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Hi David/Alan
I do not think indicated speed will be very
accurate unless operating in a 0kt current .Maybe by calculating model speeds
(dist/time close to surface )according to different power settings at 0kt
current would help.All that will then need to be established is the current
speed and direction ie paddle speedo,take note of current speed
in direction that needs to be traveled when stationary on bottom.Take the
time on starting and +or- speed from from model speed should give grounspeed
wich could be used to calculate the distance one would want to travel in that
specific direction.
Who knows there could be some thing out there that
could be bought off the shelf that does it all.
Glen
----- Original Message -----
Sent: Sunday, October 31, 2010 6:03
PM
Subject: Re: [PSUBS-MAILIST] speedo
David
On the R300, I use a pitot tube with a
differential pressure transmitter. In my PLC
I programmed an equation that correlates differential pressure and
speed. While this has worked OK, it is not as accurate
as I would like at low speeds. If I had to do it again, I
would use a paddle wheel that gives a pulse count that is proportional to boat
speed. You can get these as replacement parts for jet skis.
The results should be more linear than for a pitot tube.
Cliff
From: "ShellyDalg@aol.com"
<ShellyDalg@aol.com>
To:
personal_submersibles@psubs.org
Sent: Sun, October 31, 2010 7:28:52
AM
Subject: Re:
[PSUBS-MAILIST] speedo
In a message dated 10/31/2010 5:11:51 A.M. Eastern Daylight Time,
dbartsch2236@hotmail.com writes:
Can
anyone describe how a speedo speed indicator system
works
Hi David. I'm not sure what a "speedo" refers to here but for surface
boats that measure the speed in knots, there's usually a small paddle wheel
inset into the hull that spins as the water passes over it.
Most I've seen ( on sail boats ) use magnetics to send the signal through
the hull to a tachometer like device
that in turn sends the speed signal to the little gage on the dash.
The paddle wheel is VERY small, like 1/2 inch diameter.
Frank D.
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