Turbine Tractor

International Harvester HT-341 Turbine Tractor

Image source uncertain, but believed to be from International Harvester Corporation

IH fans will be able to see one of IH's most unique concepts, the HT-341. On display in the Smithsonian Agricultural Exhibit in Washington for many years, this tractor pushed the boundaries of technology forward. Built in 1961, this little tractor was powered by a small gas turbine engine built by Solar Aircraft Company, a subsidiary of International Harvester and a major supplier of turbine powerplants. This type of turbine engine was used in "Auxiliary Power Units" onboard jet aircraft to power the air conditioning and other systems while on the ground, plus supplying power to start the main jet engines. The turbine produces a maximum 85 horsepower operating at a constant 57,000 rpm., requiring considerable gear reduction before connecting to the hydrostatic transmission. The entire powerplant and gear reduction unit weighed in at 90 pounds. Hydraulic motors connected to each rear wheel completed the driveline, eliminating the traditional differential and gear arrangements.
Several factors prevented the HT-341 from reaching commercial production. Gas turbine engines are able to produce great amounts of power from a very small package, but high fuel consumption is their downfall. When added to the difficulty of adequately filtering the massive amounts of air required by the turbine engine, and the noise produced, it was not a practical machine. Although the turbine engine tractor never made it into production, advances in hydrostatic transmission design, and several other features later found their way into IH production tractors.
About the same time, International also experimented with a semi-tractor with a turbine engine, and Chrysler was experimenting with turbine powered autos as well. Ford also experimented with a rather unique "free piston" turbine engine in a tractor in the late 1950's. Rapid advances in diesel engine technology also helped doomed the turbine tractor to the realm of "what might have been".
HT-341

The IHC HT-341 has been on display at the I&I facilities since the 2002 Historic Farm Days/Red Power Roundup. Rumor has it the Smithsonian is interested in returning the tractor to operating condition if the funds and technological expertise can be located. The source of the picture above is uncertain, but believed to be from IHC promotional material.
Some uncertainty remains about the number of these experimantal units built, a former IHC engineer who worked on the project remembers two tractors, and thinks there may have been a third. This tractor is believed to be the second unit assembled and was originally designated HT-340 as it was based on the IH 340 Utility tractor, although the wheels and front axle are about the only thing remaining from the '340 Utility after the turbine design went through several major revisions. After being damaged when the truck transporting it overturned, the tractor was rebuilt and several improvements incorporated, gaining the HT-341 designation at that time. In the late 1960's, the tractor was donated to the Smithsonian and was on display there for many years. It had been in storage for several years when it was loaned to the I&I Club for display.

	Larry Jones(left), Curator Emeritus from the Smithsonian, and Darius Harms of the I&I Antique Tractor and Gas Engine Club inspect the HT-341 tractor after the hood was removed for the first time in 40 years. The black boxes under the cowl are wooden mockups of batteries that would have been there when the tractor was in operable condition. Photo by Rich Porter.