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Enlarger: How Does a Pantograph Work?

Author: Janice VanCleave

Problem

How does a pantograph work?

Materials

  • Scissors
  • Ruler
  • Cardboard box at least 24 inches (60 cm) wide and 24 inches (60 cm) high
  • 10d nail
  • 4 paper brads
  • 2 marking pens
  • 4 thumbtacks
  • Large sheet of plain white paper (such as butcher paper)
  • Adult helper

Procedure

Enlarger

  1. Ask an adult to cut the following pieces from the cardboard box:
    • 2 strips, labeled #1 and #2, each measuring 2 × 18 inches (5 × 45 cm).
    • 2 smaller strips, labeled #3 and #4, each measuring 2 × 10 inches (5 × 25 cm)
    • one 24-inch (60-cm) -square piece
  2. Position the 4 strips on the square so that the ends of the strips overlap as shown.
  3. Ask an adult to use the nail to make holes in each piece of cardboard at points A through F, as shown in the diagram. NOTE: C is the only hole made through the square.
  4. Use paper brads to secure the strips together at points D, E, and F.
  5. Use a paper brad to secure strip 2 to the square at point C.
  6. Insert the marking pens through holes A and B.
  7. Use the thumbtacks to secure a piece of paper to the square under the pens.
  8. Holding pen B, draw a square.
  9. Compare the sizes of the squares drawn by both pens.

Enlarger

Results

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

Why?

A pantograph, which is used to change the size of a drawing, is a compound machine (a machine made of two or more simple machines) consisting 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 3 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 twice, first using pen A to make the original drawing, then placing pen A in a hole made between points E and F. Science Fair Hint: As part of a display, show photographs of the pantograph used in each experiment and display the photos with the drawings.
  2. Would connecting the levers at different points affect the results? Repeat the original experiment twice, connecting strip 4 first to the hole made between points E and F in the previous experiment, then to a new hole made between points F and A.

Show Time!

Enlarger

Enlarger

  1. Design your own pantograph, or construct the one shown in the diagram. Place pens at different positions.
  2. A machine that makes circles can further demonstrate that the end of the lever farther from the fulcrum moves a greater distance. Construct a drawing tool by cutting a 2-by-12-inch (5-by-30-cm) strip of cardboard. Use a marking pen 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 a hole through each dot. Place the 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) so that its point is pressed against the paper. Move this pencil around until a complete circle is drawn. Repeat, placing the pencil in different holes to change the size of the circle.

Check it Out!

Christopher Scholes (1819-1890) invented the first practical typewriter in 1867. This machine has a series of levers that change a small movement (a fingertip is pressed 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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