how to make working model that converts circular motion to linear motion

Introduction to Converting Circular Motion to Linear Motion:

Converting circular motion to linear motion is a fascinating engineering concept used in various machines and mechanisms.

This process involves transforming the rotational movement of a circular object into a straight-line motion.

Let’s explore the basics of how this conversion works:

Understanding Circular and Linear Motion:

  1. Circular Motion:
    • Circular motion involves an object moving in a circular path around a fixed point, like a spinning wheel or the rotation of a gear.
  2. Linear Motion:
    • Linear motion is the straightforward movement of an object in a straight line, like pushing a cart or sliding a drawer.

Conversion Mechanisms:

  1. Crank and Slider Mechanism:
    • One common method for converting circular motion to linear motion is the crank and slider mechanism. It consists of a rotating crank (circular motion) connected to a slider (linear motion) that moves back and forth.
  2. Cam and Follower System:
    • In a cam and follower system, a rotating cam imparts motion to a follower, resulting in linear movement. The shape of the cam determines the pattern of linear motion.
  3. Rack and Pinion System:
    • A rack and pinion system involves a rotating gear (pinion) engaging with a flat bar with teeth (rack). As the pinion turns, it moves the rack in a linear direction.
  4. Screw Mechanism:
    • A screw converts rotational motion into linear motion. When a nut is threaded onto a screw and the screw is turned, the nut moves along the screw, creating linear displacement.


  1. Automotive Steering Systems:
    • Rack and pinion systems are commonly used in car steering mechanisms. As the steering wheel (circular motion) turns, it converts the rotation into the linear movement of the wheels.
  2. Reciprocating Engines:
    • Crankshafts in reciprocating engines convert the circular motion of the pistons into linear motion. This linear motion drives the up-and-down movement of the pistons.
  3. Conveyor Belts:
    • Conveyor systems often use rotating drums with a threaded screw mechanism. As the drum turns, it moves the conveyor belt linearly, transporting materials from one place to another.
  4. Machine Tools:
    • Many machine tools, such as lathes and milling machines, involve converting circular motion from the motor into the linear movement of cutting tools or workpieces.

Why Conversion Matters:

  1. Efficiency:
    • Converting circular motion to linear motion allows for efficient and controlled movement in various mechanical systems.
  2. Precision:
    • In applications like machining or robotics, the ability to precisely control linear motion is crucial for achieving accurate results.
  3. Versatility:
    • This conversion concept provides versatility in designing machines and mechanisms, enabling engineers to tailor movements to specific needs.

Creating a working model that converts circular motion to linear motion can be both educational and enjoyable.

Here’s a step-by-step guide to help you build a simple model using materials commonly found at home:

Materials Needed:

  1. Cardboard
  2. Pencil
  3. Ruler
  4. Scissors
  5. Small wooden dowel or a pencil
  6. String
  7. Small pulley or spool
  8. Tape
  9. Hot glue gun or regular glue
  10. Small weight or object for tension (e.g., a small bag of sand or a weight)

Video Step by Step Procedure:

circular motion to linear motion working model – physics science project diy | howtofunda

1. Prepare the Base:

  • Take a piece of cardboard and cut it into a rectangular shape to serve as the base of your model.

2. Attach the Dowel:

  • Attach a small wooden dowel or a pencil to the center of the cardboard. This will act as the axis for circular motion.

3. Create a Rotating Disc:

  • Cut out a circular disc from cardboard. You can use a compass to draw a circle or find a circular object to trace. Make a hole in the center of the disc.

4. Attach the Disc to Dowel:

  • Slide the circular disc onto the dowel, making sure it can rotate freely. You can secure it with glue or tape.

5. Add a Pulley or Spool:

  • Attach a small pulley or spool to the edge of the rotating disc. This will be the point where circular motion is converted to linear motion.

6. Attach a String:

  • Tie a string to the pulley or spool. The other end of the string should be connected to a small weight or object for tension.

7. Observe Linear Motion:

  • As you rotate the circular disc, observe how the string is pulled, causing linear motion in the weight or object.

8. Discuss the Principle:

  • Explain to observers that the circular motion of the rotating disc is being transformed into linear motion by the string connected to the weight.

9. Experiment with Different Pulley Sizes:

  • Try using pulleys or spools of different sizes to observe how it affects the linear motion. Discuss the concept of gear ratios.


The conversion of circular motion to linear motion is a fundamental principle in engineering, playing a vital role in countless applications.

Whether in steering systems, engines, or manufacturing processes, the ability to translate rotational movement into straight-line motion is a key factor in the functionality and efficiency of many mechanical systems.

Leave a Comment