Hart Parr was a very early American builder of gas tractors with the Hart Parr 30-60 being one of the more successful “Prairie” style tractors. However by 1919 the Prairie style tractors were obsolete being far too big and clumsy for the average farmer of the time. The need was for a smaller more nimble tractors. Hart Parr’s first attempt to meet the needs of farmers at the time, the “Little Devil”, was a complete failure and the tractors were recalled. However, the right direction was taken in 1918 with the “New Hart Parr” 12-25 model, which formed the basis for all subsequent Hart-Parr tractors. The “New Hart Parr” was a tractor equipped with a two-cylinder, slow speed, water-cooled engine with force feed lubrication and open gears used to drive the rear wheels. The design after testing in Nebraska was re-rated at 15-30. The 15-30 design was replaced in 1924 by the 16-30 design which was upgraded in 1926 to become the 18-36.
The Hart Parr 18-36 tractor was a two cylinder tractor with a cylinder bore of 6.75 inches and a stroke of 7 inches operating at 800 RPM maximum. The tractor was originally fitted with a transmission offering two speeds ahead and one speed in reverse, a dry clutch, an automotive type coolant radiator which was not pressurized and an air cleaner. The tractor used water as the coolant. Hart Parr built the 18-36 from 1926 to 1930. In 1927 the transmission was redesigned to offer three speeds ahead.
The tractor was conventional in construction for the time, with a frame built up of structural steel components, riveted together with the engine, transmission and other components of the tractor then bolted to this frame.
The option of hard rubber tires was offered on the 18-36 by Hart Parr as well as dual rear wheels. A further option was a PTO which was driven by off the right hand side of the engine using a clutch band operating on the crankshaft counterbalance which was on the right hand end of the crankshaft. For those farmers wanting to run at night,Hart Parr also offered a lighting option with one forward facing light and one light mounted on a rear fender.
Hart Parr also built versions of the 18-36 for Australia and New Zealand, the Australian and New Zealand Specials. These tractors featured a different air cleaner, a different arrangement of the engine exhaust manifold and lettering on the radiator identifying the tractor as an Australian or New Zealand Special.