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I agree with Vance on the problems associated with trying to vector
up and down with thrusters that are also used for propulsion
(although I don't have any experience with rudders). The solution I
prefer is to have a dedicated vertical thruster. The additional benefit
is that a vertical thruster allows the sub to descend while set for
slight positive buoyancy. In this configuration, it is the thruster
(with variable speed control) that pushes the sub down to the desired
depth, then the thrust is reduced to the point where the sub is
"hovering". Then the main thrusters provide propulsion only. The major
safety benefit is that the sub will naturally return to the surface in
the event of a system failure just by cutting power to the
vertical thruster. I found it to be more relaxing to dive a sub set for
positive rather than neutral or (heaven forbid!) negative.
Greg C.
From:
vbra676539@aol.com <vbra676539@aol.com>
Subject: Re:
[PSUBS-MAILIST] Rudders
To:
personal_submersibles@psubs.org
Date: Saturday, May 22, 2010, 8:05
PM
There are some issues with using pivoting thruster
pairs for this sort of double duty, especially in small thrusters on
heavier vehicles. When you vector down or up, or need to correct
steering, forward thrust is lost. Also, the lack of control surfaces
means that any correction must be powered. Vehicles will not continue
to turn, for instance, once the power is switched off. You can do very
well without those control surfaces, of course-----until you use a
rudder and dive planes for awhile-----then you see what you've been
missing.
Vance
-----Original
Message-----
From: Alan James < alanjames@xtra.co.nz>
To:
personal_submersibles@psubs.org
Sent: Sat, May 22, 2010 5:23
pm
Subject: Re: [PSUBS-MAILIST] Rudders
Thanks Pierre,
is there a discount on the posters with
Psubs membership?
Alan
----- Original Message -----
Sent: Saturday, May 22, 2010
11:23 PM
Subject: RE: [PSUBS-MAILIST]
Rudders
Yes
that’s me! Please stand in-line for a signed poster.
A
good design to control sub with 2 motor is to have them in the
center of mass (from front to rear) and as far away from each other
(side to side).
I
also have mine so they can rotate on the shaft. So I can use them
for up/down movement.
Pierre
Sorry Pierre,
It's clicked who you are.
The world famous
owner of "big".
Your email
name through me out.
below is a link
to a glossary of submarine terms found on the
"Deep search
site" that's quite good.
----- Original
Message -----
Sent: Saturday, May
22, 2010 4:13 PM
Subject: Re:
[PSUBS-MAILIST] Rudders
Any photos of
your sub you can refer me to?
-----
Original Message -----
Sent: Saturday,
May 22, 2010 2:37 PM
Subject: RE:
[PSUBS-MAILIST] Rudders
Hi
Alan,
My
use a very similair design with one motor on each side and I
don,t have a rudder. With one full foward and one full backward,
I can almost turn on the spot. Same as a bulldozer.
So
no, I would not waste time on rudders.
I have been
looking at some videos of a small 1 person semi-dry ambient sub
in action.
This sub
doesn't have a rudder & just uses differing motor speeds to
turn.
As I'm
building a small 1 person sub of a similar size with two PWM
controlled motors I'm wondering
wether a
rudder is going to be a waste of time for me. I did have a
rudder in my original design.
Any thoughts
on this thanks.
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