How to Make a Counterbalance With Pulleys

Counterbalances are invaluable in the construction of vertically moving components in a variety of applications, from attic doors to medieval catapults. Their primary purpose is to increase the ease of motion of heavy objects by balancing the load across a pivot point. One of the most efficient ways to create a counterbalance is by using a pulley counterbalance system. Pulleys provide a ready-made pivot point and are made in a variety of sizes to suit any job.

Pulley cord or rope

Instructions

- 1
  Determine the weight for your counterbalance. For commercial, high-use applications, you should determine the counterweight's necessary mass by multiplying the weight of the object being counterbalanced by the length of the string or support cable you will use. For more basic applications, a counterbalance with a weight three-fourths that of the object being counterbalanced is sufficiently accurate.
- 2
  Create your counterbalance. The material for your counterbalance will vary depending on your intended use. For simple, residential jobs, an iron billet or a canvas bag filled with sand are excellent options.
- 3
  Mount your pulley, following the manufacturer's instructions. Most pulleys are mounted using a system of bolts, which should be fixed into ceiling joists or other load-bearing components. Attach the pulley slightly off-center of the object you intend to counterbalance.
- 4
  Attach a pulley cord or rope to the object you intend to counterbalance. The specific mounting technique should be determined by your specific job.
- 5
  Thread the chord through the pulley and pull it until taut.
- 6
  Trim off any excess cord. When the counterbalance is complete, the counterweight should dangle slightly off the ground at all times.
- 7
  Attach the free end of the cord to the counterweigh.

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