Military HMMWV Motorized Turret
As discussed on the HMMWV Gunner Turret page, the Gunnerís Shield Kit (GSK) weighs over 115 pounds and the Gunnerís Protection Kit (GPK) another 320 pounds, for a total of 430 pounds (or more, depending on model) in addition to the machine gun and its cradle, ammunition box, and other components. To assist the gunner, motorized turret systems provide smooth rotation of all that mass.
U.S. Army Soldier from 2nd Platoon, 145th Engineer Company, California National Guard provides security from his HMMWV turret during road construction outside Khowst City, Afghanistan, 28 December 2006.
Battery Powered Motorized Traversing Unit (BPMTU)
The ring mount base allows the gunner to rotate the HMMWV turret a full 360į but it can be difficult to move the weight of the weapon, shielding, ammunition and other components, especially if the vehicle is not level. Motorized turret systems have been developed to solve this problem.
By 2006, engineers at the U.S. Army Tank Automotive Research, Development and Engineering Center (TARDEC) designed the Battery Powered Motorized Traversing Unit (BPMTU) which provides a HMMWV gunner with powered cupola operations.
The BPMTU consists of a user interface system with a magnetic base, a system control assembly, an emergency stop switch, a break-away connector, and a motor and drive assembly. The BPMTU is energized with its own rear-mounted power supply, positioned to help counterbalance the weight of the gun, mount and shield. In operation, BPMTU provides a variable turret slew rate, instant rotational change (clockwise to counterclockwise and vise versa), and an automatic lock. BPMTU includes motor disengagement to enable the gunner to manually rotate the cupola. Installation is accomplished with no major modifications to the turret or HMMWV. BPMTU mounts in existing holes and mounting locations.
Components of the Battery Powered Motorized Traversing Unit (BPMTU) installed in an M1114 Up-Armored HMMWV.
Photo courtesy of Armor Holdings.
The BPMTU user interface system consists of a joystick control for clockwise and counterclockwise-motorized rotation of the cupola. The system control assembly relays motor operation from the joystick control. The emergency stop switch is the power control switch for the BPMTU system. The break-away connector smoothly detaches the battery charging cable when the cupola is rotated more than 20 degrees.
The BPMTU motor has an integral brake, which is always on (failsafe mode) except when given a slew command by the operator. The clutch provides a disengagement point in case of motor failure. The complete system does not protrude into the gunnerís area thereby providing the maximum amount of room (photo above). The variable speed allows target tracking with no distractions and allows the gunner to be able to fire at a moments notice. This method of powering the motor allows continued use throughout a patrol cycle as well as its ability to recharge itself via the vehicles alternator when the engine is running.
BPMTU is also called the M1114 HMMWV Motorized Turret, although the system could be easily adapted to any vehicle sharing the same turret ring as the M1114 HMMWV.
Development of the Battery Powered Motorized Traversing Unit (BPMTU)
TARDEC observed the need for the motorized turret kit because the turret is very difficult to move when the vehicle is not level. For example, without the BPMTU, the manual rotation force needed by the soldier to rotate the cupola is 106 pounds on a 30 percent side slope. With the BPMTU on the same slope, the soldier only needs seven pounds of force to operate the joystick that rotates the turret.
The ease of control and reach for the BPMTU joystick, the emergency stop switch, the motor engagement control lever, and the .50 caliber machine gun were adequate for both the 95th percentile male and the 5th percentile female. When comparing the cupola manual traversing handle and the BPMTU joystick, both the 95th percentile male and the 5th percentile female preferred the joystick over the manual traversing handle because it was much simpler to operate and it required less arm force and less arm movement to traverse the cupola.
Durability testing included 2,000 miles throughout various durability test courses with the cupola being rotated daily to check the wear. The cupola rotation speed in the durability testing scenarios did not vary due to the slope angle.
The Battery Powered Motorized Traversing Unit (BPMTU) is manufactured by Armor Holdings, Inc. using U.S. Army facilities under contracts for production during 2006 and 2007.
In 2007, the Objective Gunner Protection Kit (OGPK) was fielded, for HMMWVs and other vehicles, an improved solution for Turret Gunners that incorporates the Battery Powered Motorized Traversing Unit (BPMTU).
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