Armored infantry vehicle T59 and T59E1
A LOWER COST ARMORED PERSONNEL CARRIER
Although it was generally satisfactory, the armored infantry vehicle T18E1 (M75) was too costly for procurement in large numbers. On 8 November 1951, OCM 33981 initiated a program to develop a less expensive vehicle for the role of the T18E1 (M75). The OCM authorized the procurement of six pilot vehicles (F1 -F6) which were proposed and manufactured by FMC Corporation.
The first four were powered by the six cylinder GMC Model 302 engine then used in the 6x6 truck M135. The last two utilized the Cadillac, Model 331, V8 engine. All pilots were fitted with a modified version of the truck Hydramatic transmission and a controlled differential. The first four pilots were designated as the armored infantry vehicle T59 and the last two became the armored infantry vehicle T59E1.
In both cases, each vehicle was powered by two engines which were installed with their transmissions in the left and right sponsons of the box shaped hull. Power passed through each transmission to a right angle drive at the front of each sponson and then to the controlled differential located in the center front of the hull. Propeller shafts from the differential drove the final drives and sprockets at the front of the tracks.
The vehicle was steered using the brake levers operating the controlled differential. The torsion bar suspension supported the vehicle with five dual road wheels per side on the 21 inch wide, single pin, tracks. These were the same T91E3 tracks used on the T18E1 (M75) and the 76mm gun tank M41.
The driver and vehicle commander rode in the front hull on the left and right respectively in both the T59 and T59E1. Three periscopes were located in front of the driver's hatch and the commander had a cupola with six vision blocks providing a 360 degree view. This cupola was fitted with an external mount for a .50 caliber machine gun.
A five man folding seat on each side of the personnel compartment provided space for a ten man infantry squad. An hydraulically actuated ramp with a small vision port formed the rear wall of the hull. When opened, it provided rapid, unobstructed, access to the interior of the vehicle. With the ramp opened and the personnel seats folded down, a jeep could be driven inside.
Roof hatches also were installed in the personnel compartment, however, their configuration varied on the six pilots. The vehicles were assembled with welded homogeneous steel armor 5/8 inches thick on the front, sides, and rear. It was 3/8 inches thick on the roof and 1 inch thick on the floor providing good mine protection.(U.S. Army)
Both the T59 and T59E1 were designed to be amphibious and the rear ramp was fitted with a rubber seal. The vehicles were propelled by track action in the water and a folding trim vane was mounted on the front. The short, manually operated, trim vane on pilots 1 through 4 was replaced by a larger, hydraulically operated, design on pilots 5 and 6. A number of other features varied among the pilots as indicated in the table.
As completed, the pilots had a loaded weight of about 21 tons. The GMC Model 302 in the T59 developed 146 gross horsepower compared to 192 gross horsepower for each of the Cadillac Model 331 engines in the T59E1.
Thus, the T59 had a gross power to weight ratio of about 13.7 horsepower per ton compared to 18.4 horsepower per ton for the T59E1. Both had a maximum design road speed of 32 miles per hour. However, in water, the track propulsion gave the T59 a maximum speed of 4.3 miles per hour compared to 5.0 miles per hour for the T59E1.
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