Two Cylinder Magazine

Two-Cylinder LP-Gas Tractor
The Biggest Bargains in the Two-Cylinder Arena?

Very likely, nearly everyone reading this article has had some experience with LP-Gas, especially if they’ve lived in a rural area. Whether it be for cooking, home heating, crop drying, or a myriad of other uses, LP-Gas has been a part of the lives of many urban and rural Americans for the last 80 years. While the first known usage of a combustible substance somewhat related to LP-Gas occurred in 1887, and the first usage in an internal combustion engine in 1912, it wasn’t until the latter half of the 1920s that the technology for producing, storing, transporting, and easy use of LP-Gas became generally available. The breakthrough year was 1927, when railroad tank cars to transport the fuel nationwide became available. The first railroad train to use LP-Gas as a fuel made a demonstration trip from Lep, Oklahoma, to Moline, Illinois, in the same year. Various new refining techniques for the components of LP-Gas (butane, propane, or a mix of the two) also made their appearance in 1927. Frank E. Pilling Sr. obtained a patent for an LP-Gas carburetor and, by 1929, he and two engineers from the Richfield Oil Company, George Holzapfel and Barton Brown, had developed practical pressure regulators and carburetors for internal combustion engines; a significant milestone.

LP-Gas was such an important development, especially in rural and urban communities, that even the Great Depression could not check its growth. In 1932–1933, the worst years of the economic downturn, production and use of LP-Gas grew at rates approaching 100 percent per year. In 1927, the industry had produced a little over one million gallons of LP-Gas. A decade later, over 141 million gallons of the fuel were produced.

Today, we tend to forget that, in the 1920s and 1930s, California produced a significant portion of the nation’s petroleum; and it was in California that LP-Gas first became a significant fuel for farm tractors. Although LP-Gas did not contain as many BTU’s per gallon as regular gasoline or other tractor fuels, and therefore developed less power per gallon, it had octane ratings as high or higher than aviation gasoline. The high octane ratings allowed higher compression ratios, which in many cases made up for the deficiency in power as compared to gasoline. The other drawback, higher fuel usage, was more than overcome by the price of LP-Gas — as low as four or five cents per gallon. This was real fuel economy; it is estimated that by the end of 1930s, something close to 20,000 tractors in California alone had been converted to burn LP-Gas. Numbers like these made the tractor manufacturing companies take notice.

The first tractor manufacturer to make the move to produce a factory-built tractor engineered specifically to burn LP-Gas was Minneapolis-Moline, who made their Model “U” Tractor available in an LP-Gas version late in 1941. Only 90 were built that year, but factory tests had proven that LP-Gas was a winner. In 1951, ten years after introducing tractors fueled by LP-Gas, Minneapolis-Moline engineer Marvin Samuelson made this statement to the Society of Automotive Engineers: “Fuel economy is the most important factor in considering the operating data of any engine. Inasmuch as fuel consumption represents out-of-pocket expenses to any operators, it is of prime importance to [them] when making the decision to use a given fuel over another fuel.” He then went on to compare the costs of operation using LP-Gas versus regular gasoline. Tests had shown that while fuel consumption of LP-Gas was 18 percent higher than gasoline at maximum load, at less than full load it was better than gasoline by some margin. Even with the higher consumption, the low price of LP-Gas made substantial savings in operating costs, especially for large operators.

No doubt the John Deere engineers in the audience took particular note of Samuelson’s comments. At that time, the Waterloo Tractor Works was putting the final touches on a new line of farm tractors to be introduced during 1952–1953. Deere, who had been the chief proponent of heavy fuels such as distillate and kerosene as the ideal fuel for farm tractors since the 1920s, had thrown in the towel in 1947 by introducing revised versions of the popular Model “A” and “B” Tractors factory-engineered to burn gasoline; and had followed that up by introducing its first diesel tractor, the Model “R”, in 1949. Although Deere would continue to offer tractors with engines capable of burning the heavy fuels it had promoted for so many years, the sales results of the gasoline-burning “A” and “B” Tractors had convinced them that even the brief flirtation with “power fuel” (a mixture of distillate and low-grade gasoline) by some farmers was a fluke, and that gasoline and diesel fuel would be the tractor fuels of the future.

