Simple Cartesian Diver




About: Showing the world what can be made with God's creation.

In this instructable I will walk you through the process of how I make a cartesian diver, or a bottle diver.
The cartesian diver uses pressure (exerted by you) to make the diver sink and rise based on the amount of pressure applied to the water bottle.

Step 1: Supplies

I have assembled a list of supplies that you will need for this project, feel free to skip ahead and see how it's made.

1) 1/2 inch smoothie strawd
2) permanent marker
3) lighter
4) BBS
5) sissors
6) needle nose pliers
7) ruler or measuring devise
8) water bottle or empty 2 liter bottle

Step 2: Prepare Straw

My straws were none inches long, so I cut them in three inch increments, or 7.6 cm peices. Easily mark the measurement with the marker before cutting for precision.

Step 3: The Build

Now you can assemble the diver, start by crimping the end with the pliers, and then heating/ melting the end shut with a lighter. Make sure you have not holes so air can't escape.
Full the straw with exactly ten BBS, and then deal the opposite end.
Done! Now drop your diver the bottle full with water, cap it and squeeze!

Step 4: Final Thoughts

These toys are great for explaining pressure in chemistry, or for just showing off at parties.
Thank you for checking out this instructable, and if you liked this one, you may like my others, so be sure to check those out too.
More to come!



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    6 Discussions


    3 years ago

    It might be interesting to try adding a couple more divers with slightly different sizes and 9 or 11 BBs, like those Galileo thermometers. Another possibly interesting variation might be filling the bottle partly with oil, so the movement of the diver is limited (what for? oh just a different look, kind of neat stopping before it goes all the way). Maybe another fluid that doesn't mix with water could provide a limit at the other end.

    1 reply

    Reply 2 years ago

    I have experimented with different length to BB ratios but for the size of straws and weight of the BBS I found the size in the instructable to be best suited for convienent purposes. For instance, 9 is divided evenly by 3 so we use the entire straw that is 9 inches long. When I have time I'll experiment some more.
    Your thought on using different liquids is intriguing, I will have to try that. Maybe it would make a good density experiment that uses a solid in a liquid, and not just a liquid on a liquid? Thank you for taking the time to comment, I like hearing others ideas.


    Reply 3 years ago

    BBS are small round projectiles fired from a BB gun.


    Reply 3 years ago

    Thanks Zeke. I should have known!


    3 years ago

    This is great! I remember making one of these when I was a kid. Thank you for sharing these steps. Will make this with my kids sometime! :)