Powering Micro Sub

[dragonfire]

it´s not the same design, but maybe someone in europe is interrested: private sub to sell on ebay ( not mine):

http://cgi.ebay.de/U-Boot-Unterwasser-UBoot-Mini-Tauchboot-Forschung-NEMO_W0QQitemZ160352146013QQcmdZViewItemQQptZSonstige_Boote?hash=item2555bb925d&_trksid=p3286.c0.m14

 

[Submariner]

KAE,

How did your meeting with Daniel Gomez-Ibanez go?

Did you mention my project? His web site is great.

4000 batteries, WOW. That's what I'm considering.

I look forward to hearing from you.

Thanks, Tom

 

[Submariner]

I have now commited to 8 - 10, 100 amp/hr SLA's for this 8kw project and welcome in-put on controller-motor combinations. Dependable reliability are of major concern for manned, subsurface operation. I would also consider re-evaluating the spark risk within the sub.

-Tom

 

[Malcolm]

Hi Tom

Sorry, I don't have any answers, just more questions

Safety is obviously the first priority in an application like this. Just to get a clear picture of your intentions: this is a one-man torpedo-like sub, with a glass fibre shell, operating at slightly above ambient pressure? What will be your maximum depth and how will you get in and out of the sub?

It's important to decide if sparking is a potential problem, as this affects the choice of brushed or brushless drive system. If there is any risk of accidental flooding this could lead to electrolysis of water and the generation of hydrogen and oxygen. If you have a brushed drive motor you have to cut power and bail out.

A brushless motor would eliminate this risk, but how will the motor and controller cope with accidental flooding? A sensorless controller would eliminate the risk of hall sensor problems, but are there any fully potted sensorless controllers?

 

[Submariner]

Hi Malcolm,

Thanks for your interest. Questions are good.

Correct, safety is the first priority with this project, then fun, simplicity, creativity, economy, etc.

A one-man, hi-performance, flying submersible. Think of it as a sub you wear. 3/8 inch (9mm) epoxy/fiber (WestSystem) tear-drop hull (shell). Crush depth ~300 feet (95 meters). Ocean operation (i.e. 3.9% w/w salt water) at 9C (47F).

The pressure system is unique, "delayed ambient". With a service depth of 33 feet (10 meters, one atmosphere) the cabin pressure will vary from 0 to + 1 ATM. Exhaled air (from the 80 cubic foot scuba tank) will compensate for pressure drops at depth while pressure vents will bleed-off cabin air on accents. The primary reason for this design is to dampen cabin pressure changes giving me a chance to equalize my inner ears. Also it provides a simple method to vent exhaled air. CO2 levels will climb within the sub during the one hour dive time but not considerably as far as fire is concerned especialy if H2 and O2 were to be generated!!

Boarding and un-boarding will be via the removeable Acylic nose cone while out of the water on the trailer. In emergency, egress may be gained by opening the equalization valve, removing the nose cone, total flooding and loosing the sub to the bottom. For this reason it would be best to make way and reach the trailer or beach for easy recovery of the vehicle. So, if flooding is the emergency, then motoring to safety would NOT be an option with sparked components, power would have to be cut and the vehicle lost to the depths for later recovery. I would prefer to go with ignition protected components but at what cost (and I don't mean monetary). My design should not leak or flood.

With 8, 100 amp/hr SLA's I have 400 effective amp/hrs to play with and only 300 if I am to have one hour reserve at part throttle. Is that reasonable for an 8kw peak demand? Only 20% of my operation would be at full throttle, 50% at half and 30% below that including coasting. Motor/controller temperature may dictate my throttle usage and/or battery life. Again, dive time would be only one hour, plus one hour emergency reserve.

I am hoping for 1000 RPM max direct drive with excellent throttle modulation to avoid cavitation.

-Tom

 

[Malcolm]

Moderators: could you move this thread into the Watercraft forum? The thread was created before the new category was added. Cheers!

Thanks for the description Tom. It all sounds well thought out. Do you plan to have a buddy accompany you using a Sea-Doo or the like, at least on initial dives? The removable acrylic nose sounds like a very good way of escaping, as you just grasp the sides of the sub and launch yourself out of it, but I know from experience that if there's any way for your air hoses or BC to get snagged, they will do / edit: now I think about you're unlikely to take air supply or BC with you if you're bailing out.

Kelly makes a range of sensorless controllers that could be suitable. There's also an option to have any one of these potted to make it waterproof. The advantage of a sensorless controller is that you eliminate another possible failure point, the Hall sensors inside a brushless motor. You can still use a motor fitted with Hall sensors, but the controller doesn't use the sensors. Instead it senses the back EMF from the motor and uses this to determine timing. This type of controller is most suitable for applications that don't involve shock loading, so should be good here.

400 effective Amp hours x 12V = 4,800 Watt hours, so your average power output should not exceed 2.4 kW for two hours duration. That sounds reasonable for a peak output of 8 kW if you only intend to use it for 20 per cent of the time. One advantage of using lead acid batteries is that the battery voltage gives a decent indication of state of charge, so you can use a cheap and simple voltmeter to monitor battery capacity.

Edit: link to Kelly controllers: http://www.kellycontroller.com/24v36v-sensorless-controllers-c-64_65.html

 

[liveforphysics]

Rather than the sub just skuttling, have you considdered a simple mechanical pressure switch that activates a small dedicated compressed air canister that inflates a dive-bag or something similar, with just enough boyancy to make the flodded sub positively boyant? If you had to egress, at least your sub would end up back on the surface. I would imagine it could be as simple as a tiny 4s LiPo pack, a mechanical hobbs pressure switch set correctly, and a little banana sized 4,500psi paintball tank coupled to a little high pressure nitrogen silenoid, and a large inflatable dive lifting bag packed like a parachute. The whole stand-alone setup could likely fit inside a 2L bottle stuck somewhere. At least while in the testing proto-type stages, it could save you a boat or two.

 

[Submariner]

Thank you Malcolm and LFP for responding. I'll look into your recomendations Malcolm.

I'm only asking for electrical/electronic assistance on this forum as this is where my near complete design is lacking.

Please trust that the rest of the design research has been thorough and changing anything now would be like changing a piece in a jig-saw puzzle, it would srew everything else up completely. Please don't waste your time on aspects other than getting this thing powered safely, reliably and efficiently.

What I've envisioned is a spring loaded trigger on the hand control (joy stick) for throttle. Could this be used to control the controller? Would a thumb push botton on top be able to give me instant-on reverse for emergency braking?

Thanks, Tom