The tri-star is a novel wheel design—originally by Robert and John Forsyth, assigned to Lockheed in 1967—in which three wheels are arranged in an upright triangle with two on the ground and one above them. If either of the wheels in contact with the ground gets stuck, the whole system rotates over the obstruction.

Design

In the tri-star wheel, all three satellite wheels are simultaneously powered through a mechanical linkage between each satellite wheel and a shaft concentric with the central hub. In the original patent, the direction of the vehicle is controlled through the

differential steering Differential steering is the means of steering a land vehicle by applying more drive torque to one side of the vehicle than the other. Differential steering is the primary means of steering tracked vehicles, such as tanks and bulldozers, is als ...

Applications

Lockheed modified an M2A2 105mm Light Howitzer and produced it from 1969-1977 with a drive unit and tri-star wheel system into an Auxiliary Propelled Howitzer they termed "Terra Star." The only surviving prototype is located at the

Rock Island Arsenal Museum The Rock Island Arsenal Museum in Rock Island County, Illinois is based around the history of Rock Island Arsenal. It is the second oldest museum of the United States Army, the oldest being the Museum at West Point. History There have been two mus ...

. Its most famous application was the

Landmaster The Landmaster is a unique 12-wheeled amphibious articulated vehicle constructed by Dean Jeffries at Jeffries Automotive in Universal City, California, for the 1977 science fiction film ''Damnation Alley''. Despite the appearance of two Landmaste ...

, a unique armoured personnel carrier (APC) from the 1977 film ''

Damnation Alley ''Damnation Alley'' is a 1969 science fiction novel by American writer Roger Zelazny, based on a novella published in 1967. A film adaptation of the novel was released in 1977. Plot introduction The story opens in a post-apocalyptic Southern Ca ...

''. Its common application is employed as a

stairclimber A stairclimber is a type of trolley fitted with rotating wheels or tracks so that it can be pushed or pulled up or down steps or a stairway. Stairclimbers can be manual or battery-powered, and are commonly found in wheel, track, push arm or walk ...

Gallery

File:M2A2 Terra Star 105mm Auxiliary Propelled Howitzer front quarter.jpg, Front quarter view of the M2A2 Terra Star 105mm Auxiliary Propelled Howitzer File:M2A2 Terra Star 105mm Auxiliary Propelled Howitzer carriage.jpg, Rear quarter view of the M2A2 Terra Star 105mm Auxiliary Propelled Howitzer File:Stairclimber.jpg, Stairclimber hand-truck with tri-star wheels

References

External links

Various tri-star vehicles

Tri-star wheels built with Lego
{{Dead link, date=July 2022 * M2A2 Terra Star (in Russian)
An article on M2A2 Terra Star

Short entry in the May 1968 issue of Popular Science (page 86)
American inventions Wheels