[PSUBS-MAILIST] Dive report: Snoopy at Seneca

Sat Jun 6 22:41:40 EDT 2015

The controller issues have been MOSFET meltdowns a couple of times, and other times just solder melting on other parts of the board due presumably to excessive heat caused by large currents. Once when I opened the enclosure to investigate, a diode fell out. It had just de-soldered itself and come entirely off the PCB.

> On Jun 6, 2015, at 8:18 PM, Ken Martindale via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Actually the long wires add inductance which can cause voltage spikes as a result of the fast switching. This can blow the devices (MOSFET) used to switch the currents.
>  
> It can overvoltage the caps also but that may not be the main problem.
>  
> I had some trouble like this when I designed my controller.
>  
> Ken Martindale
>  
> From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Alan James via Personal_Submersibles
> Sent: Saturday, June 06, 2015 6:48 PM
> To: Personal Submersibles General Discussion
> Subject: Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
>  
> Thanks for the report Alec, great stuff.
> re the motor controllers; I've been reading a bit about inductance in long wire runs from battery to
> motor controllers, that harms the capacitors on the controllers.
> This could be a problem that is unique to our submarines & not an issue with things like golf carts
> & wheel chairs.
> My reading has been mainly about BLDC motor controllers but asume PWM controllers for brushed
> motors would be similar. Because of the rapid switching on & off of the power to the motor, there is a
> current surge hitting the capacitors & the longer the wire run, the more the power in the surge.
> A water analogy would be turning a valve off suddenly as washing machines do, sometimes with
> a "thunk" sound & a rattle of the pipes.
> Hugh mentioned he had problems with his Curtis BLDC motor controllers.
> Attached is the problem & solution, which is to put capacitors in parrallel along the battery wire; 
> however there must be a better way.
> Regards Alan
> too long battery wires will kill ESC over time: precautions, solutions & workarounds - RC Groups
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> too long battery wires will kill ESC over time: precauti...
> Careful! too long battery wires will kill ESC over time: precautions, solutions & workarounds Electric Plane Talk
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> From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
> Sent: Sunday, June 7, 2015 12:20 AM
> Subject: Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
> 
> Alec,
> I don't know what type of speed controller you are using, but I like and use Curtis golf cart controllers.  They are rated for huge amperage and seem bullet proof.  I have an extra 36V controller I can send you to try out.  They use a 10 OHM potentiometer for the throttle.  They also have a battery protection mode, a sort of get home conservation mode.  
> I labeled the motor in Gamma for a jumper cable, so that I can get home without the controller.  As you said it is electronic and it will fail.
> If you want the controller send your address of list.
> Hank
> --------------------------------------------
> On Fri, 6/5/15, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Subject: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
> To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
> Received: Friday, June 5, 2015, 6:16 PM
> 
> Hello friends,
> I just got back from a dive trip to Seneca with
> Dan Lance and thought I'd share how it went. This was
> supposed to be a two sub trip with Scott Waters, but
> unfortunately a business emergency intervened and it ended
> up being just Snoopy.
> On the way up the weather was terrible, with
> driving rain so heavy I could barely see the lines on the
> road. It had been raining heavily for several days
> previously. Three times there were emergency announcements
> about floods, large hail, and damaging winds, and the closer
> I got the harder it rained. The problem with all that rain
> is that in your typical lake, the runoff ruins visibility
> for weeks. That is what happened last year when Trustworthy
> and Snoopy rendezvoused at Summersville Lake, and it looked
> very much like this would be a repeat. I'm happy to say
> Seneca must be rain-proof, because the deluge only reduced
> the visibility in the top fifty feet or so, and even those
> were clearer than most lakes.
> Here's a few things we learned:
> 1) Of props and shroudsThe stern
> thruster speed control was dead on arrival, although I had
> tested it successfully before leaving. I opened up the
> enclosure, pressed down all the spade connectors, and found
> it now worked - so attributed the issue to road bumps.