By 1951, Minneapolis-Moline had the LP-Gas tractor market to itself for 10 years, and seemed to be the only one of the “majors” interesting in producing tractors built to burn LP-Gas. However, especially after World War II, there were several aftermarket companies, notably the Ensign Carburetor Company, who were building kits to convert existing tractors to operate on LP-Gas. These kits usually supplied a tank, regulator, carburetor, and in some cases high-compression pistons to make the most of the conversion. Some of the aftermarket kits, such as the Ensign conversions, were very well engineered; others were less than satisfactory. And, of course, there were always the “do-it-yourself” types who found a usable tank, a regulator of some sort, drilled a hole in the body of the carburetor, stuck a hose barb in, attached a hose from the regulator, and called it good. When news of these conversions got back to the management and chief engineers of the rest of the tractor companies, it was a call to arms. If there truly was that much demand, the major tractor manufacturers weren’t going to let the aftermarket manufacturers have the LP-Gas market to itself for very much longer.

Beginning in late 1951 and continuing throughout 1953, all of the major manufacturers built at least one or two models of tractors factory engineered to burn LP-Gas. California was no longer a significant market, as the majority of LP-Gas production had moved east to Texas, Oklahoma, and surrounding states, and that’s where the majority of the new LP-Gas tractors were sold.

Deere wasn’t a complete newcomer to the LP-Gas field; as early as 1935, the company had built “W-lll” and “W-113” Engines equipped for burning natural gas for the Pure Oil Company, or anybody else who wanted one. The principles of burning natural gas or LP-Gas were much the same; to maintain power levels equal to that of gasoline or distillate, the compression was raised, “cold” manifolds were installed, and a special carburetor and pressure regulator were furnished. From what can be determined, these engines were available on special order, and parts assemblies were provided to convert all-fuel engines for operation on natural gas. How many of these special Type “W” Engines were built to burn natural gas is unknown. However, the Waterloo Production Log for the 1939-1940 includes production numbers for the “E” Series Stationary Engines, and reveals that there were 75 three-horsepower “EP” Engines built during that period. Although information on these engines is almost non-existent, Parts Catalogs do reveal that the “P” in the model designation stood for “propane.” How many of the “EP” Engines were built outside of that period is another unknown, but there could not have been very many as they are virtually unknown.

Because of the vast number of engineering projects going on at Deere & Company during the early 1950s (including starting development of the New Generation), factory-built LP-Gas tractors didn’t begin rolling off the assembly lines until August 1953, when Model “60” and “70” Row-Crop and Hi-Crop Tractors became available with factory-engineered LP-Gas engines. Deere may have been a bit of a latecomer to the LP-Gas party but, unlike some manufacturers who had done little more than raise the compression of the engine, add an LP-Gas carburetor and regulator, and mount a fuel tank anywhere it would fit to make their LP-Gas tractors, the Deere LP-Gas tractors were a well-engineered design that incorporated many changes for optimum operation. In addition, Henry Dreyfuss, industrial engineer and Deere’s primary stylist since 1938, was in on the project from the first. Although Dreyfuss detested exposed fuel tanks in any form, he had bowed to the necessity of an outside-mounted fuel tank for the LP tractors. Working with Deere engineers, Dreyfuss arrived at a design that gave maximum visibility for the operator, and a reasonably integrated look to the entire tractor. From a styling standpoint, the new “60” and “70” LP-Gas Tractors were the class of the field.

The requirements for adequate power and best fuel economy while burning LP-Gas were well known. To compensate for the power disadvantage of the lower BTU fuel, and to provide maximum fuel economy, higher engine compression ratios were required. This was accomplished by using high-compression pistons that provided an increase of approximately 1-1/2 points compression over gasoline models. To withstand the shock of higher compression, special steel alloy crankshafts were designed and adopted. LP-Gas is a “dry” fuel, lacking the lubricating qualities of gasoline or diesel fuel; so, to ensure good service life for the exhaust valves, and the seats on which they rested, hardened valve seats were used in the cylinder head, and valve rotators were installed on the valves of the Waterloo-built tractors.

The ignition system had to be completely revised. Previous Deere practice had been to drive magnetos and distributors directly from the governor shaft, which rotated at crankshaft speed. This meant that a spark was produced on both the power and exhaust strokes for each cylinder. To promote maximum cylinder filling on the intake stroke and scavenging on the exhaust stroke, there was some overlap in valve events; i.e. the intake valve was beginning to open before the exhaust valve was completely closed. With gasoline or distillate, this wasn’t an problem since those mixtures of fuel and air would not ignite unless compressed. However, given the nature of LP-Gas, there was a slight chance that a spark on the exhaust stroke could light off the incoming charge. To avoid any such occurrence, the engineers designed a new right-angle drive to slow the distributor to one-half engine speed, thereby eliminating the spark on the exhaust stroke.

