Six Decades Ago, International Harvester Tried To Make Trucking More Efficient By Eliminating The Diesel Engine

While diesel power has faded away for passenger cars in America, much of America’s commerce and logistics depend on trucks, trains, and equipment that rely on heavy diesel engines. Every once in a while, a technology comes around that attempts to unseat the diesel’s dominance, and in the 1960s, the gas turbine seemed like it could have been the future. The International Harvester Turbostar had an engine half as heavy as a diesel engine with fewer moving parts and, in theory, better fuel economy. International thought gas turbines were the future, right until it found out that the promises didn’t meet reality.

There was a time when corporations and their engineers were obsessed with finding the next great technology in engines. In the 1950s, 1960s, and 1970s, the piston engine was seen as sort of antiquated by some. If you believed some companies, piston engines were too complex, not reliable enough, not efficient enough, and not powerful enough for their size. The power demands of railroads, trucking companies, and consumers seemingly outpaced piston engine development. Heavy diesel engines in particular were more fuel efficient than gasoline engines, but had titanic sizes and weights. Diesels were also expensive to build in those days, too.

The engineers of this era had potential solutions thanks to the advancements in technology during World War II and beyond. There was the Wankel rotary engine, which had no pistons and a high power-to-weight ratio. Much of the world would eventually become infatuated with the Wankel, only to find out that piston engines were more reliable, more economical, and better for emissions.

One of the other seemingly global obsessions was the gas turbine. These engines had proven their worth in the air in World War II, but had now landed right back on the ground. It seems just as many companies, if not more, fell in love with turbines. From the 1940s to the 2000s, and technically even today, gas turbines have been found in all sorts of ships, cars, trucks, buses, tanks, locomotives, racecars, and even a motorcycle.

The promise of the gas turbine was too great for many of the world’s corporations and engineers to pass up on. The theoretical advantages of the gas turbine are somewhat similar to those of the Wankel. These engines can produce the same power as piston engines, more than twice the size and twice the weight. They have fewer moving parts than piston engines, and, at the time, it was believed that turbines would be more reliable than even heavy diesel engines. Some companies even touted simpler maintenance and the ability to run on a multitude of fuels as reasons why the turbine was going to be the technology to replace the piston engine.

The number of truck manufacturers that got into gas turbines is simply staggering. That list includes trucks by Ford, General Motors, Mack, Leyland, Magirus-Deutz, MAN, Berliet, Freightliner, Chrysler, Kenworth, and more than I’m probably forgetting. Basically, if you were a major truck manufacturer in operation between the 1950s and the 1980s, there’s a pretty good chance you experimented with turbines at least once.

International Harvester’s turbine big rig wasn’t flashy like the ones from Ford and General Motors. Instead, it was function over form. The International Turbostar would prove itself to be a hard worker. However, like pretty much every other turbine truck, International Harvester just couldn’t beat the quirks of turbine power.

International Harvester Plays With Turbines

International Harvester’s entry into turbines was a little different from other truck manufacturers. As I wrote in my last entry in my series on historic turbine vehicles, IH avoided the hassle of developing its own gas turbine by purchasing control of the Solar Aircraft Co. in 1960. By 1963, Solar Aircraft would become a fully-fledged subsidiary of International Harvester.

Through Solar Aircraft, IH’s first turbine went into a tractor. From my retrospective:

IH’s research team, which included IH Vice President of Engineering A.E.W. Johnson, Chief Research Engineer Carl H. Meile, and researchers J.R. Cromack and Ralph E. Wallace, decided to conduct an experiment of their own with a gas turbine engine. The turbine would come from within the International Harvester umbrella, as the company had a subsidiary called Solar Aircraft Co. in San Diego, California. Solar Aircraft donated a Titan T-62T turboshaft engine to the project. According to the Contract Journal in 1961, this engine, which measured 21 inches long and 13 inches in diameter, was originally designed for aircraft propulsion as well as an auxiliary power unit.

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IH’s turbine, as it was found on the tractor, weighed only 90 pounds with reduction gearing installed. This engine was tiny in comparison to the 450-pound lump of metal that was the 40 HP piston engine that was originally mated with the hydrostatic transmission. The turbine was also more powerful, making a healthy 80 HP for its small size. However, since the transmission was designed for 40 HP, the turbine had to be detuned.

