[PSUBS-MAILIST] right side up compensator

[Jon Wallace via Personal_Submersibles]

 I'm thinking we need someone to give a technical talk on this at our next convention.  I'm not only confused but I guessing others are as well.  I thought the simplest approach, from previous discussions, was just to use a length of hose connected to the oil filled motor on one end and open to water on the other end.  See attachment.  This allows expansion of oil into the hose (blue), but traps a gap of air (white) as water (green) enters the hose during a dive.  Water compresses the trapped air the deeper you go, so designing a large enough gap is important because that air gap can get quite small and potentially result in mixing of the oil and water.  At 300 feet for example, the air gap is only .652 inches (16.5mm) when using a 30 foot (9 meter) hose.
My understanding for the need of a bladder is in a closed system, meaning no hose open to the water, to have an expansion point (the bladder) for any increased oil volume due to heat whether it be motor operation or just sitting in the sun while out of the water.
Jon
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