The M22 "Locust" light tank was one of the smallest tanks
used by the Allies
in Europe during WWII. It was the first tank designed by the U.S.
primarily for airborne operations. It was light in weight but was
expected to add badly needed firepower to airborne forces.
DESIGN CONCEPT AND DEVELOPMENT
World War II strategists in the U.S. became aware of the effectiveness of
airborne
assault forces by studying German victories achieved in Europe.
They were also aware of the vulnerability of lightly
armed airborne infantry alone and behind enemy lines without direct support
from a main force.
Because of increasing interest in an air delivered light tank
by experienced field commanders and the British, the Ordinance
Department formulated a design concept requiring the development
of a light tank that would aid
airborne units during critical mission phases
and be sufficiently light in weight
to be delivered by airborne means. The light tank would support the airborne
infantry until reinforcements from the main force arrived.
In May of 1941 design began on the M22 Locust light tank at
the Marmon-Herrington Company.
Production began in April 1943 and ended in February 1944 with a total
production of 830 tanks. Under lend-lease, 260 Locusts were given to the
British.
ENGINEERING CHARACTERISTICS
The M22 was constructed of steel plate using welding as opposed to riveting
technology. Riveted construction methods had long since fallen from favor
because of the disastrous propensity of rivets to bounce around inside the
vehicle
when the outside rivet head was sheared by anti-tank munitions.
The front armor
was 1 inch thick with the sides being approximately 1/2 inch plate. The
sloped front and sides added additional protection by helping deflect
projectiles upward. The armor is minimal because of stringent
weight requirements limiting the vehicle to less then 16000 lbs.
Weapons included a single 37mm main gun and coaxial 30 caliber machine gun. Original models
of the vehicle had more machine guns which were abandoned in the final design
because of weight limitations. The box structure on the left front of the
vehicle is the driver's hatch and vision port.
The vehicle was equipped with M6 periscopes on the driver's hatch and the
turret.
The front drive sprocket was powered by the transmission unit and engaged
a steel track. Four road wheels connected to a volute spring suspension
provided support for the vehicle. The rear idler wheel provided minimal
vehicle support and was used to control track tension. Ground contact
pressure was 6.41lbs/sq.in., quite low for a tank.
The vehicle dimensions are: length 12ft. 11in., width 7ft. 3.75in. and
height 5ft. 8in. This resulted in an extremely tight crew compartment
consistent with sardine style packaging.
The low silhouette was somewhat unusual for American light tanks of the
era and a decided advantage by offering a low profile to enemy gunners.
The 4 major lifting
lugs on the side of the hull just above each road wheel suspension mount
are for hoisting up under the belly of a C54 cargo plane after turret removal.
The C54 cargo plane and British Hamilcar glider were the only means
available for airborne delivery of the vehicle.
The vehicle was powered
by a Lycoming O-435-T six cylinder air-cooled aircraft engine yielding
162 hp at 2800 rpm with a maximum torque of 332 ft.lbs. at 2100 rpm.
Like most tanks of the early war era, aircraft engines were used because of
their high power to weight ratio.
The tank had driving range of 110 miles with a full tank of 57 gallons
of gasoline.
Dual engine exhaust pipes merged into a single pipe and circular muffler.
The 6 cylinder opposed engine powered the vehicle
at a top speed of 35 MPH. The engine was adapted to a large clutch/fan
disk. The fan was required for cooling
of the massive aircraft engine. A drop down gear box was mounted on the
engine output shaft to bring the drive shaft
close to the floor and allow room for
the turret basket. The drive shaft was connected to a 4 speed transmission and
differential unit at the front of the vehicle.
The driver's seat is located to the left of the transmission unit.
The driver essentially sits on the floor in very cramped quarters.
Two levers control the left and right brakes of the vehicle. Pulling
the right lever turns the vehicle right while pulling the left lever
turns the vehicle left. Pulling both levers stops the vehicle.
Due to space restrictions the control panel is to the right of the
driver above the transmission unit.
The turret was manually
operated, a primitive yet weight saving feature. Behind the drive shaft
is the escape hatch mounted on the floor.
The engine was equipped with dual ignition,
typical of adapted aircraft engines of the day. Fuel delivery was
through long induction tubes which made starting difficult.
An elaborate priming system was installed to deliver fuel to each cylinder
before starting. Typical ammunition used by the 37mm
main gun includede high explosive rounds that had a terminal velocity of 2700 ft/sec
at 1000 yards.
USAGE IN WORLD WAR II
Development of the M22 continued by the Ordinance Department,
but engineering problems dealing with excessive weight and poor performance
were encountered. Testing showed the impracticalities of utilizing
American aircraft at that time. Hoisting the tank hull
under a C54 cargo plane and placing the turret in the plane proved
cumbersome and time consuming. Because of the lack of a good air delivery
system and
disappointing performance of the vehicle, the Ordinance Department
became less enthusiastic for any further development. However, the British
were still interested in the vehicle and 260 were delivered with the remaining
vehicles utilized for training purposes in the US.
The British were more active than the US in airborne tank
development having
airborne tanks of their own such as the Tetrarch, Alexto and Hopkins.
The British outfitted the 37mm guns with an extruder adapter
(squeeze-bore) that reduced
the projectile from 37mm to 30mm increasing velocity to 4000 ft/sec from
2700 ft/sec.
A new high mass and shatter resistant
tungsten carbide ammunition was developed for this
application.
Twelve of the tanks were landed using the giant Hamilcar glider
during the Rhine crossing on March 24, 1945. The British airborne crossing of
the Rhine river, called Operation Varsity, utilized over 50 large Hamilcar
Gliders delivering airborne tanks and other equipment for the 6th Airborne
Armored Reconnaissance Regiment, Royal Armored Corps, of the British forces.
One Locust tank was credited with killing over 100 enemy soldiers.
LOCUST # 110 LIVES ON IN HISTORICAL REENACTMENTS
After the war, the M22 tanks were considered surplus and marked for
disposal. Some were given to foreign governments while others
were sold to farmers without the turrets as farm tractors.
Hull number #110 was found in a farm field in the Midwest and restored.
It is now being used in World War II living history displays
and reenactments throughout the Midwest.
ADDITIONAL TECHNICAL DATA
Weight................16000 lb.
Length............12 ft. 11 in.
Width............7 ft. 3.75 in.
Height............5 ft. 8.5 in.
Ground Clearance.........10 in.
Armament:
1 37 mm Gun, M6; ammunition
A.P.C., M51B1, M51B2; A.P.,
M74; H.E., M63
1 cal .30 machine gun
Maximum speed............35 mph
Turning radius............20 ft
Maximum grade..............50 %
Copyright 1995 Charles C. Roberts, Jr
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