Roebling Alligator

The Roebling Alligator was a tracked amphibian designed by the wealthy Florida inventor Donald Roebling as a rescue vehicle for the Everglades. Its story begins with the great hurricane of 1935, after which flooded areas could not be reached by rescuers; Roebling's father John asked his son to design a machine that could travel over both swamp and water.

Design

The Alligator was a track-laying vehicle that propelled itself afloat by means of cleats or flanges fixed to the tracks, working on much the same principle as a paddle steamer. Roebling went through several versions:

• The first, completed around 1936, used horizontal paddle-like cleats and a 92 hp Chrysler engine. It reached about 25 mph (40 km/h) on land but only 2.3 mph (3.7 km/h) in the water, which was a disappointment.
• A year later a lighter four-ton version with diagonal cleats and a Ford V-8 raised the water speed to about 5.45 mph (8.8 km/h).
• A third, lighter model had an aluminium hull and curved diagonal cleats, giving about 8.6 mph (13.8 km/h) afloat and 18-20 mph on land.

Military interest

On 4 October 1937 the Alligator featured in Life magazine. Rear Admiral Edward C. Kalbfus drew the article to the attention of the Fleet Marine Force, and the Marine Corps Equipment Board sent Major John Kaluf to Florida to see it run. Although the Navy initially declined to fund a pilot model on grounds of economy, Marine interest persisted, and in 1939 Roebling was persuaded to produce a design with military features.

The result, completed in January 1940, was called the Crocodile: faster (about 25 mph on land and 9.4 mph in the water), able to climb steep slopes and unsinkable when flooded. It was demonstrated at Quantico in November 1940 and judged satisfactory in every respect except that its aluminium construction was too light for hard military service.

Legacy

The Navy then ordered 200 steel-built examples. Because Roebling had no mass-production facilities, construction was subcontracted to the Food Machinery Corporation, and the first LVT(1) (Landing Vehicle Tracked) left FMC's Lakeland, Florida plant in July 1941. The LVT-1, essentially a steel Crocodile with a 146-150 hp Hercules six-cylinder engine, was built until 1943 (1,225 in total) and served at Guadalcanal, Bougainville, Tarawa and Cape Gloucester, beginning the long line of Marine Corps amtracs.