[PSUBS-MAILIST] oil compensation

[hank pronk via Personal_Submersibles]

Hi All,Thank you Greg, just sent them a request.
I have tested my air cylinder compensator for my thrusters both in the pressure test and a couple days ago to 100 feet.   The set up seems to work with no water intrusion into the motors.  I have the cylinder mounted below the motors witch causes a small air pocket in the hydraulic fitting on top of the motor.  I am not worried about the small amount of air except the potential of oil being forced up past the air pocket.  This makes me think the compensating cylinder should be above the motors.  Then I wonder why does the compensating cylinder need oil in it at all.  As long as the bore in the cylinder has enough volume so the piston is not bottomed out at max depth.  I also have a small spring pushing the cylinder rod to create a small internal pressure above ambient.  Is my logic flawed?  it would be very convenient to eliminate the oil in the cylinder and would make the compensator  faster to react to pressure change say in a fast ascent.  Hank
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