Engineering:M422 Mighty Mite

Short description: 4x4 utility truck

M422 Mighty Mite
Initial series M422, with 65-inch wheelbase
Type	​1⁄4 ton (227kg) 4x4 utility truck
Place of origin	United States
Production history
Manufacturer	American Motors Corporation
Produced	1959–1962
No. built	1,250 (+ 2,672 M422A1)
Variants	M422A1
Specifications
Mass	1,700 lb (770 kg) empty
Length	107 in (2.72 m)
Width	61 in (1.55 m)
Height	59 in (1.50 m)
Engine	107.8 cu in (1.8 L) 55 hp (41 kW)
Suspension	independent with leaf springs
Operational range	225 mi (362.1 km)
Speed	62 mph (100 km/h)

The AMC M422 'Mighty Mite', or G-843 by its supply catalogue designation , is an extra lightweight ¼-ton 4x4 tactical truck, designed for the United States Marine Corps, to be suitable for helicopter airlift and manhandling. It is also noted for its exceptionally short length, and resulting very tight turning circle, while still highway approved for a top speed of 55 mph (89 km/h) (U.S. military), and capable of 65 mph (105 km/h) according to AMC.

During World War Two, many prototypes were already developed for a ​¹⁄₄‑ton jeep, that was still significantly lighter and more compact than the U.S. Army's lightest, all-terrain, all-purpose vehicle at the time, the Willys ​¹⁄₄‑ton jeep. They were intended for transport in small (glider) aircraft and such, but none went into full production. However, after the war, a self-taught engineer, pilot, and auto racer, Ben F. Gregory conceived a mini-jeep design and built a successful prototype, later named the 'MM-100'.

During the 1950s, it was further developed by the Mid-America Research Corporation (MARCO), including four of the former American Bantam engineers who designed and built the ​¹⁄₄‑ton jeep's first prototypes; together with American Motors Corporation. It was intended to be liftable, underslung the strongest helicopters of the era, the Sikorski H-19 being the benchmark, but development and certification of the M422 took through 1959, and when the M422 debuted, it coincided with the adoption of helicopters like the Bell UH-1 “Huey” with much more carrying capacity, and except for parachute airdrops, the vehicle quickly became obsolete. From 1959 to 1962, just under 4,000 of the M422 Mighty Mites were built by American Motors for the U.S. Marines.

History

The Mighty Mite was first conceived in 1946–47, by self-taught engineer, pilot, and auto racer from Missouri, Ben F. Gregory. Gregory designed several front-wheel drive cars after World War I but was unsuccessful in marketing them, so he turned to commercial aviation, but a crash in 1942 ended his flying career. Recovering from serious injuries, he became an aircraft inspector. After the end of World War II, Gregory found new investors and turned again to front-drive cars, this time culminating in a fully driveable prototype—an innovative 1947 rear-engined, front-drive compact car, the Gregory Sedan. No carmaker was interested in his car, but he was inspired to use some of its design features, such as leading- and trailing-arms suspension, in a more modern four-wheel drive off-road vehicle, or jeep, and he found additional investors willing to fund a prototype.

One investor arranged a 1951 demonstration for the United States Marine Corps (USMC) Equipment Board, that went so well that the investors quickly formed the Mid-America Research Corporation (MARCO), to fully develop the vehicle for military or commercial markets. That same year, MARCO presented it as the MARCO MM-100, making it the first clean-sheet ​¹⁄₄‑ton jeep to be designed for the U.S. military after World War II. The USMC executed a contract for ten test vehicles in August 1951, the vehicles were delivered in December 1952, and the USMC immediately began the test program. For further development, the company decided to hire Harold Crist, American Bantam's original chief engineer on designing the first ​¹⁄₄‑ton jeep. Joining on 1 January 1953 as project manager, Crist brought with him three of the main men who had worked on the original Bantam jeep: Chet Hempfling, Ralph Turner, and Frank McMillan, so from then the team included four of the original WW II Bantam jeep's engineers. But Gregory, in turn, was eventually forced out of the company.

