Print and build this cartesian diver, named after famed French philosopher, mathematician and scientist Rene Descartes.
Demonstrating the mechanics of buoyancy and the ideal gas law, this toy has fascinated young and old for hundreds of years.
In addition to your printed parts the only materials you'll need is a balloon, an empty big soda bottle and some glue.
The only tools you'll need are a bowl, some sandpaper and some scissors.
It creates and entertaining and appealing demonstration piece and a great gift.
Theres a complete video on how best to construct Aquabot on youtube at http://youtu.be/5lzMfchYDaM
The Cartesian Diver strikes at the heart of "Make it Float" dealing with the physical property of buoyancy and a significant example of how it finds application in the actual world. When I first pondered entering the competition, I became intrigued by the underlying physical property which allows items which are actually denser than water, to float upon it. A bit of research and I was fascinated to discover the long path of scientific fascination with buoyancy and the amount of scientist, both amateur and professional that have leant a hand to furthering our understanding of this essential component of the civilized world.
I had originally intended to go with the competition's suggestion of using coins to achieve neutral buoyancy, but it would have caused a diver that would have been displeasingly big in a soda bottle container. Because of this I suggest that the washers I urge for counter-buoyancy be regarded as currency in a mysterious and mythical kingdom, where they are used by tiny animals for day to day commerce. Hey, the competition DID suggest one could use non-US coins!
Its been a real struggle to get this entry completed in time... I can't really believe I was able to pull if off with a day to spare.
My excitement for 3d printing goes beyond simply building a functional part. I try to develop projects that while not always ready for store shelves, integrate construction and design principles which make them appealing and useful.
Were it not for the looming deadline (did I mention how amazed I am that I actually finished this in time?) , I would have made some changes to the basic design. A somewhat more ornate pedestal for Aquabot to perch upon and I would have separated the diver at the pedestal so that the use of some other color would provide a more significant transition than is accomplished with only making the bottom plate another color. Had I known about it before I was well into the project, I would also have liked to have swap Aquabot's entire head for the Antique Diving helmet at http://www.thingiverse.com/thing:128783
Nevertheless, its been a fun ride, and I hope you enjoy creating your own. I've already got a few nieces and nephews that seem quite keen to have their own.


PrintableScience.com presents a Cartesian Diver featuring MakerBot's AquaBot.

Delighting young and old alike for hundreds of years, the toy takes its title from the famous french philosopher, mathematician and scientist Renee Descartes who's credited with its creation. Along with play possible, the Cartesian Diver gives a practical illustration of they physics of buoyancy and the ideal gas law.

The mechanics of a Cartesian Diver are quite simple. It Consists of two parts: The first part: A sizable typically transparent sealable outer container or room with flexible sides and full of water, and part 2: the diver itself, which is smaller, comprises an air channel or room and most often provides a flexible diaphragm which can be used to adjust the level of fluid in the air chamber of the retina by either expelling or sucking in water.

The design of a functional diver requires that when its internal chamber is totally filled with water it will sink into the bottom of the larger container, and when the inner chamber is totally empty of water it will float to the peak of the surface. Once these two extremes have been realized in the plan, the toy is made operational by adjusting the static weight of the diver or the water level from the diver so that the tip of the top of the diver is floating just above the surface of the water in the larger container. This is known as the state of "natural buoyancy".

When the diver is naturally buoyant, it is set in the outer room, which is then sealed, and whether the container's sides are squeezed the diver will sink to the bottom. When the sides are published, the diver will then rise from the bottom and float into its original state.

What happens in this process is that if the sides of the bottle are compressed it increases the pressure level within the room, and while liquids cannot be compressed, the air in the room of the retina can. The result of compressing the air in the diver means is that water in the outer chamber is drawn up into the retina, raising its weight until it no longer has enough buoyancy to float.

When the sides of the room are discharged, the pressure is reduced, the air in the cavity of the retina pushes out the water which has been drawn in until it has shed enough water that it is light enough to go back to its state of natural buoyancy.

Well enough physics. Let us build our own Cartesian Diver.

Here's what you'll need to build your Cartesian Diver:
The pieces you have printed out in your 3d printer in the STL files which includes:

  • the diver body
  • the diver face plate
  • the diver bottom cap
  • the diver plunger

    you may also require

  • the diver spray shield
  • the diver stand

Also included are stl files for:

  • a balloon stretcher

And for our outside container the following printed parts:

  • Bottle feet
  • bottle helmet
  • bottle rim
  • bottle faceplate

You will need the following materials:
A bottle of Sparkling Ice Soda water - flavor is unimportant

  • a rubber or latex balloon
  • many different little nuts or washers
  • a little piece of fine grit sanding paper
  • gel Krazy Glue
  • regular Krazy Glue
  • water

And finally the following tools:

  • a large bowl
  • cuticle scissors or a sharp razor blade or utility knife

We encourage you to use different colored balloons and to print the various pieces of your cartesian diver from different filaments. This Will allow you to build unique individual aquaBots if you have more than 1 child or one grandchild which you aspire to amuse or gift with your Cartesian diver.

