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Finally, a robot to draw for you! If you only want to make gorgeous geometric scribbles, that is.

With one pen and four pendulums, you're bound for pandemonium with this great way to look at complex geometry, momentum, and art! With a push of the base, you can make all sorts of amazing repeating colorful shapes. You can continue to change weights, drawing implements, and paper for infinite possibilities and designs. Its original invention was back in the 1850s, but now you can do it in your own classroom or home for under \$15.

• What: Homemade Harmonograph
• Concepts: pendulums and harmonic motion, geometry, momentum, art!
• Cost: ~\$15
• Time: ~ 2 hours to make, and then infinite play
• Materials:
• 3 x 8' lengths of 2"x2" wood (or use what's available)
• 3/4" plywood (around 15" x 30" needed)
• 1/2" wood dowel
• 8 eye hooks
• 4 clothespins
• String or cord
• Paper
• Tape
• Pens
• 4 stick-on rubber furniture feet (optional)
• Tools:
• Saws
• Drill
• Hot Glue Gun

Let's harmonize!

### Teacher Notes

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## Step 1: Cut Some Wood!

Here's the original design for the basic frame, which is like a table. Mine has 4 x 36" table legs with a box frame top with 2 x 15" pieces and 2 x 30" pieces. The base is 15" x 15". Cut them up!

TIP: Save your extra 2x2 wood. I added extra base supports of two pieces that were 9.5" each. Also, you'll want to save some as spacers for the base.

## Step 2: Make a Useless Table!

It's like making a table without a top. Make the box first with the 15" pieces spanning the whole distance. Screw them together, then screw on the legs. I also screwed on extra supports about 5" above the ground to keep the legs from wobbling too much.

## Step 3: Make That Base

Cut two inches of wood the same size. Our base is 15" x 15". The reason for this is that I want the future strings of the harmonograph to be able to rest at a vertical position, so 15" can allow that. Put some 2x2 in between the two flat parts of the base, and screw it all together. This will give us a drawing surface and a space below to add weight to add to the harmonograph's momentum.

## Step 4: Eye Hooks and Rubber Feet

Start with your useless table, and screw in the eye hooks with your hand. Spread them about 14" apart along the 30" beam, and so you can get approximately a 14" x 14" square of eye hooks. Proceed to do the same on one side of the base boards to get a 14" x 14" square there, too!

Afterwards, add some sticky rubber feet (optional) to the bottom of your useless table to keep it from slipping with the weight moving around.

## Step 5: Suspense!

Take your string or cord, and it's time to attach the base to the useless table. For each corner, I started by tying a not at the top. I then measured 24" down the string, and marked it. Then I cut about 4" below that, and tied a knot on the corresponding base board eye hook so my mark was still exposed.

With a little finagling, you'll get four strings of approximately the same length for quadruple pendular action!

## Step 6: The Drawing Arm

Time to add in the drawing component. Grab a skinny piece of scrap wood that's about 30" long. Find a sturdy dowel and a drill bit the same diameter. Drill through the side of your scrap and feed the dowel through. Then choose a height just above the platform (mine was about 9.5") and drill through either leg on one side. Feed the dowel through there, and secure on sides with clothespins.

Here are some tips for making sure the drawing see-saw works:

• You want it to be almost balanced with no pen on it. Maybe just a little heavier on the drawing side.
• Make sure the dowel is loose in the table leg's holes so you can lift it up and down. You want it tight through the scrap wood.
• Make sure the height is at least 0.5" above the platform so the pen can draw with little resistance.

This is the most sensitive part, so take care!

## Step 7: Pen and Paper Holders

Glue on some clothespins to either side of the end of your drawing arm. This makes for an easy release to change out pens. Then tape down some base paper, and you're almost ready to go!

## Step 8: Throw Your Weight Around

This harmonograph is all about momentum. The longer you can keep it moving, the more tightly woven curves you're going to get. Add some weight in the hollow middle of the base. If you want to add some to the top, you can do that, too. It's pretty fun to adjust the weights to make it balanced or unbalanced, and you can get great results in the drawings.

Additionally, if you want to balance your drawing arm a little bit more, you can add some weight on the back side too (I used the roll of tape).

## Step 9: Doodle Party!

Draw to your heart's content, or let the robot do the work! Tape some paper down as a canvas. Start the base moving. Put in a pen and lower, and let the harmonograph work its magic!

You can experiment with different string lengths, weight distributions, types of drawing implement, time down, etc. If you're getting erratic doodles, try stabilizing the hole machine with your hand or with some weight!

It is so fun to see all the drawings you and/or students can make. I dream of decorating a cake this way.

This technology has been around since the 1850s, and so there is lots to see out there with other methods! Start checking them out here.

Have fun, keep doodling, and never stop exploring. Write me below!

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## 9 Discussions

Does the length of the the topless table matter? If I have wood thats only 23" instead of 30 " does that matter? Or just cut the plywood to match?? Thanks

Jürgen Richter Gebert from TU-Munich has a very nice one: https://www.youtube.com/watch?v=IM2L-Q4d07s

You are so cool!

I noticed there are two clothespins, but you only ever use one at a time. Could this be a double pen harmonograph???

2 replies

Hey Coby!

A great idea indeed. I tried it a few times, and realized it's tricky to get both pens to be in constant contact at the same time. I'll definitely play around with it to see if I can find a way to do it. Thanks for the idea!

Maybe clamp some oversized tubes in the clothespins and put the pens inside. That way they can adjust slightly to always touch the paper. Maybe they would need a bit of help from some rubber bands holding them down to the page. Just some thoughts. Keep on rockin'.

That's so cool!

so is just the platform swinging? it looks awesome! one suggestion to get more complex patterns is to put the pen contraption on a pendulum too.