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How to Make a Double Pan Balance Scale

A double-pan balance or scale is also called a beam balance. It isn't difficult to construct one, and the process of making and using a double-pan balance can help your children to understand scientific concepts such as mass, weight and size, as well as the arithmetic needed to calculate the weight of an item by comparing it to other items of known weight. A simple double-pan balance scale can be made out of common household items.

Things You'll Need

2 plastic lids
Hole punch
Scissors
String
Ruler
Drill
Cupboard door
Carpenter's level

Instructions

- 1
  Mark three equidistant spots at the rim of each plastic lid. Punch a hole at each spot.
- 2
  Cut six 12-inch lengths of string. Tie one end of a 12-inch piece of string in each hole. Gather up the three strings on one lid and tie them together at the free ends. Repeat on the other lid.
- 3
  Find the exact center of the ruler and drill a small hole at that spot. Thread a 20-inch piece of string through the hole and tie the ends together.
- 4
  Locate an upper cupboard door with a level bottom edge, using a carpenter's level. Open the door and hang the loop of string tied to the ruler over the handle of the door, so that it hangs freely from the door. Shorten the string if it is too long.
- 5
  Cut two 6-inch pieces of string. Insert one through the three strings tied to a plastic lid and tie the ends of the 6-inch string together to make a loop. Repeat with the other 6-inch string and the other plastic lid. Hang one loop at each end of the ruler, so that the plastic lids are hanging from the rule by means of the 6-inch loops.
- 6
  Calibrate the scale by sliding the loops of string on the ends of the ruler either closer to the center or closer to the end of the ruler until the ruler hangs parallel to the bottom of the cupboard door.

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