Alden Research Laboratory Rotating Boom

The idea of constructing a rotating boom for hydromechanical tests at the Alden Hydraulic Laboratory originated with Professor Charles Metcalf Allen, head of the lab from 1896 to 1950. The original boom was designed in 1908 by Professor Allen, assisted by two Worcester Polytechnic Institute students. Professor Allen needed a moving test stand for hydraulic experiments and for rating current meters. A circular test apparatus was chosen over a towing tank because the former: (a) was much less expensive to construct, (b) allowed longer test runs, and (c) enabled larger objects to be tested without experiencing boundary effects from channel sides. The original boom was constructed of wood on a submerged rock foundation located about 45 feet from shore in a pond adjacent to the Alden Hydraulic Laboratory in Holden, Massachusetts. This boom had a 42-foot testing arm balanced by a 21-foot arm loaded with counterweights. Rotational power was supplied by a 24-inch Hercules water turbine located onshore. The power from the turbine was transmitted to the boom through a rope and pulley drive system, producing tip speeds of up to ten feet per second. In 1911, the original boom was replaced by an equal-arm, 84-foot steel boom. The turbine drive system was replaced in 1936 by an electric motor located at the center of the boom, which increased the maximum tip speed to 20 feet per second. The boom has been used periodically since 1936 without any major changes.