Make an RC Submarine from RC Car!

Start by collecting the following items:

- hot glue gun and multiple glue sticks
- a hobby knife (aka exacto knife)

- one working electric remote control car
- two lego propellers*
- enough batteries for remote and car
- a sturdy** plastic bottle big enough to fit circuit board and batteris but not bigger
- the bottle's cap
- two or three corks
- electric tape
- duct tape
- a hand full of nails
- two or three feet of wire (I used wire from an old lamp but a smaller gauge (diameter) wire would probably work fine)
- WD-40 and/or automotive grease
- a plastic easter egg (optional)

Once you have collected your supplies you move on to step 1 and begin to take apart your RC car to 'harvest' the parts needed for your sub. You should know that your RC car will most likely be unrepairable after these changes.

*The best are the ones meant for lego boats or subs, though, some lego airplane propellers work... as you see in my own sub. See step 6 for a picture of these lego boat/sub propellers. You can can also buy fancy expensive propellers at any hobby shop.

**The plastic bottle must be sturdy because of the pressure that will be on it when diving deep. The deeper the dive the more the pressure.  If your bottle crushes you run the risk of it leaking and damaging circuitry. It could also loose its buoyancy due to a change in volume causing it to sink out of the range of your remote.  Unless you have a fishing line attached when this happens you could loose your sub. 

Here is a video of the finished product at play:

(We attached a string to it while test driving just to be safe.)
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Step 1: RC Car Organ Donation

Picture of RC Car Organ Donation

Step 2: Submarine Hull from a Bottle

Picture of Submarine Hull from a Bottle

Step 3: Power Wire Modifications

Picture of Power Wire Modifications

Step 5: Finish the Hull

Picture of Finish the Hull

Step 6: Propulsion Systems

Picture of Propulsion Systems

Step 7: Attaching Struts

Picture of Attaching Struts

Thank you for posting this instructable. After coming across this, I was inspired to build my very own. at first i wanted to to build a clone but then I pushed myself to make one that that has some ideas I thought up. Thank you for inspiring me.
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ScrapSmith (author)  metalhead87119 months ago
That looks awesome! I love the water-proof motor encasement. How well did she work?
neodymium2 years ago
Very nice sub. Going to try this one out as soon as I get the parts.
rajat Gyesterday

hey scrap smith this is really awesome. I'm making it for my science exhibition,its almost ready but my propellers are not like urs they are simple propellers as used in fans but I hv used 18 V batteries..its not running fast lyk urs..please help..!! thanx for inspiring me

ScrapSmith (author)  rajat G14 hours ago
Hey rajat,

I am guessing there is either a problem with your propeller being too big or too small, a problem with your batteries not being charged or being the incorrect size, or a problem with your RC car being too weak to being with.

Can you post a picture of your propellers?

Are you sure your batteries are charged and are the correct type for your RC car?

Was your car very fast/ very strong to begin with?

If you can answer these questions it would help me help you.

Good luck with your science exhibition! I did a lot of stuff like that when I was younger and I can tell you that judges/teachers are usually just as interested in seeing what you failed at, but learned a lot from, as they are in seeing what you succeeded at.

- SS
mmehzin3 months ago

did you make this?

and will it work?

dgalvan38 months ago
Hi, thank you for the instructable, I am almost done with my sub but there is two problems, my sub appears to have a leak, i do have a idea where the leak is, but how can I seal it off? I'm afraid if i use hot glue the bottle will be burned making more leaks, what can i do to seal it off? Also my motors have these metal things that are on the motors so i can't trim them. When i hot glue my propellers ( the lego ones in your picture) it fell off when it was under water so it came off and it appears that the propelleres aren't strong enough. Please help me, thank you, and respond as soon as you can, thanks dgalvan3.
ScrapSmith (author)  dgalvan37 months ago
I would suggest that you try hot gluing on a similar pice of plastic to test and see if it will burn or contort. I have glued on lots of bottles and the worst that has happened is that the plastic bottle disfigures and hardens a little but I have always been able to fill in the gaps with hot glue.

I am guessing that those little metal things are gears on the shaft of your motor. Your two options with these are:
1 Force the gear inside the propeller.
2 Remove the gear allowing the shaft to enter the propeller.

Forcing the gear inside the propeller will only work if the gear's diameter is less or equal to the lego propeller's inner diameter. That being said, the way I have found to force the gear inside the propeller is to heat up the gear using a candle or lighter and then use the hot metal of the gear to burn/melt your way into the plastic center of the propeller thereby fitting the plastic propeller over the gear. Obviously this can be a bit dangerous if you are not careful so please take precautions to keep you and others around you safe. I will not be held responsible for what you do with this information.

Removing the gear can be tricky but is usually possible with a pair of vice grips and a another pair of pliers or vice grips. Basically the idea is to loosen the gear and pry it off of the shaft. If you pry too hard there is the danger of damaging the shaft and/or the electronics inside the motor. The ideal situation is to tightly clamp a pair of vice grips to the shaft next to the motor casing. Then, with another pair of pliers or vice grips to take hold of the gear and try to wiggle it back and forth, pull it off, and use leverage to move it off of the shaft as best you can.

I hope that helps! if you don't think the "metal things" are gears then maybe you can post of picture of what you are talking about and I will be able to better help.

Happy Holidays!

dgalvan39 months ago
Hi, I have a couple of questions I would like you to answer as soon as possible, if the rc car I chose use a rechargeable battery how do I make it powered by regular batteries? And how much batteries do you need to power up the circuit board and submarine? What bottle did you use for the sub (what drink was it?) And how do i take out steering parts from car? Also the power switch wires broke so do i reconnect the wires to the switch to fix it? How much did everything to make the submarine cost?
Rc car organ donation
ScrapSmith (author)  dgalvan39 months ago
Hey dgalvan3,

Good questions. I will answer them the best I can.

