[PSUBS-MAILIST] Compensation Method Again...

[Alan via Personal_Submersibles]

Hi James,
to me the bellows look too small.
Any air in the system that is compressed, or oil that leaks out could cause the 
bellows to be forced into the connecting tube & get ruptured in the process.
This would destroy your motor with the salt water flowing in.
All commercial ROV & submarine motors I've seen have an overpressure of
about 5psi, & in an ex military paper I read on compensating motors, the over
pressure is standard. 
I would have a look at the size of commercial compensators for thrusters & 
base the size of your bellows on that.
People in the group who just dive lakes can get away with lots of things but
with you diving in seawater, you mightn't be so lucky.
Cheers Alan
 

> On 13/07/2020, at 11:21 PM, James Frankland via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Hi All,
> 
> Right, this has got to be it, surely?
> 
> Ive put in a T connector at the top with a plug so i can remove it to fill.  Then a pvc tube goes underneath to the bellows thing, contained in a housing.  I can easily fill the motor and im happy now its properly compensated and allows for any expansion.  Of course, the next day after filling it, there was a small amount of air in the tube.  No idea where it comes from.  Im putting ti down to micro bubbles collecting on things.  Anyway, at least its easy to top up before a dive.
> 
> The aft motor is different.  This has 2x tubes protruding through the main original shaft of the motor.  I have added the bellows to this also.  I am going to put another on the other tube so it has 2.  These dont need any cover as they are inside the aft fairing\main tank and so out the way.
> Regards
> James
> <20200711_150625.jpg>
> <20200711_153215.jpg>
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