One of the most popular boats at the Maker Faire Tinker Challenge was the submarine. Since the submarine is also the powerplant for many boat designs, we offer here, for your tinkering pleasure, the step-by-step instructions on how to make a submarine from recylced materials and a few simple tools.
Step 1. Collect your materials and tools. You’ll need: scissors, wire cutters (don’t be tempted to use your scissors – that’s just asking for trouble), pliers (for bending wire), utility knife (although it may be possible to do the cutting with your scissors – mine just don’t have a sharp enough point), a rubber band (make sure it’s at least big enough to stretch the length of the bottle), a piece of stiff wire, and a juice bottle.
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Step 2. Make a hole for the propeller shaft. Using the point of the utility knife, drill a hole in the center of the cap. This takes a little bit of practice, so don’t feel like you have to rush. Place the point of the knife where you want to make the hole, then lay the thumb of the same hand that is holding the knife on the flat side of the blade – this will help you brace the knife and give you a better “feel” for the work. Now, while applying light pressure, twist the knife back and forth. Don’t press too hard, just enough to get the point to “bite.”
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  As soon as the point comes through the cap, turn the cap over and widen it from that side as well. Remember, the hole is for the propeller shaft, so it only needs to big enough to poke the wire through.
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Step 3. Create the propeller shaft. We will craft the shaft from the wire (if you haven’t straightened the wire yet, now is a good time to do it). Measure about an inch down from the end of the wire and grasp it firmly with both your hand and the pliers. Bending wire accurately with pliers also takes a bit of practice, so if you have some more wire you might want to practice on that before making a bend in your nice straight piece.
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 Make the bend nice and square like it is shown here. I’m holding it against my thumb so you can see that the part we bent is about one inch long. Did you know that the word “inch” comes from the same latin root as “ounce” and that they both mean “one twelfth”? Anyway, if your bent wire doesn’t look exactly like mine, that’s OK, just try to make it a good bend.
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 We don’t want the propeller shaft to go through the cap and out the other end of the boat, so we’ll have to trim it. Accuracy is not very important here either, so if you are under 14 years old, try cutting it to be the length of your longest finger. I’m using my index finger as a guide, but I have pretty large hands. Hey, did you know that the bones in your fingers are called “phalanges”? It’s true.
It’s easier to cut wire at the deepest point in the mouth of the wire clippers. Most people try to cut with the tip of the wire clippers, but that’s the hardest place to try and cut with. It all has to do with getting leverage. |
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Step 4. Make a bearing. The first step is to drill a hole. We’ll use the exact same technique we used to make the hole in the cap. Making the hole now is easier than making it in the little piece that we are about to cut out. This hole can be just barely big enough to fit the wire in, so you shouldn’t have to drill it much – especially because the bottle is thinner plastic than the cap.
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 A bearing is a device which lets one thing slide against another. We know that the rubberband is going to pull pretty hard on the propeller shaft, so to make sure that our new little loop doesn’t get stuck on the surface of the cap we’ll make a bearing. Some bearings are made out of steel and shaped like marbles, those are called ballbearings. We don’t need that so we’ll make ours out of one of the corners of the juice bottle.
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 Using the same way of holding the knife we used to make the hole in the cap, we’ll carve a circular disc from the shoulder of the bottle. This is pretty useful technique and can help you make accurate cuts in lots of different kinds of materials.
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 Now you should have a slightly curved disc of plastic about the size of a quarter with a hole in the middle. Mine doesn’t have the hole because I actually cut it out before I remembered that it is easier to do the drilling which it is still part of the bottle. Yours should have a hole in the middle. If it doesn’t, you’ll have to make one now.
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Step 5. Assemble the propeller mechanism. Put the new bearing disc on the shaft. Make sure that the shaft goes through the concave side, which is just a fancy way of saying that it should curve towards the little loop that we made on the shaft. If you put it on the other way, it will still probably work, but not as well (and you might have to take the mechanism apart fix it).
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 Slide it all the way up to the stop-loop that we made. It’s ok if it doesn’t spin freely – the stop-loop usually sticks to the disc once we wind it up anyway. If it all sticks together once you wind it up, try adding a drop of vegetable oil to the spot where the disc touches the cap.
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 Add the cap from the bottle and our mechanism is almost done. Notice how the bearing-disc curves away from the cap? That means that only a little bit of the disc touches the cap, which means that we will have less friction between the two surfaces. Too much friction and the propeller will stop spinning.
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 In order to connect our power-plant (the rubberband) to our propeller shaft mechanism, we’ll have to make a little hook. Turn the cap over and bend another “U” shape. Mine is a little bigger than it needs to be, yours can be smaller if you want.
