How to Turn a Toothbrush Into a Torpedo!





Introduction: How to Turn a Toothbrush Into a Torpedo!

Do you have an electric toothbrush you don't use anymore or are thinking about throwing away? Do you have time on your hands? Why not turn it into a SUPER-AWESOME TORPEDO AND ACHIEVE POOL DOMINATION!!!!!! FIRST THE POOL THEN THE WORLD!!!!!

First, why use a toothbrush? I have found that toothbrushes are great waterproof motors. I have tested them so far to depths greater than 5 feet with no leaks. Most other store bought submarine motors leak at these depths and eventually rust up.

Step 1: Obtain Materials

Materials(listed from left to right)
1.Duct tape(shiny silver duct tape is better, but it is more expensive)
2.Anything buoyant enough to float your toothbrush, I used a Bawls bottle, but you could use anything else, I have even used a plastic bag.
3.Colgate motion toothbrush
4.Half an easter egg, mine was 3.4 cm(1 1/4 inches) in diameter and fit the toothbrush perfectly
5.Lego propeller
6.Lego axle 3 studs long.
7.Lego axle connector
8.Alignment tool 10 stud long axle and what I like to call an i-piece
9. Cowling, Axle 3 studs long, i piece, and cowling piece.(Optional, cowling piece helps prevent the propeller from undergoing "spontaneous mechanical failure" if it hits a wall)
10.Disposable lithium batteries(optional, but they will make your torpedo go much faster)
11.Hot glue gun with hot glue

Step 2: Attach Cross Axle to Toothbrush

First remove the toothbrush's head and discard. Next clean out any gunk that is inside the toothbrush, use maximum cleaning firepower.

Heat up the hot glue gun and read the following, twice, this is a hard step.
Turn on the toothbrush and keep it on. Then insert the 3 stud axle into the axle connector Inject glue into axle connector. Don't put so much glue in that it overflows, try to fill it about ¾ full. Then push the axle connector stud assembly onto the part that turns the toothbrush head. Now quickly push the alignment tool onto the stud assembly until the stud is aligned. Let it cool and check quality by holding the spinning axles in front of a CRT display. If it wobbles it will work fine if it doesn't it will work great. To fix a mistake wobble the axle off and extract the glue with a paper clip.

Step 3: Attach Easter Egg and Propeller

Now attach the propeller and the Easter egg half. If the Easter egg doesn't fit the toothbrush perfectly use hot glue or epoxy. You should end up with what is shown in the picture.

You can skip the next step if you have lithium batteries and you can get the toothbrush out of the water if it crashes. Lithium batteries are lighter and more powerful than normal batteries so they provide enough thrust to keep the toothbrush afloat, however it will mostly go in circles, and will sink if the propeller stops moving.

Step 4: Attach to Buoyant Object and Begin POOL DOMINATION!!!!

Now apply a liberal amount of hot glue to the side of the toothbrush that doesn't have the switch, and then attach it to the buoyant object and then add duct tape to make sure that the toothbrush doesn't fall off. Now let the glue cool.


Or you could just race them against each other. The rules of toothbrush racing are simple get from point A to point B before everyone else. Oh yeah, you also can't use a rudder to keep it going straight to make things a little interesting.



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    You could also use the toothbrush to power more than a sub you can build cars and anything you want to move with it aswell

    Hmm - I like this - perhaps make two of them as nacelles for a foam body, then a simple and well insulated tiny controller rewired where those switches are. Hey presto - smallish water robot. Add servo's to angle those nacelles and it can dive too.

    you should totally add a war head and some explosives!.... That would be awesome!

    1 reply

    i have the technology and info to do that but im thinking bigger 2 ft bigger

    I built a couple of these torpedoes.  They work great!    I intend to use them to power a toy submersible.  These instructions are clear and easy to follow.

    Kudos, Gene Hacker, for a great Instructable!

    someone tell me how i could make these remote control, and i'll make an instructable on a R/C boat launched torpedo that can take out an R/C boat

    2 replies

    hack up a foam r/c plane and replace the motor w/ propeller for the toothbrush motor.

    Well, you can hook it up to a control device by putting two screws in the battery cover, and attaching wires to the screws.

    Is there a submarine on the bottom of your pool? If it is make it fire the torpedo!!!

    Sorry about double posting but, Couldnt you put a slightly bigger prop on it to make it go faster if your toothbrush could take it?

    I need to make this. it would be cool to put this thing in our pond. Wonder what the fish will think....

    It goes faster than you would think. I had trouble taking a good picture of it because of it's speed. It is even faster if you use fresh lithium batteries. You could get additional speed by drilling a hole in the battery cover and threading some wires through to the battery leads and then covering the hole with silicone(marine grade works best), so you can wire up more batteries. Of course you risk burning up the motor, so add a heat sink if you are really ambitious. If you are even more ambitious wire 2 toothbrushes into a pool-roving robot.

    2 replies

    what is a heat sink? does it absord heat?

    a heat sink is a little device that helps keep temperature in a component (the motor in this case) lower by dissipating it so you don't burn it out.

    Think of this: You are really and truely in need of a drink at the pool and you don't want to get out. What do you do? Have one of of your friends jet you a drink!!

    bawls bottle for great justice?