Our diver is a mashed up version of the Thingiverse AstroBot which we have affectionately renamed AquaBot. It was altered by hollowing it out and including a pedestal to increase the amount of the air channel in the diver. In addition, we replaced the helmet's visor using a hole into the air channel. This hole subsequently will be covered with a sheet of rubber or latex and function as our flexible membrane for adjusting the level of water in our diver.

In its finished form, our diver is made up of 3 printed pieces. The diver body, the base cap and the face mask ring. The STL files provided also provide for a small rounded plunger which we use for pushing from the rubber membrane. There is also STL files for a diver stand and a spraying mask which aren't required if your printer can print watertight objects.

While watertight is a word often used to describe a 3d object that has no accidental gaps or holes in the STL file, we mean it literally. When you print your model, it can't allow air from the diver or water in... except through the hole at the bottom which was put there expressly for that purpose.

But don't worry, if your prints aren't watertight. Its a simple matter at this point to spray your diver with a sealant spray, like the one shown here. If you only discover your diver isn't watertight after you have finished construction you can use the printed stand and spray mask to assist you apply the sealant later. The small pedestal receives the diver up off the surface so the sealer aerosol can reach under, and the spray mask stop sealant getting on the balloons surface and interfering with its flexibility.

There's also an STL file for a balloon stretcher. Our intention is to have the rubber gently stretched out of its resting state. We don't want it as taut as in an entirely inflated balloon though. If you discover the stretcher we provided is either too big or too small for the balloons you have it can easily be sized up or down to meet your needs.

So let us begin by extending a balloon over our stretcher.
The next step is to take a little piece of fine sandpaper and use this to smooth out any rough edges on the face ring of our diver. Because that area of the diver is printed at an angle, it might not come out perfectly smooth, which is what we want so as to secure a watertight seal between the diver and the balloon rubber.

Next take some GEL Krazy glue or equivalent. Krazy Glue in GEL form provides us with only a bit more bonding ability and helps eliminate any unevenness in our diver's faceplate. Squeeze a little blob onto a level surface. In the video we utilize the larger end of the ballon stretcher for this purpose... and then using the tip of the applicator, smooth outside the blob until you receive a light even layer of adhesive spread out over about a nickel sized circle on the board. Then take the diver, and gently push it in the gel spread you have created. Move it around a bit, but don't push it in and hold it. We don't want it to bond to the paddle, we only want to move an even coating of the adhesive onto the faceplate of the retina.
Having done this, press the diver's faceplate onto the stretched balloon neck and hold it securely applying even pressure and without moving it around for about 30 seconds. This will provide the adhesive enough time to place so that you can then remove your finger and allow the glue to cure for about another 15 minutes.

When the glue is dry, have a little pair of scissors, or razor blade to cut the diver free in the balloon. Do NOT pull the balloon off the stretcher, this will put too much strain on the rubber and it might pull free from the diver. Rather, cut away the rubber from around the diver when it is on the stretcher.
Once the diver has been cut free, then use your scissors or razor blade to trim around the outside of the faceplate until the rubber edge is flush with the faceplate's border. We find manicure scissors work best, or a single sided razor blade, but the key is sharpness. Even a slightly used razor blade will make getting a nice clean trim job hard to realize.

In case you have enough time and resources, feel free to construct your diver from different colored parts and or balloons. It offers you the opportunity to craft unique individual aquaBots if you have more than 1 child or one granchild which you aspire to amuse or gift with your Cartesian diver.

The next step is to secure the face mask ring. Press it onto the faceplate of the retina and a drop Or two of REGULAR krazy glue will seep into the seam and seal it.

The next step of our construction is to determine the amount of weight we need to sink our aquabot if it is full of water. ABS and PLA unweighted will either float on the surface of water, which isn't what we want. As mentioned earlier, we want our diver, when full of water to sink convincingly (but not as hard as a rock) when it is put in the water. Here a little experimentation is required. Small dishwashers, or nuts can be used and added to the diver until the desired result is reached. Get a large bowl and fill it with water... the best choice is a bowl that will easily allow you to get both your hands in.
One needed to hold the model and the other to operate the plunger. Have a washer or two, pop it in the pedestal part of the retina, snap on the base, place it in the water and see if it sinks. Its best if you perform this operation with the diver submerged, because we must add only enough weight to sink the aquabot if it is totally full of water. Use the plunger you printed, and holding the diver upside down, so the hole at the bottom is facing upward while it is under water, pump out any remaining air.

Adjust the weight up or down and repeat the process until the diver, fully full of water, sinks to the bottom of the bowl.

Now that you have determined the correct amount of weight, it's time to paste the weights to the base plate of the diver. Remove your aquabot in the water, snap off the cap, remove the weight and dry your diver, weights and bottom cap completely.

You might have seen during your buoyancy testing that your aquabot was tilted as it sank. So in gluing the weights into your baseplate, glue them slightly off-center. This will allow you to compensate for the tip by rotating the base cap to achieve a degree ascent and descent of your model before you seal on the bottom cap. Using krazy glue in moderation, paste in your weights so that they don't obscure the hole, and that they don't get in the way of the rim that's necessary for gluing the baseplate into the diver body.

