Zippydogg wrote:

One way to control damage from a seized unit is to use a frangable member

in the power system.  I know of one outboard motor manufacturer who uses a
"shear" pin of soft brass between the propeller and the drive shaft.  When
the prop "seizes" (by being stopped when hitting a log, rock, etc,) it
shears the easily replaceable pin rather than trashing the drive system.

The v-belt is intended to fulfill this same purpose.  The only problem is
that the v-belt
must be driving only one load and must be physically isolated from other
critical
v-belt driven loads.  This is what Jeff is talking about - he is physically
preventing one
blown belt from failing another - such as the water pump belt!  Using a
single belt
to drive multiple loads or using adjacent belts is asking for a single
failure to take the
whole aux drive setup (belts) with it.

It might be possible to make a modified alternator with a shear pin, but you
would
need a pair of bearings to keep the tensioned belt in place while spinning
at full speed for hours after a shear pin failure.  Sounds like a much
bigger project
than a belt isolation or guard system.  I drive my alternator via a v-belt
pulley
which is clamped to the short section of crankshaft between the case and prop
flange on a Lyc O-235.  If one added a similar pulley for the alternater
belt on a
PSRU, you might move the alt belt far enough away from the water pump belt for
safety.

Bill

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