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This Instructable explains how to make a simple yet very effective wave machine.

When most people think of wave motion they picture a static graph of a sinusoid or waves on a beach. Attempting to understand wave phenomena by thinking about how the graph should change or by simply observing waves at the beach can become very tedious.

This Instructable makes visualising wave motion much more enjoyable and encourages hands on experimentation. Despite being a very simple build there are a lot of complex ideas embedded in the wave machine. I have included ideas about the various properties of waves that can be explored using the wave machine at the end of the Instructable.

I hope you enjoy the build and if you have any questions just let me know.

***I will include more images of the finished wave machine and some videos very soon!***

Conor

Step 1: What You Will Need

The materials and tools required for the wave machine are both very cheap and many of them may already be lying around the house.

Materials

  • Packet of wooden BBQ skewers
    • I used 60 skewers in this build with each one measuring roughly 25cm before the pointed end was clipped off. The holes in the beads are slightly larger than the diameter of the skewers which is ideal.
  • Packet of wooden beads, preferably assorted colours. Will need twice the amount of skewers used.
    • These don't necessarily have to be beads or wooden for that matter. I have seen these machines made with sweets stuck on either end of the skewers which can make this build even simpler. My only gripe with sweets is that they will perish over time which is why I opted for a longer lasting solution.
  • 2 cut pieces of plastic tubing. Roughly 2cm in diameter and 20cm in length.
    • These act as handles on either end of the wave machine. Wooden blocks or even pencils could work here if you don't have access to the tubing.
  • Roll of Duct Tape
    • Gaffer tape is also a good option here and is designed to be cleanly removed, duct tape is not. This could be useful if you think you may make a mistake when laying down the tape in the build.
  • Thin elastic bands (Optional)
    • These are optional and are an easy way to complete the build if you do not own a glue gun. You won't need too many of these but I find elastic bands usually come in large quantities anyway.

Tools

  • Snipping Tool.
    • This is used to cut off the pointed ends of the skewers. A nail clippers could even work here but I would give it a good wash before using it for nails again...
  • Safety Glasses/Goggles.
    • A necessity when working with a snipping tool. The pointed ends of the skewers can fly off in any direction and could easily damage your eyes if not properly protected.
  • Standard Size Credit Cards.
    • These are used for spacing the skewers when placing them on the tape. "The size of credit cards is 85.60 × 53.98 mm(3.370 × 2.125 in) and rounded corners with a radius of 2.88–3.48 mm, in accordance with ISO/IEC 7810#ID-1" (Wikipedia).
  • Glue Gun (Optional)
    • If you choose to use the elastic bands you will not need the glue gun. The glue gun I used is quite small and is hot melt as opposed to cold melt. I found the size of the gun particularly useful when working with the small beads
  • Clamps (Optional)
    • These are used for holding the handles on either end of the wave machine so that the tape is kept under tension. This is very important but can also be achieved by simply taping the handles to the surface you're working on. Keep in mind though that duct tape is not designed to be removed cleanly.

Step 2: Preparing the Skewers (Option: Glue Gun)

If you do not have access to a glue gun and have decided to use elastic bands instead please disregard this step and move on to Step 3: Preparing the Skewers (Option: Elastic Bands).

I prepared 60 skewers but did not end up using all of them due to space constraints. Around 50-60 skewers with the credit card spacing results in the best wave I found.

  1. With the glue gun heated but a drop of glue into a bead. Taking the blunt end of the skewer push this through the bead until it is flush with the other side of the bead. Wipe off any excess glue. I repeated this on all of the blunt sides before then repeating the process with the pointed side of the skewer. When working with the pointed side I pushed the skewer through until the bead was entirely on a constant diameter section of the skewer. Essentially, push the bead until the entire pointed part is visible for removing later.
  2. Removing the pointed ends. Wearing you safety glasses and using your snipping tool remove the pointed end of the skewers once the glue has completely dried. Please see the included images.

