On Sat, 08 Sep 2012 17:28:04 -0500, Rick Morel
wrote:

On Sat, 8 Sep 2012 15:42:47 -0400, "Wilbur Hubbard"
wrote:


Actually, inboard diesel boats that need meticulous shaft alignment and
countless hours to accomplish this alignment are an anachronism.

Isn't it about time yacht builders took a cue from automobile manufacturers?

Why not use a universal joint instead of the dreaded flange set? After all,
when one properly aligns a pair of flanges one is pretty much assuming the
motor is fixed but the motor actually rides on rubber foot pads that can and
do compress thus tending to throw off the careful alignment especially under
hard usage. A proper universal joint would allow the motor to 'float' and the
hull to be more isolated from vibrations.

Just a thought.


Wilbur Hubbard

I've often wondered about that. Why take all that care and time and
cussin' when the motor is going to move around on its mounts, with the
rubber hose part of the stuffing box flexing as the motor moves about.

I would think, though, that one would need to use two universal joints
with a very short "shaft" section between. This would allow for any
side-to-side, up-and-down, and all directions in between for the motor
to move. See what I mean? One U-joint would take care of angular
misalignments, but it takes two to take care of positional
displacement.

With this scenerio, would then the stuffing box have to be rigid to
prevent possibly destructive shaft movement/vibrations? Or an added,
rigidly mounted, bearing, such as a pillar bearing?

Rick

If you were to use two universal joints and a short intermediate
shaft, as you suggest, then you would require a thrust bearing
somewhere on the propeller half of the shaft installation. Not that
this hasn't been done, it has, and is done. BUT, it adds to the cost
and space required for the engine/shaft installation and isn't really
necessary in most smaller boat installations. The rigid shaft and
coupling has worked successfully for years and years.

Look up aqua-drive (I believe it is called).

..