Allpar Forums banner
1 - 1 of 1 Posts

Premium Member
2,290 Posts
Jeep MA and MB, Military Jeeps: 49-Day Miracle Worth the Weight

by Ken Massey • largely based on the 1991 ASME paper "The Jeep MB"

Sometime during World War II, a corporal was found sitting in the charred wreckage of a Jeep that had been shelled. He refused to be comforted by assurances that he would get a replacement Jeep, but, he said between sobs, "You don't understand. I loved this one."

Land vehicle Vehicle Car Jeep Motor vehicle

Even before Pearl Harbor, the highest-ranking officer in the Armed Forces, General George C. Marshall, described the Jeep as "America's greatest contribution to modern warfare." What was it about this drab and boxy little machine that inspired such affection and far into the future, makes it one of the most widely respected and imitated designs in automotive history? How did it
come to be as the embodiment of Yankee ingenuity, tinkering, and functional design?

For much of 1940, the Army searched for a light, rugged general purpose and scout car. The current motorcycle and sidecar vehicle was unsatisfactory, as was a proposed a 4x4, known as the "Bellyflopper" and built by Colonel Robert G. Howie and Master Sergeant Melvin C. Wiley. It required the driver to lie on his stomach, was too light for rough terrain, and had virtually no ground clearance.

Land vehicle Vehicle Car Jeep Motor vehicle

Germany's specifications for its own light go-everywhere car, given to Ferdinand Porsche, did not include four wheel drive, but did require high mobility and a weight of under 1,210 lb. The car, developed over the course of two years, had to have a low speed matching that of marching soldiers (Germany would eventually make around 50,000 of them).

The U.S. Army wanted four-wheel drive (it had bought Jefferys Quads in the 1910s), with a two-speed transfer unit and 85 foot-pounds of torque; it needed to carry 660 pounds, including a machine gun and three passengers. Other requirements were a fold-down windshield, running from 3-50 mph, and weighing no more than 1,300 pounds.
The specs were sent to 135 automotive companies on July 11, 1940, with a deadline of just eleven days - and a working prototype due in 49 days.

Given the deadlines, only Willys Overland and American Bantam replied. Willys asked for more time (and did not get). The bankrupt American Bantam Car Company had no engineering staff left on the payroll, but, with some help from the Army, convinced freelance designer Karl Probst to work on it, without salary.

Land vehicle Vehicle Car Jeep Motor vehicle

Probst completed the plans for the Bantam prototype in two days, and on the third day estimated the total cost. Bantam's bid was submitted on July 22, 1940; the prototype was driven frm Butler, Pennsylvania, to Camp Holabird, Maryland, on 21 September 1940.

Much of it was made from existing parts; the custom four-wheel drive train components were supplied by Spicer, which had moved from Plainfield, New Jersey, to Toledo, Ohio. It met the Army's criteria, except for the engine's torque, but the Army felt that Bantam was too small to build all the cars they needed. Therefore, the Army gave Bantam's design to the rivals Willys and Ford, who were both encouraged to make their own changes and modifications.

The Ford Pygmy and Willys Quad prototypes looked similar to the Bantam BRC (Bantam Reconnaissance Car) prototype, and Spicer supplied similar 4-wheel drive train components to all three. The Probst/Bantam "Blitz Buggy" was first tested by then-Colonel Dwight D. Eisenhower, and was accepted after twenty days, with a contract ordering 70 more units.

Land vehicle Vehicle Car Motor vehicle Vintage car

Willys-Overland's chief engineer Delmar Roos delivered their Quad prototype on November 11, 1940, ten days ahead of Ford.

Roos had arrived at Willys-Overland in 1938, after working for Pierce Arrow, Locomobile, and Studebaker. Willys' "Go Devil" 4-cylinder L-head engine had the same bore and stroke as the version that would later power the Jeep MB, but it only produced 45 horsepower at 3,400 rpm. When operated at full throttle for 22 minutes, the cylinders began to score and the bearing burned out.

Roos pulled the engine out of production, redesigned the cooling system, replaced the cast-iron pistons with tin-plated aluminum ones, and ran the engine for 50 hours at 3,600 rpm. Now the valves burned out. After more modifications, Roos was able to produce an engine that would run at 4,000 rpm for 100 hours without engine failure; as used in the future Jeep, sources claim it made an impressive 60 horsepower (all power figures are gross, not net).

The Willys' test at Camp Holabird set higher standards of performance, but the Willys prototype weighed 2,423 pounds, well over the target of 1,600. Ross had to decide whether to redesign the car to meet the weight requirement, or use the 40-horse Continental engine in Bantam's prototype.

