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From: (no name) (no email)
Date: Sat Nov 19 2005 - 19:28:15 EST
In a message dated 11/17/2005 12:54:28 AM Eastern Standard Time,
writes:
I turns out
that the pressure of the line between the prop and bearing had forced the
whole shaft aft about 3" pulling it out of a bolt-on clamshell coupling.
When I removed the coupling, there was only 1/4" of shaft still holding.
This can be prevented by pinning the coupling and shaft together.
I have known at least three boats whose shafts pulled out from the gearbox
couplings when going astern while approaching a dock with resulting damage to
the boat/dock/other boats.
For the simplest setup, the set screw holding the shaft in a sailboat, simply
remove the shaft from the coupling and find the mark on the shaft the set
screw has made. Drill into the shaft there with a drill the same size as the set
screw about an eighth inch deep. Put everything back together and use a
square headed set screw with a hole drilled through the head. After tightening
the set screw, safety-wire it in such a way that it cannot back out.
For a muff coupling such as Andina had, the maker of my CP propellor,
Hundestead of Denmark milled key pockets into both shaft and muff coupling pieces
with a key that just fit the pockets so that there was no way the shaft could
move in any direction without shearing the key and was not dependent on friction
between the shaft and coupling.
I did the same when I installed my double tapered roller bearing (like a
car's front wheel bearings) thrust bearing on the prop shaft. I installed shaft
collars, split circles that bolt around the shaft, on either side of the
bearing inner race. I used a 1/4" drill to drill into the shaft and one piece of
the collar, then installed a short piece of 1/4" rod in the pockets thus formed
so the collars could not "walk" away from their positions, and they never have.
Remember, all your machinery is trying to fall apart and do so at the worst
possible time. You must prevent this by any means necessary.
Norm
S/V Bandersnatch
Lying Beaufort SC
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