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Enlarger: How Does a Pantograph (a Machine Used To Change the Size of Drawings) Work?

Author: Janice VanCleave

Problem

How does a pantograph (a machine used to change the size of drawings) work?

Materials

  • scissors
  • ruler
  • cardboard box at least 2 feet (60 cm) wide and 2 feet (60 cm) high
  • adult helper
  • nail (10-penny)
  • 5 paper brads (round paper fasteners)
  • 2 marking pens
  • thumbtacks
  • large sheets of unlined paper (butcher paper)

Procedure

  1. Cut the following pieces from the cardboard box:
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    • two strips, labeled #1 and #2, each measuring 2 inches × 18 inches (5 cm × 45 cm).
    • two smaller strips, labeled #3 and #4, each measuring 2 inches × 10 inches (5 cm × 25 cm).
    • one 2-foot × 2-foot (60-cm × 60-cm) square.
  3. Position the four strips on the cardboard square, as indicated in the diagram.
  4. Ask an adult to use the nail to make holes in each piece of cardboard at positions A through F, as shown on the diagram. NOTE: C is the only one made through the cardboard square.
  5. Use paper brads to secure the paper strips together at positions D, E, and F.
  6. Use a paper brad to secure the paper strips to the cardboard square at position C.
  7. Place marking pens through holes A and B.
  8. Use thumbtacks to secure a piece of paper to the cardboard square under the pens.
  9. Hold pen B and draw a square.
  10. Compare the size of the square drawn by both pens.

Results

The square drawn by pen A is larger than that drawn by pen B.

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Why?

A pantograph, which is used to change the size of drawings, is a compound machine made up of levers. The length of a lever and the position of its fulcrum change the distance that the end of the lever moves; the end farther from the fulcrum moves a greater distance. Strips #1 and #2 are levers with the fulcrum at points E and D. Pen A is farther from its fulcrum than is pen B; thus, pen A is moved a greater distance.

Let's Explore

  1. Can a reduced-scale drawing be made? Repeat the experiment using pen A to make the original drawing. Repeat the experiment again, this time placing pen A in a hole made between holes E and F. Science Fair Hint: As part of a display, show photographs of the pantographs used in each experiment, and display with the diagrams.
  2. Would changing the position of the connecting piece affect the results? Repeat the original experiment, moving connection F closer to connection E. Then repeat the experiment again, this time moving connection F farther from connection E.

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Show Time!

  1. Create your own pantograph. The example diagram gives you an additional design to construct Place pens at different positions.
  2. A machine that makes circles can further demonstrate that the end farther from the fulcrum moves a great distance. Construct the drawing machine by cutting a 2-inch × 12-inch (5-cm × 30-cm) strip of cardboard. Use a marker to make a dot near one end of the strip. This will be the starting point With a ruler and a marking pen, mark and label dots every 2 inches (5 cm) from the starting point (see diagram). Ask an adult to use a nail to make holes through each dot. Place the cardboard strip in the center of a sheet of paper. Stand a pencil in the hole at the starting point, with the eraser touching the paper, and hold this pencil steady. To make a circle with a 10-inch (25- cm) diameter, place a second pencil in the hole labeled 10 inches (25 cm). Move this pencil around with its point pressed against the paper until a complete circle is drawn. Repeat, placing the pencil in different holes to increase the size of the circle.

Check It Out!

Christopher Scholes invented the first practical typewriter in 1867. This machine has a series of levers that change a small movement (pressing your fingertip on a key at one end of the lever) into a larger movement (the other end of the lever goes up and strikes the image of a raised letter onto a piece of paper). Find out more about the connection of the levers in this machine, and display simple diagrams of the connecting levers.

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