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Simple Machines: The Lever

Build this simple machine to demonstrate the power of the lever.

Archimedes said, “Give me a place to stand and with a lever I will move the whole world.

The lever is one of the six classic simple machines. A simple machine is a mechanical device that changes a force’s direction or magnitude. The other five simple machines are the wheel and axle, the pulley, the inclined plane, the wedge and the screw. Explaining simple machines to kids can be a fun learning experience, especially if you include some demonstrations in the lesson. Here’s how I built a lever for a demonstration of simple machines for my son’s 3rd grade class.

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Steps

Step #1: Gather Your Materials

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Simple Machines: The Lever

Here are the materials you need to build the lever.

  • Two (2) 2x6 boards, each 64 inches long
  • Four (4) 2x4 spacers, each 8 1/2 inches long
  • Two (2) standing platforms, each about 11 inches by 15 inches (I cut mine from outdoor stair tread)
  • One (1) 2 foot section of schedule 40 4 inch PVC pipe
  • Two (2) 4 inch PVC caps
  • Twenty Four (24) 2 1/2 inch exterior grade deck screws

Step #2: Measure and Mark the 2x6 Boards

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Simple Machines: The Lever
  • Ensure that your 2x6 boards are cut square at the ends, and that they are as close to 64 inches long as possible. You are going to cut three semi-circular holes in each 2x6 board.
  • Mark the center point of one 2x6 (32 inches if your board is 64 inches long) right at one edge of the board. Now make two more marks 2 1/4 inches to either side. Make another mark 2 1/4 inches from the original mark towards the other edge of the board. (Look at the images in the slideshow for some additional guidance.)
  • Now place the end of the 4 inch PVC pipe so that it is centered on the original mark. Since the pipe is 4 1/2 inches in diameter, the marks you made 2 1/4 inch to either side and above the original should exactly line up with the edges of the PVC pipe. Carefully trace a semi-circle around the end of the pipe.
  • Mark two more points 16 inches in from each end of the 2x6, right along the same edge of the board as you marked before. Repeat the procedure above to make two more semi-circular marks.
  • You should now have three semi-circles traced along one edge of the 2x6, one at the center, and two at 16 inches in from each side. Repeat this for the other 2x6 board.

Step #3: Cut Out the Semi-Circles with a Jigsaw

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Simple Machines: The Lever

Use a jigsaw to cut out each of the three semi-circles on each 2x6 board. Cut right on the line you drew, so that the cut-away will be at least as big as the diameter of the PVC pipe. A little bigger is better than a little too small.

Step #4: Build the Frame

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Simple Machines: The Lever
  • Cut four spacers from some 2x4 board. Each spacer should be 8 1/2 inch long.
  • You will position one spacer at each end, and two along the top edge as shown above (the frame is upside down in the picture). The two spacers along the top should be centered at 24 inches in from each end.
  • Position the spacers and pre-drill two holes on each side. Pre-drilling will help keep the wood from splitting. Use four 2 1/2 inch screws to secure each spacer.

Step #5: Cut and Pre-Drill the Standing Platforms

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Simple Machines: The Lever
  • Cut the standing platforms. I used outdoor stair tread, because it is grooved for better grip. These treads are 11 inches wide. Cut the boards 15 inches wide.
  • Place the lever frame on the ground with the semi-circular cut-aways facing down. Position each standing platform at one end of the lever frame, centered from side to side and flush with the end of the frame.
  • Pre-drill four mounting holes in each platform board and directly into the frame.

Step #6: Sand, Prime and Paint the Frame

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Simple Machines: The Lever
  • The frame should get a rough sanding to remove any splinters or rough spots. I used 50 grit sandpaper and a belt sander. I didn't sand the stair tread, since it comes ready to finish.
  • While not required, you can paint the lever frame and standing platforms. One coat of primer and two top coats look nice.
  • I picked pink for the frame color. Because pink is powerful, persuasive, progressive, and perfect. Also, I had some pink paint left over from another project.

Step #7: Assemble Frame and Platforms

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Simple Machines: The Lever
  • Allow the paint to dry overnight.
  • Once the paint is dry, re-position the standing platforms over the frame and attach with 2 1/2 inch screws. Be sure the boards all line up with the pre-drilled holes you made.

Step #8: Make the Fulcrum

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  • Cut the 4 inch PVC pipe down to 15 inches long. Place a 4 inch end cap on each end. This should leave just over 12 inches of space between the end caps, which will allow the lever frame to rest on the fulcrum.
  • It is nice to sand the markings off the PVC with some medium or fine grit sandpaper.

Step #9: Assemble and Test

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Simple Machines: The Lever
  • Assembly is easy. Just place the frame over the fulcrum. I told my daughter what Archimedes said about moving the world, and then we tried it out.
  • First I stood on the platform furthest away from the fulcrum. I asked Anna to stand on the other side. Of course, she couldn't move me. I asked her why and she could tell we needed to move the fulcrum.
  • Next, I had her step off and moved the fulcrum so that it was closest to me. Then I stepped on the platform, raising her side. When she stepped on, even with my greater weight, she had no trouble lifting me.

Conclusion

This project can be used by teachers, museums, home schoolers and other educators as part of a program on simple machines. Stay tuned for future projects on other simple machines.

Andrew Terranova

Andrew Terranova is an electrical engineer, writer and an electronics and robotics hobbyist. He is an active member of the Let's Make Robots community, and handles public relations for the site. Andrew has created and curated robotics exhibits for the Children's Museum of Somerset County, NJ and taught robotics classes for the Kaleidoscope Learning Center in Blairstown, NJ and for a public primary school. Andrew is always looking for ways to engage makers and educators.


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