If you just have a single shaft bearing, just ahead of the prop, you
don't need to weigh the shaft. Just suspend it so it is centered as
closely as possible in the stern tube. Be sure to hang and fix it by
the coupling or close to it. Some stuffing boxes also incorporate a
bearing so check carefully. If there is a bearing in the stuffing
box, it's a bearing. If your stuffing box isn't flexible, there
probably is a bearing in there somewhere.
If you have two bearings, measure the length and diameter from the
forward shaft end to the bearing and calculate the volume and weight
(.28 lbs / cubic inch is close enough). Divide by 2. Then calculate
the volume and weight of the coupling. Add the two weights. Hang the
coupling so a pull scale inserted in the wire reads this amount. You
will then not be lining up to a shaft that is drooping under it's own
weight.
On further reflection: shafts in most sailboats are probably so short
that this isn't a big issue. On power boats, there will often be
several feet of shaft between the bearing and the gear. Still, it
wouldn't hurt to hang and weight it. We're talking about very small
tolerances here.
--
Roger Long
"Skip Gundlach" skipgundlach at gmail dotcom wrote in message
...
"Roger Long" wrote in message
...
Skip the drive saver. Line up your shaft carefully calculating the
overhanging weight of the shaft and using a scale to hold the end
up. Make sure the flanges are true and the pilot concentric. Then
hard mount it. The metal parts will then be more precision than a
plastic disk can ever be and will stay that way. It will run fine.
If you see my pix of the installation to come, at
http://justpickone.org/skip/gallery/...06&sta rt=297, I
believe I qualify on the pilot/hard mount bit.
However, my question has to do with weighing the shaft. Currently
the packing's out of the gland, awaiting mount/alignment before
repacking, so it's floppy on its hose, so far as it can move.
Reading Calder on the subject, I'm not clear on how I measure the
weight and position the flange for alignment with the transmission.
Of course, there's some possibility it was done properly the first
time, when they changed out the engine, rebuilt the tranny and
changed to SS shaft, but given what I've seen in our refit, and the
simple fact of the current, were it bolted back up, misalignment, I
doubt it.
So, could you elaborate on that (weighing and positioning)?
Thanks.
L8R
Skip, sore from PT today, not lifting 125# batteries, but wishing it
were...
--
L8R
Skip
Morgan 461 #2
SV Flying Pig KI4MPC
http://tinyurl.com/384p2 The vessel as Tehamana, as we bought her
"Believe me, my young friend, there is *nothing*-absolutely
nothing-half so much worth doing as simply messing,
messing-about-in-boats; messing about in boats-or *with* boats.
In or out of 'em, it doesn't matter. Nothing seems really to
matter, that's the charm of it.
Whether you get away, or whether you don't; whether you arrive at
your destination or whether you reach somewhere else, or whether you
never get anywhere at all, you're always busy, and you never do
anything in particular; and when you've done it there's always
something else to do, and you can do it if you like, but you'd much
better not."