Museo Galileo
Virtual Museum
Balance beam
Balance beam

Metal or wooden bar, usually divided into two parts of equal length and size. The ends of the beam are fitted with the hooks or grommets for the ropes or chains holding the pans. The center of the beam may carry the fork and the index. The surface of the beam arms must be smooth and even; they must be of similar shape and equal weight, and sturdy enough not to bend when the weights are placed in the pans. For this reason the beam is thicker to the right and left of the suspension point. For the scales to operate properly, both parts of the beam must have exactly the same weight.