Lockheed Twister

The Lockheed Twister was an experimental eight-wheeled, two-body articulated vehicle developed by Lockheed Missiles & Space Company in the 1960s. It led to the US Army's XM808 prototypes, one of which was set up to test amphibious capability.

Origins

In the early 1960s Lockheed studied the limits of military combat vehicles as part of a plan to diversify beyond aerospace. Its studies concluded that no single-body vehicle could greatly increase cross-country speed while keeping a tolerable ride and a stable weapons platform. Lockheed's answer was an eight-wheel-drive vehicle in two bodies, joined by a patented pivot yoke that gave freedom in pitch, roll and yaw. The front body worked as one large walking beam, and the rear body had independently sprung walking beams. Steering combined Ackermann front-wheel steering with powered yaw of the joint. The company funded the project itself from February 1965 and rolled out a full-scale testbed in October 1965.

Testbed

Each body carried its own identical power train with no mechanical link between them, and all wheels were driven at all times. The testbed used two stock Chevrolet Corvair six-cylinder engines, with modified carburettors and oil pans for steep slopes, each driving an Allison automatic transmission. The power-to-weight ratio exceeded 50 hp per ton. As refurbished in 1968 it weighed 11,400 lb (about 5,170 kg) and was 16 ft 2 in (4.93 m) long and 8 ft 7 in (2.62 m) wide. It reached 65 mph (105 km/h) on roads, accelerated from 0 to 40 mph in 17 seconds and climbed 30 in vertical steps. To save time and money, the waterproofing that a production military vehicle would have was left out.

Over three years the testbed covered more than 400 miles of hard testing, gave 121 formal demonstrations and was driven by more than 525 guest drivers. After its public debut in June 1968 it toured US Army and Marine Corps bases. The Army then ordered three development vehicles.

XM808

The Army's XM808 was larger, about 10 tons against 5.5. It replaced the Corvair engines with two 291 hp Chrysler 440 cu in V8s. Three prototypes were built and tested from 1971, and one was equipped to test amphibious operation. They performed well, but historian Fred Crismon judged the vehicle "overkill" as a scout, with the twin power trains too costly and hard to maintain. At least one XM808 survives at the Detroit Arsenal in Warren, Michigan. Much of the technology went into Lockheed's Dragon Wagon 8x8 truck.