Fordson Model N replaced the Fordson Model F. It was an improved variant of the F. Production of the Model N started in Cork in 1927. Production of the Fordson Model N was transferred from Cork to Dagenham in 1933. The Model N featured a 27 HP engine, standard rear fenders (mudguards), a higher voltage ignition system, and optional pneumatic tires. In 1935 power take-off (PTO) was available as an option on the Model N. The Fordson Model N was probably the most important tractor in the United Kingdom during World War II. The Dagenham plant produced over 136,000 Model N tractors during the war. Ford of the U.S. also exported Model 9N tractors to the U.K. during the war. Later Fordson tractors (made in England) 1930s experimentation at Dearborn After U.S. Fordson production ceased in 1928, Irish-built and later English-built Fordsons were imported to the U.S.; Eber Sherman was a principal importer. Development of new Fordson/Ford tractors in the U.S. remained mostly inactive for about 10 years after the end of U.S. production, although Ford did experiment with a number of designs during the 1930s. Most of them never left the drawing board, which was intentional; Henry Ford was interested in continuing R&D (and continued paying Ford engineers to work on it), although he wasn't going to put any models into production until all conditions (design, market) were right for commercial success. A Fordson row-crop model, essentially a "Fordson version of the Farmall" with tricycle design and high clearance, was prototyped at Dearborn in 1930-1931 but waited until 1936 to be produced, when Ford Ltd of Britain produced it as the Fordson All-Around. (It was not without precedent, for the aftermarket had presaged it, although not with the high clearance; in 1939, Ford filed a patent for raising and lowering the clearance on the fly.) The idea of variable front track for row-crop tractors was also considered at Ford during this era. Achieving it via pivoting cantilevered wheel mounts was one of the options, although Ford never put that method into production (it later reached production in the form of the Avery Ro-Trak in 1938). The thought devoted to the topic paid off later, when the Ford 9N achieved it with another, simpler method. Between 1928 and 1932, Henry Ford's attention became consumed mostly by the development and introduction of his company's first V8 engine, which was introduced by