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Working Under Pressure - How Much?

R/C Submarine modelers

Postby Ramius-II » Fri Oct 17, 2003 9:13 pm

Hi All:
How high does the internal pressure of the WTC in a sub with piston tank ballast get at say 3 feet of depth? ???

Thanks, Ed :)
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Postby KOEZE » Sat Oct 18, 2003 3:17 pm

Depends on three things.
1. Rigidity of the WTC. How does it handle the pressure.ie is it compressed by the water pressure (very small factor)
2. How much does the temperature rise from the internal components engines, esc, etc.
3. most important factor. What is the displacement of the piston tank against the volume of the wtc.

Pressure1 x Volume1 = Pressure2 x Volume2
This means, when the volume decreases the pressure rises.
Half the volume, twice the pressure.

EJK
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Postby Ramius-II » Sun Oct 19, 2003 1:16 pm

Hi EJK:
Thanks, what I was really after is what internal pressure is typical. Like 20 to 30 PSI, or is it more?

Ed
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Postby KOEZE » Sun Oct 19, 2003 2:24 pm

Sorry Metric system.

I'd say a couble of tenths of bar. Every meter the water pressure rises with a tenth of a bar. If you plan to dive to 1 meter an overpressure of one tenth of a bar should suffice. Added to that, the pressure in the hull rises by the piston of the piston tank compressing the air in the hull.

Internal pressure has 2 major advantages.
Leaks are easily spotted as bubbles come out.
Internal pressure makes it harder / impossible (when the internal pressure > external pressure) for water to get in.

PS, I intent to pressurize my sub till 0,2 bar as my depthregulator allows me to dive to 1,5 metres.
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Postby Sub culture » Sun Oct 19, 2003 2:28 pm

Hi,

The answer to your question is difficult to answer, because the pressure inside the WTC will vary from boat to boat.

However, the lower the pressure on the back of the piston, the better, as this will result in less current being drawn by the piston tank motors.

I would say between 6-12 PSI would be a good figure to aim for, 20-30 PSI will require a very well constructed WTC and powerful motors.

Andy
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Postby Ramius-II » Mon Oct 20, 2003 12:09 pm

Thanks so much guys. :)
I had often wondered what internal PSI to design for. This helps alot. :D

Ed
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