Oruktor Amphibolos

The Oruktor Amphibolos ("amphibious digger") was a steam-powered dredge built by the American inventor Oliver Evans in Philadelphia in 1805. Evans himself claimed it was the first self-propelled amphibious vehicle in the world, and the first self-propelled land vehicle in the United States.

Origins

The Philadelphia Board of Health wanted a way to dredge and clean the city's docks. Evans persuaded it to order a steam dredge from him. His workshop stood some way inland from the river. He also wanted to prove his long-held view that steam could drive vehicles on land. So he put the hull on four wheels and, by his own account, drove it under its own power through the streets and around the town square, down to the Schuylkill. Once afloat, a paddle wheel at the stern drove it downstream to the dredging site.

Design

No drawings survive. Everything known comes from Evans's own descriptions, which contradict each other and are probably exaggerated. He described a flat-bottomed scow about 30 ft (9.1 m) long and weighing about 15 tons, driven by a 5 hp steam engine of his own design. The engine could turn two of the wheels, the stern paddle or the dredging gear. Later historians doubt that such a small engine could really have moved so heavy a machine overland. Accounts agree that it handled well in the water but was awkward to steer on land.

Fate

The Oruktor did not succeed as a dredge. It lay at the dock for some years before being broken up and sold for parts. Evans kept writing about it, and the claims grew with each telling. He later "corrected" the date to 1804, possibly because of a steamboat patent dispute, and that mistake has been repeated ever since. An engraving of the machine appeared in The Boston Mechanic and Journal of the Useful Arts and Sciences in July 1834.