Paul, I don't think that being out of the water would be a problem, the reference was probably made because of the need to remove the gland packing part of the assembly without sinking the boat.
The tube seems fairly rigid, and the cutlass bearing is bound to be a bit forgiving, as far as alignment goes, just think of the sideways movement over a cutlass bearing length of say an inch, if the top end of a shaft that is, say, 3 feet long, moves sideways about a quarter inch or so. It would be about 80 thousandths per foot, so about 6 or 7 thousandths per inch of bearing length. If the Tartan is anything like the boat I have, which can be grounded on sandy beaches to clean the bottom, any distortion would give movements that are really small percentages of the figures above, and would likely be in the order of ten-thousandths, (less than a thousandth) and that is at a location where the (cutlass) bearing clearance itself is no doubt several thousandths.
Again, my experience with this is not from marine - but as far as the top bearing goes, you can get ones that are self-aligning, they have the square flange part, and a spherical part that allows the centre part to kind of swing around at angles, then in the middle that is the actual bearing. A self aligning bearing gives you the comfort zone to have the main mounting plate installed without getting it at precise right angles to the shaft axis. This leaves you only the radial positioning to worry about. And the final criteria is that side loads that try to bend the shaft are avoided once the setup is finished.
A way to set it up, would be to get a collar with a bore to fit the shaft, and grind a 45 degree taper onto the outside, down to meet the bore - then slide it down the shaft until the small end of the taper goes into the tube bore enough to stop side play. The shaft will then be centred.
So your proposed method sounds ok, the limitation would be if the hanging assembly were heavy enough to bend the shaft! Once you have it all in place, you can gently release tension on the bolts holding the bearing, and just check that there is no side pressure.
The toothed belts seem to be the thing. Actually some cars (Toyota) have the cam belt adjuster locked in position as far as tension goes, rather than a spring loaded floating type.
You will still get side loading on the shaft, but it will vary, and only be equal to the torque being created.
This whole thing might be simpler than I thought. It's a bit annoying really, I bought an Atomic 4 for parts in case I need any, and then after that, a 15 HP outboard came along as a backup motor. If I had initially known about the outboard, my original not yet running Atomic 4 would be outa there right now, and the parts engine money would have bought an electric motor, or a battery or two.
John
----- Original Message -----
From: tartan27hull157
To: electricboats@yahoogroups.com
Sent: Thursday, September 30, 2010 10:00 PM
Subject: [Electric Boats] Re: Tartan 27, setting up bearing
Thanks everybody for all the thoughts and advice on the bearing.
It sounds like what I was planning to do might not be careful enough.
I was going to fabricate a transverse plate to hold the bearing
and fit it loosely in the shaft alley, then mount the bearing into it
off the shaft.
Then I was going to mark the current play in the shaft up, down,
left, and right; find the center of that play, assume that was where
I wanted the shaft to end up...then slide the bearing (already
installed in the transverse plate) onto the shaft it and block the
shaft at its "center of play" position. Then tab the plate to the
hull.
Basically I would be hanging the bearing from the 1in shaft, with
the shaft supported forward by blocks and aft by the cutlass bearing,
until the epoxy cured.
I used a similar technique when I replaced my chainplate
knees--hang the knee from the chainplate until the epoxy cures, to
ensure that the knee (and the holes in it) were in the right place
relative to the chainplate.
But I am concerned that bearings in the drivetrain need to have
better alignment than the chainplate knees did.
I am also worried about doing this out of the water -- doesn't the
boat change shape some between the water and the hard?
Thanks again, Paul
--
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