International Harvester HT-340 Concept Tractor

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Back view of the HT-340. “The turbine really was not a feasible means of power,” Brian says. “It’s very inefficient, even today. But it was a means of carrying a big amount of power at a low weight and compact size.” Brian estimates his reproduction gulps a gallon of kerosene or jet fuel in 5 minutes.
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A reproduction of the International Harvester HT-340 prototype, built by Brian Harris. Brian had never heard of the HT-340 until about 10 years ago, but when he decided to build something using a turbine engine, the 340 became the ideal – if challenging – project.
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Flanked by traditional farm tractors at the New York Steam Engine Assn. Show in Canandaigua, the 340 looks like a thoroughbred among workhorses.
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Brian at the wheel of the HT-340 on parade at the New York Steam Engine Assn.’s show in Canandaigua.
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The fabricated dash fairing. Brian ended up working a total of 2,600 hours on the reproduction over a three-year period. “I knew the whole project would be quite a challenge,” he says. “A lot of the work I hadn’t done before.”
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The front view of the 340 brings to mind a racecar on tractor tires.
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The 2-to-1 ratio Triplex chain box to run the hydraulic pump; building this piece was one of the most challenging aspects of the entire project.
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Brian’s 340 with engine placed. “Thirty years ago, I bid on an auxiliary power unit at an auction, but I didn’t get it,” Brian says. “I always regretted that.” When he got another chance to buy one, it didn’t get away; now it’s the centerpiece of his HT-340.
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Forms for the back and hood.

During a career as a machine repairman at General Motors, Brian Harris worked with state-of-the-art technology. On his own time, he operates the largest working steam traction engine collection in New York. “For a living, I worked on the most modern technology,” he says. “And for my hobby, the oldest.” His most recent project – reproduction of the International Harvester HT-340 tractor – defies neat categorization, other than to say it’s a terrific re-creation of a concept tractor.
Ironically, the HT-340 (for Hydrostatic Turbine), a product of International’s experimental group, was never intended to go into production – and didn’t. International began working on development of a hydrostatic drive tractor in the 1950s. When a 340 prototype tested well, the engineers cranked up the volume, installing a small gas turbine engine from the company’s Solar Aircraft Co. subsidiary (which was named not, apparently, for an energy source but for the sunny skies in San Diego, where the company was founded in 1927).
The HT-340 made its debut on the show circuit in July 1961. But on the return trip from Lincoln, Neb., where it was displayed at the University of Nebraska’s 10th annual Tractor Day, the tractor was extensively damaged in a traffic accident. Emergency repairs were made and the 340 was displayed at several events that summer.
Later that year, more extensive repairs and modifications were completed. The retrofitted prototype was unveiled in 1962 as the HT-341, complete with three-point hitch, stabilized steering, larger tires, rear lights, enhanced controls, a new fuel-filtering system – and a new color scheme. The 340 was blue and white; the 341 was red and white. The 341 was used in displays and demonstrations. In 1967, it was donated to the Smithsonian Institution in Washington, D.C.

Tackling the turbine

His long-standing passion for steam traction engines notwithstanding, Brian had been interested in gas turbines for more than 30 years. “I always wanted to put one in something,” he says. “Since I’ve also always been interested in farm equipment I thought a tractor would be ideal. I considered others but this – the IH HT-340 – seemed to make the most sense.”
Just as International engineers did years before, Brian started with a stock IH 340 tractor. “I used a lot of its components, like the steering, frame, wheels and other parts,” he says. Earlier, he’d acquired an auxiliary power unit (APU) powered by a turbine. “It’s the same thing International used,” he says, “but with 150 hp and 60,000 rpm, mine has more power and is slightly larger.”
His turbine was designed as a lightweight power source for jet aircraft. “It was used as a generator to start the plane,” he says. “It’s lightweight, but not very fuel efficient.”

