Invention of the Crawler Tractor
Exactly 95 years ago, on Thanksgiving Day, Nov. 24, 1904, three men stood on Aurora Street in Stockton, Calif., watching as Holt Junior Road Engine Number 77 passed. The engine was quite different from other steam traction engines of the day, even from other Holts. The familiar round drive wheels had been exchanged for a pair of tracks 9′ long and 2′ wide. Track shoes were wooden 2″x4″ slats bolted to endless link chains, driven by sprockets. The machine’s weight was supported by rollers that rode on top of the lower loop of chain.
40 hp Number 77 was on its way back to the Holt factory after a highly successful field test in the spongy peat soil beside Mormon Slough, just outside Stockton. The machine had pulled four two-bottom plows two inches deeper than a Holt 60 hp wheeled steamer could. As Benjamin Holt and his friends (photographer Charles Clements, and painter John Shepard) watched the machine clank past, Clements, struck by the sight of the moving tracks, said “It crawls just like a caterpillar!” Ben Holt supposedly said “Caterpillar it is! That’s the name for it!” A world-famous trademark, one still in use today, was born.
The tracks of Holt’s first crawler had several names: “paddle wheels,” “mud turtle wheels,” “treadmill wheels,” and “caterpillar wheels.” Holt’s nephew, C. Parker Holt, later recalled: “… the first ‘Caterpillar’ wallowed around so successfully in the soft mud of Mormon Slough that it was sent down to the Holt Ranch, where it operated steadily for an entire winter.” The May 18, 1905 Farm Implement News reported that “In the Roberts Island tract, where a man could not walk without sinking to his knees, and where tule-shoed horses could not be used, the new traction engine was operated without a perceptible impression in the ground.”
Benjamin Holt is generally credited with developing the crawler-type tractor still in wide use. Holt began building steam traction engines in 1890 with his first, “Betsy,” 24′ long and weighing 24,000 pounds. A single 10 1/4″ x 12″ cylinder developed 40 to 70 horsepower, depending on the steam pressure. The drive wheels were powered from a countershaft by means of massive link chains.
The fertile San Joaquin Valley runs northwest from Bakersfield between the eastern Sierra Nevadas and the Diablo and Temblor ranges on the west, to end just north of Stockton. Here the San Joaquin joins the mighty Sacramento, forming the Delta Region of the central valleys of California. The Delta country comprises 250 square miles of peat bogs, much of which is slightly below sea level.
Because of its vast potential for growing produce, the rich Delta islands were protected from flooding by dikes.
The Holt Ranch was located on Roberts Island in the Delta where, as attested to by the Farm Implement News article, a man would sink to his knees in the rich peat soil. If tractors could be adapted to negotiate the soft, fertile land, the Holts knew its huge agricultural promise would be realized.
Ben first tried adding wheel extensions to one of his steamers. On each side, he mounted three large drive wheels, each 6′ wide and 7.5′ high. The 10′ wide traction engine now had 18 feet of drive wheels sticking out on each side. The single front steering wheel was changed to a 10′ wide wooden barrel to keep the front end up out of the mud. Needless to say, the unwieldy monster couldn’t go through gates or cross bridges, or turn around at the end of a field. Also, in spite of the large wheels, it frequently buried itself in the peat. You can imagine what it took to pull one of those things out of the mud. Every horse and mule in the San Joaquin Valley was probably needed to do the job.
The concept of a vehicle that carries, lays, and then picks up its own tracks had been around for years. In 1713, M. D ‘Hermand, of Paris, drew a goat-pulled cart that ran on a treadmill of 26 rollers running on a belt. In 1770, Englishman Richard Edgeworth tried unsuccessfully to power a similar vehicle with steam. In 1825, Sir George Cayley won a patent for a wagon supported on an endless chain belt around the two wheels on either side. Unfortunately, he made no provision for steering, and it was soon forgotten. John Heathcoate of Great Britain built a steam plowing engine in 1832 that ran on two 7-foot wide belts. The engine weighed 30 tons and the belts were to keep it from sinking into marshland. Heathcoate’s machine drew much praise -until it sank into a swamp and almost disappeared. Warren P. Miller, Marysville, Calif., demonstrated a tracked steam plow at the 1858 State Fair for which he won a cash prize, and a gold medal. According to the patent drawings, Miller’s machine had most of the features used on later, successful crawlers, but for some reason, only one was ever built. George Minnis broke sod near Ames, Iowa, with a tracked steam engine in 1869 and, in 1871, a Philadelphia man, R.C. Parvin, demonstrated a crawler-type steamer at the Illinois State Fair. Parvin later started a company to build his machine, but it failed.
Even though these early tracked machines had possibilities, none were successful. It was left for Alvin Lombard to build the first steam-powered, crawler-equipped engine to meet with commercial success. More on this, as well as Lombard’s and Holt’s patent squabbles with each other, later. FC
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