Hi, Lists,

Thanks for all the responses to my line cutter question. To put one on will
require some more space, and, in general, I've come to think that a
break-away (with built-in safeguards to allow continued use until
replacement) spacer is also a good move.

Who here has had one, and, best, has had to use it to save their gear?

Thanks again.

L8R

Skip
Morgan 461 #2
SV Flying Pig KI4MPC
http://tinyurl.com/384p2 The vessel as Tehamana, as we bought her

"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail
away from the safe harbor. Catch the trade winds in your sails. Explore.
Dream. Discover." - Mark Twain

In article ,
"Skip Gundlach" skipgundlach at gmail dotcom wrote:

Thanks for all the responses to my line cutter question. To put one on will
require some more space, and, in general, I've come to think that a
break-away (with built-in safeguards to allow continued use until
replacement) spacer is also a good move.

Who here has had one, and, best, has had to use it to save their gear?

We've had one for about a decade. Hasn't broken from normal use.

So far, we have avoided wrapping a line while the engine was running, so
I don't know if it'll work when the time comes, but I worry less.

Nice side-effect was that it takes up slight misalignments, smoothing
the slight vibrations out.

Note: Ours is solid "rubber". The pics of the more recent ones make them
look more engineered.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

For what it's worth, I deal often with one of the foremost drivetrain
and propulsion specialists in the country in connection with designing
boats like this:

http://home.maine.rr.com/rlma/WHOIrv.htm

The shipyard that builds these boat specializes in fast,
sophisticated, high powered craft. Both told me that they hate
"Drivesavers". The boat in the picture has two 710 horsepower engines
with the engines flex mounted and the shafts connected with solid
couplings. There is just one bearing, in the shaft strut. They run
smooth as silk.

I do have a drivesaver disk in my boat but they cut the shaft short
when they installed it so I have to buy a whole new shaft to take it
out. It's not causing any problems that I can see though other than
making it a pain to repack the stuffing box.

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.

There's a whole range of prop strike forces where the drive saver
could break but the solid coupling would still leave you able to limp
off a lee shore with the engine vibrating and shaking. I like that
scenario better. I've heard of a lot more broken shafts and totally
trashed props than gear boxes that failed due to prop strike. The
gears are a lot more rugged than you would think. Remember that there
is a friction clutch in the system that will give some under an
extreme shock load.

--

Roger Long



"Skip Gundlach" skipgundlach at gmail dotcom wrote in message
...
Hi, Lists,

Thanks for all the responses to my line cutter question. To put one
on will require some more space, and, in general, I've come to think
that a break-away (with built-in safeguards to allow continued use
until replacement) spacer is also a good move.

Who here has had one, and, best, has had to use it to save their
gear?

Thanks again.

L8R

Skip
Morgan 461 #2
SV Flying Pig KI4MPC
http://tinyurl.com/384p2 The vessel as Tehamana, as we bought her

"Twenty years from now you will be more disappointed by the things
you
didn't do than by the ones you did do. So throw off the bowlines.
Sail
away from the safe harbor. Catch the trade winds in your sails.
Explore.
Dream. Discover." - Mark Twain

Hi, Roger, and List/Group,

This really has more to do with a spacer than drive saver, though I like the
flexibility of it in case the alignment isn't perfect.

Those of you who have been around a couple of years know how we jacked the
tranny out of the mounting plate (now replaced, no harm done other than
inconvenience in making up a keeper to stay moving with the engine, and the
packing gland needing redoing cuz of the weight of the tranny on the shaft
when it came out, also redone). Recent readers also know of my search for
line cutters, which would have prevented that (which shouldn't have
happened, but stupid sailor tricks happen all the time, anyway, so a mooring
line overboard isn't guaranteed against for all time on our boat, as much as
we'd like to think so, and, of course the occasional lobster/crab pot warp I
don't see in the middle of the night) - which will require a longer shaft,
or...

.... a spacer - so why not a flexible one?

And, I was looking for input from those who'd had a use for one preferably
where the thing sheared and left the 'limp home' mode in place.

I agree about proper alignment - and that will happen before we insert a
spacer or drive saver...

