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Hi Alec. Just a quick thought. If you wanted the thrust bearing and shaft
to be able to move inboard just a little, how about this. The whole
shaft/bearing/seal assembly is mounted inside a nipple type through hull. The
bearing "stop" is a great big threaded nut that is screwed onto the welded
thru-hull nipple. To let the shaft move in a little, a quarter turn on the nut,
and the whole assembly moves in-board. This whole assembly including the nut, is
encased with all the other seals and devices you've planned. The shoulder on the
shaft is on the outside of the sub, and so moves hard up against the nipple
face. If the shaft isn't spinning anymore, a rubber washer or floating O ring
would
OK......now for the "Frank method".........
You've all heard me rant about having a valve on EVERY hole. Here's what
I'm thinking.
The shaft goes through the hull with all the bearings, seals, and what ever
else is required to make it water tight. As the shaft enters the hull ( again,
through a welded nipple ) there's a big ball valve on the end of that nipple.
The prop shaft has a coupling on it, inside the valve, so the part that
exits the sub is locked in place, but the inboard shaft section can be simply
pulled out of the valved nipple and the valve is closed. This removable shaft
section could be removed several ways. The coupling is made from the splined
shaft from a truck transmission, that way it stays aligned, ( and you won't need
a complicated and expensive machining process to make it.) The connection
to the motor armature is one of those rubber fingered things used for vibration
dampening. If the shaft thru-hull starts leaking bad, stop the spin, pull off
the retainer ring on the rubber vibration coupling, slide the short section of
shaft out of the valve, close the valve, and feel secure that water isn't
getting past a ball valve. Low cost, simple, almost fool proof, definitely won't
leak, and you can buy replacement parts at the junk yard cheap. Frank
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