Page:Popular Science Monthly Volume 89.djvu/75

 An Excavator Which Walks

��A BIG excavating machine which literally walks to its job is being used by the United States Govern- ment on one of the great irrigation proj- ects of the Southwest, and the advantages (if this pedestrian accomplishment are ni.iny. Most of the machines of this character arc built to roll over the ground on wheels, but its movements are neces- sarily limited, for it dare go only where the ground has been carefully prepared for it. l^nless the ixith is most favorable, planks must be carried ahead and laid for it to move over. Otherwise the wheels would tear up the road and such a thing as making a short cut across the country would be out of the question, for it would soon be hopelessly stalled and its . extrication only made possible by remov- ing it piecemeal. In fact, this is the way in which these machines are generally transported from one job to another. They are taken apart and transported in convenient parts and reassembled at the

��new point in the field of operations.

This perambulating excavator will "walk" al(jng the road without any re- gard to the character of its structure and not leave a footprint behind; and further- more, if the road does not happen to be the shortest route, the machine will walk across country over soft ground which will barch- hold a man. If a house, tree, or hill hajjpens to be in the way this machine will walk around it, covering the ground at the rate of twenty-five or thirty feet a minute, a very respectable speed for such a lumbering sprinter.

When the digger is at its regular work of excavating, it rests on a heavy central platform on which it is revolved so that activities of the bucket may be accurately controlled. When it is de- sired to have the machine move, the engine is connected with a dri\ing-shaft extending across the width of the excavator. On each end of this, outside of the house of the operator, are

���Two footlike pieces are suspended beneath the cams on either side of the driving-shaft. In moving, the feet arc Ufted and lowered alternately, producing a steady, deliberate walk. To change the course of the machine, it is turned when resting on the central revolving platform

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