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 Make sure that the end of your hook doesn’t touch the inside of the cap. If it does, use the clippers to trim some wire off and make it shorter, or straighten out the hook and make a new one – which ever you like. All we need here is some shape that will hold onto the rubber-band, so precision is not important here either.
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Step 6. Build the motor. We’re going to make another hole in our bottle. This one can be a little trickier than the ones we’ve made so far because it has to be big enough to put the rubberband through. Pick a spot near the center of the bottom of the bottle. Even though this bottle has a big seam across the bottom, I’m going to put my hole right in the middle because that’s the kind of person I am. As it turns out, the exact placement is not very important, so don’t fuss if your hole is off the side.
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 When you are done, the hole should look something like this – a little smaller than a pencil, a little bigger than a shrew’s nose – just big enough to poke the rubberband through. Hey, I just learned that some shrews use echolocation, just like bats. Don’t worry if your hole is not very round either, this end of the rubberband is not supposed to spin.
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 It’s time to put the rubberband through our new hole. This is a bit of a puzzle, but I’ll tell you how to start – push some of the rubberband through the hole, then remember that you are primate with opposable thumbs (is the thumb-bone a phalange too?) which means that you can make and use tools. You’ll figure it out. Need a hint? Go fish.
No, really, that’s a hint. |
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  To keep the rubberband from pulling all the way through (once you have fished it out from the other end), put a bit of wire through the pokey-out bit of the loop like this.
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Step 7. Attach the motor to the propeller shaft. Pull the rubberband out the mouth of the bottle (good thing we put that bit of wire on the other end to keep it from pulling through, right?), and try not to imagine that you are pulling on a submarine’s tongue. Did you know that the people who work on submarines are called submariners? It’s true. And just in case you are wondering, my favorite submarine is Alvin.
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 Hook the hook that we made on to the end of the propeller shaft onto the rubberband. I like this bit of the mechanism because it’s usually a lot more difficult to get a motor connected to whatever you are trying to turn. Although, airplanes are the exception, their propellers are mounted right on their motors just like we are doing with our submarine.
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  Now screw the cap on and pull the rubberband tight from the back. It doesn’t have to be super tight, just enough tension to keep it from falling off the hook on the end of the propeller shaft. The tighter we make the rubberband, the fewer turns it will be able to store, and the more turns we can store, the longer our motor will spin our propeller. Your rubberband might not need to be tied off, in which case just leave your wire (feel free to clip it if it’s too long) so that it doesn’t pull through.
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 Here’s a trick for tying off a rubberband (or tying a balloon) quickly and easily. Wrap the rubberband around two fingers and then pull the tail back between your fingers and under the loop of rubberband (the picture shows right before I tuck it under). I made up this technique when I was seven, and you can use it whenever you need it, you don’t even have to ask me.
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 If you had to shorten your rubber band like I did, it probably looks like this now. It’s like a little ponytail poking out – cute (but cute in a kind of serious mechanical submariny sense, right?).
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Step 8. Smoke Test. Now is a good time to give our system a quick test. In the world of mechanical engineering they call this a “smoke test”. I think that’s because when you are making a new machine, you want to make sure it isn’t going to go up in smoke after you have put it all together. Better to find out now before we put all the finishing touches on.
Hold the juice bottle in one hand and wind up the propeller shaft with the other. Just give it a couple of turns until it starts to push back against your winding finger, then pull your finger away quickly (so that the end of the wire doesn’t nick it) and watch it spin. If it doesn’t spin, try winding it more. If it still doesn’t spin, check over all the assembly steps and make sure your submarine construction looks the same at each step along the way. |
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Step 9. Make a Propeller Cut a piece of your waterproof metal tape (if you don’t have any handy, you can use double-sided tape and tinfoil, or you can cut a piece of aluminum from a soda can, or…) that is about as long as your fingers. My fingers are a little too long so I cut mine shorter (guess what, it doesn’t have to be perfect!).
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 Now fold the tape longways (be sure to leave the backing on the tape so that the sides don’t stick together yet) with a nice sharp crease. |
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 Tape is not quite strong enough (actually, it might be, I’ve never tried it with just tape, but it seems a little flimsy) on it’s own, so we are going to cut a piece of wire to fit in the crease and add some strength to the material. Lay a bit of the straightened wire in the fold so that one end is even with the end of the tape. It’s like a hot-dog in a bun, or a rake lying in a furrow, or bit of wire lying in a bit of tape.
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 And clip the other end so it’s flush with the end of the tape as well. You should have a piece of wire that is exactly as long as your tape. If it’s not exact, it’s ok, it doesn’t have to be perfect.