L8R

Skip, back to the boat for two weeks in a few days


--
Morgan 461 #2
SV Flying Pig KI4MPC
http://tinyurl.com/384p2 The vessel as Tehamana, as we bought her

"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail
away from the safe harbor. Catch the trade winds in your sails. Explore.
Dream. Discover." - Mark Twain
"Roger Long" wrote in message
...
For what it's worth, I deal often with one of the foremost drivetrain and
propulsion specialists in the country in connection with designing boats
like this:

http://home.maine.rr.com/rlma/WHOIrv.htm

The shipyard that builds these boat specializes in fast, sophisticated,
high powered craft. Both told me that they hate "Drivesavers". The boat
in the picture has two 710 horsepower engines with the engines flex
mounted and the shafts connected with solid couplings. There is just one
bearing, in the shaft strut. They run smooth as silk.

I do have a drivesaver disk in my boat but they cut the shaft short when
they installed it so I have to buy a whole new shaft to take it out. It's
not causing any problems that I can see though other than making it a pain
to repack the stuffing box.

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.

There's a whole range of prop strike forces where the drive saver could
break but the solid coupling would still leave you able to limp off a lee
shore with the engine vibrating and shaking. I like that scenario better.
I've heard of a lot more broken shafts and totally trashed props than gear
boxes that failed due to prop strike. The gears are a lot more rugged
than you would think. Remember that there is a friction clutch in the
system that will give some under an extreme shock load.

--

Roger Long



"Skip Gundlach" skipgundlach at gmail dotcom wrote in message
...
Hi, Lists,

Thanks for all the responses to my line cutter question. To put one on
will require some more space, and, in general, I've come to think that a
break-away (with built-in safeguards to allow continued use until
replacement) spacer is also a good move.

Who here has had one, and, best, has had to use it to save their gear?

Thanks again.

L8R

Skip
Morgan 461 #2
SV Flying Pig KI4MPC
http://tinyurl.com/384p2 The vessel as Tehamana, as we bought her

"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail
away from the safe harbor. Catch the trade winds in your sails. Explore.
Dream. Discover." - Mark Twain

I would just put in a very accurately machined spool piece or steel
disk with proper pilots. As I understand it, having just had the
opportunity to sit at the feet of some masters and listen but not
being an expert myself, the really critical alignment issue is that
the shaft be exactly centered. Steel will do this better than
plastic. Bolts will not maintain it reliably. You need those
machined pilots.

I know that the drivetrains I have used so successfully must develop
some angular misalignment as the engine moves around on the mounts but
the shaft accommodates it without a problem. The single stern bearing
and flexible stuffing box (or shaft seal) on these boats is actually
almost exactly the same setup as on many sailboats.

If you are relying on something between the flanges to accommodate
misalignment, it has to be very, very, soft. Otherwise, there will
still be enough force transmitted to create vibration. Just think how
hard it is to dent or deform that drivesaver disk even a small amount
and then imagine that force on your system a few hundred times a
minute. If the coupling is soft enough to accommodate misalignment,
then you will need a thrust bearing and all sorts of other
complications. I've designed and built successful shaft lines for
auxiliary equipment with big rubber tire couplings, CV joints and
thrust bearings, etc. None ran a smoothly as these high power
research vessels do.

Say, I'm awake too early, how about a sea story?

I worked at Woods Hole Oceanographic Institution converting the ship
that Bob Ballard later used for the first mapping of the Titanic site
and the Alvin dives to the ship. We were taking out the steam engines
and installing a diesel power plant. We took two of the propulsion
motors out of the old diesel electric salvage tug "Chain" the was in
the process of being scrapped and turned them into DC generators to be
driven by big PTO's on top of the new reduction gears. One of my jobs
was to design the shaft system which had to penetrate the main
watertight bulkhead just aft of the reduction gears.

My boss wanted to build two tall pedestals with pillow blocks to
support the shafts. It would have been really tight and complicated
and alignment very critical with the bearings so close to each other.
I suggested that we just let the ends of the shaft hang on it's own
bearings by modifying a big rubber tire flex coupling at the generator
end with a pilot bearing inside. My boss explained that there were
buoys down south of Cape Horn that the ship had to retrieve before the
batteries in the acoustical locator beacons and anchor releases ran
down. If my idea didn't work, years of research would be down the
tubes and several Ph.D. candidates might have to spend and extra year
or two in school to get their doctorates. Was I sure? I was pretty
young but I gulped and said, "Yes".

"What did you say?", he asked, "I couldn't hear you."

"YES"

So, I designed the rig. Time and people were short so I ended up
assembling it myself. The engines for the ship were two surplus
railroad locomotive engines that came from a Navy warehouse still
wrapped up from 1942. Finally, the day came to fire things up and
test it.

