Mechanical Refrigeration

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This page was last updated on May 13, 2026.

The Technology of Mechanical Refrigeration

(The focus of this page is to establish a timeline of mechanical refrigeration on U. S. railroads, 1945 to 1959, using sources not previously readily available. Sources include a wide variety of internet searches, online newspapers, and current websites and abandoned websites and magazines at Archive.org.)

Mechanical refrigeration of the late 1940s and early 1950s required two basic components of the refrigeration unit: a refrigeration compressor, and an engine fueled by diesel or gasoline to drive the compressor. Some were direct-drive between the engine and the compressor. Others were electro-mechanical, with the engine driving a generator to create the electricity which in-turn was used to drive an electric mother that drove the compressor. Each rail car also had a fuel tank for the engine. The engine was connected to the compressor, and the two were usually mounted to a common platform to allow easy maintenance, removal and replacement. These common platforms were at times called generator sets, or gensets.

From the time of early adoption in the late 1940s and early 1950s, through to the last cars built in 1971-1973, the basic technology did not change. There were regular upgrades and rebuilding programs to modernize the fleets with better engines and better refrigeration compressors, but the concept did not change.

Then in the early 1990s, there was a move to adopt the well-established designs used in the trucking industry, which mounted a smaller and more efficient refrigeration unit (engine and compressor) to the front wall of highway trailers. The operators of large mechanical railroad refrigerator cars began limited rebuild programs to remove the older inefficient refrigerator units of the 1950s-1970s, and replace them with the trailer-style front-mount designs.

Engine Suppliers

Detroit Diesel

Railroad refrigerator cars from 1948 to 1972 were typically powered by small, reliable Detroit Diesel two-stroke engines. These engines were used to drive a generator that powered the refrigerator car's electric refrigeration system. Theses diesel engines were compact, robust, two-stroke workhorses. Their sound was distinctive. The Detroit Diesel engine had unit fuel injection and overhead valves, and was governed to run at a relatively low, constant speed of about 1200 RPM for generator duty. The Model 2-71 had two cylinders with 71 cubic inches displacement per cylinder. Their distinct sound remains the defining audio signature of a classic railroad mechanical refrigerator car.

After WWII, technological advancements made mechanical refrigeration systems practical for freight cars. This shift allowed for more reliable temperature control and larger car sizes. Instead of powering the cooling unit directly, the diesel engine drove a generator, which in turn powered the car's electric refrigeration system.

The engine and its generator were known as a "genset," typically mounted at one end of the car. The genset was a self-contained unit with a radiator for cooling, an air filter, and a fuel tank mounted on the car's underside. For maintenance, the entire unit could be slid out to hang over the trackside for routine service or completely removed for major repairs. The diesel's exhaust was routed through visible stacks on the car's roof, a key spotting feature for mechanical reefers.

These Detroit Diesel-powered reefers were a common sight across North America, used by nearly every major railroad and private car company. They were widely used by the Pacific Fruit Express (PFE), Fruit Growers Express (FGE), Santa Fe Refrigerator Despatch (SFRD), and other major lines.

Some of these Detroit Diesel-powered mechanical refrigerator cars remained in service until the 1990s. Over time, many railroads replaced the original Detroit Diesel-powered gensets with more modern, quieter, and more fuel-efficient truck-type refrigeration units (like those from Carrier Transicold).

(On Pacific Fruit Express, all mechanical refrigerator cars used Detroit Diesel model 2-71 engines except for 536 cars in 1958 that used the opposed-piston Witte, and 26 in 1961 that used Deutz engines.)

(AT&SF used Detroit Diesel 3-71 engines in their Rr-88 cars rebuilt from liquid nitrogen in 1972, and 3-53 engines in their Rr-89 and Rr-90 cars built in 1966 and 1968.)

(AT&SF records show Detroit Diesel 2044-C engines in their Rr-65 class, and 3044-A engines in their Rr-61 class, but internet searches for these model designations fails to find any additional information.)

(Some, if not all, Detroit Diesel engines for AT&SF were furnished by the Western Engine Company, a distributor of OEM Detroit Diesel engines, which assembled their own branded ready-to-run package consisting of a base engine (like the 3-53) integrated with a radiator and control panel.)

