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.
--- On Sat, 5/22/10, vbra676539@aol.com <vbra676539@aol.com> wrote:
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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