Cargo tractor, Cargo carrier
HIGH SPEED TRACTORS AND CARGO CARRIERS
Although the tests of the cargo tractor were not complete, a study indicated that it would be more economical to replace the T43, M8, and the T44 series of vehicles with a new line of two tractors as prime movers for the medium, heavy, and very heavy artillery. Two separate approaches were followed to achieve this objective. The first involved modification of the tractors already under development.
This produced two vehicles designated as the cargo tractor T85 and T86 which were based upon the cargo tractors T43E2 and the M8E2 respectively. International Harvester Company assembled four pilots of the T85 using many components from the T43E2. Combat loaded, it had a weight of41,000 pounds including a payload of 12,000 pounds. OTCM 36445, dated 14 February 1957, standardized the T85 as the cargo tractor M85.
Allis-Chalmers Manufacturing Company modified two M8E2 cargo tractor to meet the T86 specification and they were submitted for test. Intended for use with the heavy of very heavy artillery having towed loads of 53,000 to 62,500 pounds, the T86 had a payload capacity of 12,000 pounds.
The second approach to obtaining two tractors that could meet all of the requirements involved the development of two new designs. Both of these were intended to provide lower cost prime movers for the artillery.
For medium (tank) and heavy artillery loads, the cargo tractor T93 was proposed based upon major components from the armored infantry vehicle M59. With an estimated combat weight of42,750 pounds, the T93 was powered by a Chrysler V8, liquid-cooled, engine producing 400 gross horsepower at 4,200 rpm. Built by FMC, the T93 utilized the suspension and tracks from the M59. Four pilots were authorized and two of these were fitted with solid sides and hatch seals to permit amphibious operation. The amphibious vehicles were designated as the cargo tractor T93E1.
The proposed low cost prime mover for die very heavy artillery was designated as the cargo tractor T94. A new design by the Allis-Chalmers Manufacturing Company, it had an estimated combat weight of 72,000 pounds with a 12,000 payload. The T94 was powered by the AOSI-895, air-cooled, engine developing 525 gross horsepower at 2,800 rpm. It used the XT-500 transmission. Four pilots were authorized for construction.
LOW GROUND PRESSURE VEHICLES
As early as April 1945, the U.S. Army Ground Forces had requested the development of an amphibious cargo carrier with a payload capacity of 1/2 tons. The T34 Paddy Vehicle had been a partial response to that requirement. On 16 August 1945, OCM 28777 approved the development of the 1/2 ton amphibian carriers T37 and T37E1. The requirement also was included in the War Department Equipment Board Report.
On 30 October 1947, OCM 31792 recommended that two pilots of the amphibian cargo carrier T46 be built in lieu of development of the P/2 ton amphibian carriers T37 and T37E1. The objective of this program was to provide a light amphibian carrier and prime mover, convertible to a winterized vehicle, suitable for cargo or personnel and capable of being transported by air. General Motors Corporation was awarded the contract to design and build the two pilot vehicles.
Later, the number of pilots was reduced to one when it became necessary to redesign the suspension and transmission. The initial configuration used a trailing idler, flat track, torsion bar suspension with five dual road wheels per side. Each road wheel was fitted with a 6:00 x 12 pneumatic tire. The sectional, band type, tracks were 28/2 inches wide. The boat-like hull had the engine compartment in the front, the crew compartment for the driver and assistant driver in the center, and the cargo compartment in the rear.
A door in the rear of the cargo compartment was hinged at the bottom and could be swung down to serve as a loading platform. The pilot vehicle was powered by the Continental AO-268-2, air-cooled, engine with the CD-150-1 transmission. A wobble stick control was used with this transmission. The T46 was driven in the water by two shrouded propellers at the rear which could be folded up for land operation.
The first modification to the new cargo carrier was to the suspension. The trailing idler was eliminated and replaced by a small raised idler. The remaining four dual road wheels per side retained the 6:00 x 12 pneumatic tires and rode on the same 28/2 inch wide tracks. At this stage, an access ladder was attached to the left side of the vehicle and a spare wheel was mounted on the left side at the rear. The engine exhaust pipe came out of the engine compartment, extended toward the rear along the left side and then up to the top.
Additional changes replaced the two propellers with a single propeller and a late model CD-150 transmission was installed which was controlled by a handle bar. The earlier engine was replaced by the AO-268-3 and the fuel cells were mounted on the outside with one on each side of the hull. The engine exhaust pipe was relocated now extending inside the hull up through the roof.
The suspension rode on 6.60 x 15 pneumatic tires and the track width was increased to 30 inches. The rebuilt vehicle was designated as the amphibious cargo carrier T46E1 and it was shipped to Aberdeen Proving Ground for tests in November 1949. After a successful test program, production of the T46E1 began at the Pontiac Division of General Motors in January 1951 and continued until June 1954. Standardization was approved in March 1953 as the amphibious cargo carrier M76 and it was named the Otter.
Further modifications were made during the production run. The external fuel cells installed near the center of each side were shifted toward the rear on the later vehicles. This required the relocation of the fuel and water cans, spare wheel, pioneer kit, and shutter stowage cover.
A folding propeller guard was provided for water operation. The steps on the rear were moved lightly and a swivel type towing pintle was installed on the late vehicles. The hull was assembled by riveting aluminum alloy sheet and the production vehicles were equipped with the AOI-268-3A fuel injection engine. A 5,000 pound capacity winch was located under the rear seat in the cargo carrier compartment.
The Otter had a combat weight of 12,045 pounds and a rated payload of 3,000 pounds resulting in a ground pressure of 2.0 psi. It had space for ten men including the two man crew. The maximum speed was 28 miles per hour on roads and 4 1/2 miles per hour in water. A fuel capacity of 70 gallons provided a cruising range on roads of about 200 miles.
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