How to Build a Pulley Car for a Science Project

A pulley is a system consisting of generally one or two wheels attached by a strap or rope. This system reduces the amount of work needed to lift or move an object. It can also be used to rotate wheels to cause movement, such as in a vehicle. As a science project, students can create a pulley car to study the relationship between movement and pulleys.

Things You'll Need

  • Balsa wood
  • 4 small pulleys, with "O" rings
  • 1 small pulley without an "O" ring
  • 4 steel rods, 3 mm in diameter
  • 4 pieces of rigid plastic tubing ¼-inch in length and slightly larger in diameter than the steel rods
  • 1 solar motor (low friction)
  • 1 photovoltaic cell
  • 2 wires with crocodile clips
  • 1 rubber band
  • 1 small fine-toothed saw
  • Glue gun


    • 1

      Using the saw, cut the balsa (for the chassis) to the following dimensions: 6 inches x 2.5 inches. Cut a 1/4-inch-wide piece out of the rear end of the car. Cut this groove parallel to the length of the vehicle, about one inch in length, and down the center.

    • 2

      Glue the tube sections onto the wood. Place each piece parallel to the ends, ¼ inch in from each end. Project the tubes slightly past the sides of the rectangle, making sure each pair is directly opposite each other. Let dry.

    • 3

      Slide the "O" rings over the four pulleys (wheels). Push a rod (axle) through one rear tube section and slip the fifth pulley and a rubber-band onto it before continuing to slide the rod all the way across and through the adjacent tube. Push the second rod through the front tubes; place the pulleys onto the ends of all four axles.

    • 4

      Glue the solar motor onto the top of the car base. Make sure it is positioned so that the spinning end is directly behind and parallel to the groove.

      Stretch a rubber band from the motor to the center wheel, fitting it into the grooves.

    • 5

      Affix the photovoltaic cell, using straps, onto the balsa wood. Place it in front of the motor, lengthwise to the car. Attach the cell to the motor using two wires and crocodile clips.

Tips & Warnings

  • Use a 9-volt battery instead of a photovoltaic panel.
  • The bottom (chassis) of the car can be made out of a lightweight material other than balsa: corrugated cardboard or a sheet of plastic.
  • Saw blades have sharp teeth. Be cautious when cutting the chassis.
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  • Photo Credit pulleys image by Galyna Andrushko from

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