When it comes to tractors, how big is big? Western and Great Plains farmers buy the biggest tractors they can find, justifying expensive purchase prices by the rate at which their massive fields can be tilled.
Midwestern, Eastern and Southern farmers are less interested in size, instead basing their tractor size and power on specialized needs like rice, orchard or high-clearance specials. But size is subjective: do you go by weight comparison, drawbar horsepower, tire/wheel size or price?
In the beginning, large tractors had a lot less horsepower than their modern counterparts, but that just meant they traveled more slowly, pulling the same number of plow bottoms. The weight of the biggest grew over time, beginning in the 1920s at about 20,000 pounds for an internal combustion tractor (double that for steam) to as much as 50,000 pounds in the 1970s, when weight and horsepower peaked.
Originally, high horsepower numbers came via steam, but steam ratings are often confusing and not always based on “torque times speed.” The need for traction in the days before rubber tires led to steel rear wheels 7 or 8 feet in diameter, and in some cases, crawler tracks. In modern times, four-wheel drives and articulated steering became the norm.
Massive early units
In the early days, Case led the way with steam. Their 110 hp monster weighed about 40,000 pounds. Case built several 150 hp engines, but it is thought that they were never used for farming. The Case 110 used a single 12-inch bore and stroke cylinder. Rated for a 12-bottom plow, it had 7-foot diameter drive wheels with a 3-foot face. Another big steamer of the time was the 90 hp Avery, which used two 7×10-inch cylinders. It weighed 40,800 pounds.
Internal combustion (gasoline/kerosene) tractor manufacturers copied the big steamers, in some cases just putting a gas/internal combustion engine on a steam chassis.
Metallurgical limitations meant that to get equivalent horsepower, very large displacement engines were needed. Compression ratios were low, as was rated rotational speed.
A problem with these early heavyweights was that it often took more than half the engine’s horsepower just to propel the tractor, not leaving much for drawbar work. As an extreme example, the 1909 Joy-McVicker gasoline traction engine had a 3,300-cubic-inch, 4-cylinder engine rated at 140 hp on the belt, but only 50 for drawbar work.
Drive train life, from engine to wheels, became the challenge for engineers. Sometimes massive chain drives provided much of the final drive, but also huge ring gears inside the rear wheels were sometimes used with a small pinion gear for the final reduction. Lubrication of either of these methods in the farm application proved problematic. Improvements in chain drive technology, however, did lead to development of crawler tracks.
Crawlers make big showing
In the 1920s, things became more reasonable, tractor-wise. Manufacturers were able to get a useful drawbar power percentage through improved metallurgy, thereby reducing weight while still using large diameter and width wheels. Belt horsepower peaked at about 70 with 40 or 45 hp available at the drawbar. The Caterpillar 60 proved the flotation value of tracks, with a drawbar rating of 57 hp from an engine with a belt rating of 66 hp.
Another factor in those ratings and others of the time was the fact that the University of Nebraska had begun scientific testing of tractor-rating claims in 1920. Those ratings became, and remain, global standards.
Rubber tractor tires debuted in the early 1930s. Although traction was lacking at first, better flotation and lessened soil compaction benefits were realized. The 1930s delivered other major changes to tractors as well. The rise of the all-purpose tractor, generally much smaller than previous models, averaged about 28 hp. Crawlers were the big tractors of the 1930s. Introduced in 1931, the giant Allis-Chalmers Model L crawler weighed 22,000 pounds and had an 844-cubic-inch gas engine. Horsepower was 92 on the belt and 76 on the drawbar. The Model L sold new in 1938 for $5,300 (roughly $92,700 today).
The largest of the wheel tractors of the 1930s-40s topped out at 50 to 60 hp, and that was considered by most to be the practical upper limit for two-wheel drive. That was disproved by the 1940 Caterpillar DW-10, a 90 hp diesel tractor used primarily in construction to pull scrapers and speed them to their destinations.
World War II curtailed most tractor development and, in some cases, production. Even the Nebraska tests were discontinued for the duration. After the war, manufacturers sought to fill the pent-up demand with mainly the same tractors that had been in production earlier. Before the war, farmers had the choice of standard-tread or row-crop tractors. After the war, the semi-squat utility configuration gained popularity.
