[PSUBS-MAILIST] Dive report: Snoopy at Seneca
via Personal_Submersibles
personal_submersibles at psubs.org
Mon Jun 8 18:52:08 EDT 2015
Sounds to me that internal engines in the pressure hull with through shaft and packing glands are the only way to go.
Keith T
Private via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Hang on, I'm not understanding Brian's suggestion. What exactly are the "oil traps"?
>
>
>
>> On Jun 8, 2015, at 5:26 PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>>
>> Actually Brian's idea is picking up steam in my mind! The power loss your experiencing would not happen if the motor is open to the water because the motor is truly equal on both sides.
>>
>> Hank--------------------------------------------
>> On Mon, 6/8/15, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>> Subject: Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
>> To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
>> Received: Monday, June 8, 2015, 5:16 PM
>>
>>
>> Alec,
>> I have the same problem with my drive on Gamma,
>> when returning to the surface the shaft tube is under
>> pressure. I have a ball valve mounted to the tube and even
>> a month later there is pressure until I open the ball
>> valve. I have tried a softer compensation bladder with no
>> luck. There has to be an air pocket that we are not
>> getting rid of. Brian's suggestion is not bad at all,
>> forget the bladder and rig an open hose with traps so the
>> oil can not escape. There would be an air space trapped
>> between the oil and water in the length of tube. That air
>> bubble would simply move in two directions depending on
>> depth. A very simple solution, more tricky for you because
>> your motors rotate. I think I will test this idea since I
>> have my tail assembly off for repairs anyways.
>> Hank--------------------------------------------
>> On Mon, 6/8/15, Alec Smyth via
>> Personal_Submersibles <personal_submersibles at psubs.org>
>> wrote:
>>
>> Subject: Re:
>> [PSUBS-MAILIST] Dive report: Snoopy at Seneca
>> To: "Personal Submersibles General
>> Discussion" <personal_submersibles at psubs.org>
>> Received: Monday, June 8, 2015, 4:48 PM
>>
>> OK, let me
>>
>> try to reason this through again. Lets say the standard
>> trolling motor shaft seal is watertight to 50
>> feet, and that
>> initially I had 1 cubic inch
>> of bubble in the system. Dive
>> to 250 feet
>> and what I would have thought would happen is
>> that the 1 cubic inch of air would be reduced
>> to 1/8th in3
>> due to 8 atmospheres of
>> pressure increase. I would have
>> expected
>> that the compensation bladder would have just been
>> squeezed by that volume, and that upon
>> surfacing the bubble
>> would go back to 1 in3
>> and the pressure in the motor to 1
>> atm.
>> However, what we found was that the motor upon
>> surfacing was significantly pressurized. The
>> compensation
>> bladder (i.e. hose) was
>> visibly distended by internal
>> pressure upon
>> surfacing. There was no leak at the hose
>>
>> clamps, but oil was leaking from the shaft seal.
>> Since there was over-pressure
>>
>> surfaced, clearly water had to have entered the system
>> during the dive, and as the hose clamps were
>> leak free and
>> the seal was not, I suspect
>> the seal. Now the question is
>> why water
>> would get in. Bubble greater than the compression
>> range of the hose? Seal offering less
>> resistance than the
>> hose to compression?
>> Shaft pumping water under the seal
>> during
>> operation due to abrasions? Thermal contraction?
>> I'm actually not sure - any theories are
>> welcome. One
>> interesting detail - the stern
>> thruster, which was not
>> working due to the
>> issue with the speed controller, did not
>>
>> have any oil leaks. Both side thrusters, operating,
>> did.
>> The side
>> thrusters being feeble can be explained by
>> pressure on their
>> seals, or just by their
>> age and related wear on the
>> commutators. I
>> will be changing them, or at least their
>>
>> internals.
>>
>> Best,
>> Alec
>> On Mon, Jun 8, 2015 at
>> 2:54
>> PM, Jon Wallace via
>> Personal_Submersibles <personal_submersibles at psubs.org>
>> wrote:
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> It sounds like at some point water pressure at
>> the
>> seal was able
>>
>> to compress the bubble of air in the tube,
>> the
>> opposite of what
>>
>> was expected.
>>
>>
>>
>> I'm kind of stumped by
>> the description of the
>> motors
>> performance
>> being
>> "feeble" however. This couldn't
>> have been primarily due to
>>
>> pressure I don't think. Also,
>> isn't an easy
>> fix just to
>> "clamp"
>> the
>> tube any place where liquid appears assuming the
>> tube is held
>>
>> in a vertical position and the bubble is at
>> the top
>> (ie vise grip
>>
>> the tube).
>>
>>
>>
>> Jon
>>
>>
>>
>>
>>
>> On 6/8/2015 12:01 PM, Brian
>> Cox via
>> Personal_Submersibles wrote:
>>
>>
>>
>>
>>
>> Hmm,
>> guess I'm not getting what is
>>
>> happening
>>
>> Brian
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
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