Submarine Turns

Hello. I am making a mini Arduino submarine (Funny, because I saw someone else on this thread making one too. I am not the same person as him/her, if you were confused. Read the usernames)

Anyways, my sub needs to turn. I am planning on using two dc motors with propellers for propulsion. (Hooked up to relays, wich are controlled by the Arduino To turn, I was thinking turn one motor off and leave the other on. (Close one relay and leave the other open.) And to go forward, have both motors on. (Both relays open.) Would that system work? Or would one motor have to spin backwards and the other forwards to turn? If so, how can I do that? Thanks!

love the name, fits the question. LOL

you 'close' the relay to allow it to power the motor. 'close' both to go forward

but, use an H-bridge to not only control speed but direction
but why not add a rudder ? or of you want extreme manoeuvrability, use a motor on a swivel.

google pod thruster

dave-in-nj:
you 'close' the relay to allow it to power the motor. 'close' both to go forward

Oops. Sorry. :wink:

dave-in-nj:
but why not add a rudder ? or of you want extreme manoeuvrability, use a motor on a swivel.

How could I make a rudder? Tell me more...

make a tail fin, have a lever on one side.
run a rod in and out, linear stroke. it moves the lever and the lever moves the tail fin.
the problem is water proofing it.

dave-in-nj:
make a tail fin, have a lever on one side.
run a rod in and out, linear stroke. it moves the lever and the lever moves the tail fin.
the problem is water proofing it.

Oh. I was thinking more along the lines of: Micro Servo's arm attached to fin, Micro Servo moves back and forth. Would that work?

Assuming I could waterproof the micro servo, of course!

You have to waterproof the propellor shaft anyway :slight_smile:

Boardburner2:
You have to waterproof the propellor shaft anyway :slight_smile:

If you’re using a brushless motor you don’t need to seal it. I’m sure the lifetime of such a motor is limited (the bearings will rust) but it shouldn’t be that bad. If you’re really looking for extended periods of use then you’d need to invest in bronze or ceramic bearings to replace the original bearings when they rust out.

And then along those lines if you’re using RC “ESCs” then you just control the motor like you would an RC servo. Just make sure you buy one that can go in reverse (under the assumption that you DO want to be able to drive the motor in reverse)

Just to throw my idea your way, I'm looking at using bilge pumps from boats for my propulsion. I have seen they can be modified to run a rc boat propeller and are quite inexpensive. I am then looking at ducting them in some drain pipe and attaching rudders to the ducts controlled by servos. I haven't worked out the waterproofing part either but am willing to help with any info I can as I find it out.
I am on my phone ATM but when I get to my laptop I will post the site where I have been researching if you want.

Chagrin:
If you’re using a brushless motor you don’t need to seal it.

You do if you do not want it to sink.

Stern tubes do not work well on submarines.

That link is interesting , no detail though , i suppose there may be if i spoke japanese.

elephunk:
Just to throw my idea your way, I'm looking at using bilge pumps from boats for my propulsion. I have seen they can be modified to run a rc boat propeller and are quite inexpensive. I am then looking at ducting them in some drain pipe and attaching rudders to the ducts controlled by servos. I haven't worked out the waterproofing part either but am willing to help with any info I can as I find it out.
I am on my phone ATM but when I get to my laptop I will post the site where I have been researching if you want.

bilg pumps are waterproof to a few feet, maybe a meter ?
you can mount them outside of the sub and rotate the whole thing.
remember there are two forces, suction and propulsion. the suction will alter the direction of the vessel, so you might want that to be in some form of equalibrium or maybe at the front for added

neat idea though.

dave-in-nj:
the suction will alter the direction of the vessel…

Cheers, I am still thinking things through at the moment and am just collecting parts, no real work done, but that is one of my concerns. One of the ideas I did have that I want to investigate is ducting the input and output from the thrusters to balance out any misplacement of the motor itself, so the push and pull forces were more central to the sub. I dont know how this would work out though.

Anyway, sorry to hijack the OP’s thread, here is the site what I’ve been reading through
HomeBuiltROVs
it has given me a few ideas along the way.