The MM-100 used a 44 hp (33 kW), 79 cu in (1.3 L) flat-four engine from the "S" version of the Porsche 356, but this choice proved problematic, as using a foreign-built engine would violate regulations requiring U.S.-built equipment in U.S. military vehicles. Attempts were made to substitute the Lycoming O-145, an American aircraft engine, but it was deemed too expensive and difficult to adapt to a ground vehicle. A solution presented itself when MARCO discovered that American Motors Corporation (AMC) was developing a lightweight, air-cooled 50 hp (37 kW), 95 cu in (1.6 L) V4 engine for a proposed economy car to be sold under AMC's Nash Motors brand. AMC quickly took a strong interest in the MM-100 because it needed a new product to keep a former Hudson commercial vehicle plant operating, and by 1954, AMC had completely taken over the project.

Problems were encountered with the designers' decision to save weight by not using a conventional exhaust system. The prototype did not have a muffler or pipe – rather the exhaust was routed through some frame tubes. This proved to be an inferior design because the condensation and acidic fumes caused premature frame failure. A competing prototype by Willys, the 1953 Bobcat or "Aero Jeep", which would share as many parts as possible with the M38 and M38A1 to save costs, was rejected in favor of the more advanced M422. In April 1958, AMC and the USMC executed a contract for delivery of 250 production M422 vehicles contingent upon successful trials of the first seven.

Although the vehicle was to be used only by the U.S. Marine Corps, and it was therefore clear from the beginning that production numbers would remain limited, the vehicle was extensively engineered and incorporated many innovations.

Engineering

M422 Mighty Mite, 65-inch wheelbase with the early thin windshield

M422A1 Mighty Mite, 71-inch wheelbase

Gregory car and M422 suspension

Gregory's designs cantilever ¼-elliptic leaf-springs, clamped to the hinged base of each arm, extending inwards, opposite to each arm's length from its hinges to the wheel-hubs

The Gregory Sedan's plan view (bottom left) shows the car's 4-wheel independent suspension, using leading- and trailing-arm suspension, with the front-wheels' leading-arms laid closer to the car's center-line.

Photo of a correctly detailed M422 toy, showing the space-use under its floor, with the front arms' ¼-elliptic leaf-springs laid inside those of the rear trailing-arms

To keep the weight down, the M422 became the first U.S. jeep to be fitted with an aluminum body. At 1,700 pounds (771 kg), it is the lightest conventional U.S. military truck to date. Also, this was the first U.S. small military vehicle designed with independent suspension all around (front: leading arms/trailing arms rear), sprung by ¼-elliptical leaf springs. Among the M422's many other unique features were front and rear limited-slip differentials, inboard differential mounted drum brakes, center-point steering, and the aluminum "AMC AV-108-4" V4 engine developed by American Motors. The air-cooled 107.8 cu in (1.8 L) developed 52 bhp (39 kW) and 90 lb⋅ft (122 N⋅m) of torque, which propelled it to a top speed of 65 miles per hour (108 km/h), with a 55-mile-per-hour (89 km/h) military rating. As with the M151, the transfer case only engages/disengages the front wheel drive and is part of the transmission. The full synchronization meant it could be shifted from 2-wheel drive to 4-wheel drive on the fly.

Although basically a two-seater, the little vehicle could theoretically move six people, thanks to two additional fold-up seats that were integrated into the functional tailgate, as well as two folding backrests on the rear fenders. Also, the M422 was rated to carry 850 lb (390 kg) off-road, while all other standard GI 1/4 ton vehicles (even the M151) were rated at 800 lb (363 kg). And if needed, there was even a version of the M416 trailer specially adapted for towing by an M422: the M416B1.

Like other Marine Corps contract vehicles, the M422s came from the factory with all deep-water fording equipment installed, except for the pipes. In its early development stage the Marines developed a lightweight flotation kit that could easily be stored on the M442 when not in need, in which four large tubes inflated by exhaust encompassed the bottom part of the frame that allowed the vehicle to swim deeper waters. The vehicle's spinning wheels provided propulsion and steering in the water.

