DERRICK (from D. (Tick, a Tyburn hang man). A device for hoisting heavy load, and •Tivvying them short distances. In ordinary nomenclature the distinction between derricks and is eonsiderably confused. The most common form of derrick consists of a %•rtical mast pivoted at it bottom into a fixed bed-plate and maintained in an upright position by guy cables or other forms of stays, which radiate trout a loose collar or spider encircling a pin in the top of the mast: of a boom hinged to this %ertical mast near the bottom so that it may be made to assume various inclinations relative to the mast. and of the tackle and motors neces sary to impart motion to the boom and mast and to the load which they carry. The load is suspended from the end •4 the boom by rope.' which pass through a block and thence to the motor at the foot of the mast. The end of the boom is sustained by a cable pa—ing through it block at the top of the mast and thence to the motor at it foot. The mast i, revolved on its bottom pivot by means I if a horizontal wheel around a rope passes or by other mechanism. The motions permitted by such a derrick are the vertical hoisting of (lie load. a swinging motion through the rotation of the shaft on its pivot, and a radial motion due to the eliairte in inclination of the boom. Per
haps the most salient dist MOM!' derrick and a crane that the boom of the der rick is hinged at its connection with the mast. %Odle the of a is always rigidly eon n•eted with the npright member. If this dis tinction is maintained in classifying these two conveying devices, how ev•r. it throws many devices now. Balled derricks into the class of cranes. of the type are extensively employed in quarrying, masonry work. exeavating, and building erection. line of the largest in the world lo cated at the .1vondale Nlarble Onarries at Ches ter, Pa.. ;Intl will hoist a load of The general of this d•rriek are as follows: Length of mast. feet : length of boom, 901. feet : the mast is :II inches square at the base and 21: inehes in diameter at the top: and the boom is 25 inches and 21 inches in diameter at the two ends. The main hoi.ting-rope is in diameter and is made of crucible-step' wire. The mast and boom are Oreglm fir. For lloating derricks; see CRANE.