[PSUBS-MAILIST] thruster sizing etc

[Alec Smyth via Personal_Submersibles]

Hi Alan,

Standard operation is to lock the side thrusters horizontally when on the
surface and vertically when diving. On the surface they're very useful for
things like maneuvering around a dock or getting on or off the trailer.
They provide zero-radius turning, which a single stern thruster never can.
The ramp down, ramp up when switching from forward to reverse or vice-versa
is a feature that is built into the speed controllers to prevent arcing on
the motor commutator. From the driver's perspective, you can just slam the
motors from full power in one direction to full power in the opposite
direction, and nothing will happen to the motors if your speed controller
has that functionality. The transition despite being smooth is really
quick, maybe just a couple of seconds.

I dive Snoopy slightly positive because that way the wash from the props is
directed upwards and doesn't muck up visibility. I found it a real
disadvantage of the original design that the side thrusters tied up your
hands if you are holding them all the time, hence the indexing plates to
lock them in position. My new sub, however, uses four fixed thrusters. That
arrangement gives you more degrees of freedom and has no moving parts.


Cheers,

Alec

On Sun, Sep 28, 2014 at 5:40 AM, Alan via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> 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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