pulling a large wedge
underneath. As they tightened a large nut on the end of the
wedge, the shaft slowly rose up to connect with the yoke on
the main beam at the bottom of the turret. Once the shaft was
in place, crew members turned the control wheel in the turret,
which increased the steam pressure to the donkey engines and
put the turret in motion.