Ralph H. Kress, “The Father of the Off-Highway Truck,” spent almost fifty years designing and developing mining trucks. His ideas are still evident in the configuration of mine haulage trucks at surface mines throughout the world.
In 1930, working as a highway truck salesman in New England, Ralph Kress designed an automatic clutch for his Packard car, received a patent, and drove it for 35,000 miles without incident. Bill Crawford, VP Engineering at General Motors, recognized Ralph’s ability and suggested that he get an engineering degree, so he could fully realize his potential. From 1933 through 1939, Ralph attended night school at MIT. After receiving his degree, he began working for GM. When the war began, he went to Washington as a GM. representative.
In March of 1943, Ralph Kress received a commission in the Transportation Corps. For his exceptional war efforts, he was awarded the “Legion of Merit,” which states “foresight, initiative, perseverance, and aggressive action marked the valuable duty accomplishments of Major Kress in skillfully producing improved cargo hauling equipment of vital need to the military effort.”
In 1950, Ralph Kress became General Manager of the Dart Company. There he was the first to rely exclusively on full power steering, a basic requirement for larger trucks. His Dart 75-TA rear-dump hauled 75 tons, the largest truck at that time. The front axle, with four front tires, was suspended in the center on the first off-highway oleo-pneumatic suspension, a revolutionary advance that replaced leaf springs. During Ralph’s Dart tenure, through 1955, Dart increased its sales six times, and no mining truck other than a Dart was sold west of the Mississippi during his last two years with the company.
In December 1955, as a consultant to WABCO, now Komatsu, Ralph Kress configured a truck incorporating the most efficient components available at the time, recognizing that tires are not suspensions, driver comfort is essential, and reducing shock loads on structures enhances efficient design. To accomplish this, he incorporated a short wheelbase with a high angle of turn and a deep, sloped, flat body. In 1957, the first 32-ton Haulpaks were delivered, along with 75-ton tractor-trailer coal haulers using the 32-ton Haulpaks as tractors. Haulpaks soon increased in size and became the truck of choice at many large surface mines.
In 1962, Ralph Kress joined Caterpillar, where he developed a line of 85-ton, 105-ton, and 240-ton electric drive trucks, again pointing the way to the future. After retiring from Caterpillar in 1969, Ralph joined his son, Ted Kress, who had started Kress Corporation four years earlier. There, he developed the Kress unitized bottom-dump coal hauler, featuring a long wheelbase with two axles and four tires on each axle for improved stability and safety and 90-degree steering on the front axle, giving exceptional maneuverability.
Ralph Kress was without question the preeminent designer of mining trucks during his years in the business. His innovative 1957 design for the WABCO Haulpak was recognized 1998 at the “Haulage 2000” Conference as the “Truck Configuration of the Future.”
