contrapeso

Contrapeso, or counterweight in English, is a weight used to balance another weight or force in a mechanical system. By providing an opposing gravitational force, a contrapeso helps reduce the net torque required to move a load, improving control, stability, and energy efficiency. It is used in a variety of contexts, including vertical transport (elevators and escalators), cranes and hoisting devices, and stage rigging systems in theaters.

In mechanical systems, the counterweight is connected to the moving element by a rope or chain and runs over pulleys. When the load increases, the counterweight rises or falls to maintain balance; if the counterweight matches the moving load, motor effort is mainly used to overcome friction and inertia. Counterweights can be fixed or adjustable, and some configurations use multiple weights to fine-tune balance.

In theatre, contrapesos are part of a counterweight fly system. They are loaded into a counterweight arbor and balance the lift lines so scenery, curtains, or props can be raised and lowered safely by stagehands or automated mechanisms. This setup relies on careful load calculations, proper locking mechanisms, and regular safety inspections.

Design and safety considerations include selecting a counterweight mass to balance the expected load plus a safety margin, ensuring compatible hardware (arbors, cables, pulleys, hoists), and implementing procedures for routine maintenance and inspections. Properly designed contrapesos reduce motor load, minimize motion irregularities, and enhance overall control while reducing the risk of uncontrolled movement or equipment failure.