Other Small Engines

Beyond the ubiquitous Detroit Diesel units, a variety of other small diesel engines kept the nation's produce moving in the mechanical reefer era from 1948 to 1972. Other manufacturers like Hercules, International Harvester, and Witte were all key players, alongside newer names that emerged as the technology evolved.

There was later competition for these small diesel engines that powered mechanical refrigeration in railroad cars. These included Caterpillar, Cummins, and Mack. While these companies' engines are not prominently listed in the primary sources for early mechanical reefers, they were powerhouses of the diesel world in the mid-20th century. It's plausible that some of their smaller industrial engines saw use, at least according to some automotive websites.

This competitive landscape began to shift in the late 1960s and 1970s as a new type of refrigeration power unit emerged; the front-mount trailer-type unit. The market moved away from the large diesel-electric generator sets toward smaller, self-contained, and quieter front-mount refrigeration units. There were early test installations on railroad cars of these "bolt-on" units similar to those used on highway trucks.

Several other manufacturers also supplied engines for railroad mechanical refrigerator cars. These included Hercules, as found in an AT&SF mechanical refrigerator car built in 1953; International Harvester, also used in a 1953 AT&SF car; Witte, as used in a Pacific Fruit Express (PFE) R-70-7 car, now preserved at the Pacific Southwest Railway Museum. A later brand was Continental. An earlier brand was Buda, with its Lanova model being used in earlier mechanical refrigerator cars.

Crosley

Thermo King used the Crosley Cobra gasoline engine in the early years, while the Crosley Cobra was in production from mid-1946 to early 1949. The Crosley Cobra engine used sheet metal parts in its construction, and too many did not survive the long hours of continuous operation of a railroad refrigerator car. Crosley replaced the Cobra with the CIBA, or Cast Iron Block Assembly, which was in production from 1949 to mid-1953.

Originally developed as a military generator engine during World War II, Crosley's engineers refined the engine's design for automotive use and eventually altered its construction from a brazed tin block (CoBra) to a cast-iron block (CIBA). Although the Crosley CIBA gasoline engine was designed for use in Crosley's automobiles, the engine continued to power generators, small sports car and small boat racers.

Crosley built its small gasoline engines in Cincinnati, Ohio. When the company began building automobiles, due to lack of space, it was in Marion, Indiana, 140 miles east of Cincinnati. Production of engines remained in Cincinnati until 1952 when Crosley sold the rights to the CIBA engine to General Tire, which renamed the engine the AeroJet VIP (Vertical Inline Power) and marketed it specifically as a boat engine. The AeroJet engine remained in production until about 1955 when the design was sold to Fageol, who continued to market the engine as a boat engine.

(Research suggests that Thermo King used the Crosley/AeroJet engine until 1955, with Thermo King furnishing very few refrigeration units between 1955 and the company's change from gasoline engines to Diesel engines in 1958-1959.)

(An example of the limited use on Thermo King refrigeration units on railroad cars were the 11 cars built for AT&SF in 1955. Santa Fe did not buy any additional cars with Thermo King units.)

Hercules

The Hercules Motors Corporation was organized in Canton, Ohio in 1915 to supply high-speed, lightweight gasoline engines for the fast-growing transportation industry. These engines became the standard power for the then-major independent truck manufacturers. Demand for the engines grew in other industries, including farm machinery, construction, oil-field equipment, generator sets. Hercules pioneered again in 1956 with a new line of interchangeable, overhead-valve gasoline and diesel engines with three, four, and six cylinders. Identical cylinder blocks, crankshafts, valves, connecting rods, gear covers, and bell housings were used for both gasoline and diesel engines. Although mentioned in some sources, research has found no specific mention of Hercules engines being installed in railroad refrigerator cars.