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 It’s time to peel the backing off the tape. If you figure out a good way to get a grip on the backing, let me know, it makes me crazy. Be careful, once you have the backing off the tape will start to stick to everything, including your fingers. To help us keep from sticking it to everything, we will just peel back one half of the backing – just to expose the crease.
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 Now, set the bit of wire that we cut to the right length into the crease. You only get one shot at this, because once that wire sticks in there, it’s very difficult to get it to come free – so be especially careful when you do it. This is one step where accuracy counts for something.
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 Attach the propeller (you knew that was what the tape was, right?) to the propeller shaft. Make sure that the propeller shaft comes out of the middle of the tape. This is another step where a little bit of precision pays off in the end. So before you press it to the tape, take another look at it and make sure it’s nice and centered.
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  Ok, peel the rest of the backing off the tape and stick the two sides together so that they sandwich the shaft between them.
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Step 10. Water test! Tah dah! It’s almost working! Go ahead, wind it up, stick it in the tub and let it go! Stand back, have a towel handy. It’s going to be a bit splashy…
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Step 11. Fine tuning. The first thing is to shape our propeller – this is something that you can keep tinkering with. The “pitch” of the propeller blades determines how much water gets pushed when the propeller spins. Make sure that each blade of the propeller is twisted in the opposite direction. Now wind it up and let it go (not in the tub) and you should be able to feel it pushing air in one direction or the other.
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 The direction you wind it will determine which end of the boat your propeller “likes” to be on – it can either push or pull the boat through the water. Which is better? Go ahead and try it in the water. See what works.
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One reason that it still may not be working is that it is too floaty. This is supposed to be a submarine, so it needs to be under the water. The way to make it less floaty is to cut a lot more holes in the sides so that it will fill up with water.
I cut three more holes in mine. Here’s a video of how it works at this stage. |
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 I noticed from doing the water tests this time is that my propeller is too wide. It keeps bonking into the bottom and the sides of the tank. Plus, it looks like the rubberband is having trouble turning it. I could adjust the pitch of the propeller blades, but then it would still bonk into things. So I decide to trim the propeller. Since we put that wire in there, we will have to use the wire clippers to cut it.
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  I also observed that the body of the submarine is spinning almost as much as the propeller (this is a demonstration of Newton’s Third Law). So I decided to put some fins on the sides to give the submarine body some resistance to spinning.
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And here’s a video of how this version of it is working. It’s not too bad. It certainly goes through the water. But I think it could be better, don’t you? Why don’t you experiment with the design and let me know.
Here’s some things I can think of off the top of my head that might be interesting to try:
Have fun, and let me know how it turns out. Remember, you are never done tinkering with something until you understand it completely or you stop having fun. |
10 Comments
10 Comments so far
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Great project!
A couple of suggestions Rather than use a knife to cut holes in the cap and bottle I suggest using a piece of wire and a candle. A heated wire (held in a potholder) will cut holes through the plastic a lot easier and more safely than using a knife on hard slippery plastic.
Also if you make the side fins on the side of the sub larger and angle them opposite the propeller angles, the sub will go even faster.
Hi,
First, I really like your design. The prop gave me a bit of trouble, so I’ve been playing around with plastic water or soda bottles and have made a prop out of two diagonally cut strips from the side of a bottle. Overlap the pieces and either staple them together or use hot glue. Poke a hole in the center and thread it onto the shaft. A sharp bend in the wire will hold it into place. Duct tape might help as well.
Cheers!
Sarah
yeah its a good but i can’t use a propeler.
Comment by brittany 01.22.08 @ 6:04 pmdude this is so awesome i have to do this same kinda thing for my final in science and your whole idea really helped me out big time
Comment by kandice 06.03.08 @ 4:00 pmThis is so great!! I’m gonna try this right away.
Comment by Khai 08.14.08 @ 12:30 amhey dude this is the best experiment i ever read.. (: ..plz have more experiment.
Comment by syafiqah 08.14.08 @ 1:03 amhey im in 6th grade and we r doing a project and we have to make a plane,a boat or a submarine. guess what i chose? u guessed it-a submarine! all i can say is oogle is a wonderful thing.
Comment by Cryssie 09.16.09 @ 11:16 pmGüzel bir çalışma. Fen ve Teknoloji dersi için yaratıcı fikirler sunuyor. Tinkering School etkinliklerinin tamamı oldukça faydalı bana göre.
[http://translate.google.com Turkish -> English]
Beautiful work. Science and Technology offers creative ideas for lessons. Very useful to me all of the Tinkering School events.
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