High compression ratios take a hot spark, because of the increased resistance of the spark to jump the air gap of the spark plug, especially when starting. To overcome this problem, the Deere engineers turned to a system known as “bypass starting.” Deere tractors equipped with a 12-volt ignition system had used a resistor in the ignition circuit that reduced the voltage to the distributor to 6 volts, which was adequate for gasoline and all-fuel engines, and contributed to extended point and condenser life. With the “bypass” system, a switch was incorporated into the starting circuit that bypassed the resistor when the starter pedal was depressed, sending the full 12 volts to the ignition coil and giving a much hotter spark for easier starting. Once the engine started and the starter pedal was released, the resistor was switched back into the ignition circuit, reducing voltage to the 6 volts that was adequate once the engine was running. To ensure that adequate cranking speeds were obtained with the higher compression ratios, heavy-duty starters and higher-amperage batteries were also regular equipment on the LP-Gas tractors.

Considering that their main sales area was more or less limited to the southern states and the southern and western borders of the High Plains, with the practical northern border being southern half of central and western Nebraska, the new LP-Gas tractors sold well from the start — especially the Model “70” LP — for the same reasons that the Californians had converted so many tractors twenty years before; fuel economy and low-operational costs. In many areas in the southern states, LP-Gas was priced at about five cents a gallon for bulk delivery. A reason that was left unstated in most literature is that operators of LP-Gas tractors could leave them in the field at night and be reasonably assured that there would be no fuel theft by siphoning.

In 1955, the LP-Gas option was extended to the Model “50” Tractor and the New Style (known today as the “High Seat”) Model “60” Standard Tractor. Field experience had shown that the single-barrel carburetor initially used on the Model “60” and “70” LP-Gas Tractors had developed some serious shortcomings, so it was replaced by a new dual-induction carburetor. The improvement was deemed important enough that a mandatory recall and replacement program was instituted to replace the single-barrel carburetors on tractors already in the field with the new dual-induction setup at no charge to the customer, a move that earned kudos from dealers and customers alike.

In the summer of 1956, the new “20” Series Tractors were introduced, featuring 20 percent more power for the spark-ignition models via completely new engines. Many of the features that had been developed for the LP-Gas tractors of the “First Numbered” Series, such as stronger alloy crankshafts, bypass ignition systems, exhaust valve rotators, hardened seats, revised governor linkages, and heavy-duty starters, had proved so successful that they were adopted for all of the spark-ignition tractors of the Waterloo “20” Series. During 1956, the LP-Gas engine option was also extended to the Model “60” Orchard, which had continued in production after the “20” Series Tractors had been introduced. For such limited production tractors, the LP option for the “60” Orchard sold well; 45 tractors in only four months of production.

Sales of the “20” Series LP-Gas Tractors continued at a rate equal to their predecessors. While sales of the smaller “520” LP were not substantial, the larger “620” and “720” LP Tractors did quite well. Sales of the “720” LP were especially good, accounting for just over 40 percent of spark-ignition tractor sales, but a recession in 1958 eventually slowed sales of all tractors.

In retrospect, 1958 wasn’t a good year to debut anything, but the Dubuque Tractor Works introduced LP-Gas engines for the “420” Series Tractors, beginning with serial number 125000. Just why this was done is somewhat of a mystery, since it had been proven from Model “50” and “520” sales that farmers who bought smaller tractors weren’t as enthusiastic about LP-Gas. Regardless of the reason, all of the Dubuque models except the Special (V) and Hi-Crop (H) were advertised as being available with LP-Gas engines.

However, regardless of what printed advertising said, if a customer wanted a “420” Hi-Crop with an LP-Gas engine, apparently Dubuque would, on special order through the Custom Job system, build one for him. Four of these tractors are known to have been built, but there may have been as many as six; we cannot absolutely say for sure, because some were built as Custom Job tractors and the Dubuque factory order code for an LP-Gas engine (Code 22) is not present on all of them. However, examination of these tractors, along with the “430s” that succeeded them, combined with careful examination of the Parts Catalog which reveals some parts that would be unique to an LP Hi-Crop, leaves no doubt that “420” and “430” Hi-Crops were available from the factory with LP-Gas engines. The same is not true concerning the Special (V) Tractors, as none are known to have been built with an LP-Gas engine.

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