We clutched in the port generator. It ran beautifully. Then we
started up the identical starboard engine and clutched in the PTO.
Instantly, the six foot diameter generator and twelve foot long engine
started violently lunging back and forth so hard that you could almost
see the structure of the ship deform. We stopped everything
instantly. Took it all apart, checked the alignments, put it back
together. Same result. Everyone was spending a lot of time staring
at me.

We checked and rechecked. We tried to reproduce the problem on the
other side. It was a total mystery. Finally, my boss said that there
was only one guy who could figure it out and flew someone up from
Texas. The Texan arrived and we fired it up for him so he could watch
the whole thing thrash around. This is tons of machinery solidly
bolted to the heavy engine bed of a ship shaking it so you feel like
you are standing in a moving train. Very scary.

He watched for two seconds and yelled, "Shut it off!". Then he
jumped up on the engine and opened up the cover of the engine
governor. "Give me a drill.", he asked. He drilled a hole, did
something else, put the cover on, and told us to start it again. It
ran smooth as silk and both sides continued to for years until the
ship was sold.

Turns out that the governor of the starboard engine had a device in it
that would give the engine a little boost of power if it suddenly
slowed down. This is so that it wouldn't stall when the locomotive
took all the slack out of the couplers when starting up the train.
When we clutched up the PTO, the inertia of starting the big generator
would wind up the rubber tire coupling and slow the engine. The
governor would give it a goose winding up the coupling some more. The
coupling would then unwind, unloading the engine. The timing was such
that these impulses would travel back and forth through the system in
such a way as to amplify each other with each cycle and build up to
enormous force in about two seconds. All the guy did was drill a hole
and drop a pin into the boost mechanism of the governor. He was on
the ship for ten minutes and then in his car headed back to the
airport.

The next day, we tied pulling power from the generator. The other one
had worked fine so this was pretty casual. When the switch was
thrown, a ring of fire, like a circular lightning bolt appeared around
the commutator of the big, open frame, motor cum generator. I'd
always wondered whether those little round escape hatches in ships
were big enough but, six guys can go up a ladder and through one in
less than three seconds when sufficiently motivated.

Turns out that the guy who overhauled the motor put the brushes in
backwards. He came down and turned them around. No harm done and the
whole system worked perfectly thereafter.

--

Roger Long



"Skip Gundlach" skipgundlach at gmail dotcom wrote in message
...
Hi, Roger, and List/Group,

This really has more to do with a spacer than drive saver, though I
like the flexibility of it in case the alignment isn't perfect.

Those of you who have been around a couple of years know how we
jacked the tranny out of the mounting plate (now replaced, no harm
done other than inconvenience in making up a keeper to stay moving
with the engine, and the packing gland needing redoing cuz of the
weight of the tranny on the shaft when it came out, also redone).
Recent readers also know of my search for line cutters, which would
have prevented that (which shouldn't have happened, but stupid
sailor tricks happen all the time, anyway, so a mooring line
overboard isn't guaranteed against for all time on our boat, as much
as we'd like to think so, and, of course the occasional lobster/crab
pot warp I don't see in the middle of the night) - which will
require a longer shaft, or...

... a spacer - so why not a flexible one?

And, I was looking for input from those who'd had a use for one
preferably where the thing sheared and left the 'limp home' mode in
place.

I agree about proper alignment - and that will happen before we
insert a spacer or drive saver...

L8R

Skip, back to the boat for two weeks in a few days


--
Morgan 461 #2
SV Flying Pig KI4MPC
http://tinyurl.com/384p2 The vessel as Tehamana, as we bought her

"Twenty years from now you will be more disappointed by the things
you
didn't do than by the ones you did do. So throw off the bowlines.
Sail
away from the safe harbor. Catch the trade winds in your sails.
Explore.
Dream. Discover." - Mark Twain
"Roger Long" wrote in message
...
For what it's worth, I deal often with one of the foremost
drivetrain and propulsion specialists in the country in connection
with designing boats like this:

http://home.maine.rr.com/rlma/WHOIrv.htm

The shipyard that builds these boat specializes in fast,
sophisticated, high powered craft. Both told me that they hate
"Drivesavers". The boat in the picture has two 710 horsepower
engines with the engines flex mounted and the shafts connected with
solid couplings. There is just one bearing, in the shaft strut.
They run smooth as silk.