The power unit had some fascinating stats to go with it. The turbine’s maximum speed was 57,000 RPM, and when it spooled up to a constant speed, the output shaft spun at 6,000 RPM. This went through a 3-to-1 reduction to get it down to a constant 2,000 RPM. Reportedly, if the transmission input spun any faster than 2,000 RPM, then the hydraulic pump would overspeed and burn itself out.

The idea here was that a turbine could make tractors better by being easy to operate, more durable than a piston engine, and able to run on whatever fuel a farmer had lying around. IH also thought that a turbine was the perfect complement to its then-new hydrostatic drive system.

Something that I did not write in my previous story is that International Harvester did have at least one previous gas turbine experiment. In 1954, IH began turbine research and eventually tested the feasibility of turbine power in tractors by strapping a Boeing gas turbine to a TD-24 crawler tractor. When that turned out to be a success, IH decided to get a turbine of its own and bought Solar Aircraft, which was looking for some help after losing military contracts.

International Harvester was transparent that the turbine tractor was an experiment from the start. The tractor was half a science project and half a PR stunt, and it was brilliant at both purposes. However, ultimately, International Harvester concluded that the turbine was too loud, too complicated, too chaotic, and too ridiculously thirsty to ever go any further than a fun experiment. The HT-341 tractor was retired from the show circuit in 1962 and then was retired for good in 1967.

While International Harvester gave up on the turbine tractor, it was not yet done with gas turbines. It was thought that, maybe, the true home for a turbine was not a farm tractor, but a semi-tractor. In 1967, IH’s turbine research continued with the birth of the Turbostar, which was shown to the public on January 11, 1968.

The Turbostar

While International Harvester was a major truck manufacturer, it didn’t quite have the resources of giants like Ford or General Motors. As a result, the International Harvester Turbostar was not a flashy truck like the other concept trucks of its era. It didn’t look like it came from 50 years in the future. But what IH lacked in style, it made up for in performance.

The Turbostar started life as a CO-4000 6×4 cabover semi. IH made some changes to the cab, like reducing the grille opening size and elevating the cab higher. The rig also got stylish quad headlights and was finished in a beautiful sky blue. While it didn’t look nearly as futuristic as the works of General Motors and Ford, the Turbostar was still a classy-looking truck.

The real magic is what was contained under the cab. In a production CO-4000, which would also be known as the TranStar in 1968, buyers had options for a variety of engines. If you fancied your IH with a Cummins straight-six diesel, the CO-4000 had everything from the 195-horsepower Cummins NHE-195 to the turbocharged NTC-335, which, you guessed it, had 335 horses in its stable. If you were a Detroit Diesel kind of person, you had access to everything from the Detroit Diesel 6-71N to the 8V-71N with horsepower ratings ranging from 195 HP to 318 HP. These power numbers are all gross numbers rather than net, so these rigs lost a bit of power on the way to the wheels. Here’s what a regular CO-4000 looks like:

For the Turbostar, the diesel engine was tossed out, and in its place sat a Solar Aircraft B series gas turbine. This was a substantially larger and more powerful unit than the Solar Aircraft Titan T-62T turboshaft that powered the turbine tractor. It also benefited from the latest research and lessons learned from the turbine tractor project.

The Solar B engine measured 1,585 pounds, approximately half that of an equivalent diesel. At 50 inches long, 41 inches tall, and 36 inches wide, it was also able to fit under the cabs of short cabover trucks. The February 2, 1968, issue of Commercial Motor magazine continues with how IH’s engineers improved their turbine design:

Among the important features claimed for the two-shaft, free-power-turbine engine is its stationary heat exchanger. This is of the recuperator type which takes waste heat from the exhaust to improve fuel economy especially at part-load operation. IH selected the stationary recuperator rather than a rotary regenerator-“because it is inherently rugged, has low maintenance and is highly durable”. Work on fabricating stainless steel parts (such as honeycomb structures) solved the problem of high efficiency in a compact stationary heat exchanger and it is said to be the first practical design for a stationary heat exchanger integral with the turbine.

Other features of the power unit include variable-geometry nozzles, which are reported to have brought fuel economy of the turbine much closer to that of a diesel.

The recuperator was also said to dramatically cut down on the high noise that plagued other gas turbine projects. The changes above were important because early turbines, including IH’s turbine tractor, were horribly inefficient and loud. For example, when Boeing made a gas turbine for Kenworth, the engine was so absurdly thirsty that it averaged 1 mpg. That was so impressively bad that even gasoline engines seemed frugal in comparison. The average big rig got 5 mpg back then. Some of the few turbines that did go into production, like the Union Pacific Gas Turbine-Electric Locomotive, worked only because the gas turbines gulped down fuel that was significantly cheaper than diesel. Other manufacturers made their turbines eat coal.

