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Re: [PSUBS-MAILIST] speedo



Hi,

I think there would be quite a bit of value in knowing
the vessels water speed, regardless of how well you know
you throttle positions.  Move the throttle for 0 to 50%
and you will be accelerating for while (until you hit
terminal velocity), i.e. not traveling at a constant speed,
so knowing the your water speed will know when you've
finished accelerating.  I recall not having a good
sense of acceleration when in a sub, so just going on
throttle position alone won't give you much sense of
speed or position.


And don't forget the coriolis effect if you are trying
to determine position! :)

Cheers,
  Ian.

-----Original Message-----

From: Alan James 

Sent: Oct 31, 2010 9:32 PM

To: personal_submersibles@psubs.org

Subject: 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 ----- 
  From: 
  JimToddPsub@aol.com 
  To: personal_submersibles@psubs.org 
  
  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 
      To: personal_submersibles@psubs.org 
      
      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 ----- 
      
        From: 
        David Bartsch 
        To: personal_submersibles@psubs.org 
        
        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 ----- 
          From: 
          David Bartsch 
          To: personal_submersibles@psubs.org 
          
          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



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