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The Mighty Jeep
Rugged, versatile, and nearly indestructible, this four-wheel substitute for the horse has become one of World War II’s enduring legends
December 1960 | Volume 12, Issue 1
The heart of the jeep was its engine, and the man who made that heart tick was the late Delmar G. Roos, known to automotive engineers as Barney. Barney Roos had designed a 100-mile-an-hour Locomobile staff car in World War i. Later he became chief engineer for Fierce-Arrow, Marmon—where he designed the Marmon Straight 8—and Studebaker. When he came to Willys early in 1938 he was shown a four-cylinder engine that was being used in a Willys light car, and given the job of improving it.
What Barney Roos wanted was an engine that could develop (15 horsepower at 4,400 r.p.m. and run for 150 hours without failure. What he started with was an engine that developed 48 horsepower at 3,400 r.p.m., and could run continuously for only two to four hours. (For comparison, a 1939–40 Ford developed 60 horsepower at 3,500 r.p.m.) It used oil excessively, its bearings wore out fast, the water pump and cylinder head leaked, it shook loose its starter, and it had a congenital pre-ignition knock.
It took Barney Roos two years to perfect his engine, by a whole complex of revisions that included closer tolerances, tougher alloys, aluminum pistons, and a flywheel reduced in weight from fifty-seven to thirty-one pounds. He had also heard, by the time the job was done, that the Army was interested in a light vehicle. A homemade product called the “belly-Hopper,” a low springless platform on nine-inch airplane wheels, had in fact been built by Colonel Robert G. Howie and Master Sergeant Melvin C. Wiley. “It looked,” Roos said, “like a diving board on wheels.” It was too light for really rough terrain. It had to be transported from point to point by truck. It had virtually no ground clearance. But it was easy to conceal—and, above everything else, it had the power to stimulate the imagination.
Roos described his own ideas for a low-silhouette vehicle to Major General Walter G. Short, later to have the misfortune of commanding at Pearl Harbor. The Army had appointed a technical committee, which had tested small cars made by the American Bantam Company and arrived at specifications for a military vehicle. These called for four-wheel drive and a low speed of three miles an hour. Top weight was to be 1,000 pounds with a Goo-pound pay load. The first seventy vehicles were to be delivered within seventy-five days. Bids were requested of 135 manufacturers, but only two of them were interested, Bantam and Willys.
The Bantam response must have been one of the fastest on record. Plans and a bid were submitted in less than a week, and the first pilot model was completed in forty-nine days. Willys had asked for an extension of the contract time, and had been refused. Barney Roos knew the weight limit was impossible for his engine, but he also knew no similar engine was available that could match his for endurance and performance. He wanted to show the Army what Willys could do. Prodded, the Quartermaster Corps invited Willys to develop a model at its own expense and agreed to test it.
The Army drivers at Camp Holabird expected to make short work of the Willys model, but they were considerably surprised. The Willys’ test set even higher standards of performance than Bantam’s. There was only one flaw: the Willys jeep weighed 2,423 pounds, far over the target of 1,600. Specifications for new bids raised the maximum, including oil and water, to 2,175 pounds, but Willys was told to get under that limit or forgo future orders, and Ford too was asked to participate.
Barney Roos now had to decide whether to scrap his tough engine and buy a lighter and less powerful one on the open market, as Bantam had done. He decided not to, and so the ordeal of reducing weight began. Body and chassis were stripped and every part studied. First, all unnecessarily long bolts were shortened. Then the thickness of the steel was reduced on body and lenders. Tough alloys were substituted in the frame for heavier carbon steel (aluminum and magnesium were unavailable). Reinforcing plates were reduced. New paints were tested and spray methods analyzed; eventually nearly ten pounds of paint were eliminated! Pound by pound, and then ounce by ounce, the weight came down. When the slenderized model was assembled it weighed 2,164 pounds. Willys was in.
The first vehicles to come from Ford, Bantam, and Willys were tested by all the interested units, but the report of the Infantry Board is representative of the rest: “Willys performance was superior to that of Bantam and Ford in acceleration, maximum speed, grade climbing and cross country. The reason lies in its greater horsepower and torque … engine, transmission, frame …”
The report concluded that “the standard vehicle should be based upon the Willys chassis, with the Ford shift lever and hand brake arrangement, and the power and performance characteristics of the Willys.” ft was clearly a triumph for Willys’ design and for Barney Roos’s pet engine.
Bantam soon dropped out of the running. Edsel Ford tame to pick up the Willys’ blueprints, and Ford and Willys settled down to the job of turning out 651,068 jeeps for the war effort. With the 2,500 produced by Bantam, the total of military jeeps came to 653,568.