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Our sailboat has a VD 72C and when I bought it, it was equipped with a
shaft brake of the disc type, which was spring loaded. It was released by a small
cylinder via a hydraulic port atop the gear near the centerline, next to the
pump discharge to the cooler. This effectively stopped the shaft immediately
upon being shifted into neutral and released it when shifting ahead or
astern. I removed it when I replaced the wheel with a feathering type.
Virtually all large direct-reversible propulsion engines have a brake,
usually bearing on the periphery of the flywheel, to stop the engine in a short
time. But when there is way on, the wait can be a long one. Waiting for the
engine to stop so you can reverse it while the telegraph bell rings and the
indicator is pointing to "full astern" brings with it a high pucker factor for
the engineer, especially when the cargo is gasoline and naphtha. Perhaps just
below the pucker factor of those on the bridge, who can also see what's
coming.
Regards,
John
"Seahorse"
Always waiting until the prop shaft stops completely is a good idea in theory
but often not practical. I agree that it's best and easiest on the gear but a
lot of times we need to apply the "brakes" and the only way to do that is to
reverse the prop, which, if you're moving, is still turning, unless you have
a
bind in your drive system. The VD's have enough lag time and slow enough
pickup to allow this (I still think they are a weany little gear, and I own a
couple) without undue wear and tear. I would not recomend shifting above an
idle. If you need more control power the single stick Morse control will
help,
and at least let the engine "try" to get to an idle befor you shift. I
understand how difficult it can be to run four controls while trying to back
into a slip, and with a 3 to 1 gear you don't seem to get much of a response
when shifting, but increasing the rpm is not a good idea, even if the gear
will take it. You wouldn't shift your car into reverse befor stopping (and it
probably has a beefier clutch than the Velvet Drive).
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