"Trane. A Hercules 52-hp 6-cylinder diesel engine drives a 25-kw 220-volt, 3-phase, 60-cycle generator. The condenser on the first PFE installation." (Railway Age, April 18, 1955)

Perkins

Perkins was a successful small engine design used in a limited number of mechanical refrigerator cars, in the form of limited test installations. The engines were built by the Perkins Engines Company Ltd. originally based in Pertersbough, England. The company was founded in 1932 to build small high-speed diesel engines, and today is owned by Caterpillar (since 1998).

Witte

The Witte engine is one of the most fascinating examples due to its opposed-piston design, which featured two pistons moving in opposite directions within a single cylinder. While an innovative and efficient concept, it was complex and ultimately less common than traditional designs.

From Railway Age, November 19, 1956.

Refrigerator Car Power Plant. - Series "100" Witte diesel engines are now being used on mechanical refrigerator cars. These water-cooled, four-stroke cycle engines have two horizontally opposed cylinders. The balance that results from this design is intended to produce smooth operation. This design also provides a strong, box-like unit. At 1,800 rpm the "100" will produce 18 hp for continuous 24-hr-per-day operation, and a maximum of 24 hp for intermittent service.

Support pads are spaced far apart for secure mounting and stability, and are located below the crankshaft center line and close to the center of the engine mass to assure positive anchorage when subjected to severe shock. Engine speed range is 600 to 2,400 rpm, and engine displacement is 100.5 cu in. with 4-in. bore and 4-in. stroke.

Fruit Growers Express car No. 208 had the first "100" engine installation. This car went into experimental service in June 1955, and was designed to handle fresh fruits and vegetables at controlled temperatures between 32 and 70 deg F. It has accumulated over 2,000 engine-hours handling such loads as oranges, tangerines, grapefruit and cucumbers. Fruit Growers reports that to date, its performance has been satisfactory.

Pacific Fruit Express car No. 300290 was equipped with a "100" engine in March 1956. Fitted with a Delco 12-kw alternator, the engine powers the two 7.5-hp compressor motors of a Carrier Model 66E-3 condensing unit, a 1-hp evaporator blower motor and a 2-hp condenser motor. It was necessary to limit compressor back pressure during initial "pull down" so that the engine would not be overloaded when initially cooling the car in hot weather.

In August 1956, PFE car No. 300141 had a "100" engine installed in conjunction with a Frigidaire refrigerating system. The first of these two cars has now accumulated over 2,500 hours of service. Pacific Fruit Express has been attracted by the initial cost of the power plant, its fuel consumption rate, and its ability to use lower grade fuel oil.

Design features of the "100" engine include wet-type, replaceable cylinder liners; aluminum bearings; replaceable valve guides and inserts; and full-pressure lubrication. Witte Engine Works, Dept. RA, Oil Well Supply Division, U. S. Steel Corporation, 1614 Oakland ave., Kansas City, Mo.

Refrigeration Unit Suppliers

1954
"Four companies are principal suppliers of fruit car refrigerating equipment: Trane Company; Frigidaire Division of General Motors Corporation; Carrier Corporation and United States Thermo King Railway Corporation." ([Norfolk] Virginian-Pilot, July 30, 1954)

"In 1955 there were at least six different refrigeration systems in use for mechanical refrigeration of railroad refrigerator cars. In addition to these six systems which have already been developed to the point of use. York and International Harvester are working on this problem and will probably have refrigerator-car systems ready soon." (Railway Age, April 18, 1955)

"Production of a 50-ft mechanical refrigerator car based on a 40-ft prototype developed by the Electro-Motive Division of General Motors is now under way. The welded all-steel body is an envelope container mounted resiliency on the underframe. It may be lifted off as a unit. Insulation is structural plastic foam. Refrigeration is by Frigidaire. Doors are 8 ft wide." (Railway Age, April 18, 1955)

Carrier

"Carrier. The diesel-electric power plant is rated at 20 kw and weighs 2,000 lb. Two compressors are driven by 7-1/2-hp motors. The two compressor-motor combinations may be used singly or as two separate refrigeration systems. For light loads with only one compressor operating, approximately 60 per cent of full capacity can be attained. Electric heaters are used for automatic defrosting plus car heating. Refrigeration equipment totals 2,490 lb." (Railway Age, April 18, 1955)

Carrier Transicold's innovation included the first front-wall refrigeration unit for containers in 1968. The use of front-wall mounted refrigeration units began in the late 1990s.