Getting the ratio right
Considerable gear reduction was required before the APU could be connected to the transmission. “That was one of the biggest problems,” Brian says. “The generator is 6,000 rpm but that’s still too fast to run anything with hydraulics. So I had to make a special gearbox to get it down to 2,000 rpm in order to use the hydraulic pump. If it had been over 2,000, the hydraulics would cavitate, causing vapor bubbles to form in the pump.”
Hydraulic motors connected to each rear wheel completed the driveline, eliminating the traditional differential and gear arrangements. On the International prototype, hydraulics were used for the brakes as well. “It didn’t work very well,” Brian notes. “If the engine wasn’t running, you had no brakes.” On his 340, he used more traditional brakes, as did International on the 341.
The reproduction is faithful to the original as a whole, but Brian made concessions to modern technology. “I took a modern approach with hydraulics, but the outside appearance looks the same as the original,” he says. “You just couldn’t use the same things they did. For example, International used nautical anchor chain winch motors for the wheel motors. I had to use parts that were available now.” Even with that compromise, the project moved slowly. “I couldn’t have done it without the computer and eBay,” he says. “I lost track of the hours I spent looking for parts on eBay.”

Little to go by

Getting the right look was another challenge. Brian traveled to Penfield, Ill., home of the Illinois & Indiana Antique Tractor & Gas Engine Club, where the HT-341 is currently displayed, on loan from the Smithsonian. “It’s the same, basically, as the 340,” he says, “but modified. I took 50 photos and a lot of dimensions, and that’s all I had to go by.
“There’s really very little information available on the 340,” he adds. “I talked to the Smithsonian curator, and he said nothing came with the tractor when it was donated. That was one of the biggest hurdles–not having anything but a few pictures to go on. I’ve rebuilt several steam tractors, but always have something to work from. On this, I had to create parts from photos and sketches.”
In the 1960s, tractor manufacturers had begun experimenting with fiberglass, a new material in that era. “I’d never worked with fiberglass,” Brian says, “but I built the hood out of it.” He carved complete molds for the hood (and many other parts) from wood, carbon steel and Styrofoam, and then molded fiberglass over those forms. “I’m a lot better working with steel,” he admits, “so after the hood, I made the rest of the body out of sheet metal. Even that was quite a challenge. I didn’t expect that. I thought the mechanics and hydraulics would give me the most trouble.”
Armed with 58 years’ experience in welding and fabrication, and extensive work with steam engines and other farm equipment, Brian did the vast majority of the work himself. “The only help I got was on the floor panels and painting,” he says. “I wanted a nice finish on it.”

Marking a milestone

When the tractor was finished, Brian towed it to a field for the moment of truth. “I didn’t want to start it by a building,” he recalls. “I didn’t know where it would go. But it started right up; it ran excellent. I didn’t have to do anything major to it. But I tell you, it gave me goose bumps the first time I drove it. I need to run it some more so I can get used to it.”
One thing’s for sure: The 340 is no shrinking violet. “It is very loud,” Brian concedes. “It’d be like standing next to a fighter plane when it starts. But it’s a very high frequency sound: If you stand 200 feet away, you hardly know it’s running. High frequency sound dissipates quickly.”
Fifty years after the prototype was built, Brian’s reproduction made its debut in August at the New York Steam Engine Assn.’s 50th annual Pageant of Steam in Canandaigua – a total coincidence, he says. “It never occurred to me, while working on the tractor all that time, that its 50th anniversary would coincide with Canandaigua’s 50th anniversary,” he says. “It just happened that way.”
Over the course of the three-year project, Brian had plenty of time to consider the state of technology in the late 1950s and early 1960s. “What surprised me the most was how far ahead International was in their thinking and their design,” he says. “The HT-340 was built as a concept tractor, not a production tractor. But look how close they were to modern-day tractors. It could have been designed last year. They were right on with the look, but way off with the mechanics. At that time, people thought the turbine was the wave of the future, but it wasn’t.” FC

See video of the IH HT-340 here!

For more information: Brian Harris; e-mail:; online at
For information on the HT-341 on display at the I&I Antique Tractor & Gas Engine Club, contact Robert Chamberlain, 9288 Poland Rd., Warrensburg, IL 62573; (217) 674-3334; e-mail:

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