ROV stands for Remotely Operated Vehicle. These robots are used by scientists to explore the waters both offshore and in the deep sea, and often bring back samples and/or take video of their underwater findings. ROVs usually have a tether from the vehicle to the boat, which lightens up the load quite a bit (as it no longer needs to carry its own power or data storage). Powerful motors, such as bilge pumps or 24VDC motors, enable this robot to move in all six directions. ROVs are designed to be slightly positive in buoyancy, so they can surface automatically during power failures.
Of the robots we’re going to build, waterbots have the highest instant-success rate. You basically attach a motor to a piece of foam, stick it in the water, and it either floats and zips around, or capsizes and acts like an odd submarine. Either way, kids shriek with delight that their creation actually moves.
We’re going to use foam to create a waterbot, which will be powered by a simple electrical circuit. The hardest part of this activity will actually be building it stable enough so it doesn’t capsize. Boats are always built in a way so they don’t get pushed or flipped over easily by carrying a ballast, or extra weight, at the lowest part of the boat. You’ll need to figure out where to out your motor and batteries (which weigh a lot compared to a foam block) in order to balance your boat.
One of the biggest hurdles to overcome when building junkyard robots is friction. Since the motors have high speed and low torque, they can be difficult to use without a gearbox (which is both hard to find and out of the scope of this class). Since water has little friction, the robot will move about quite easily in the wet environment. We offer kids waterproof materials to build their robots with so that in the event their invention has trouble moving, we usually toss it in the pool to see if it can swim… which sparks another avenue of creativity and another round of improvements. Just be sure to keep the batteries out of the water. Are you ready?
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The propeller actually isn’t foam, it is plastic. So it would be fine if it gets wet. But, the propeller shouldn’t be in the water. Also, but sure to keep the motor, wires, and battery dry.
We don’t recommend using floral foam. It will sink once it soaks up water.
just wondering if foam propellers will get ruined in the water?
does floral foam work or will it sink?
Let us know how it goes. But keep in mind that popsicle sticks will absorb water, so you’ll want to be sure they don’t get wet.
I think I’m going to make my propeller out of craft sticks
Aline, 11 yo
Yes – go for it!
can I use a water bottle?
Yes, however since it operates in cool water, it works just fine without overheating. Good observation!!
Hi, I was wondering, I saw how you water proof the motor for the underwater ROV, but in that video the silicone surrounds the entire motor. Wouldn’t this effect the cooling system, I mean like block those little slits in the motor from getting air flow? or is it OK to block those vents on the motors?
Thanks
Yes, look in the Master Shopping List for the Camp labs and you’ll find direct order links for the projects. https://www.sciencelearningspace2.com/e-camp-shopping-lists/
hi can you tell me where to buy the materials for the water-bot please?
It sounds like you’re off to a good start! If you send me photos of what you’re working with ([email protected]) then I will probably have more suggestions!
I took apart a old RC car and found two Motors!
I got a propeller from spare parts for my drone. I have some wires but they don’t have alligator clips I haven’t been able to get a complete circuit but everything works. I tried to wrap the exposed part of the wires(the ends) to the battery pack. (The other ends were already saudered unto the motor. Any suggestions on how I can work with these pieces… If not I can try to find some alligator wires somewhere. i just didn’t know if you had suggestions.
-Enoch Gilbert (12)
I would try both and see which works best for you (like a real scientist would). The hot glue rips off easily so you can be flexible in where you mount the motor. Use plastic propellers for the water so they don’t get saturated with water and bend. Those summer personal fans are really great (and cheap) because they come with a motor, propeller and battery case all in one that you can rip apart to use the pieces!
Okay thank you! Should I add it behind the propeller or beside or under….where would you suggest? Also would it be good to make it out of cardboard?
-Lucy Aslinger-
Without seeing your invention, my guess is that it’s because of the torque the motor generates as it spins the propeller. Have you ever noticed how helicopters stay put even though they are spinning their main rotors? They have a tail rotor that counteracts the spin generated from the engine turning the main rotor. The rotor spins one way, and the motor spins the other unless it’s bolted down or held in place by friction (like a helicopter that’s still on the ground).
So for your waterbot, if you add a rudder, you can make it go straight! Just stick a fin in the water at an angle (make it adjustable so you can make it at just the right position). The hovercraft project in Unit 1 has ideas for this very same thing.
I tried to make the water bot, but it only went in circles! How can I fix that?