> However, it died within a minute on the first dive. I had a
> spare speed controller, so switched it out. 
> The replacement died within five minutes on the
> second dive. This time at least the cause was obvious, the
> prop was jammed by weeds. The current Minnkota props have a
> little twist at the end of the blades, and Snoopy's
> shroud is made with almost no clearance. The little twist to
> the blade tip causes any object coming between prop and
> shroud to jam tight, and had already smoked one controller
> during the convention in the Keys. I'm going to put the
> prop on the lathe and take off the tips to eliminate the
> pinching effect and to reduce the amperage draw a little so
> the motor goes lighter on the speed controller. By the way,
> the speed controller was protected by a fuse rated a little
> below the controller spec current draw, so perhaps those
> specs are optimistic. Anyway, as a result of the double
> failure all of our dives were done on just the side
> thrusters because I was out of spare speed controllers.
> Lesson for next sub: Design the electrical system with a
> controller bypass, so I can operate thrusters with simple
> on/off switches if a speed controller fails. They're
> electronic, they will fail.
> 2) Of air bubbles in compensation oil
> Snoopy is now routinely diving deep (250 ft) and
> this has showed up a puzzling issue with the thrusters. They
> were feeble during dives, one died altogether on one dive,
> and they kept coming up leaking oil. At first we thought the
> seals were failing, perhaps due to some chemical
> incompatibility. We found suitable seals at an Amish farm
> supply store that sold things like tractor spares (viva
> trolling motor simplicity!) When I disconnected the bladder
> hose I got quite well sprayed with oil. The motor turned out
> to be pressurized. 
> Previously, I thought if one had a small quantity
> of air left in the system it would not be an issue so long
> as the compression volume of that air could be handled by
> the flexibility of the hose (aka compensation bladder.)
> Wrong. I now think what happens is that if the dive exceeds
> the pressure rating of the shaft seal and there is a bubble
> of any size, you will get water added to the oil and the
> bubble stores the pressure. Upon surfacing, the bubble
> squeezes oil and water back out until the pressure in the
> motor falls to the "cracking pressure" of the
> seal. Thus, you get an oil leak even though the seals are
> fine. Lesson: Zero tolerance with oil bubbles, even a small
> bubble is unacceptable if you are diving deep. I'm going
> to put set screws on the motor caps so I can get rid of the
> bubbles more easily.
> 3) An easy way to add
> buoyancySnoopy's buoyancy is adjusted by
> placing trawl floats in PVC tubes. On one occasion, the
> oncoming passenger's weight required the addition of
> just one float (i.e. the new guy weighed seven pounds more
> than the one getting off). The support diver wasn't
> suited up and the water was 42 degrees, so I just pushed a
> float under the lip of the forward MBT. It worked like a
> charm, and the float even stayed in place throughout the tow
> back to the ramp. Lesson: You can easily add a few floats
> for buoyancy on a standard K sub, no special tubes
> required.
> Most of our dives were along a very steep
> incline, not quite a wall but more like a series of ledges
> and very steep slopes. Between the steep terrain and the
> good visibility, the K250 dome for once offered a really
> good view. We typically made our way down the slopes using
> very slightly negative buoyancy, trailing the back corner of
> a skid on the slope. Looking aft, you could see a zigzagging
> trail of silt hanging motionless in the water and tracing
> our path. The sub compresses with depth, so slightly
> positive buoyancy at the surface turned into slightly
> negative at depth, but we're speaking of just a couple
> of pounds and not anything that caused difficulty. In fact
> at one point we stopped dead in the water four or five feet
> above a flat bottom for about five minutes, just waiting for
> a pre-arranged touch-point call on comms. The sub didn't
> rise or sink an inch, she just hung there completely
> immobile for five minutes. At about 140 feet the visibility
> would improve significantly, and the water changed from
> green to blue. It looked like ocean instead of lake water.
> I'll post a video, but that'll take a few days to
> put together. The only "incidents" we had were a
> cold bath we took when we closed the hatch over a corner of
> the crew's shirt, and when we got hooked on a log at 220
> feet - fortunately reversing got us right off
> it.
> 
> Best,
> Alec 
> 
> 
> 
> 
> 
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