Here’s a fun STEM challenge: Build working gears out of plastic caps, popsicle sticks, and a cardboard box! This project demonstrates mechanical concepts using materials you probably already have. Kids will be able to explore how gears mesh together to create motion.

We started our project with a sturdy Amazon prime box, an assortment of plastic lids, popsicle sticks, scissors, and hot glue. I used mini popsicle sticks, but regular ones will work fine. The ones we used are the same width as regular popsicle sticks, but not as wide as craft sticks.

(By the way, I have an assortment of photos of materials spread out like this that never make it onto the blog… sometimes I have these crazy ideas, and they don’t work out. So I don’t post those. But this project is lots of fun! Just thought I’d point out that I don’t hit on a good idea every time… ha ha!)

We made our gears to have 8 teeth. It’s easy to glue the popsicle stick segments to a plastic lid, and if you use low-temp glue guns, kids can do it themselves.

I glued small water bottle caps to the tops of the lids to make the gears easier to hang onto and turn. One of them has a nail through the cap – I’ll explain more about that in a minute.

The way the gears work is that there are smaller caps glued to the box itself. Then the gears sit on top of those. This allows the gears to turn, but they can’t scoot very far from side to side. Jonathan suggested that we just glue the gears down to the box, but then he quickly realized why that wouldn’t work. These are good projects to do to develop thinking skills!

You can explore how gears can be used to change the direction of motion by mounting one on the side of the box. I used a hammer to drive the nail through the lid (adult job) and then poked a hole in the box. Yes, the sharp point of the nail sticks out on the other side, but I wouldn’t recommend doing this project with young kids anyway. Best for ages 5 and older.

The gears are not sturdy enough to have more then 3 or 4 in a sequence. Four gets a little tricky at times because there’s just not enough torque to turn that final gear. Three gears work well. We glued down more than 3 caps so that the kids could experiment with the position of the gears.

We love doing STEM challenges with supplies from around the house! Here are some more of our favorite ideas:


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  1. Betty Sep 8, 2018

    This is such a clever idea! I love all of your STEAM projects especially with recycled materials. Bookmarking this to do with my kids!

  2. Yolande Sep 10, 2018

    Could you cover the exposed nail with a glued on bottle cap, or would that impede the movement of the gears? Thanks for this idea ?

  3. Mohamed Borhami Sep 20, 2018

    Thanks for the idea and your time too

  4. Lolitia Johnson-Dore Feb 1, 2022

    Thanks for this amazing idea. I will explore it for our simple machines unit this month.


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