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Re: [PSUBS-MAILIST] speedo

Hi Jim,
No you're not missing anything, I think I'm having trouble thinking this through.
Yes, If you knew your boat speed at various increments of your throttle then there
wouldn't be much more of an advantage having a speed indicator, other than it would indicate your
speed as you got up to speed. Because of current speeds relative to the Psub norm of 3 knots,
any accuracy with reguard to real speed or tracking of distance travelled would go out the window.
I think this has something to do with the theory of relativity.
Alan
----- Original Message -----
Sent: Monday, November 01, 2010 2:50 PM
Subject: Re: [PSUBS-MAILIST] speedo

Alan, doesn't the equipment you described measure the sub's water speed so that it would indicate the same at a given power setting regardless of no current, head current, or tail current?  Only the ground speed would be different.  Or did I miss something completely?  Wouldn't be the first time or the last.
 
Thanks,
Jim
 
In a message dated 10/31/2010 8:43:23 P.M. Central Daylight Time, alanjames@xtra.co.nz writes:
David,
In hindsight ignore the bit about a current indicator. If you were being carried along in a
10 knot current you would be flowing with the water & the indicator would
hardly indicate.
Alan
----- Original Message -----
From: Alan James
Sent: Monday, November 01, 2010 2:26 PM
Subject: Re: [PSUBS-MAILIST] speedo

Hi David,
I'll keep the idea percolating. I have some ideas; it could be used with the rotary pot.
The beauty of the position sensor circuit (wich I didn't design) is that the circuit can
be tuned by two pots to light the full range of LEDs even though the magnetic potentiometer
might be used only through a small degree of it's range. So it can be easily adapted.
It might be a good water current indicator. If you were mid ocean with no visual reference &
you knew what your boat speed should be by experience, & found that you were going faster or
slower according to the speedometer, then you could calculate the current. That's providing the
current isn't coming from the side.You would probably need another one for that.
I believe another Psubber was working on an expensive system involving a computer & using
all sorts of data input to log their progress.
Regards Alan
 
Original Message -----
Sent: Monday, November 01, 2010 1:07 PM
Subject: RE: [PSUBS-MAILIST] speedo

Alan,
 
   Being able to determine the speed at which you are traveling while submerged when no visual aids are there to help you would be of great importance to me. This idea you mentioned would be a much desired device. I would like to encourage you to undertake its development as the end product would be worth the while.
   I had considered a paddle that would be forced against a spring to give a mechanical indication of speed but your idea looks much better.
 
David Bartsch
From: alanjames@xtra.co.nz
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] speedo
Date: Mon, 1 Nov 2010 08:55:54 +1300

Hi David,
You've got me thinking on this speed indicator idea.
On my projects page is the "Position sensor". I'm using a rotary magnetic potentiometer,
but there is a linear magnetic potentiometer shown also.
You could have a slider over the top of the linear potentiometer, with a vane that is pushed
by water movement against a spring. The vain portion has the magnet & as it slides further
along the potentiometer it changes the voltage wich is registered on the circuitry also on
my projects page. You could have the speed indicated by the LEDs as is, or output to a
panel meter. This could be calibrated in a swimming pool by either adjusting the spring size
or tension, the size of the vain, or by adjusting the display range with the pots on the circuit board.
Regards Alan
 
 
----- Original Message -----
Sent: Sunday, October 31, 2010 10:10 PM
Subject: [PSUBS-MAILIST] speedo

Can anyone describe how a speedo speed indicator system works and would such a system be suitable for small submarines? Is'nt such a system deployed on the R-300 Cliff?
 
David Bartsch