Model D (Spoker Model D)
Despite a rather severe farm economy depression at the time, Deere management decided to build a Model D prototype in 1923, designed by Muir L. Frey (father of Ford Mustang designer Donald N. Frey). The Deere Model D was produced from March 1, 1923 to July 3, 1953, the longest production span of all the two-cylinder John Deere tractors. Over 160,000 were made.
The first Model D rode on steel wheels with a 6.5 in × 7 in (170 mm × 180 mm) (later 6.75 in × 7 in (171 mm × 180 mm)) two-cylinder hand-cranked engine rated 15–27 hp (11–20 kW). It was not, however, the first tractor to bear the Deere name - as a number of Deere experimental tractors, and the John Deere Dain "All Wheel Drive" tractor (of which approximately 100 were produced during 1918 and 1919) had all carried the Deere name before the D.
By 1925, the company realized the standard Model D did not meet customers' needs for industrial applications. Steel wheels were not suitable for hard surfaces, and the gearing was too slow for safe road speeds. Solid rubber tires were added, and engineers fitted a 28 tooth sprocket to the final drive, giving a road speed of 4 mph (6.4 km/h). The company replaced the 465 cu in (7.62 l) 2-cylinder engine with a 501 cu in (8.21 l). In 1926, Deere advertised the model the "John Deere Industrial Tractor" with 40 × b inch rear wheels and 24 in × 3.5 in (610 mm × 89 mm) fronts with solid tires. This would become known as the DI. Options also included wheel weights.
Read more about this topic: List Of John Deere Tractors
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