[PSUBS-MAILIST] thruster sizing etc

Sun Sep 28 13:03:25 EDT 2014

Alan I will put my two
cents in on thruster for psubs.

I went down a similar
path to yours in trying to sort out thrusters for the upgrade on the R300 and
the new boat I am designing, the R500.  I looked at existing off the shelf
thrusters for ROVs.  They are nice but expensive.  I got a quote
about 6 months back from Robo Marine in Indonesia as well, the company you
visited during your recent Indonesian trip.  My assessment was they were too
costly for a home built for a 100 lbf thruster.  I also looked into
designing a thruster with a kort nozzle.  It looked like it was going to
take quite a bit of engineering to sort this out so I abandoned this approach.

I have settled on using four Minn Kota 101 lower
units for each boat. I have them sitting in my shop. For the R300, I am
using two fixed horizontals for propulsion /yaw control and two fixed vertical
for pitch control /vertical station keeping.  You have to love
the MK 101's.  They are super quite, powerful and the motor controllers
work great with built in protection against slamming the units from full forward
to full reversion. They are also potted.  On the motor controller, I did dome playing around with these with a
MK-101 lower unit.  I removed the hardwired potentiometer that comes with
the controller so that I could confirm that it was just a 0-5 analog VDC signal
that was driving the controller and it was.  If you listen to the
controller, there is a built in relay that electrically isolates the controller
when you are in the deadband around 2.5 VDC.  This keeps the thruster
from draining the batteries when the boat is parked.   About two
weeks ago, I gave the machine shop I use the drawings for mounting the kort
nozzles and for the nozzles themselves.  I
am waiting on these parts.   I went with a Wageningen series 37. This is a
good shape when both forward and reversing thrust are important.  I decided
to go with Kipawa high performance three bladed props.  These are also in my shop ready to be
installed in the kort nozzles.  I have decided to go with air pressure
compensation on the MK's and am using the pressure reducing regulator that Hugh
Fulton came up with mounting upside down for the reasons you mentioned.  I
place an order using the Psubs discount through Subconn for MCBH3M bulkhead connectors
and all the cables for the four thrusters for the R300.   I designed
an adaptor to mate with MK 101 lower unit and the machine shop is currently
fabriacating these.  I have one three
axis joy stick Digikey (APEM) 679-2264-ND (HFX33S10) in my shop that I am going
to use to control all four thrusters.  I
am going to run these through the PLC in the R300 so that I can program
different interaction between the thrusters but you could use the joy stick to directly
to control the thrusters as each axis gives a 0-5 VDC analog output signal with
a 2.5 VDC centralized position.

I am using he exact same
set up on the R500 with the exception that I have tilted the vertical thrusters
to get sidal movement of the boat.   

I agree with both Alec
and Hank, yes, there are some nice features to being able to rotate the
vertical thrusters but to me, the KISS aspect of fixed thrusters out ways these
for psubs.   Hopeful I will have the
workover done on the boat in time for Islamorada next summer if we hold the
2015 Psub convention in Florida again.

Cliff

 From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Sunday, September 28, 2014 4:40 AM
Subject: Re: [PSUBS-MAILIST] thruster sizing etc

Thanks Alec that was helpful.
Is that the normal mode of operation, having the side thrusters locked
vertical? Were you putting them in reverse or just relying on positive buoyancy.
I was planning on having side thrusters that are rotated by electric motors, so my 
hands are just on a couple of joy sticks controlling all the motor functions.
I liked the idea of using rotating side thrusters so that I could have double the power travelling
horizontally if need be. Also there would be no need to ramp the motors down to change 
from forward to reverse.
Any thoughts on the pros or cons of this anyone?
Alan

Sent from my iPad

On 28/09/2014, at 4:55 pm, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Hi Alan,
>
>
>On the stern, snoopy has a 55 lb Minnkota. The side thrusters are actually of unknown thrust, they came with Snoopy and are Motorguides but I'm not exactly sure which model. My estimate would be about 40 lbs (each). What you saw in Florida would have been forward motion based on the stern thruster alone, as I was using the side thrusters just for depth keeping, locked vertical. The K250 has very limited battery capacity, carrying three batteries in the standard design and four in Snoopy. I find the thrusters well proportioned to the limited battery capacity. The bottom line is that a K250 has perfectly adequate thrusters and batteries for diving, but not enough for surface runs. Something in the league of Minnkota 101s is great, but only on subs with battery pods.
>
>
>Best,
>
>Alec 
>
>
>On Sat, Sep 27, 2014 at 8:17 AM, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>Alec,
>>what size motors do you have on Snoopy?
>>I remember watching you disappear into the blue surprisingly quickly in Florida.
>>Were you using the stern & side thrusters simultaneously?
>>Are you happy with the speed?
>>I have spent a LOT of time Googling brushless motors & haven't come up with
>>an easy solution.
>>I was looking particularly at inrunner motors, as they have a couple of advantages
>>over outrunners, however outrunners have lower revs. Whatever, they are both going
>>to need gearing down majorly & matching up with a planetary gear isn't looking easy.
>>Most of the motors that are available are found at Hobby King & are lightweight & made
>>mainly for model planes. So their strength & ability to sustain several hours of
>>continual operation are in question.
>>Must be a solution out there because 9 out of 10 thruster manufacturers are using brushless motors & I doubt they would be making there own.
>>Alan
>>
>>
>>
>>Sent from my iPad
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>>
> 
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