[PSUBS-MAILIST] coupler design flaw

[hank pronk via Personal_Submersibles]

It seems my magnetic coupler has a design flaw.  When the drive assembly is installed in the sub, it is in the horizontal position creating an air pocket inside the barrier.  When I fill the shaft tube with oil, I can not remove this air pocket.  I can fill the assembly with oil before installation, but that is a pain if I loose some oil for whatever reason.  I have some options, first I have just installed a small bicycle inner tube to act as a compensation bladder inside the ballast tank.  My thinking is that it has enough volume of oil to offset the air pocket.  I can also replace the shaft bearings with a cutless type bushing, eliminating the need for oil.   The last solution is to fill the assembly with oil prior to installation and add a small oil reservoir above the assembly to insure there is always enough oil in case some escapes.
Hank