Cargo vehicle LVT3 LVTPX3
THE LEGACY OF WORLD WAR II
At the end of World War II, large numbers of landing vehicles, tracked (LVTs) were in use by the U.S. Army, Navy, and Marine Corps. At that time, all production of new LVTs was stopped. The majority of the latest versions, the LVT3 and the LVTA5, were still in the United States.
Since they represented sufficient numbers for the expected postwar requirements, most of the earlier vehicles were disposed of as surplus. However, even these new vehicles had open tops and were not only vulnerable to artillery air bursts, but also it was impossible to keep personnel and cargo LVT3 vehicle dry when operating in rough water.
Two standard LVT3s were modified for arctic operations during 1947 by the U.S. Naval Engineering Experiment Station. Living quarters were installed in the cargo carrier compartments of both vehicles. Double tracks were fitted on one of the vehicles to lower the ground pressure and improve performance on soft terrain. Although the double tracks did reduce the ground pressure, the increased friction load resulted in a decrease in the power available for propulsion. As a result, the maneuverability of the double track vehicle was inferior to that of the standard LVT3.
In 1949, Continental Aviation and Engineering Corporation modified an LVT3 to provide overhead protection for the troops and cargo. The modifications included a higher deck, cargo covers, and escape hatches. A later change sloped the rear deck to provide clearance when leaving an LST. The power train, suspension, and tracks of the standard LVT3 were retained, in 1950, 1,200 of the LVT3s were modified to the new configuration and designated as the LVT3C.
The cargo covers were fabricated from aluminum alloy and a turret armed with a machine gun was installed on the top front of the vehicle. Portable side armor plate added 860 pounds to the loaded weight of 39,190 pounds. The cargo LVT3 vehicle carrying capacity was 6,100 pounds. in 1951, the Continental Aviation and Engineering Corporation modified an LVTA5 to obtain data on underwater track return systems.
They also replaced the standard 250 horsepower air-cooled engine with a Ford GAA, liquid-cooled, engine. This 500 gross horsepower engine was the same as used in the M4A3 Sherman tank. The new suspension consisted of four, two wheel, bogies on each side with torsilastic spring assemblies. Shrouds enclosed the upper track run for the underwater track return. The test of this vehicle did not show any improvement in performance with the new suspension arrangement.
Also in 1951, FMC modified two LVTA5s in the hope ofimproving the performance. A large curved bow was installed on one of the vehicles extending out to the front and down to about 30 inches above the hull bottom. A fairing on top stretched from the bow back to the cab top deck. The second LVTA5 was fitted with an out-of-the-water bow cap covering the bow from the bumper back to the top deck of the cab. Detachable tanks were installed on the front simulating a rounded or a flat bow for test purposes. After evaluation an armored cover was added to the open top turret and the LVTA5s in stock were brought up to the new standard.
Early in 1946, FMC began a development program under contract to the Bureau of Ships for an improved LVT. Designated as the cargo vehicle LVTPX3, it had a new submerged track suspension fitted with center guide tracks. A monocoque type hull was welded from 3/8 to 3/4 inch thick steel armor plate. The cargo compartment was covered and the rear consisted of a two section ramp. When closed, the upper section of this ramp sloped forward and upward from the water line. The vehicle was powered by an Allison V1710E32, liquid-cooled, engine.
It drove the vehicle through a Twin Disc, direct drive, torque converter, the planetary gears of a Torq-matic transmission from an M26 tank, and the controlled differential from an Ml8 gun motor carriage. The latter was shortly replaced by the M26 tank controlled differential. Later, a new power train was installed consisting of the Continental AV-1790-5B air-cooled engine with the Allison CD-850-4 transmission. The maximum road speed of the LVTPX3 was 30 miles per hour. Apparently the Twin Disc torque converter and the controlled differential were more efficient in water than the CD-850-4 transmission.
The maximum water speed dropped from about 8 miles per hour to 5.5 miles per hour with the later transmission. Six dual road wheels per side were suspended by internally mounted torsilastic springs. The drive sprockets were at the rear and the compensating idlers were at the front of the 25 inch wide, center guide, tracks. The single prototype cargo vehicle LVTPX3 completed in December 1950 weighed 52,890 pounds and had a payload of 10,000 pounds. A fuel capacity of 328 gallons allowed a cruising time of ten hours on land or six hours in water. The vehicle was manned by a crew of three.
During 1946, the Bureau of Ships also awarded a contract to the Pacific Car and Foundry Company to design and develop a new LVT. Referred to as the prototype A 105mm gun carrier, it actually was armed with a turret mounted 105mm howitzer. The composite hull vehicle was a welded assembly of steel armor plate varying in thickness from 3/8 to 5/8 inches.
The single prototype A was delivered in early 1949. Like with the LVTPX3, a variety of power train components were evaluated before selecting the Continental AV-1790-5A engine and the Allison CD-850-4A transmission. Several bow designs also were tested. The torsilastic suspension supported the vehicle at nine individually sprung road wheel stations per side. Several tracks were tested with the final choice being the type VIII, center guide, track with a width of 20 3/4 inches. The vehicle had a combat weight of about 75,000 pounds and it was manned by a crew of five. The maximum speed was 33 miles per hour on land and 7.6 miles per hour in water.
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