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Picture of How to build a thruster for a homemade submersible or ROV
Some time ago I started building an underwater robot. One of the main difficulties (for me) was building the propulsion system. In this instructable I'll show you an easy to build a quite powerful 12VDC thruster. The original idea came from "Build your own underwater robot" by Harry Bohm and Vickie Jensen, but wasn't really worked out.So here it is.

Step 1: Tools and materials you'll need:

Picture of Tools and materials you'll need:
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Materials:

- 1 Rule 1100 GPH 12VDC Bilge pump.
I used these because I could get them, other sizes or manufacturers might do fine too.

- 1 RC model boat propeller for example Graupner No. 455/10.
This is a 2-wing 70mm diameter prop with 4mm threading. Don't use to big propellers.
4-blade are also ok, but use a smaller one.

- 1 Coupling bush for smaller than 4mm diameter shaft. Graupner No. 3346 (3.2mm) is ideal.

- a 20mm long 4mm bolt with the head removed.

- a 4mm spring washer.

- Heat shrink tube of different sizes with glue or (better)a waterproof cable repair set like Raychem XBL22 (also, this is what I could get overhere).

- round circumference 2 conductor wire capable of carying 4A.

- adhesive rubber pads, like the stuff to put under furniture.
- waterproof cable gland (for example Velleman CPG135)

Tools:

- Hacksaw or dremel
- sharp knife
- electric paint stripper
- threading tool with 4mm bit.
- soldering iron
- pliers, screwdrivers etc...

 
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MikeV111 month ago

I just installed that exact pump a few weeks ago at my work. Just in case anyone is wondering, it was about $100CAD if I remember correctly. Not that cheap, but still a lot cheaper than buying a ready made underwater thruster.

amitk157 months ago

i am a trainee student , i am glad to see how simply you made a thruster out of a dc motor , i have tried the same and obtained a good result , this will help me in completing my final year project , but please tell me is there any good driver circuit available for this motor , as in water it draws more than the rated current ,, around 5 amp , please suggest

Kajnjaps (author)  amitk157 months ago

Hi,

I used a custom made PWM motor driver. Long time ago...

amitk15 Kajnjaps7 months ago

will that pwm controller work online ? i mean will the speed go to zero before setting to its new speed ? or speed control will be continuous ?

amitk15 Kajnjaps7 months ago

will that pwm controller work online ? i mean will the speed go to zero before setting to its new speed ? or speed control will be continuous ?

amitk15 Kajnjaps7 months ago

will that pwm controller work online ? i mean will the speed go to zero before setting to its new speed ? or speed control will be continuous ?

amitk15 Kajnjaps7 months ago

will that pwm controller work online ? i mean will the speed go to zero before setting to its new speed ? or speed control will be continuous ?

amitk15 Kajnjaps7 months ago

will that pwm controller work online ? i mean will the speed go to zero before setting to its new speed ? or speed control will be continuous ?

amitk15 Kajnjaps7 months ago

will that pwm controller work online ? i mean will the speed go to zero before setting to its new speed ? or speed control will be continuous ?

amitk15 Kajnjaps7 months ago

will that pwm controller work online ? i mean will the speed go to zero before setting to its new speed ? or speed control will be continuous ?

amitk15 Kajnjaps7 months ago

will that pwm controller work online ? i mean will the speed go to zero before setting to its new speed ? or speed control will be continuous ?

would 3 of these attached to a PVC pipe pull me in the water?

Kajnjaps (author)  watersports1 year ago
probably not. Look for trolling motors for that.
Halphinian1 year ago

Would this system be small enough to fit inside 2" PVC pipe, if not, what size? I need to know this before I buy all my parts to prevent finding out that I bought the wrong size pipe and have to go buy more.

