Mack NO

The Mack NO was a heavy 6x6 cargo truck designed in the 1940s by the American manufacturer Mack Trucks. It was used by the U.S. Army as an artillery tractor for heavy artillery during and after World War II. The official U.S. Army designation was: Truck, 7 1/2 ton, 6x6, Prime Mover. It’s G-number was (G-532).

History
In 1940 Mack Trucks started the development of an artillery tractor for the U.S. Army, with a payload of 7.5 tonnes, to tow the 155mm “Long Tom” field gun, the 8 inch howitzer, and the 240mm howitzer. A contract for the production of the vehicle was awarded in September 1940, and in January 1942 a vehicle of the NO-1 type towed the first 240mm howitzer carriage from the Bucyrus plant in South Milwaukee, Wisconsin to the Aberdeen Proving Ground test facility.

The NO-1 was the first in a series of five very similar prime mover vehicles. The NO-2 differed in details, among them a canvas cabin roof (the NO-1 had a metal roof) and the winch behind the front bumper (above the bumper in the NO-1). A total of 403 units of the NO-2 were delivered in 1943. The next prime mover models, which marginally differed from the NO-2, were the NO-3 and NO-6. A total of 1,097 units of these were ordered and delivered in 1943 and 1944. The last of the series was the NO -7 model, of which 188 were delivered in 1944 and 362 in 1945. Several NO-7 were provided after the war to the European armies being rebuilt, inclufing those of United Kingdom, France, Belgium and Netherlands.

The models NO-4 and NO-5 were prototypes of heavy salvage vehicles, equipped with a Gar Wood crane which could swivel to the left and right. Neither model was put in production.

Description


The vehicle had a typical configiuration, with a bonneted front engine behind which was a large driver cabin that could seat five soldiers, and a rear cargo area.

The engine was a Mack EY, 6-cylinder gasoline with of 11.6 liters displacement; generating 159 hp at 2100 rpm and 534 lbfft at 800 rpm. The transmission had 5 gears forward and one backward. The installation of a transfer case with an additional reduction gear allowed high and low gearing (5F1Rx2).

Traction was in all six wheels (6x6), with 14.00-24 tyres. The empty weight of the vehicle was about 13.2 metric tons when empty, and more than 20 tons fully laden.

The petrol tanks were located on both sides of the vehicle, with a total capacity of 640 liters. At the front of the vehicle a Gar Wood winch was installed with a pulling capacity of 18 tons. It could be used to assist in placing the gun, or to help moving the vehicle if it was stuck.

The cargo area was 3.35 meters long and 2.4 meters wide and could carry 7.5 tons of cargo. Starting with the NO-2 model, at the rear of the cargo compartment a small crane was installed to assist in in placing the gun.

Variants
In total 2,053 Mack NO vehicles were built, in 7 variants as described in the following table.