Models 520, 620, 720, 820
1956 saw the replacement of the 50, 60, 70 family of tractors with a new family, the "20" Series. These tractors incorporated advancements in virtually every aspect of tractor design and engineering.
Hydraulics—Custom Powr-Trol was introduced on the "20" Series. Raising and lowering of equipment was accomplished through a position-responsive rockshaft, which enabled the operator to set working depth precisely. An adjustable stop let him return implements to a preset working depth after raising them. Exclusive Load-and-Depth Control kept implements working at a uniform depth, automatically transferring weight to tractor drive wheels as needed to maintain traction. In extremely tough conditions, the system raised the implement just enough to relieve the load and allow the tractor to move steadily.
Engines—All new. Improved cylinder head and pistons increased combustion-chamber turbulence and increased horsepower. These engines set five new fuel economy records at Nebraska.
Operator comfort and convenience—The "20"s introduced a new Float-Ride seat, supported on a rubber torsion spring, with tension adjustable to match each operator's weight. A hydraulic shock absorber mounted between seat and seat pedestal also helped smooth the ride over rough ground. Foam-rubber seat cushion and backrest, and optional cushioned armrests, added still more comfort. There was a roomy stand-at-will platform, easy-to-reach controls, and easy-to-read instrument panel as well.
Styling--The first John Deere Tractors to wear a two-tone paint job.
The 520 was rated at 25.63 drawbar hp and 32.38 belt hp.
The 620 was rated at 34.34 drawbar hp and 42.79 belt hp.
The 720 was rated at 40.63 drawbar hp and 50.67 belt hp.
The 820 Diesel, a continuation of the diesel-powered, standard tractor tradition established by the "R" and continued through the 80, handled a 21-foot disk with ease, and had plenty of power to pull multiple-drill hookups or field cultivators as wide as 24 feet.
A 6-speed transmission allowed the 820 to operate at speeds from 2 1/3 to 12 1/2 mph. Additionally, an optional "creeper" first gear could be installed to provide a 1 3/4 mph speed.
The 820 Diesel was rated at 52.25 drawbar and 64.26 belt hp.
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