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:

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...

Comments

[MINDFREAK9189]

please suggest me a method for protecting my Rf module circuit.....without causing interference as the setup is wireless

[Wazzupdoc]

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 :)

[Kajnjaps]

Did you do any reading on RF and water? Here's a very good link: http://www.qsl.net/vk5br/UwaterComms.htm

[MINDFREAK9189]

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]

I used pvc tubing with endcaps as housing for all the electronics. pretty much standard.

[MINDFREAK9189]

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]

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).

[MINDFREAK9189]

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]

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.

[MINDFREAK9189]

thanks so much. give me a procedure to protect my circuit or rf module which is wireless.

[Kajnjaps]

The actual procedure will depend on the materials and tools you have access to.

[MINDFREAK9189]

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

[MINDFREAK9189]

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]

I'm not sure I understand your question. Once you remove the white part with a hacksaw, you end up with a watertight motor.

[Hunter4000695]

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.

[Krenath]

Translated: "For all the people that want to make scooters (yeah that's what they're called) trolling motors will work, but I'm going to use RC airplane motors. The big ones, and put them in a case. Basically a jet engine, but with water instead. The motors are very high torque. Yes, the picture is bad but I drew it in one minute."

[ErikSR71]

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]

Hi,

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

[Danny_Payne]

 Hi, could you give me a linky or a model number and price for the pump you used?

Thanks!! :)

[Kajnjaps]

It's a Rule 1100 GPH 12VDC Bilge pump. Price will depend on where you buy them.

[ExploreFLoutdoors]

if i make 2 of these, could i use them to push an inflatable raft/boat carrying two people.?

[woodNfish]

 A 12V electric trolling motor will is what you need. The small ones are are 30lbs - 42lbs of thrust.

[aflacgoose]

No way!

[Kajnjaps]

No way, they are not powerful enough for that.

[dabombmaker]

ps. In this instructable I'll show you an easy way to build a quite powerful 12VDC thruster.

[nomejodaslavida]

If you're going to use the submersible bilge pumps as motors, why not use them as they are, without propellers,  for jet propulsion?  You could even increase the force of the jet by by graduating the discharge down to a smaller size.

[Kajnjaps]

Using them this way, with propellers, seems to yield more thrust.

[tmjones]

 where did you get the propellers from?

[Kajnjaps]

From some model shop.
The manufacturer is Graupner.
Check out www.graupner.de

[roverman]

nice idea using a pump for the motor

[six7evan]

Out of curiosity, what is the top speed and battery life of this? I would love to get something that can get me going 5-10 mph underwater.

[Kajnjaps]

Battery life depends on battery capacity.
The motor consumes somewhere between 2 and 4 amps I guess.
Suppose you use a battery of 7 amp-hours, then it would be about 7/4amps= 1.75hours for one thruster.

Likewise speed is linked to other parameters; drag, propeller you use, watter currents etc. Force of thrust, expressed in force kg or newtons would be a better parameter.

I've seen my rov go about 1m/s with two of these.

best regards,
Kajnjaps

[BJCK1990]

Where is a cheap place to purchase bilge pumps or replacement cartridges?

[Kajnjaps]

I bought them at a local boat supply shop. Maybe check Rule's webpage to find a local dealer.

[daniel2008]

hey, nice instructable.
would you consider submitting it to the new ROV group ?

[awang8]

Umm... Why don't you submit it? PS: Ha ha! I did it before you!

[Kajnjaps]

Thanks ! I forgot to reply to your message. Indeed, this Instructable belongs in there.

[SunShine.1111]

is there any way to turn it into one of those things that scuba divers use to move around in water with? like maybe a bigger motor... and a cage or smthn to protect the diver from the propeller...

[Kajnjaps]

if you want to build something like that, I'd recommend getting real trolling motors. The modified bilge pumps don't have enough power to drag a human through the water.

[awang8]

You could always connect 100 1500GPH pumps and that would be powerful enough...