In 1958, seven prototypes passed grueling tests, and the first 250 vehicles were built by American Motors. These units went into mass production in 1960 and AMC built 3,922 Mighty Mites through 1962 for the U.S. Marine Corps. Over the years, the vehicle was produced in two model versions: the M422 and M422A1. The M422 had a tiny 65-inch (1,700 mm) wheelbase. After production of 1,045 units, the Mighty Mite evolved into the M422A1, six inches (152 mm) longer in both wheelbase and length, and 80 pounds (36 kg) heavier. The first Mighty Mites to have the 71" wheelbase were an experimental model fashioned from an M422. They had an extended, frame and aluminum added behind the seat and crudely fashioned tool storage boxes. This model was the M422E1 of which only a few were made. Once put into production the 71" wheelbase model was designated the M422A1. Either model could be fitted with rear-mounted spare tire and a sturdier windshield similar to the Willys M38A1 that, along with top bows, would facilitate the use of a canvas winter top. The addition of the rear-mounted spare tire rendered the tailgate unusable.

At over United States dollar 5,000 per unit, it was relatively expensive, and by the time the Mite went into full production, the military's helicopters had become so much more powerful that the vehicle quickly became obsolete. The Marine Corps' Sikorsky H-19 with its 2,650-pound (1,202 kg) cargo limit (including crew and fuel), for which the M422 had been developed, was being superseded by the Vietnam era UH-1 “Huey", that could carry more than 1½ times that load. These factors quickly rendered the Mite an obsolete, redundant supply chain complication, more expensive and largely less capable than a regular ​¹⁄₄‑ton jeep, which accounts for the short production time period, as well as the small production total.

Dimensions and weights

	M422	M422A1
Wheelbase	65 in (1,651 mm)	71 in (1,803 mm)
Length	107 in (2,718 mm)	113 in (2,870 mm)
Width	60 in (1,524 mm)
Weight	1,700 lb (771 kg)	1,780 lb (807 kg)

See also

• Crosley Farm-O-Road, a 1950 jeep-like, highway-legal utility vehicle that was under ten feet long
• The British Royal Navy equivalent solution in the same period was to use Citroen 2CV pickup trucks.

General references

• Crismon, Fred W. (2001). US Military Wheeled Vehicles (3 ed.). Victory WWII Pub.. pp. 221–222. ISBN 0-970056-71-0. 
• Doyle, David (2003). Standard catalog of U.S. Military Vehicles. Krause Publications. pp. 40–42. ISBN 0-87349-508-X. 
• Doyle, David (2011). Standard catalog of U.S. Military Vehicles (2 ed.). Krause Publications. pp. 37–39. ISBN 978-1-44022-799-8. 
• Ware, Pat (2010). The World Encyclopedia of Military Vehicles. Lorenz Books. p. 221. ISBN 978-0-7548-2052-9. 

External links

• Colwell, John. "M422 Mighty Mite Page". Vintage Military Trucks. http://www.vintagemilitarytrucks.com/M422%20Mighty%20Mite%20Page.htm. 
• "TM 9-2805-217-35 Field and Depot Maintenance Manual: Engine and Clutch - AMC MODEL AV-108-4". Department of the Army. May 1960. https://drive.google.com/folderview?id=0Bz-n7H_Ed9pDYTNiZjkyMWEtOTMwMC00OTJmLTkxMjctYWMwYjRmYmJkNDVl&usp=sharing. 
• Doyle, David (2003). "Quarter-ton Trucks M422". Standard catalog of U.S. military vehicles (Second ed.). Krause Publications. pp. 40–42. ISBN 9780873495080. https://books.google.com/books?id=Ljdma-SYU0gC&q=mighty+mite+military+vehicle&pg=PA42. Retrieved 17 August 2015. 
• Wenderoth, Jason (30 November 2005). "Jeeps Unlimited - The Mighty Mite". Jeeps Unlimited. http://www.jeepsunlimited.com/mambo2/index.php?option=com_content&task=view&id=54&Itemid=31. 
• "Mighty Mite". U.S. Veterans Memorial Museum. http://www.memorialmuseum.org/displays/military-jeeps/item/mighty-mite. 
• AMC M422 at the Internet Movie Cars Database
• Airborne Lightweight Jeeps Research Archives page