Platform Scale: Four Knife-Edge Hinges and Two Levers to a Steelyard (Fairbanks, 1831)

A scale for wagons and carts, reading the same wherever the load stands. Erastus and Thaddeus Fairbanks of St. Johnsbury, Vermont, patented it in 1831. A plank platform nine by twelve feet rests on four knife-edge hinges, one at each corner, and two levers gather the load from all four onto one rod. The rod pulls on an ordinary steelyard, which then reads only a tenth or a twentieth of the load. Result: a platform scale reading ten times (or twenty times) what the steelyard shows, the same wherever the load stands on the platform. Source: E. & T. Fairbanks, US Patent No. 118 (1837), restating their patent of 13 June 1831. Unknown: the material and sizes of the hinges, knife-edges, fulcra and levers. Picture: patent drawing.