Step 3: Preparing the Skewers (Option: Elastic Bands)

If you do not have access to a glue gun then you can still complete this build using elastic bands. The bands will provide a pretty good hold and you could make it more permanent using your favourite tube of glue.

  1. You begin by cutting one of the elastic bands so that it no longer makes a ring. Thread this part of the way though one of the beads.
  2. Take a skewer and push the bead with the elastic band onto the skewer. Trim the excess on both sides of the bead and repeat on the other side of the skewer. You can use the excess elastic for the next beads.
  3. Repeat for as many skewers as you require.

Step 4: Preparing the Tape and Handles

  1. Begin by wrapping some tape around the handle as shown in the first image. Ensure you center the tape on the handle, this is very important. Do not cut the tape when you have wrapped around the handle once or twice.
  2. Fix this taped handle to the surface you're working on. I used a clamp to do this as you can see in the included image. Make sure the sticky side of the tape is facing up.
  3. Pull the tape to the desired length. You could easily achieve this using the floor but I used a table instead. To extend the length of the wave machine I used an ironing board. The pictures explain this better than I can. Keep the tape parallel to the edge of the table or to some feature on the surface you're using.
  4. When you've reached the correct length take your other handle and center it on the tape like you did for the first one. Bring some of the tape around the handle and stick it down, roughly a credit card width. See the images for more detail. You may now cut the tape. Clamp the handle down and ensure the tape is under tension.

Step 5: Placing the Skewers

  1. Starting at the first clamped handle, place two credit cards as shown in the first image.
  2. Center a prepared skewer on the tape. I used the credit cards to do this as the length of the credit cards almost exactly matched the remaining length of the skewer on either side of the tape. Press the skewer onto the tape.
  3. Repeat this process for the rest of the skewers. Ensure you maintain the same spacing and positioning of the skewers throughout this entire step. Make sure the skewers are perpendicular to the tape. Leave about a credit card distance between the final skewer and the other handle.

Step 6: Finishing Up With the Tape

  1. Take the roll of tape and stick some to the second handle. Do not cut the tape. Pull the roll of tape and see the first image. Ensure the wave machine is kept under tension for this entire process.
  2. Start slowly pressing down the tape to match the tape underneath it. Continue pulling more tape from the roll and continue this process until you reach the other handle.
  3. Pass some tape over the other handle and then go back and smooth out the tape on the entire wave machine.
  4. Congratulations, you're now the proud owner of a wave machine!

Step 7: Exploring Waves With the Wave Machine

You can explore many properties of waves using your new wave machine.

  • Hit the second skewer out from the handle for the best results.
  • What happens to the speed of the wave when you pull the machine taught versus when the machine is slack?
    • You can explore the relationship between the elasticity of a medium (the tape) and the speed of a travelling wave. You could talk about the restoring force the skewer feels due to the tape and why it returns to equilibrium faster when the tape is taught versus slack.
  • What happens to the wave when it reaches the other handle? Does it reflect?
  • What happens if the two people holding the wave machine both send waves to each other at the same time?
    • You can explore the superposition principle and interference of waves. Why don't the waves crash like cars driving towards each other?
  • If you hold a skewer close to your handle and then move it up and down at a at a steady rate you can make standing waves. You can explore higher harmonics by increasing the rate you move the skewer up and down at.
  • You can talk about digital representations of waves. The skewers are essentially sample points that record the the wave as it passes through the wave machine. More skewers packed closer together would give a better representation of the wave. What would happen if you increased the spacing between the skewers? You could even talk about Nyquist's sampling theorem here if you like, about how to build up accurate digital representations of analog phenomena such as waves.

A lot of the concepts above can be very difficult to visualise if you're trying to understand it solely on paper. The wave machine allows you to see these concepts in action like never before and it can be made large enough to use in a classroom for everyone to see.

Cool
<p>Cool idea</p>

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