Kajnjaps (author)  Halphinian1 year ago
Unsure, your best bet is to build the thrusters first and then get the pipe that fits accordingly.
What I meant to say is do the thrusters vary in size in terms of voltage, because I need a small thruster (that fits in 2" PVC pipe) that has a lot of power.
Kajnjaps (author)  Halphinian1 year ago

They do. best to check manufacturers websites for sizes/voltages etc.

Generally the larger will mean more powerful motor.

Kajnjaps (author) 1 year ago
Sure, look up 'Build Your Own Underwater Robot and Other Wet Projects' by Harry Bohm for a good description on using DC motors.
cant we use dc motors or something other
i am making a rov for school fair so i want something cheap
donlakin1 year ago
On your pump, how many RPM's does it turn? and does it have any torque to it?
Kajnjaps (author)  donlakin1 year ago
Don't know the RPM but it does give quite some torque for such a small motor.
ErikSR715 years ago
I'm part of a robotics class at my high school. We have only ever competed on land before and this is our first time trying anything underwater. Our main problem has been figuring out our propulsion system, so I've found this article immensley helpful. The one question I have right away is, can the direction of the propellor's rotation be reversed?
Kajnjaps (author)  ErikSR715 years ago
Hi,

yes, you can reverse the direction by reversing the applied voltage.
Good luck!

and to reverse the voltage look up "H-bridge", it's a circuit that allows this to be done easily
please suggest me a method for protecting my Rf module circuit.....without causing interference as the setup is wireless
Kajnjaps (author)  MINDFREAK91895 years ago
Did you do any reading on RF and water? Here's a very good link: http://www.qsl.net/vk5br/UwaterComms.htm
thanks for the article,its really gud.but i need some methodology to protect my circuit from water as the robot is under water.... thanks
Kajnjaps (author)  MINDFREAK91895 years ago
I used pvc tubing with endcaps as housing for all the electronics. pretty much standard.
if you want to allow waterproofness to greater depths you could flood your pvc tube with cooking oil too (oil won't make electronics short circuit). It will help avoid problems with higher water pressure at greater depths trying to seep into your container
Most of us do a lot of reading and research before we post our projects here. You need to do some research too.You might do well to experiment and do some basic skill-building with the materials used in the project. You'll soon answer your own questions. It's part of the process :)
can u please detail me about raychem cable repair kit......... i am not understanding that step. like i am getting dat two wires cumin frm pump.but a what after dat.
Kajnjaps (author)  MINDFREAK91895 years ago
The cable glands that I use in my housing are for a round cable. Therefore, a round cable is attached to the wires of the pump. The cable repair kit makes a watertight connection between the pump wires ( two separate wires) and the cable (a round cable with two conductors in it).
i want to make a underwater robot.....can u suggest me any way to protect my circuits.....and wiring frm gtn sort...........and wer will i get dis bilge pumps of 12v dc
Kajnjaps (author)  MINDFREAK91895 years ago
do some research, check if there is a local distributor for the bilge pumps. I assume 'frm gtn sort' means 'from getting short circuited by the water', right? I used pvc tubing with endcaps and IP68 waterproof cable throughputs.
thanks so much. give me a procedure to protect my circuit or rf module which is wireless.
Kajnjaps (author)  MINDFREAK91895 years ago
The actual procedure will depend on the materials and tools you have access to.
i am using a RF module, a 12 v dc nd two propellers..........the Rf module is wireless,so i need some aarangemnt in whch the circuit is protected widout casuin interference in the signal
please explain hw to remove that white part, becs the white part ahs a outlet kinda thng which is missin in the main picture
Kajnjaps (author)  MINDFREAK91895 years ago
I'm not sure I understand your question. Once you remove the white part with a hacksaw, you end up with a watertight motor.
For all the people that wont to make skooters, ya thats what there called. Trollers will work, but I'm going to yoos RC air plane moders. The big ones and put then in a case. Basically a jet enjin, but with water in stead. the moders ar vary hi tork. Yes the pik is bad but I drue it in one minet.
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