Motor vehicle Engine Auto part Machine Automotive engine part
Roos disassembled piece by piece seeking weight losses, then stripped the body and chassis. Unnecessarily long bolts were shortened; sheet metal thickness was reduced. Alloys replaced carbon steel in the frame and reinforcing plates were reduced. Only one coat of paint was sprayed on, eliminating nearly ten pounds of paint. The car now made the weight restriction - by a mere seven ounces. Barney Roos' faith in the "Go Devil" engine and its future performance would prove that it was indeed "well worth the weight."

The Army raised their maximum weight to 2,160 pounds, contracting for 1,500 of each of the three prototype models, and extensively field-tested each vehicle.

Looking back, the car that became the Jeep MB has roots that go deeper than the three prototype entries. The driveline layout was used by Spyker, a Dutch car manufacturer, in 1902; the driven front axle was pioneered by Otto Zachow, a Wisconsin blacksmith, in 1907; and, mechanically, the Willys Quad was a scaled-down Marmon-Herrington half-ton 4x4 originally designed in 1936.

In the end, the Jeep MB was an amalgam of the prototype designs. The bodywork and general design derives from Bantam; the shift lever, hand brake arrangement and pressed metal grille were from Ford, to save money. A dominant design element was Willys' powerplant; its 60 horsepower and 105 foot-pounds of torque dwarfed Bantam's and Ford's engines, and had, in the Willys Americar, proven to be rugged and reliable.

Land vehicle Vehicle Car Off-road vehicle Jeep

The Willy Quad was tested by many groups, but the report of the Army's Infantry Board is representative of them all:
"Willys performance was superior to that of Bantam and Ford in acceleration, maximum speed, grade climbing, and cross country."

The War Department needed many cars quickly, so Willys-Overland granted the United States Government a license to allow other companies to make them. Ironically, American Bantam, the creators of the first Jeep, spent the rest of the war building Army trailers.

Willys-Overland and Ford turned out over 650,000 jeeps, one every other minute. Nearly 30% of it was supplied to allies.

The origin of the name "Jeep" remains a topic of debate (see our history of the name).

When General George Patton's armored divisions raced across France the lead vehicle, in front of the foremost tanks, was often a Jeep. It was in the Ardennes during the Battle of the Bulge, in New Guinea, the sands of the Sahara, and the snow of Iceland.

The MA and MB was a reconnaissance vehicle, a frontline ambulance, a mobile command post. Jeeps hauled planes to dispersal bunkers; soldiers raced them uphill and climbed forty per cent grades. As illustrated in a famous cartoon by Bill Mauldin, the Jeep even provided hot radiator water for shaving.
In the Philippines, a Jeep with flanged wheels pulled a fifty-two-ton supply train for nineteen miles at twenty miles an hour.

Jeeps were modified for long-range desert patrol, snow ploughing, telephone cable laying, saw milling, and fire fighting (with pumps); stateside farmers would use it as a tractor. Jeeps could be loaded into transport aircraft for rapid deployment and were small enough to fit into the large gliders used in the D-day invasion of Europe.

Land vehicle Vehicle Motor vehicle Car Jeep

One of the most dramatic Jeep offensives was an attack on enemy aircraft was led by David Stirling, the "Phantom Major." Each jeep was armed with four Vickers "K" machine guns capable of firing one thousand rounds a minute. Formed in a flying wedge, the Jeeps charged out of the desert onto an airport at Sidi Haneish, all guns blazing. After one complete circle of the airfield, they attacked planes on the perimeter; then they roared away into the desert. Just 75 men, on 18 Jeeps, destroyed 25 planes and damaged a dozen more.

Jeeps MBs were used by every division of the U.S. military and supplied to every infantry regiment.

Land vehicle Vehicle Car Jeep Truck

Willys MA and MB: the original Willys Jeeps

Only 1,500 of the first Willys Jeep production model, the Jeep MA, was produced, in 1940 and 1941. The second and final wartime version, the Jeep MB, was built by Willys-Overland in Toledo from 1941 to 1945. Ford versions were designated "Model GPW" (G = government vehicle, P designated the 80" wheelbase, and W = the Willys engine design).

Land vehicle Vehicle Car Jeep Motor vehicle

The Fords had every component (including bolt heads) marked with their monogram; Willys followed this by stamping its name into some body parts until the governmet put an end to it, around 1942.

The two had slightly different frames, and Ford used a torque reaction stabilizer spring under the left spring (as did some Willys units); Ford engines used studs instead of bolts for connecting rod bearing caps (the rods were the same).

Ford also made a few amphibious jeeps, the model GPA, or "Seep" (Sea Jeep), but it was not good off road nor in the water, and the government used on GM's amphibious design instead.

The Jeep continued to be improved. Willys switched to a standard government 2-H 6-volt battery, moving the hand brake, and changed the driving lights, tie rods, and spring shackles, while adding more seals. There were field improvements for winter and desert conditions, including oversized tires, surge tanks, and better heating, cold starting, and engine cooling. Upgrades were made so it would be easier to work with 12-volt radio equipment.

