Question About Submarine Motor and Battery

Welcome.

There have been a few recent posts on small submarine design and construction you can have a look at to start

Link 1

Link 2

It's a big project but not impossible.

Do you have a budget in mind?

Thanks for the reply. Those links are great! The images and aritcles of other personal submarines have given me many ideas for the overall design, but I am more concerned about the details (the ones that could kill me if over-looked).

Would you happen to know if is better to use an AC or DC motor? For example, would both work with a typical car battery? Im hoping to spend under $3000. I plan to design to a maximum depth of about 25 feet. Again, the I am comfortable with the mechanics, and I am fully aware of how to do all the pressure and stress calculations necessary to ensure my safety, I just don't fully understand the electronics. They are my Achilles heel, so to speak.

-pepper240

Sounds like a great project.

If you use an AC motor:

1. The extension cord will severely limit the range of travel and increase the risk of water leaks..

or

2. You will have to carry the extra weight of a DC to AC converter.

I would use DC components.

You also need to use sealed non-acid type batteries so that you are not exposed to the hazardous fumes and to avoid explosion risk from the free Hydrogen generated during/by the battery discharge.

Marathon offers a liquid free, deep cycle battery that is exceptional for this type of service.

AC WOULD REQUIRE A LOg extension CHORD, stick with DC

I would stick to DC for everything. Also, try to keep your electronics to a minimum. no need to reinvent the wheel.

If you use a trolling motor for instance (great idea by the way), you could fix it in place, and use mechanical linkage for your vertical and horizontal stabilizers.

In my view, mechanical components are less likely to fail underwater.

Bad ideas: Electronic steering, electronic ballast control

Good ideas: Electronic communication system, lighting

Good luck with this fascinating project and keep us informed.

I'd take a look at trolling motors to get some idea of thrust and power usage.

Minn Kota EDGE 45‑42...$336.00 One battery should be sufficient, since that's all most fishermen use. Don't forget your emergency air supply.

I never thought about trolling motors. Great idea! Will definitely look into them. Also, I completely agree about that silly anonymous poster. I read that exact article about the 18 year old kid who built his own submarine, and though 'hey, I could do the same'. He's practically my inspiration.

Thanks for all the great tips!

There are a lot of smart people here who will be glad to help you.

Good luck with your project.

Keep us posted on your progress.

It's been done....

http://inhabitat.com/eighteen-year-old-builds-one-man-submarine-out-of-drainpipe/

Biber sub....

"...13 horse power electric motor powered by three Type T13 T210 battery troughs....^[1]"

^"...powered on the surface by a 32 hp (24 kW) Otto blitz petrol engine..."

http://www.youtube.com/watch?v=xIJkwj6MxG4

http://www.leeson.com/Literature/pdf/b1600IEC.pdf

Anonymous Poster #1,

You make an excellent case FOR BANNING ANONYMOUS POSTERS FOREVER!!!!

We had a person in our area built himself a personnel submarine. He contacted a naval architect that worked at the shipyard, of which the naval architect who did not want he's name published agreed that he really should NOT build the sub. He built it anyways.

But if I remember, it was either Mechanics Illistrated, or Popular Science had plans for a hybrid sub it was from the mid 70's issue. I had saved that a read it from time to time.

Where were you when others were posting inappropriate questions on how to build substations or power plants.

<sigh> Given the information provided by 'pepper240' and the nature of the project and the open-source technology likely to be involved and detailed here on CR4 anything applicable we post were is unlikely to cause an ethical dilemma.

_{Jack - A Marine Military Contractor (among other things).}

What about something like this for size?

or this...

this....

http://seabreacher.com/watercraft

On Ebay....

Deep cycle marine batteries....

http://forums.iboats.com/electrical-electronics-audio-trolling-motors/trolling-motor-battery-size-534335.html

17' propane tank....

http://www.ebay.com/itm/1150-gallon-propane-tank-/320848215378

http://www.blanson.com/case_studies/submarine_domes

Here's a list of sport subs for sale with all the specs.....gives thrust, battery capacity, dive length capacity, total weight, and more....these seem to be fiberglass mostly

The first one is 1750 lbs with 2 ea 74 lb thrusters on either side and min 175 amp hr batteries @24 volts

http://www.silvercrestsubmarines.co.uk/sportssubinfo.html

You keep coming up with great links and ideas. Many thanks! The idea of using a propane tank is wonderful. Though the one you linked to is out of my price range, I will definitely look for a smaller, more affordable one. Also, the marine-grade motor is excellent as well. I will do some research on how I might implement it into my design.

-pepper240

Here's one 500 gal $600....got it's own trailer...

http://www.americanlisted.com/iowa_15/misc_117/500_gallon_propane_tank_mounted_on_trailer_good_condition_600_il_15854539.html

I'd be more inclined to go with a lighter material.

This looks promising:

Credit SE.

This is the best deal I've seen....the fiberglass tends to cost double the steel equivalent...trailer is included, you're going to need one....a new fiberglass tank is about $3600 with no trailer....

http://westechequipment.com/product/ugwt-sw-pw-1000-4

Try this.

