John Deere · Letter Series series

John Deere Model R

Name: John Deere Model R
Brand: John Deere

Standard tractor · 1949–1954 · Diesel

The John Deere Model R, built at Waterloo from 1949 to 1954, was the company's first diesel-powered production tractor and the largest and final member of its two-cylinder Letter Series. Its big 415.5-cubic-inch two-cylinder diesel was famously fired to life by a second engine — a small horizontally-opposed gasoline "pony motor" that cranked and warmed the diesel until it could run on its own. Tested at Nebraska (Test 406), the R produced about 43 drawbar and 49 belt horsepower and pulled a stout 6,644 pounds, and it also became the first Deere tractor with a live, independently-clutched power take-off. Just 21,293 were built, making a well-kept R a prized collector's machine today.

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Photo: Acroterion. License: CC BY-SA 4.0.

belt power: 48.6 hp
Weight: 7,603 lb (3,449 kg)
Displacement: 416 ci (6.8 L)
Total built: 21,293

Overview
Type	Standard
Series	Letter Series
Production	1949–1954
Factory	Waterloo, Iowa, USA
Total built	21,293
Original price	$3,650 (1954 USD)

Engine
Make	John Deere
Fuel	Diesel
Cylinders	2
Displacement	416 ci (6.8 L)
Bore × stroke	5.75x8.00 in
Rated speed	1,000 rpm
Compression	16:1
Cooling	liquid-cooled
Aspiration	Naturally aspirated

Power
Drawbar power	43.2 hp (32.2 kW)
Belt power	48.6 hp (36.2 kW)
Nebraska test	Nebraska Test 406

Transmission
Transmission	sliding-gear, unsynchronized — 5 forward, 1 reverse
Chassis	4x2 2WD
Steering	manual
Brakes	mechanical drum

Hydraulics & hitch
Rear PTO	live
PTO speed	540 rpm

Dimensions & capacities
Weight	7,603 lb (3,449 kg)
Wheelbase	85.5 in (217 cm)
Length	147 in (373 cm)
Width	79.5 in (202 cm)
Height	78.1 in (198 cm)
Fuel capacity	22 gal (83.3 L)
Aux fuel	1 gal (3.79 L)
Coolant	54.5 qt (51.6 L)
Crankcase	13 qt (12.3 L)
Front tires	7.50-18
Rear tires	14-34

History

For decades John Deere had resisted diesel power, relying on gasoline and "all-fuel" versions of its Letter Series tractors. The Model R changed that in 1949, arriving as Deere's first true diesel production tractor and its heavy-duty standard-tread flagship, aimed squarely at large-acreage and Great Plains farmers who needed maximum drawbar muscle and the fuel economy diesel promised. It marked the end of the lettered A-through-R lineage that had begun with the Model A and pointed toward the numbered generation to come.

The R's most memorable engineering feature was its two-engine starting system. Diesel engines of the era were notoriously hard to spin over and start, especially in cold weather, before electric starting and glow plugs were common on this class of machine. Deere's answer was a self-contained two-cylinder, horizontally-opposed gasoline "pony" motor with its own carburetor, ignition, and one-gallon fuel supply. The operator started the little gas engine, which cranked and warmed the big diesel until it fired — turning a physically demanding chore into the pull of a lever. The R was also the first Deere tractor with a "live" PTO, driven through its own clutch for independent control.

The Model R proved the concept so thoroughly that it became the template for Deere's entire early diesel line. It was succeeded in the new numbered series by the John Deere 80 (1955), then the 820 and 830 — each an evolutionary refinement of the R's basic architecture. In that sense the R is the ancestor of Deere's big two-cylinder diesels, the machine that finally committed the company to diesel power and set the direction for its standard-tread heavyweights through the end of the two-cylinder era.

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