Mack » AC / AK / AP
The most significant contribution to developing of the Mack company was made by engineer Alfred Masury. In 1916 he designed the most famous Mack truck - the AC model with the informal name "Bulldog", which was given for its massive tapered hood, low silhouette and widely spaced wheels, huge headlamps and ability to work in the toughest conditions. The AC model offered in several versions with a capacity of 3,5-7,5 tons and wheelbase of 3962, 4267 or 4572 mm. In-line 4-cylinder engine with an output of 75 hp was located directly above the front axle. The radiator was placed in front of the driver's seat and cooled by air flow from the impeller, mounted in the flywheel. The four-speed gearbox was placed in the middle of the chassis and combined with the main gear and differential. The truck had chain drive.
The company received 18 patents during developing of the AC model. Among them is the frame, stamped from chrome-nickel steel, pistons made of cast iron and cast in pairs of stainless steel cylinders with a heat treatment, metal working parts, reinforced by the surface seal and a number of parts from aluminum alloys. Crankshaft and pinion were cemented, and a beam front axle was made by free forging of steel billets. Other features of the AC model included long-leaf springs with a small thickness, the widespread use of roller bearings, brakes on rear wheels and a transmission shaft, and a wide cast tires.
From 1923 all AC trucks were equipped with a 6-cylinder engine with an output of 97-120 hp. From 1932, construction dump trucks AC6 with a 6-cylinder 150-horsepower engine were produced. The AC series is well known for its strength and durability. Without great technical changes it produced till 1938. Totally 40,299 copies were made. The first modification of the AC model became the lightweight 5-ton AK, shown in 1927. It has a driveline, 70-horsepower engine with aluminum head block and a double main gear. Until 1936, totally 2,819 copies were made. From 1929 to 1938, 2- and 3-axis models AP have been producing. The AP has a capacity of 7,5-10 tons and was equipped with a new 6-cylinder 150 hp engine. 2-axle models used driveline, but 3-axle 6x2 trucks had a chain drive of the middle axle, but in 1931 received a center differential and offered with the 6x4 wheel configuration. Only 285 copies were made. In 1919 and 1920 one copy of AD and 1 copy of AF model was released. Details about them are unknown.