[PSUBS-MAILIST] DC Systems Primer

Wed Oct 16 17:51:43 EDT 2013

Yeah Alec, I forgot about him.

I actually saw Lake Diver on that tender once. I passed the rig in Key Largo, it was stopped at a marina on the Intracoastal as I went by on my boat. Or maybe the other way around, (foggy on the detail), but I remember the sub and the pontoon rig.

Joe

________________________________
From: Alec Smyth <alecsmyth at gmail.com>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Wednesday, October 16, 2013 5:37 PM
Subject: Re: [PSUBS-MAILIST] DC Systems Primer

Hi Joe, 

Actually I would say a K-250 might be inadequate, mainly due to the low freeboard and small 12 volt thrusters, but that you might find a 350 quite suitable. A 350 has way better freeboard, big battery pods instead of just three batteries, and about three times the top speed of a 250 (useful in a pinch given the currents you have there). Although there are lots of things that could be modernized, my impression is you would find the K-350 quite seaworthy for Southern Florida. I haven't actually used one there, just my 250, but 350s have operated plenty in open water. Including for instance Harold Maynard operating one in your neighborhood for decades.

Best,

Alec

On Wed, Oct 16, 2013 at 4:49 PM, Joe Perkel <josephperkel at yahoo.com> wrote: 
Dan,
> 
>No expert either, the learning curve is steep here. I do know however that they are harder to control and more costly than brushed, with the advantages they offer though that seems acceptable.
>I noted that very "squrrillyness" and your comments on that one video, but I was also encouraged by the capability of that motor and your side thrusters. The Islamorada convention demonstrates for the most part, my conditions here. The USS Spiegel Grove wreck and others like it for both day and night conditions, is the pinnacle of what I would strive for as far as capability. A maximum 5 - 7 miles to tow a submersible is reasonable and brings within range more stuff than I could do in a lifetime. It just really can't be anything bigger that a Nekton boat.
> 
>Obviously the K-350 as drawn now is wholly inadequate but, it has really good "bones" to work with here. Think an Alvin or Shinkai type of exoframe covered with FRP panels, and you get the idea of what I'm contemplating. I have a thing for replicas, and this little bugger could be made pretty dam close and be quite functional.
> 
>I'm liking George's thruster design more and more as I dig further. Six interchangeable 1 HP spam cans in Alvin's configuration, just may do the job. I have to see where the weight and size fall to be sure.
> 
>Thanks Dan!
> 
>Joe
> 
> 
> 
> 
>
>
>From: Dan H. <jumachine at comcast.net>To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> Sent: Wednesday, October 16, 2013 3:26 PM 
>Subject: Re: [PSUBS-MAILIST] DC Systems Primer
>Joe,
> 
>I have to plead ignorance on the BLDC motor.  I'm guessing it's some kind of permanent magnet field DC motor... Correct?   Typically they are smaller in diameter then a wound field type.  
> 
>For my rear thruster I got the last of the three horsepower motors George had.  So my rear thruster in pretty much as the plans show.  
> 
>My side thrusters are even a bit larger then the plans since I found two 3/4 HP brush type, 36 volt motors for very cheep in a surplus close out.  I built around them but similar to the plans.  
> 
>To get props for them I called Michigan Wheel and gave them my HP and RPMs and a description of my sub.  They recommended the props and sold them to me.  
> 
>When I was doing my wet testing, I put a amp meter in the motor power line and found the side thrusters were fine but the rear thruster was drawing a little to many amps.  A little hand grinding to reduce the area of the prop blades brought the amperage down to the max rating for the motor.  I don't know if that the best way, but it worked for me.  
> 
>Now if your thinking of building a true Kort nozzle your definitely going to have to do some experimenting.  Even the prop guards as called out on the plans effect the prop efficiency and so also the motor load.  
> 
>You may be better off to find your motors then figure out what you can attach to them, open prop, shrouded prop or Kort nozzle.  Anything will move the sub.  I have a total of 4.5 HP and I don't know if I could control any more power as the sub gets squirrelly when trying to travel fast.  When submerged, the side thruster are almost all that's needed.
> 
>Dan H.
>----- Original Message ----- 
>>From: Joe Perkel 
>>To: personal_submersibles at psubs.org 
>>Sent: Wednesday, October 16, 2013 2:08 PM
>>Subject: Re: [PSUBS-MAILIST] DC Systems Primer
>>
>>
>>Dan,
>>
>>What I was hoping to find was BLDC motors matching 36v 1800 - 3600 rpm, 1/2 to 2 hp range. They don't seem to be out there.
>>
>>I have matched up brushed motors with those specs at both Baldor and Leeson with the appropriate face plates. But, then we are back to the same large / heavy motors at least there in the $500 range.
>>
>>You have the standard motors on Persistence, what are the size and pitch of the respective props?
>>
>>I'm going to just have to suck it up and draw these up with new Kort nozzles.
>>
>>Thanks!
>>
>>Joe
>>
>>Sent from Yahoo! Mail for iPad 
>>From: Dan H. <jumachine at comcast.net>; To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>; Subject: Re: [PSUBS-MAILIST] DC Systems Primer Sent: Wed, Oct 16, 2013 1:48:13 PM 
>>Those high voltage DC motors are designed for variable speed drives where the power is first line voltage AC then converted to DC through a motor controller for accurate motor speeds and torque.  They aren't practical for a battery powered system.
>> 
>>For battery powered systems your probably better off to stick to the lower voltage motors.  With an inverter I guess you could convert the battery power to high voltage AC then convert it to DC, but I'm pretty sure you'd find it impractical with the extra equipment.  
>> 
>>It's hard to beat golf cart controllers for speed regulation and there's tons of them out there.  Battery powered floor scrubbers use a variety of DC motors too. 
>> 
>>Dan H.
>> 
>>----- Original Message ----- 
>>>From: Joe Perkel 
>>>To: Psubbers Mailist 
>>>Sent: Tuesday, October 15, 2013 11:02 PM
>>>Subject: [PSUBS-MAILIST] DC Systems Primer
>>>Since my Navy "A" school is some 30+ years ago, I need a little help in trying to understand and match up something close to Georges motors. What I dont understand is why is there such an array of DC motors in the 1 - 3 hp range with wildly varing input voltages?
>>>
>>>If you notice those Tecnadyne thrusters have stupendous input voltages up to 330vdc. I dont understand why and need a primer on DC systems for this application. Can anyone point me to one?
>>>
>>>What I'm trying to do is to slim down the housing, get more bollard thrust from the prop by adding a real kort nozzle, and use a mag coupling instead of a shaft seal, all else remaining essentially the same.
>>>
>>>I want to slim down Georges T-Rex cans with similar power specs, but new and improved components, keeping the items conducive to homebuilding, like the housings and mountings, electrical penetrators, shaft seals if I cant do mag couplings. 
>>>
>>>What I've found so far http://www.baldor.com/support/literature_load.asp?LitNumber=FL1210  fractional hp and up to 3 hp @ 1800 rpm but, here again @ 320vdc !?
>>>
>>>Whats attractive about this one is the dimensions, 6.5" on the mounting flange would fit quite nicely in the 6 nom SCH40 pipe which is 6.625"
>>>
>>>But I dont know what im doing with regard to the input voltage / output power / torque relationship and how to match this all up correctly.  All Ive confirmed so far is that Georges motors were TENV (totally enclosed non-ventilated), 36vdc @ 1800 to 3600 rpm for 1/2 and 3 hp respectively.
>>>
>>>Joe
>>>
>>>
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