Chagrin:
If you're using a brushless motor you don't need to seal it. I'm sure the lifetime of such a motor is limited (the bearings will rust) but it shouldn't be that bad. If you're really looking for extended periods of use then you'd need to invest in bronze or ceramic bearings to replace the original bearings when they rust out.

And then along those lines if you're using RC "ESCs" then you just control the motor like you would an RC servo. Just make sure you buy one that can go in reverse (under the assumption that you DO want to be able to drive the motor in reverse)

So you are saying to NOT have a tail fin. when I want to turn, one motor reverses and the other goes forward. So I CAN'T just turn one motor completly off and have the other continue forward? One motor HAS to go in reverse?

elephunk:
Just to throw my idea your way, I'm looking at using bilge pumps from boats for my propulsion.

from my understanding, (and a quick google) bilge pumps push water through a pump system, and the pushing water moves the craft forward. Great! But how do I TURN with bilge pumps!

Thank you all SO much for the deluge of help so far! Its really been great! :slight_smile:

stupid-questions:
So I CAN'T just turn one motor completly off and have the other continue forward? One motor HAS to go in reverse?

I don't see any reason why you can't turn one motor off, or slow it down when turning instead of having to have the two motors running in opposite directions. I think it is mainly on how big of a turning radius that you are looking for; having them motors run in opposite directions will give you a much smaller turning radius than having one on and one off.

Someone suggested using an H-bridge for motor control, and I have experience with this method and really like this way. You can buy pre-built modules for motor control that will allow you to run too motors at completely different speeds, one off and one on, or even both running in opposite directions.

stupid-questions:
from my understanding, (and a quick google) bilge pumps push water through a pump system, and the pushing water moves the craft forward. Great! But how do I TURN with bilge pumps!

You take the top housing off the pump which reveals an impeller(??dont know if thats the right name for it) remove that and attach a rc boat propeller to the shaft. That gives you a (from my understanding up to now a submersible motor) up to a depth. Then you can run one forward and one reverse for turning.
Or you can use the bilge pump as is and just position the output from the pump in the direction you want thrust. Although from my understanding you will get better thrust from modding it.

Being able to run one in reverse will give you better manoeuvrability and tighter turning circle.

How do you control buoyancy on those things? Or do you need constant propulsion fighting whatever buoyant force there is?

stupid-questions:
Hello. I am making a mini Arduino submarine (Funny, because I saw someone else on this thread making one too. I am not the same person as him/her, if you were confused. Read the usernames)

Anyways, my sub needs to turn. I am planning on using two dc motors with propellers for propulsion. (Hooked up to relays, wich are controlled by the Arduino To turn, I was thinking turn one motor off and leave the other on. (Close one relay and leave the other open.) And to go forward, have both motors on. (Both relays open.) Would that system work? Or would one motor have to spin backwards and the other forwards to turn? If so, how can I do that? Thanks!

Driving a submarine under water is just like flying and airplane in the air. To make a turn you need to bank the submarine/airplane. The Wright brothers discovered this. Otherwise all you get is a "yaw" and not very much change of direction.

Paul

same way as a real sub.
Ballast pumps.
big problem is that radio does not penetrate water well.

Technical challenge but makes for a boring model.
It goes down,you cannot see it , will it come up again.

Submersibles really need a tether to be interesting to get pictures back.

Unfortunately 'the bit of string is' very expensive.

Boardburner2:
You do if you do not want it to sink.

Stern tubes do not work well on submarines.

The entire motor sits outside of the ROV. The only things piercing the watertight chamber of the ROV are the three wires.

...but technically you do want it to sink, y'know :wink:

BTW, continuing the yaw comment above...

The fins do more than just act as a rudder, When you apply rotational/turn forces to the hull, consider the hull may roll on axis - rather than turn! (embarrassing)

Another point to keep in mind, is the concept of contra-rotating props/impellers... whatever you want to call them - to optimise thrust, and reduce the directly applied 'roll' forces on the hull. Reducing cavitation is a whole different post!