I have a copy of the K-250 plans, but never got around to building one. I think it would be a little small for a guy my size, XX monster but certainly looks workable. uses 36 VDC torpedo motors if I remember correctly. They mount in pods on the side and rotate for up down.

www.psubs.org/store/

For sale drop tank $595 on Ebay...

sounds ambitious

If you don't have it figured out already, putting some thought into the atmosphere in your submarine.

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Maintaining sufficient oxygen and preventing the buildup of ozone (electric motors), carbon dioxide (you), chlorine gas, hydrogen gas, sulfuric acid fumes (the three previous potential hazards of lead acid batteries), and other undesirables is of the utmost importance.

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Additionally controlling the pressure of the atmosphere in your bubble could make the tasks of sealing and integrity of your vessel much easier. Maintaining the interior pressure close to the pressure of the water at the bottom of the vessel will help any small leaks to favor bubbling out rather than dripping in.

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The pressure regulation could be done with scuba equipment and some sort of bleed system. That same system could help a lot in maintaining air quality.

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I would really want to be in a separate space than the batteries. If you are separating the space, you might as well put the motors and most other equipment in the same pressure space with the batteries. As an added benefit, if the person space and equipment space were completely separate, the equipment space could be flooded with CO2 or Argon or Nitrogen to reduce the chance of fire and to slow corrosion.

A separate space would require a separate system to control pressure if the equipment space isn't going to be filled with air.

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Another reassuring option would be the ability to inflate two or more air lift bags (typically used in salvage) to assure positive buoyancy.

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The illustration Fredski posted, suggesting pedal power, seems very attractive. Forgoing the additional complexity, displacement, expense and risk of tying yourself underwater to a couple hundred pounds of lead acid batteries, motors and controllers would be very appealing to me.

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Just so you know, I've spent my fair share of time submerged.

I didn't see depth anywhere in the requirements. This will have a significant impact on the structure and the nature of the propulsion and maneuvering system. Trolling motors are probably a good, economical choice for near surface operations. Expect to replace them pretty frequently due to water intrusion if you go more than a few feet below the surface.

For deep submergence vehicles, the motors are generally permanent magnet synchronous motors or 'brushless' if you prefer because the motor will be filled with oil and pressure compensated to maintain a slightly positive pressure relative to the vehicle depth. Yes, this requires a variable frequency motor drive or inverter to operate. Brush type DC motors are simpler to control but will have to have suitable seals to keep the water out.

Rather than controlling planes and rudders, for this type of vessel, I might suggest the use of trolling motors to provide both propulsion and steering similar to Z-drives used on surface vessels. A pair forward (port and starboard) could be oriented to provide pitch control and if they were independently adjustable your could also control roll. A motor or two would be mounted aft to provide yaw control.

Ballasting is not trivial. Be very careful about the relative positions of your center of gravity and the center of bouyancy. You can either pump water in or out of forward and aft ballast tanks, but a simpler system would use pressurized air to fine tune the trim of the vessel by either adding air to the ballast tank or bleeding air off the top with solenoid valves. Again, if your depth is reasonable, you might find that for pumping water, a 12-V RV water pump might work pretty well for ballast and trim. You would then need to devise a manifold system for reversing flow.

I would suggest using separate pressure vessels for your batteries for safety's sake. Make sure you create a power budget for all your electrical loads and plot that against your energy storage. You might want to slide batteries secured to some type of "tray" into a PVC pipe with threaded end cap(s). Two of those mounted low against your main pressure hull would help lower your CG. If you use two battery 'bottles', you would generally run them in parallel, but give yourself the option to isolate either of them with switch panel in case one of them floods or has some sort of failure.

Another safety tip is to make sure you have a completely separate back up method that will take you back to the surface. A high pressure air flask that can inflate a "ballon" or other inflatable shape firmly attached to your vessel is one way to save your hide. Make sure you can escape your vessel. Water pressure will tend to keep hatches/ports closed. You might need to "flood" the vessel to escape. Become SCUBA certified and carry a bail-out bottle.

This is a rather daunting undertaking and I wish you well. Be very, very careful. Think long and hard about everything you do. Look at every possible failure, mechanical, structural, and electrical and be sure you have a reliable way to get back to the surface. This was "my" boat for about 12 years of my engineering career.

Your comment reinforces much of what I wrote in the previous comment.

I actually intended to mention becoming SCUBA certified, but forgot to include it. I'm glad you did.

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It is interesting that DSRVs or DSV use permanent magnet synchronous motors. Squirrel cage motors are often preferred in other submarines when you don't want the fluid being pumped getting into the space wherein the pump resides. Having the fluid isolated completely without relying on packing or seals is a huge advantage.

Hey, Brave Sir Robin;

I'm curious to know more about the sub that was your boat for 12 years. Care to share some details?

I thought that looked like an SDV, but figured if you wanted to talk about it, you would. Glad you still have a zipped lip. Too many don't, nowadays.

I respect your restrain in disclosure. You did provide enough info to get me on track. I appreciate it!