Q1: "If the rc car I chose uses a rechargeable battery how do I make it powered by regular batteries?"

A1: I have a don't fix what ain't broke design mentality so if your rechargeable battery is working then keep it and design the sub hull around it. That being said, if your rechargeable battery is not working then you can try replacing it with regular AA batteries.

Q2: "How many batteries do you need to power up the circuit board and submarine?"

A2: Most rechargeable battery packs for RC cars are really just made up of rechargeable AA batteries in series so you could theoretically count the number of AA batteries in your old rechargeable battery and just use that many regular AA batteries and shown in the instructable.

Q3: "What bottle did you use for the sub (what drink was it?)"

A3: I think the drink was a small apple juice bottle. I chose it because it was made of a harder thicker plastic (good for keeping the hull from collapsing) and because it had a large opening (good for easier access to electronics inside. However, I would really recommend you tailor your sub hull (bottle) to what you have on hand and to the shape required by your circuit board and batteries. For example if you are using a rechargeable battery you will probably have to build the hull around the battery and circuit board and make sure to be able to disconnect the battery for recharging and reconnect for use via the bottle cap opening. If you are interested in a drawing of this I would be glad to add it to the instructable.

Q4: "How do I take out steering parts from car?"

A4: The specifics of this depend on each RC car but in general you will find that towards the front of the car there is a motor connected to some gears all encased in a plastic housing. Usually you can use a screwdriver to take out screws and open this housing and take out the motor, leaving the gears. If the housing is snapped together or glued together you will have to use some sort of prying or cutting tool. Please be careful when prying or cutting this open! I will not be liable for any injury or frustration that may result. :-]

Q5: "The power switch wires broke so do I reconnect the wires to the switch to fix it?"

A5: In my thinking this depend on where the power wires broke off. If it is broken off from the switch then, yes, reconnect. If they are broken off of the battery system reconnect there. If your power wires have broken off from the circuit board and there are only little metal nubs left sticking out of the board then you are in trouble; unless you know how to solder.


Q6: "How much did everything to make the submarine cost?"

A6: For me is costed nothing because I was using materials that I had on hand. If you take a look at the supplies list at the start of the instructable you can get an idea of what is needed and then look up the costs of the items you do not have to figure out how much it will cost you.

Good luck with your sub! I hope I was a help.


Ok ok this is really cool but I think if u want it to dive deeper add a little container to it with holes in it so the water can get in and add some more wieght
james03x1 year ago
Wow, you are a genius. You did it really wonderfully, i will try to get materiel and start this project very soon. Thanks
radiografisch auto
jjapitan1 year ago
will trying this on seawater somewhat do damage on the motors??/
ScrapSmith (author)  jjapitan1 year ago
I have never tried it out in salt water but my guess is yes. Technically exposure to any type of water will eventually cause rust and corrosion to your motors but especially salt water. One of the major drawbacks of my design is that it will eventually succumb to water damage. I traded longevity for simplicity. :-)

Your best defense against this is to put a water displacement chemical like grease or better yet WD-40 (stands for Water Displacement formula 40!), or both, in your motors and then dry it out as best you can after each use.
gonna do the same thing, but with a 200-watt brushless motor, and an actual rudder moved by a servo =D
Sounds awesome! If you send me a picture or video of it we can start a hall of fame at the end of the instructable.
will do. just have to get my old 72mhz radio system working (2.4ghz does NOT like water)
Overall, it is a very nice design. However, I was wondering if you have any ideas on how to make the diving and movement independent. The current design binds the diving and movement controls together so you can't dive without going forward or go forward without diving. Would it be possible to fit a small water pump inside the hull. It would pump water in and out of a separate compartment (like a ballast tank). This could be a solution but I am not sure if a water pump like this could be powered by simple batteries. What do you think?
ScrapSmith (author)  Instructable Maker1 year ago
Hey Maker, thanks for the thumbs up! I have been pondering the same questions for some time now and have a few ideas you could try out. Check out the last three steps I just added on Alternative Dive Designs.

In the past I scratch built sub with a balast tank and while it did work I was frustrated to discover it worked more like an on/off switch between floating and sinking. After tinkering around I found that making your sub to be just above neutrally buoyant and then controlling the depth with fins or motors gives much more control and flexibility.

However, if you are still interested in a balast tank I imagine your idea would work well. Another idea I had was to use syringes with a home made actuator to pump water in and out. If you are interested I could make a graphic and add it to the Alternatieve Designs section.

use a real r/c system (can get a transmitter/receiver, servos, motor and speed controller for under $40 at and put the dive fins on a pivot hooked up to a servo.
Oh and by the way, I think that the pictures of the building process are very detailed and well designed. I could see each component and it's orientation in every picture. A very good job :)
DadhieMJ1 year ago
is it ok for the motor to submerge too? or it is needed to seal it too? :)
ScrapSmith (author)  DadhieMJ1 year ago
Just leave the motors unsealed because the mechanics and electrical physics of the motors are not hampered by exposure to fresh water. I try to dry them out after a dive so as to avoid rust as long as possible. Avoid salt water as it contains more ionized particles which could corrode the parts faster. Enjoy !
Arap Tala2 years ago
Great idea. Looks fun and the diagrams help a lot.
ScrapSmith (author) 2 years ago
Thanks Capn' and neodymium!
I would love to include any videos of the subs guys you build here on the instructable. That goes for everyone else too!
nice graphics

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