The Solar B engine cranked out 300 horsepower and spun at 34,000 RPM, which was geared down to 4,000 RPM at the output shaft. Other changes under the skin were a five-speed transmission instead of the common 10-speed, and no radiator because the truck didn’t have a traditional cooling system.

IH also said that thanks to the variable speeds of the turbine, a retarder system was built right in, and that the low internal mass of the turbine meant that it didn’t take long for the engine to spool up. Due to the turbine’s design, it was also possible to stop the output shaft but keep the gas producer running. Therefore, the truck was “stall-proof.”

International Harvester was ambitious in its marketing of the Turbostar, calling it the “Truck Of The Future.” When talking to the press, IH said that gas turbine technology was advancing so well that the fuel economy, lighter weight, smaller size, lower maintenance, and higher reliability would make the turbine a strong competitor for diesel in the future. IH went as far as to tell Commercial Motor magazine that “gas turbine truck engines will be commercially feasible in the early 1970s.” The marketing also said that “From fifty feet away, all you hear is the sound of the tires on the road.”

In speaking to Nathan’s Business in November 1968, IH CEO Harry O. Bercher was confident in the future of the gas turbine, from Nathan’s Business:

I think it still may be three years before we can say we can produce them at a price competitive to a diesel engine and have enough production facilities to warrant going forward with it. We are producing more of these prototype engines, will have them in more vehicles and we will learn from that application.

Since the truck itself wasn’t terribly flashy, International Harvester made it haul three long trailers on its massive proving grounds. Apparently, the Turbostar pulled with ease.

International Harvester Drops Its Turbine Truck

As A Corporate Tragedy: The Agony Of International Harvester Company by Barbara Marsh writes, International Harvester learned that the juice probably wasn’t worth the squeeze. By the late 1960s and early 1970s, diesel engines had become more powerful, more reliable, cheaper to make, and more efficient. Piston engines didn’t have a long delay between requesting more power and getting it, and truckers largely preferred the proven technology of the piston engine, anyway.

Reportedly, the Turbostar did prove itself to be pretty reliable, but that didn’t matter in the end. IH saw how other companies were burning hundreds of millions of dollars on turbines without getting any closer to production vehicles than IH was. So, International halted turbine truck development and let the companies with more money and more resources, Ford and GM, keep experimenting with turbines. Reportedly, Ford and GM both spend over $200 million on their turbine projects, so, in hindsight, it was wise for IH to give up earlier.

But IH didn’t throw away the whole thing. Solar’s gas turbines were popular as stationary engines, especially in oil field operations. Between 1966 and 1975, Solar’s sales reportedly increased ninefold to $254 million. In 1975 alone, Solar was responsible for a third of IH’s profits. So, it was a cash cow worth keeping around. In 1969, Solar’s parts even made it into Saturn V rockets and onto the Moon through Apollo 12 (below). Reportedly, not all executives thought that keeping Solar around made sense for IH because IH wasn’t a turbine or aviation company. However, IH kept Solar around until 1981, selling it to Caterpillar when it needed a cash infusion.

In many ways, the gas turbine is seemingly as cursed as the Wankel engine. All of the companies that worked on gas turbines for the road had varying levels of success, but most of them eventually reached the conclusion that the established engine, the piston engine, has the fewest disadvantages. Yes, turbines have fewer moving parts and can be fuel agnostic. Yes, turbines are also lightweight and powerful.

However, many of these companies found out that their gas turbines were too thirsty, too loud, too hot, too expensive, not as responsive as piston engines, or just otherwise not really ready for public consumption. Remember, Union Pacific’s gas turbine ran so hot that, if parked under a bridge, the jet blast was hot enough to melt the asphalt on the bridge. The MTT Turbine Superbike infamously has an exhaust hot enough to melt car bumpers. It’s a shame because, even today, turbines look and sound like the future.

Despite the fact that nearly all of these projects failed, I’m still so happy that they happened. I can only imagine how gratifying it must have been to build these vehicles and test them out. There are people out there who can tell stories about hauling loads up hills behind an engine that sounds like a jet. It’s also awesome when engineers get to flex their muscles like this. I hope projects like these never really go anywhere, even if they never go into production, because they’re just plain fun.

Top graphic image: International Harvester