Fairbanks-Morse

"Saylor-Beall, Dole, Fairbanks-Morse. This system employs cold plates to distribute the cooling effect instead of evaporators and fans. The cold plates constitute a refrigerating reservoir the temperature of which will rise at the rate of about 1 deg an hour after a failure. The Brunner compressor is rated at 5 hp. The system weighs 6,100 lb." (Yes, over 3 tons; not hard to see why this design was not adopted.) (Railway Age, April 18, 1955)

Frigidaire

The Frigidaire Corporation was organized in 1919 when the original company, the Guardian Frigerator Company, was purchased by General Motors and renamed. The predecessor Guardian Frigerator Company was incorporated on April 4, 1916, with Detroit as its headquarters. First located in Detroit, producing only 50 machines in its first year. After being sold to William C. Durant in 1918 and then to General Motors in 1919, the company was renamed Frigidaire Corporation. In 1920, operations were transferred to Delco-Light Company in Dayton, Ohio, where, with the help of inventor Charles F. Kettering, the product was re-engineered for mass production.

By 1926 Frigidaire was separated from Delco-Light. After the separation, the Frigidaire company went on to create innovations in metal cabinets, porcelain enamel, and commercial cooling equipment, as well as its emerging leadership in air conditioning. In 1932, the company began its efforts in the air conditioning of railroad passenger cars.

"Frigidaire. The power plant is a 34-hp Detroit two-cycle diesel engine directly connected to a Delco 20-kw, 3-phase, 220-volt, 60-cycle generator which operates continuously. There are two sealed compressors, each driven by a 5-hp motor. Two condensers are assembled in a single structure. The cooling unit has two evaporator sections, and one condensing unit is connected to each section." (Railway Age, April 18, 1955)

Thermo King

Before the 1945–1960 period, the company—then known as U.S. Thermo Control—developed foundational refrigeration technologies that would later enable the designs used in railroad refrigerator cars. From 1938 to 1940, it created the "Model A," the world’s first successful mechanical transport refrigeration unit, a gasoline-powered, 2,200-pound system designed for trucks. In 1941, the lighter, more reliable, nose-mounted "Model C" was introduced, using the brand name "Thermo King." During World War II, the U.S. military extensively used the Model C to transport blood, medicine, and food, proving its ruggedness and reliability.

In the late 1940s, Thermo-King began its move into refrigeration units for railroad freight cars, building directly on its proven Model C refrigeration for trucks, which was adapted for rail transport in 1948. At the time, railroad cars still relied on manual ice loading for cooling, which caused rotting floors and cargo contamination, whereas Thermo-King’s gasoline-powered, onboard units offered a cleaner, more efficient, and more reliable solution. During this period, the company’s annual revenues reached approximately $3–4 million, it employed 200 people, and it opened a training school for mechanics, also in 1948.

In 1948 the Thermo King company furnished equipment for rail cars operated by Fruit Growers Express, the Canadian National and Western Fruit Express. To ensure dependable service each car had two 28 horsepower, three-ton capacity refrigeration units, with both units operating to precool the car, and when the desired temperature was reached, one unit shut down. It would then automatically start up if the other unit should fail for any reason. Gasoline for the car was carried in a 155 gallon tank. The fuel, maintenance and depreciation costs were figured at 27 cents an hour.

The Trane Company

By the time the Trane company became involved in the mechanical refrigeration of railroad freight cars, it was already well established in the air conditioning of railroad passenger cars. The Trane company became involved with railroad passenger car air conditioning (refrigeration/cooling) in the early 1930s, coinciding with the broader industry introduction of rail passenger car air conditioning.

The Trane Company's factory was in La Crosse, Wisconsin.

