[PSUBS-MAILIST] Motor modification

Mon Dec 5 17:36:38 EST 2016

Rick - he's talking about cases where there is no bladder implemented, other than a flexible PVC hose which is intended to serve the compensation function when the required volume is low.  Counter intuitively, even with a so-called "flexible" hose, the internal volume can be quite rigid against external pressure because the cross section is round and dimensionally stable. If you partially crimp such a hose, you put it out of round and essentially initiate its "collapse", allowing it to serve the compensation function instead of merely resisting the external pressure. If you add a conventional bladder shaped oil reservoir, (e.g. hot water bottle) your plumbing doesn't need to be flexible because the bladder has no strength against external pressure.

Sean

On December 5, 2016 3:04:54 PM MST, Rick Patton via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Alan,
>
>I am confused (which doesn't take much) but you talk about doing a test
>to
>collapse a PVC hose. I assume that the hose leads from an oil filled
>vessel
>to a bladder both being completely filled with a dielectric fluid/oil.
>So I
>was thinking that the hose and bladder were to allow for slight
>expansion
>as the oil warms up from use so that the factory prop shaft 0 rings
>would
>not be extruded outward from excess pressure?. This is based on there
>being
>NO air in the vessel, hose or bladder. I didn't realize that there were
>two
>0 rings on the Minn-Kota prop shaft so I do see what you are saying
>about
>the outer most 0 ring pushing in with increased pressure. The way I
>understand it though is if you have ANY air in the system than you are
>defeating the purpose of having a hose and bladder, correct?
>
>Rick
>
>On Mon, Dec 5, 2016 at 11:03 AM, Alan James via Personal_Submersibles <
>personal_submersibles at psubs.org> wrote:
>
>> Some compensating thoughts.
>> On James Cameron's sub they used IV drip bags. I am not sure what
>they
>> were compensating.
>> These come with various means of hose attachment.
>>    With regard to the wrap around hose method; I did some
>calculations on
>> a standard pvc hose, & surprisingly
>> the colapse pressure was around 100psi. I am sure one of Nuytco's
>> technicians told me they crimped the hose
>> that was compensating their lights, to initiate the collapse of the
>hose
>> for compensation.
>>    The industry standard for thrusters seems to be around 4psi
>internal
>> overpressure,
>> but the compensators they use for this are relatively expensive. Hugh
>came
>> up with
>> the novel idea of using a releiving regulator set at 4psi (Parker
>PR364).
>> Cliff is using this.
>> This could be used for air or oil compensation.
>>    The seals need oil for lubrication, & I have read that they can
>use
>> about a teaspoon a day. Based
>> on that I would have some sort of reservoir.
>>    Depending on the motor it may be tricky to get all the air out. If
>you
>> have a bearing in a bore
>> followed by a seal, the air / oil would have to move through the
>bearing
>> which may be a sealed type
>> or packed with grease. The Minn kotta diagrams I have seen show 2
>seals;
>> so how do you get oil or
>> ambient pressure between those? One will fail when you exceed it's
>> pressure limit.
>> Alan
>>
>>
>> ------------------------------
>> *From:* James Frankland via Personal_Submersibles <
>> personal_submersibles at psubs.org>
>> *To:* Personal Submersibles General Discussion <
>> personal_submersibles at psubs.org>
>> *Sent:* Tuesday, December 6, 2016 4:44 AM
>> *Subject:* Re: [PSUBS-MAILIST] Motor modification
>>
>> Hi Antoine\Hank.
>>
>> Thanks guys.  drinking bladder looks good.  I was thinking of a
>furniture
>> lift bag, which is very similar.  I use a hot water bottle for the
>aft
>> motor.
>>
>> Hank, what do you use for a bladder?
>>
>> Thanks
>> James
>>
>> On 5 December 2016 at 13:18, hank pronk via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>> James,
>> I put my fill plug under the prop, in the flat end cap,  and it works
>like
>> a dream.
>> Hank
>>
>>
>> On Monday, December 5, 2016 5:37 AM, Antoine Delafargue via
>> Personal_Submersibles <personal_submersibles at psubs. org
>> <personal_submersibles at psubs.org>> wrote:
>>
>>
>> Hi frank
>> I have done something like that for my prop shaft seal oil filled
>> compartment.  But first i removed the hose and filled with a serynge
>with
>> long steel needle. Then put the tube and filled it with the serynge.
>> The tube is flexible and transparent, from endurance sport
>> platypus drinking bladder
>> Works well
>> Regards
>> Antoine
>> On Monday, December 5, 2016, James Frankland via
>Personal_Submersibles <personal_submersibles at psubs.
>> org <personal_submersibles at psubs.org>> wrote:
>>
>> Hi All
>>
>> I have been talking to Rick about motor compensation which has got me
>> thinking.
>>
>> I originally did my motors like other psubbers have done with the
>rubber
>> tubes around the sides, but have found them a real pain to fill. 
>Problem
>> is the location of the tube, plus the tiny bit of protruding pipe
>nipple on
>> the inside.
>>
>> So, I modified the motors by drilling a hole in the top part of the
>> aluminium endcap and use that now as the vent\final fill.  Its
>better, but
>> still awkward.
>>
>> I have suggested to Rick this idea, which I am tempted to adopt
>myself.
>> Blocking off the existing side mounted pipe nipples and
>> filling\venting\compensating all from the one top hole.  There would
>be a
>> rubber bulb of some sort on the end of the pipe.  2x pictures show
>filling
>> and operation.  Appologies for rubbish drawings, im at work.
>>
>> What does everyone think?
>>
>>
>> 
>> 
>>
>>
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