A new generation of power
The next phenomena to hit the tractor industry was the consolidation of smaller farms into larger, more profitable ones. But farmers did not want to increase labor costs, so opted for more powerful tractors. Kerosene burners were out, with diesel and LPG the fuels of choice.
Willys and Dodge offered their military vehicles as the first four-wheel drive farm tractors, and the Wagner TR-9, first sold in 1957, became the first of the articulation-steered four-wheel drives, a portent of things to come. That first Wagner boasted a 125 hp engine, weighed 16,200 pounds and sold for $7,500 ($65,800 today).
By the end of the 1950s, it became obvious that size mattered. John Deere, known for its reliance on 2-cylinder engines, came out with an articulated Model 8010 with a 215 hp, 6-cylinder engine. It cost farmers a handsome $30,000 (roughly $254,000 today) plus the cost of some gigantic implements.
The 20,000-pound 8010 had some interesting features: air brakes, built-in stairs accessing the seat and a massive 3-point hitch capable of lifting implements (such as an 8-bottom plow). It also had some unfortunate problems that led to a recall and revision of those sold and those yet to be sold: 100 tractors, total. Apparently, all but one were rebuilt and sold as Model 8020 tractors. The single remaining 8010 is now in the Keller collection in Brillion, Wisconsin.
Of course the appearance of the JD 8010/8020 caused International Harvester to react in kind with the 30,000-pound, 300 hp, 4-wheel steer International Model 4300 in 1961. Some may say the 4300, manufactured by Harvester’s Hough Industrial Division, was not a serious farm tractor, but 44 were built, along with appropriate 3-point implements, including a 10-bottom plow! Harvester made a proper follow-on to the 4300: the Model 4100 with a production run of more than 3,000. At 19,000 pounds, the 4100 was a more reasonable size, with a 116 hp diesel, but still with four-wheel steer like the Model 4300.
Go big or go home
The 1970s saw all manufacturers producing big, articulated-steer, four-wheel drive tractors. Horsepower gradually crept up to 150/175, but then rose quickly to the 300-plus range with turbochargers and intercoolers. Then some wildcat builders, like Northern Mfg. Co., builder of Big Bud, jumped to the lead with 525 hp. Their 6-cylinder engine displaced 1,150 cubic inches and the tractor’s weight was around 52,000 pounds. Cost, in 1979, was $190,000 (roughly $645,000 today).
Next came some “show off” tractors. Jon Kinzenbaw’s Big Blue 640 had two 320 hp V-8 engines, one for each axle. Versatile’s 600 hp 1080 “Big Roy” had four axles and eight tires. Weighing in at about 60,000 pounds, the tractor was hinged in the middle. Steiger experimented with a three-engine tractor of about 750 hp. Certainly the biggest so far is the Big Bud 747, weighing in at about 95,000 pounds. The behemoth is powered by a 1,472-cubic-inch V-16 GM 2-cycle, 900 hp diesel engine. This biggest of the Big Buds has actually done some legitimate farm work around the country.
After the horsepower race of the 1970s, things in the big tractor business began to settle down. Farmers liked the size and traction of the articulated tractor, but only wanted to pay for the power they needed. Most were satisfied with tractors in the 300 hp segment, while those with the biggest fields could opt for up to 500 hp. Purchase price and fuel cost helped make the decision.
Toward the end of the 20th century, great changes were transforming the farm tractor industry. Only Caterpillar and John Deere avoided mergers. Many common names, like Ford and Case International, disappeared altogether. Dealers consolidated in order to survive. Today, horsepower and weight continue about the same, but conventional-steer four-wheel drive tractors are making a comeback, as are rubber-tracked versions. FC
After 36 years in the aircraft industry, Bob Pripps returned to his first love and began writing about tractors. He has authored some 30 books on the subject and several magazine articles. Pripps has a maple syrup farm near Park Falls, Wisconsin. In harvesting the maple sap, he relies on a Ford Jubilee and a Massey Ferguson 85.