Once the weights have been glued in place and the glue has dried, then return your diver to water, pump out all the air and observe your diver as it sinks. If it is tilted, give a small twist to the bottom plate. Since you glued the weights slightly off centre, you'll have the ability to adjust the angle of your diver in the water by turning the base plate before the aquabot sinks and rises perfectly vertical.

Your Cartesian Diver is now complete.

The outer room used for our project is a Sparkling Ice 750 ml soda bottle. It was chosen for its compact size, and relatively affordable price. You can buy a bottle of it for about a dollar at the local grocery store. If you can actually drink the stuff, then its even more practical. You can use any size soda bottle you like, so long as it's a standard sized cap. Our diver is printed so that it will slip neatly into a standard size soda bottle opening. You can of course use a bottle with a larger opening also. The main requirement is that it is sealable and that the sides are flexible. From an aesthetic standpoint, you might want to steer clear of bottles which have designs or lettering embossed in the sides which obscure the view of the retina from the room. However if you wish to use the fancy bottle helmet and feet we have provided, it will have to be a Sparkling Soda bottle.

The next step is preparation of your water room. If you're using the Sparking Ice soda container as we did, then you'll first have to remove the label. Remove it from the bottle, but require a little care... try not to squeeze the bottle too much or it will leave permanent crinkle marks. We used the small scissors to cut a small piece away which enabled us to remove the balance of the label easily.

The adhesive left on the bottle is soluble in Naptha... which you can grab at any home improvement store. We just put a bit on a folded up paper towel and the paste dissolved quite quickly. A second clean paper towel enabled us to remove any of the naptha and paste residue and we were left with beautifully clear bottle. As you clean your bottle note that there are two very fine seams on opposite sides of the bottle. Observe how they are positioned, as we'll be using them for alignment purposes afterwards.

First of all lets build the faceplate. Take the face collar, put a few dabs of adhesive on the inside lip and then press on the emblem plate face outward to the collar. The up and down orientation of the plate isn't important at this moment.
After you have glued the emblem plate into place and the glue has had an opportunity to dry, apply glue to the outer border of the Helmets mask, and then, taking the collar with the inset logo plate, then press it onto the diver, so that the M is in the proper orientation and hold the face collar into place until the glue dries.

Now it's time to paste the head onto the bottle. To begin with, screw the bottle cap that came with the soda onto the bottle nice and tightly... as tightly as you would if you were putting a cap back on a bottle of soda that you wanted not to loose its fizz. After that, do a test match. Take the helmet and press it firmly onto the surface of the bottle. You want to make certain that the bottle cap is inserted completely in the hole in the helmet, and you want to be able to do this so that the ears of the helmet line up with the seams on the side of the bottle. Aligning with the seams isn't something that you want to do when you've got the helmet set up as that might cause loosening, or over tighenting the the bottle cap which you have already put on with the ideal force.

If that all looks good, remove the helmet by from the cap by pulling and rocking it back and forth but not twisting it. Once removed, Apply a liberal amount to the top border of the bottle cap on the bottle, and slightly down its sides. Do not over apply glue to the sides of the bottle cap or you run the risk of it bleeding down and cementing the cap into the bottle. We want it to adhere to the helmet only.

With the adhesive applied, push down the helmet onto the bottle cap, lined up with the seams on the side of the bottle. Make certain that the helmet is pushed as far as it can be. Having accomplished that, don't rush the setting of the glue. An hour's patience for a gelled krazy glue isn't unreasonable for a lasting strong bond.

Once the adhesive has dried, you should have the ability to untwist the helmet and remove it easily. If you used the ideal amoutn of adhesive and gave it enough time to set properly, the bottle cap that's now glued to the helmet will be removed too.

Now take the soda bottle, and apply a generous drop of glue to the top surface of each of the legs of the bottle. Once that's been accomplished, push the bottle into the foot base, making sure the bottle seam is aligned with the middle of the side of the feet.

You are now ready for final construction of your Cartesian Diver.

Fill the jar with water, up to about 1/3 of an inch below the neck of the base of the cap stem and place it aside.
Take your diver and submerging it in the water bowl use the plunger you printed to empty the air. Now, you're going to be setting the diver to its state of natural buoyancy. If you recall, natural buoyancy is achieved when only a small tip of of the AquaBots mind is floating above water. So using trial and error adjust the floating level of the diver until the required effect is achieved.
To pump in more water, hold the diver upside down beneath the water level and use the pump to pump out air. To expel water, hold the diver from the water right side up and use the pump to pump water from the diver.

After you have set the diver to its natural buoyancy, drop it in your water room and twist on the helmet cap snugly and securely.

Your cartesian diver is complete.

Simply adding pressure to the sides of the bottle with your fingers and thumb should sending your aquabot diving into the bottom of the container. Conversely, once at the bottom of the chamber, releasing the pressure on the surfaces of the container will cause your diver floating once again to the surface.

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