Today I am going to show you how to design and print a completely 3D printable pendulum wave. Click on the vid link to see it in action.

A pendulum wave is a great way to teach children about the factors that do and don't impact the speed of oscillation for a hanging object (pendulum).

It is mesmerising to watch the changing pattern and will hopefully inspire your little ones to wonder how it works and become curious about the science behind the motion.

This project tells you all the steps to design and print your own pendulum wave.

I have also included some suggestions at the end for extra prints and set ups that will help to explain the science behind the pendulum wave.

**I have had a couple of requests for the stl files so have added them at the very end of this instructable :)

Supplies

3D printer

PC or tablet

Filament

Step 1: Making the Post

To build our pendulum wave we need a stand and a post to slot across the top of it, as well as the pedula themselves.

Lets start with the post

Open Tinkercad (www.tinkercad.com)

Select a cylinder and resize it to 12mm x 12mm and 180mm tall.

Make sure it is standing vertically as this will print more smoothly.

Export your post as an stl

Add a cylinder 15mm diameter and 5mm height and a cylinder hole 12.5mm diameter and 3.5mm height. Align the two cylinders, x and y in the centre and z to the top edge and group. This is a cap to go on the end of your post. Copy and paste to create two and download.

Now lets design the stand

Step 2: Designing the Stand

Create a rectangle 170mm x 80mm and 6mm tall - this will be the base of your stand.

Now add a triangle shape, rotate by 90 degrees and make it 80mm wide, 6mm deep and 180mm tall. This will be the side of our base.

We need to add a loop at the top for the post to thread through.

Add a cylinder 18mm wide and 6mm high, add a cylinder hole 12.5mm wide, align the two shapes and group them.

Now rotate your tube shape and raise it up so that it is a little higher than the top of triangle. Align the two shapes on the x and y axis.

Click on the tube and ungroup it then without moving any of the objects group the cylinder, hole and triangle together.

Copy and paste the side piece and align one to each end of the base and group (see picture)

OPTIONAL

I wanted my stand to print quickly so added a triangle hole slightly smaller than the original triangle into each side to cut down on filament.

Step 3: Designing the Pusher

To get the pendulum wave moving you need a flat pusher. You can use a ruler, piece of wood or cardboard but I wanted to add a 3d printed one that slots into the base (see pics).

Add a rectangle 147mm x 23mm and 4.5mm tall - this is your pusher and you can export this as an stl now.

To create a hole to slot your pusher into add a hole cylinder that is about 0.6mm wider than your pusher in all directions, align this with the top of the base of your stand. Centre it on the x and y axes and group.

You can now download your stand.

OPTIONAL

I added a finger hole to make the pusher easier to access. Create a half sphere 18mm in diameter and the same height as your pusher hole. Position the sphere upside down on one edge of the pusher hole and group (see pic).

Now all we need are our pendula and we will be ready to print

Step 4: Designing the Pendula

We want to have around 20 pendula to get a good wave going.

The pendula are identical except that each one is slightly longer than the last.

To thread them on to the post we will use the same tube as we used for the top of the stand.

Add a cylinder approx 20-25mm in diameter and 4.5mm thick.

Add a rectangle 45mm longer 4.5mm wide and 4.5mm thick

Take the tube we created previous and reduce the height to 4.5mm

Overlap the tube at the top of the rectangle and the cylinder at the bottom, both by 1mm.

Align the objects in the x and z axes and group - this is your smallest pendulum.

Copy and paste the pendulum, ungroup, increase the size of the rectangle by 4.5mm, align the objects in the same way and group.

Do this 18 times more, each time increasing the length of the rectangle by 4.5mm

Now you should have 20 pendula in increasing length (pic 2)

Finally copy and paste the tube you used for the pendula 26 times, these will be out spacers (allowing our pendula to swing freely without becoming caught on each other)

Time to print and build

Step 5: Printing and Building Your Pendulum Wave

Print your pieces using your normal slicer settings.

None of the pieces need supports.

To build your pendulum wave thread the pendula onto the post with one spacer between each pendulum (see pic 1).

Once all your pendula are on your post slide the post ends through the holes of the stand.

If the pendula are loose on the post add spacers at either end until they sit snuggly but still rotate freely. I needed an extra 3 spacers on each end.

Add your end caps onto each end of the post and slide your pusher into its slot.

Now we are ready to give it a go

Step 6: Testing Your Pendulum Waves

Use your pusher to raise all pendula to just beyond half way (see pic)

Place a find on the edge of the base to steady it and let go in a smooth motion.

Watch your wave create beautiful patterns :)

But what about the science?

Step 7: Explaining the Science

The speed of the movement of the pendulum from one edge to the other (oscillation) is dependant on the length of the pendulum - this is what creates the changing patterns.

To illustrate this take off some of the intermediate pendula and compare the swing of a large and small pendulum - the difference in speed can be clearly seen.

Although you may think that the weight of the pendulum would also impact the speed of oscillation this is not the case.

To illustrate this, design and print some pendula of the same length but with a different width of cylinder (or no cylinder at all) on the bottom - make sure the overall length stays the same.

Weigh the pendula to show that they weigh different amounts then test them on your pendulum wave - they should all swing at the same rate and no changing pattern should occur.

Have fun, playing and experimenting with your Pendulum Wave!

Be sure to watch the video to see the wave in action.