BEAM (AS. bedm. Ger. baum, tree). In engineering and architecture, a long piece of wood, stone, or metal used in a horizontal posi tion to support a weight. Timber beams are usu ally rectangular in section, and may consist of one large piece of timber or of several smaller pieces joined, butted, or spiked together. Beams of steel or iron may be a single-rolled steel shape, such as an I-beam, or they may be composed of a number of suitable steel shapes riveted together to form a single structure. (See STEEL SHAPES; GIRDERS.) The term also has many special tech nical applications, as the beam of a weighing scale, the weaver's beam, the beam of a plow. In ship-building the beams are the strong, trans verse pieces of timber, iron, or steel, stretching aeross a ship from side to side to support the decks and retain the ship's sides at their proper distance. For this reason the term is used to de note the widest part of a vessel's hull. The ends of a vessel's beams are supported by clamps and knees, and the centre by stanchions. The beams are given a crown in order that the decks may have a slight convexity to shed water. A built up beam is formed of smaller beams, notched, scarfed, and bolted together. Cellular beams are formed of wrought-iron plates riveted together with angle-irons in the form of longitudinal cells, with occasional cross - stubs. Composite
beams are composed of wood and metal, or of two different metals. Beefed beams have slits in one side, made by saws, in order to facilitate bending the beam in that direction.
On the beam is an expression applied to any point or object at right angles to the keel, and is known as on the starboard, or port, beam, accord ing to the side of the ship. On the weather beam is on the weaiher side of the ship, and on the lee beam. is on the lee side. Forward or abaft the beam is the bearing of any object when seen in advance of, or astern of, a bearing on the beam. On her beam ends is the position of a ship that heels over so much to one side that her beams ap proach a vertical position; hence, to be on one's beam ends is to be thrown or lying on the ground, or to be in had circumstances. Beam also means the oscillating lever of a steam-engine vibrating about a centre, and forming the medium of com munication between the piston-rod and the crank shaft; also called wo•king-beam or walking-beam.