Land vehicle Vehicle Car Jeep Motor vehicle

Accolades for the MB continued to pour in during and after the war; according to General (soon to be President) Dwight D. Eisenhower, "America could not have won World War II without it."

Before the fighting was over, the Department of Agriculture had already begun publicizing Jeep solutions to farm labor problems, since the Jeep could plow, harrow, or disc; plant corn or cotton, all on one gallon of gas to the acre (claims that were exceeded in practice). Civilian desire to own a Jeep was widespread by the time the first ex-combat vehicles were put on the market in November 1943.

At the end of the war, production ran to 2,642 from Bantam, 350,000 from Willys, and 290,000 from Ford. Willys had done quite well, despite the Army's concerns. Ford used six plants across the country, from New Jersey to California. The high production led to much greater use of the Jeep in combat that original plans called for.

Land vehicle Vehicle Car Mode of transport Jeep

Willy sought a trademark on the name "Jeep" in 1943; it was opposed for years, and in 1947, Bantam sued Willys to stop using the term, since Bantam had created the concept. Willys won and, in 1950, finally gained the trademark in the US.

The first post-war Jeep was the prototype Jeep CJ-1A (CJ stands for Civilian Jeep); the production model, Jeep CJ-2A, was unveiled in August 1945, at $1,090. Closely based on the Jeep MB military design, it was manufactured under the "CJ" designation until 1986. At that point, there were many changes, and the key Jeep was renamed "Wrangler." Today, the Jeep is much, much heavier and more powerful than the original, not to mention far larger, but still has similar versatility in mind - and still has the removable doors and a fold-down windshield.

Motor vehicle Vehicle Car Vintage car Classic car

Matthew Parij wrote,

Mitsubishi acquired the rights to locally produce the Jeep CJ-3 in Japan around 1948, and did so for fifty years, finally ceasing production in 1998. They adapted the Willys Go-Devil and Hurricane engines into diesel engines (KE31 and KE36, respectively) for their Fuso medium-duty truck and bus line, and kept those versions going until at least 1965.
Auto part Engine Vehicle Fuel line Car

The basic Jeep was modified, upgraded, and enlarged for later military use, resulting in, among others, the Jeep M38 (1950-52) and M38A1 (1955-1963).

The utilitarian looks of the original Jeep have been hailed by industrial designers and museum curators alike. The Museum of Modern Art described the Jeep as a masterpiece of functionalist design, and has exhibited one as part of its collection. The famous WWII news correspondent Ernie Pyle called the Jeep, along with the Coleman G.I. Pocket Stove, "the two most important pieces of noncombat equipment ever developed."

Motor vehicle Vehicle Car Steering wheel Classic car

Motor vehicle Vehicle Car

There is no mistaking the Jeep; it was the inspiration for the sport utility vehicles of Land Rover, Toyota, Nissan, Mitsubishi, Suzuki, Mahindra, and AM General. The mystique and unique place of the Jeep as a rugged, versatile, and nearly indestructible World War II legend remains… the love affair with the brand continues.

The original Jeep MB can be seen on display at the Smithsonian Institution in Washington D.C., the General MacArthur Memorial and Historical Center in Norfolk, Virginia, the Chrysler Museum in Auburn Hills, and the Jeep House in Toledo, Ohio, the original site of the Willys-Overland factory.

Land vehicle Vehicle Jeep Motor vehicle Car

Jeep MB Specifications
Power: 60 hp @ 4000 rpm (54 net hp); 105 lb-ft (95 net) @ 2,000 rpm
3.125 x 4.375 bore x stroke, 6.48:1 compression ratio
Champion or AutoLite spark plugs, .030 inch; Carter WO-539S downdraft carburetor
Borg & Beck 11123 clutch with a Warner T-84-J gearbox
First gear: 2.665, second 1.564, top 1.0; Reverse 3.554, OTGR 4.880 / 9.614
Spicer ovoid axle,
hypoid-bevel final drive, 30-35 psi in 6.00/16 tires

Ladder type frame
Four-wheel Bendix hydraulic brakes with a parking brake on the transfer case
80" wheelbase; 131-132 inch length; 62 inch wide, 8.25 inch ground clearance
Curb weight, complete, ~ 2,453 lb.
Max trailer load, 1,000 lb; payload, 800 lb

Dig into the genesis of the Jeep with Curtis Redgap's "The Bantam Jeep"

The 2018 Jeep Wrangler JL: suspension aluminum vs steelopen or fixed roof pickup
body engineering
weight, strength, and safetytransmissionsengines


Chrysler 1904-2018

Spread the word via <!--Tweet or--> Facebook!

We make no guarantees regarding validity or accuracy of information, predictions, or advice - .
Copyright © VerticalScope Inc. All rights reserved. Dodge, Jeep, Chrysler, Ram, and Mopar are trademarks of Fiat Chrysler Automobiles.

1 - 1 of 1 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.