Landing Vehicle Tracked (LVT, amtrac)

The Roebling Alligator

The amtrac began as a civilian rescue machine. After hurricanes struck South Florida in 1926, 1928 and 1932, financier John A. Roebling asked his son Donald, an engineer living in Clearwater, to build a vehicle that could reach people stranded in flooded swamps ^[1][3]. Donald Roebling, a member of the family behind the Brooklyn Bridge, started work in early 1933 and finished his first Alligator in early 1935 ^[1]. It had an aluminum hull, a 92 hp Chrysler engine and tracks fitted with cleats that worked like paddle wheels, driving it on land and in water ^[1][2]. Roebling patented the track system in 1938 ^[1][3].

Roebling kept rebuilding the machine. The second model, finished in 1937, was 4 ft (1.2 m) shorter and used new tracks that ran in steel channels without bogie wheels, which made it faster in the water ^[1]. A Life magazine article on October 4, 1937, caught the eye of Rear Admiral Edward Kalbfus, who passed it to Marine Corps leaders looking for a vehicle that could cross the coral reefs around Pacific islands ^[1][3].

Adoption by the Marine Corps

Marine Major John Kaluf inspected the Alligator in Clearwater in March 1938 and came back with a favorable report, but the Navy at first declined to pay for a test model ^[1][3]. In late 1939 Brigadier General E. P. Moses persuaded Roebling to design a military version. Roebling spent about $18,000 of his own money on the Alligator 3, completed in May 1940 ^[1][3]. A Navy contract then paid for a more powerful fourth model, finished in October 1940 and tested in the Caribbean under Captain Victor Krulak ^[1][3]. ASME gives the contract value as $20,000, the National WWII Museum as $24,000 ^[1][2].

The Marines adopted the design with a steel hull as the Landing Vehicle, Tracked (LVT-1). Food Machinery Corporation (FMC) of Dunedin, Florida, completed the first of an initial order of 100 in July 1941 ^[1][3]. The LVT-1 had a 146 hp Hercules engine, could carry 4,500 lb (2,040 kg) and reached about 15 mph (24 km/h) on land and 4 knots (7.4 km/h) in water ^[3].

How it works

Unlike wheeled amphibians, the LVT used no propeller. Cupped cleats, or grousers, on its tracks gripped mud and sand on land and pushed against the water when afloat, much like the paddles of an early steamboat ^[1][2]. Because the same tracks worked on land and in water, the vehicle could crawl from deep water over a coral reef and up a beach ^[1][4]. Later models used bolted-on aluminum grousers that were easier to replace, and rubber-cushioned suspension ^[5].

World War II

LVTs were first used mainly to haul supplies ashore in the Solomon Islands, starting at Guadalcanal in 1942 ^[1][3]. Their role changed at Tarawa on November 20, 1943. Tides left too little water over Betio's reef for landing boats, and LVTs carried the first 1,500 Marines across the reef ^[3][4]. The cost was heavy. The 2d Amphibian Tractor Battalion lost more than half its men and all but 35 of the 125 LVTs it used at Betio ^[4]. Afterward, Marine officers called for more armor, heavier weapons, stronger engines and at least 300 LVTs for each division ^[4].

Later models answered those needs. The LVT-2, called the Water Buffalo, used the radial engine of the M3 Stuart light tank and rubber-cushioned suspension ^[5]. The LVT-4 moved the engine forward and added a rear ramp, so troops and vehicles could leave from the back. With 8,348 built, it was the most numerous model and first saw combat at Saipan in June 1944 ^[3][5]. Armored versions, sometimes called amtanks, carried a tank turret, first with a 37 mm gun and later with a 75 mm howitzer on the LVT(A)-4 ^[2][5].

LVTs also served in Europe. The British Army, which called them Buffaloes, used them in the Battle of the Scheldt in 1944 and in the Rhine crossing of March 1945, and the U.S. Army used them on several European rivers ^[1][5]. By the end of the war seven different versions had been used, by Marine and Army units against Japan and by U.S. and British forces against Germany ^[1].

Production and legacy

The National WWII Museum and Defense Media Network both give more than 18,000 LVTs built during the war, and Wikipedia gives 18,616 ^[2][3][5]. The 1997 ASME landmark plaque gives a lower figure of over 15,000 ^[1]. Roebling allowed the government to use his patent without fees during the war ^[1].

The line continued after 1945 with the LVTP-5 and then the LVT-7, which was later renamed the Amphibious Assault Vehicle and is built by FMC's successor, BAE Systems ^[3][5]. In 1997 the American Society of Mechanical Engineers named the Alligator a Historic Mechanical Engineering Landmark. The vehicle honored, believed to be Roebling's Alligator 3, was then on exhibit at the Marine Corps Air-Ground Museum in Quantico, Virginia ^[1]. The National WWII Museum displays a preserved LVT-4 ^[2].

Related entries

• GMC DUKW "Duck"Military amphibians · 1942 to 1945