October 1, 1947
"It is understood that these expansion plans are contingent upon success of certain new products being worked on in Trane laboratories. The company says it is "engineering minded." Among the projects nearing the commercial production stage are a railway car air conditioning system and a new, light-weight radiator for automobiles." (La Crosse Tribune, October 1, 1947)

July 30, 1952
"Pacific Fruit Express, one of the principal transcontinental perishable food carriers, placed a substantial order [with Trane] for special cooling units for refrigerator cars. The units will maintain sub-zero temperatures for shipping frozen foods from the coast. An experimental refrigerator car unit, for shipping either fresh or frozen foods at most favorable temperatures, was built for the Canadian Pacific Railway." (La Crosse Tribune, July 30, 1952)

From the Cornwall, Ontario, Daily Standard Freeholder, December 12, 1952.

The first of its type in Canada, a mechanical refrigerator car capable of keeping its lading at a constant 10 degrees below zero, Fahrenheit, or if needed, of heating it up to 60 degrees above zero, will arrive in the [Montreal] Place Viger terminal tomorrow on the Canadian Pacific Railway’s Toronto run. The car is making a series of test runs between the two cities, and has as its cargo tonight a load of beer.

The car is a standard C.P.R. overhead refrigerator car, previously capable of lowering the temperature under maximum refrigeration to 10 degrees above zero, which was remodeled at the Angus Shops in Montreal as part of a joint program of refrigeration development being carried on by the C.P.R., the C.N.R. and the National Research Council.

The overhead ice tanks and floor level baffles are being removed and in their place the mechanical refrigeration unit was installed in one end of the car, taking up six and a half feet from the end bulkhead. This leaves the car with an overall capacity of 1895 cubic feet.

Where the tanks used to be in the roof of the car, there is now an air distribution duct leading from the evaporator coils and electric strip heaters situated over the motors. The refrigeration unit is a Trane 6-cylinder compressor, using Freon as the refrigerant. A separate diesel motor drives an alternator which supplies power for the refrigerating and heating equipment.

The car carries 340 gallons of diesel fuel, enough for 12 days of constant operation. The heating units are also used to defrost the refrigerating coils, this being done automatically. The equipment for the installation was supplied by Trane Company of Canada.

It is expected that the car will run between Montreal and Toronto until July 1st, when a joint test will be run to the west coast from Toronto.

July 7, 1953
A Canadian Pacific mechanical refrigerator car successfully completed a nine-day test run from Vancouver to Montreal, carrying nearly 43,000 pounds of frozen halibut. The test, a joint effort by Canadian Pacific, Canadian National Railways, and the National Research Council, was deemed highly successful by the railroads and the council. The car can maintain internal temperatures between -10 and 65 degrees F despite external temperatures ranging from -40 to 110 degrees F. During the trip, the fish started at 15 degrees F with the car's thermostat set to -10 degrees F. Although outside temperatures ranged from 46 to 87 degrees F, the fish arrived in Montreal at 9 degrees F below zero. The refrigeration system, supplied by the Trane Company, is housed at one end of the car and includes an evaporator, condenser-radiator, motor compressor, and a diesel engine/generator power plant. (The Montreal Star, July 7, 1953)

Waukesha

The Waukesha Motor company attempted to build a diesel engine for refrigerator car service in 1954-1955, to match its successful propane-fueled Engineator used in the air conditioning units of railroad passenger cars. But the design did not make it through the company's internal testing and the effort stopped.

July 30, 1954
"Waukesha Motor Company, Waukesha, Wis., says that within 60 days it will introduce a new gasoline motor that will simplify the design of mechanical refrigeration units, and will sell for roughly one-third less than current makes. Company spokesmen also claim the equipment will be easier and cheaper to maintain, aiming to reduce the barrier of entry." ([Norfolk] Virginian-Pilot, July 30, 1954)

"Waukesha. A 42-hp 6-cylinder diesel engine, directly connected to a 20-kw, 220-volt, 3-phase, 60-cycle generator, is mounted under the car. There are either one or two air-conditioning packages. Each contains a compressor, condenser, evaporator, motors and fans. Each is mounted in a bunker hatch with the cold section down in the bunker and the hot section above the hatch. The power unit weighs 2,100 lb." (Railway Age, April 18, 1955)

Quoting the Waukesha ad in Railway Age, April 18, 1955.

