Celebrating 80 years of Caterpillar diesel power
Eighty years ago, in October 1931, the Caterpillar® Tractor Co.'s first diesel tractor, the Caterpillar Diesel Sixty Tractor, went into full production in East Peoria, Ill. The engine powering the tractors was the revolutionary Caterpillar D9900 Diesel Engine, which set the stage for Caterpillar to become the world's leader in diesel power - a distinction it still holds today.
In honor of the 80th anniversary of the introduction of our first diesel engine and tractor models, the Corporate Archives will present a series of three articles on the development and introduction of the diesel engine and tractor; a look at the projects they have made possible and where some of the early tractors are today; and, finally, an overview of the history and development of Caterpillar diesel power since the first diesel tractors.
Economic necessity fuels diesel development
The first diesel engines developed in Germany by Rudolf Diesel appeared in the late 1890s. Large and heavy, the first applications of diesel engines were in stationary power plants in Europe and marine units.
Consideration for a small, mobile diesel engine did not begin until the early 1920s, and it wasn't until 1925 that the newly formed Caterpillar Tractor Co. began planning for its own diesel engine.
The development of the diesel engine was driven by the need for an internal combustion power unit, which would burn cheaper fuels available throughout the world and would use less fuel overall.
In March of 1928, Carl G.A. Rosen was hired as a consulting engineer to experiment with fuel systems.
In his writings, Rosen notes that the difference in fuel priceâdiesel fuel was, on average, 63 percent cheaper than gasolineâwas a driving factor behind the development of diesel power.
"The pressure of our times has molded the engineer into a practicing economist. The products of engineering thought are therefore the resultant of economic necessity. The diesel tractor is no exception to the inevitable dictates of evolutionary progress," Rosen wrote in 1932.
Rosen and his team faced several challenges in adapting the bulky, slow-speed diesel engines to mobile applications. One obvious problem was weight. Diesel engines of the 1920s usually weighed more than 100 pounds per horsepower.
Another problem was variability of fuel the engine would have to operate on from the lighter burner-oils such as kerosene, to the heavy fuels that represented the least refined and heaviest fraction of crude oil distillation.
A third problem was that fuel systems on early diesel engines had to be individually calibrated by trained engineers on site. The Caterpillar diesel engine had to use an injection system that was factory calibrated and nonadjustable in the field.
After examining alternative diesel engines, Rosen and his team decided to design an entirely new diesel engine. To provide an acceptable weight-to-horsepower ratio, the design eliminated unneeded iron and incorporated stronger and lighter materials capable of operating at higher speeds. A precombustion chamber, which provides better vaporization in an engine burning a wide range of fuels, was used to allow the engine to operate on diverse fuels. Factory set fuel pumps and injectors would eliminate field adjustment.
The first D9900 prototype was assembled in June 30, 1930, and nicknamed Old Betsy. After almost being scrapped, she is now housed at the Smithsonian Institution.
More than $1 million (about $13.5 million today) was spent on research and development. And, in October 1931, after 18 months of prototype design and testing, Caterpillar released its first, commercial, mobile diesel engine, the D9900. It was placed in the frame of the gasoline-powered Model Sixty Tractor. The engineweighed 5,175 lbs and developed 86.8 horsepower at 700 rpms.
Introduction of the Caterpillar Diesel Sixty Tractor
In a small shop in San Leandro, California, Rosen and his team built the first two Caterpillar Diesel Sixty Tractors, serial numbers 1C1 and 1C2, by hand using the new Caterpillar D9900 Diesel Engine.
Full production of this tractor began in October when 1C3, the third Diesel Sixty Tractor, came off the assembly line at the plant in East Peoria, Ill. Caterpillar built only 157 of these Diesel Sixty Tractors before the model was discontinued in 1932, but this early diesel tractor paved the way for several more models in 1933 and three new diesel tractor models in 1935: the RD6, RD7 and RD8, which, two years later, became the D6, D7 and D8.
These tractors are still produced today more than 75 years later.