[PSUBS-MAILIST] oil compensation

[Alan James via Personal_Submersibles]

I found some comments that Carsten made about oil expansion & compensation.
Someone was interested in hearing them if I found them. The thread was 5 Dec 2010.
Alan
Alan and the other gentlemens,  our expierence with oil filled motors, batterys or even propeller shafts is that the oil expand if the motor is runing longer time. 
Simple because its warm up. We had that problem on Eurosub on the first dives. 
And on Euronaut we filled the bladder complet up and the get pretty hard in the hot summer just by sun heating the sub. 
A full filled bladder with over pressure creates a lot of interal 
pressure in the wrong direct - a lot of force for the bladder itself and hose work.  Therefore our bladder are only half expand during the filling. But still free of any air. 
An other point is that the bladder has to be not to small. To create a slightly overpressure on the motorseal you just install the bladder below the motorcasing. 
But we found out that on trolling motor (electric outboards) this is not nessesary. There seals are good for some 
douzend feets at least - so you can install the bladder else were. 
Filling is simpler if the bladder is slightly over the motor - you can vent the system direct on the filling point. Another point is that we install now one bladder per motor  - in the earlier sub (Sgt.Peppers) we install a central
one for all motors. Hard to find a leak after a dive with all the T-crossing piepings and motorseals..  vbr Carsten
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.whoweb.com/pipermail/personal_submersibles/attachments/20140722/6292b705/attachment.html>