The Waukesha Diesel-lcer System consists of a 20 KW Engineator (a 6-cylinder, 4-cycle Waukesha horizontal Diesel engine direct-connected to a 220-volt, 3-phase, 60-cyde alternator) and two motor-driven Cooling-Heating units for low temperature or all-purpose cars. Only one Cooling-Heating unit is required in cars used exclusively in 35° service.

(Unlike the very successful Waukesha "Engineator" for railroad passenger cars, this new Waukesha unit for freight cars, branded as the "Diesel-Icer," would be, as mentioned, diesel-fueled, a version of the propane-fueled Engineator. Quoting the Waukesha County Freeman newspaper, February 18, 2014, "In 1955, the company introduced the “Diesel-Icer” which was to be used to refrigerate box cars. The company equipped a car at its plant, and was the first to do so, but because of competition with Ford and Westinghouse, Waukesha’s unit never caught on. The refrigeration arm of the company was re-purposed in 1956 and named the Special Products Division. It concentrated on stationary power units." Ads show that the car tested was Fruit Growers Express FHIX 41127.)

(Waukesha advertised its Diesel-Icer in Railway Age magazine from May 1955 through May 1956.)

Early Attempts

From the Smithsonian

In 1883 Cassius Clay Palmer of New York, NY applied for and received a patent for a railway refrigerator car that was cooled by mechanical refrigeration. This model was not filed as part of his application but was used for display purposes to explain the car's operation and promote sales. At the time of Palmer's patent refrigerated railcars depended upon large quantities of ice being loaded into the cars. Palmer claimed that his system was "..the first which has been devised by means of which the use of ice can practically be dispensed with…." The Palmer design took power from one axle of the car via a pulley and belt which drove the machinery. To provide a constant speed drive for the refrigeration compressor and to provide power during periods when the car was not in motion, Palmer used stored compressed air. The axle driven belt ran a two cylinder air compressor which fed compressed air to storage tanks mounted beneath the car. A check valve and pressure regulator supplied constant pressure air from the cylinders to an air-driven engine which in turn powered the compressor for the refrigerant (chloride of ethyl) returning from the cooling coils inside the refrigerated compartment. Palmer made provisions for some of the compressed air to be used to keep a positive pressure differential with the outside environment. This discouraged warm air and dust from entering the refrigerated portion of the car. The compressed air engine also powered an air circulation fan to aid maintaining a uniform temperature throughout the car. Palmer's design proved successful in tests, and in 1888 Armour & Company had eight cars built for them. However, the Palmer car did not find lasting commercial success. The then existing refrigerated car infrastructure was based on ice, and those in charge of the industry did not want the status quo disturbed. As a result mechanical refrigerator cars were not a commercial success in the United States until 1950.

The display model is constructed of wood, brass and iron. It is of a natural wood color. The model includes details of double door openings on the sides as well as the compressed air cylinders beneath the car.

Sturtevant

The B. F. Sturtevant company, Boston, Massachusetts, furnished the fans used in railway car air conditioning. These fans were used to blow air across bins of ice stored on railway cars in the earliest versions of air conditioning. Known as "Ice activated" systems, this type of air conditioning began to be replaced in the high priority and premier trains when the later steam injector system was developed.

"Henry L. Galson's career as an engineer who played a key role in the development of self-contained air-conditioning equipment is traced. He was a co-recipient of the City of Philadelphia's John Scott Medal for the development of the De la Vergne air-conditioning apparatus (1933), the first self-contained, hermetic, air-cooled room air conditioner with a reverse cycle. Galson's basic patents for the De la Vergne unit were purchased by five companies (GE, Westinghouse, Frigidaire, Carrier and Sturtevant). His application of the packaged heat pump to room and railway car air conditioning was visionary." (International Institute of Refrigeration)

"It was also in 1910 that Sturtevant took out its first patent for railway car cooling. On this foundation Sturtevant has built up through the years a patent background that covers nearly all of the moving vehicle field, including railway coaches of all types and sleeping cars. Since the air conditioning of railway cars began to go forward about 1930, Sturtevant has supplied the equipment for nearly 8000 cars of all types in this country and Canada." (Charlotte Observer, May 15, 1938)

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