-Lucy Aslinger-
Above or below water… just keep the batteries clear of the water and it’ll work just fine.
when you make a waterbot, can it go underwater?
This is made from really easy to find stuff if you know where to look. Can you find a piece of foam left over from the packaging from a box? And the motor and propeller are found from old toys – if you can get one of those handheld or personal fans, they come with the propeller, battery pack, and motor all in one that you can rip apart to use.
I am trying to make a waterbot but I do not have the right materals to build it 🙁 were do you even get the supplys? I can’t wait to get all the supplys so I can make it:) (we have a pool so when I build the waterbot i can put in the pool!
We used a pool noodle for our foam base. Instead of top or bottom for the motor we fed the wires through the tube, connected them to the motor, then push the motor back into the tube. We have renamed the ‘bot to “Splash-a-lot Bot.” Water was everywhere! Unfortunately, we were not outside at a pool, but indoor at a sink.
There are a couple of different ways. If it’s out of the water, like on top of the foam, then you don’t have to worry about it. If you wrap the motor in tape and seal the holes carefully with hot glue (make sure the hot glue doesn’t drip *into* the holes), that will keep most of the water out. If you really want to go water-proof the motors for extended underwater use, then look at the instructions for the ROV – the motors are completely sealed using silicone, vasoline, and wax. However when I do the waterbot project with kids, I find that the motors work find underwater for about a week or two without doing any waterproofing at all. Hope this helps!
How do you make your motor waterproof?
I’ve sent you a secret email…
Hi Aurora,
Could please tell me where to purchase the gear pully for the jiggle bots? I’ve searched everywhere and no one seems to have them.
Thank You
Sure – sounds like fun! Be sure to send me a picture!! You can extend the wires by clipping on additional alligator wires, or making your own out of aluminum foil strips wrapped in masking tape.
Is there a way to make longer wires and put the batterieson a piece of styrofoamand make the robot with remote control motors and sliding doors that can be raised by blowing on a tube after the doors close?
Hello Aurora-
I will post a picture as soon as I gather the stuff to make it,
haven’t had time to go and get the stuff for the robots.
Yes, that’s a great idea. Real boats do this very thing (you can research what a ‘keel’ is). Try it and send me a photo!
Hello Aurora –
I was wondering would weighting the bottom of the ship would it in turn balance the boat, so you can cut the foam to a more desirable shape and not just blocks.
Dylan Bingham age 13
son of Louise Bingham
Try it and send me a pix! 🙂
What do you think would happen if you put foam on the front, back AND sides, Aurora?
This was Skylar talking. Thank you!
Thanks Aurora! My husband was able to drill the holes a little larger and they worked just fine. I think we’ll wait and use these for now.
My kids had a lot of fun today with the waterbots. Unfortunately, they didn’t tip over and no one was interested in any modifications. 🙁 Buuut… they are interested in building more. 🙂
You might have to get out your small drill bits to make the hole large enough to fit the shaft diameter.
Yes – this offer is still good if you’re int he USA. Contact me directly if you’re outside the USA for a specialty international parts packet. 🙂
We’re having trouble finding propellers as well. Our local hobby shop closed down a while ago. We tried taking the prop off a balsawood flyer but the hole is too small to fit on the motor shaft. Might be able to make it work for now but would like to find something that works better.
Is your offer still available for $3 and a SASE per prop?
Hmmm… it seems Home Training Tools keeps changing the type of propeller they sell. Sometimes it’s an airplane propeller, other times it’s a water (boat) propeller. Ok – we’ll send you the one we have in the experiment video when you send us a SASE (include two stamps) and $3 per propeller. Just be sure to let us know how many you want. The props we have work for both air AND water, so you can use it with the Waterbot, Hovercraft, and more!
Hi Meredith,
You want to press-fit the motor firmly onto the shaft – make sure it’s a snug fit that would take a lot of yanking to get it back off. If the shaft of your motor is too small (or the propeller hole is too large), then use a small dab of crazy or hot glue to fix that right up. If you’re using glue, be sure to keep it only on the shaft and not let it drip to the motor, or you’ll glue the shaft to the motor (and the shaft won’t spin). The reason it flies off in the water and not in the air is that the water drags more on the propeller, so the prop feels more weight (notice how it spins slower in the water than air). Have fun!
Hello. We are wondering why the propellor flies off of the waterbot when in water, whether we turn it on while in the water or before it is placed in the water. Do we need to glue it to the motor?
Thanks!
Yes, we caught that. Thanks for your eagle eye! They should be working now.
There is no volume… help!