I do have a drivesaver disk in my boat but they cut the shaft short
when they installed it so I have to buy a whole new shaft to take
it out. It's not causing any problems that I can see though other
than making it a pain to repack the stuffing box.

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.

There's a whole range of prop strike forces where the drive saver
could break but the solid coupling would still leave you able to
limp off a lee shore with the engine vibrating and shaking. I like
that scenario better. I've heard of a lot more broken shafts and
totally trashed props than gear boxes that failed due to prop
strike. The gears are a lot more rugged than you would think.
Remember that there is a friction clutch in the system that will
give some under an extreme shock load.

--

Roger Long



"Skip Gundlach" skipgundlach at gmail dotcom wrote in message
...
Hi, Lists,

Thanks for all the responses to my line cutter question. To put
one on will require some more space, and, in general, I've come to
think that a break-away (with built-in safeguards to allow
continued use until replacement) spacer is also a good move.

Who here has had one, and, best, has had to use it to save their
gear?

Thanks again.

L8R

Skip
Morgan 461 #2
SV Flying Pig KI4MPC
http://tinyurl.com/384p2 The vessel as Tehamana, as we bought her

"Twenty years from now you will be more disappointed by the things
you
didn't do than by the ones you did do. So throw off the bowlines.
Sail
away from the safe harbor. Catch the trade winds in your sails.
Explore.
Dream. Discover." - Mark Twain

"Roger Long" wrote in message
...
I would just put in a very accurately machined spool piece or steel disk
with proper pilots. As I understand it, having just had the opportunity to
sit at the feet of some masters and listen but not being an expert myself,
the really critical alignment issue is that the shaft be exactly centered.
Steel will do this better than plastic. Bolts will not maintain it
reliably. You need those machined pilots.

I know that the drivetrains I have used so successfully must develop some
angular misalignment as the engine moves around on the mounts but the
shaft accommodates it without a problem. The single stern bearing and
flexible stuffing box (or shaft seal) on these boats is actually almost
exactly the same setup as on many sailboats.

If you are relying on something between the flanges to accommodate
misalignment, it has to be very, very, soft. Otherwise, there will still
be enough force transmitted to create vibration. Just think how hard it
is to dent or deform that drivesaver disk even a small amount and then
imagine that force on your system a few hundred times a minute. If the
coupling is soft enough to accommodate misalignment, then you will need a
thrust bearing and all sorts of other complications. I've designed and
built successful shaft lines for auxiliary equipment with big rubber tire
couplings, CV joints and thrust bearings, etc. None ran a smoothly as
these high power research vessels do.

Say, I'm awake too early, how about a sea story?


Marvelous story, Roger,

Back to mine, however, the spacer is just between a couple of flanges, both
flat on the mating surfaces, with no pilot or other bearing or bushings or
pins. If the shaft and the tranny plates aren't perfectly aligned fore-aft,
they aren't going to want to go together. Twiddling, if needed, the engine
mounts will take care of any minor differences (I'm into tight tolerances -
I think .005 or less? might do it). Whenever it was converted from bronze
to SS shaft, the intermediate bearing was removed (still aboard, but would
require removing the Max prop and flange and pulling the shaft far enough
for remounting. As it made it for however many years it was from the change
to now, successfully, it's my presumption that it wasn't needed any more,
perhaps due to the greater rigidity of the SS over the original bronze.

I understand and "get" what you are saying about the drivesavers - but years
of use by others, successfully, makes me wonder why the problems you
cite/project don't make it so nobody uses them?

I also don't "get" what you are saying about spool piece or pilot - I need a
spacer of some sort to accommodate the line cutter. If I wanted to save a
bunch of money (having to buy it originally; there may be one in my cockpit
when I get there from someone who had it available, and if it fits, it's
cheap), I'd just get the proper thickness scrap steel machined to fit the
proper size and holes, easily enough done by a rubbing of both pieces, I'd
think. (Curiously to me, some of the line cutter folks want several
hundred - as much as the device - for their machined steel spacer...)
However, if I align it first, then slide it aft only enough to use the
spacer (whatever it is), should not that alignment persist through the use
of - the only difference I'd see - longer bolts? Of course, I'd check,
using the modus recommended by DriveSaver, if that turns out to be what I
use, but I'd expect that it would come out right.

Thanks for your insight(s) - and thanks again for the story, as well as
getting to see your Titanic thoughts.

L8R

Skip


--
Morgan 461 #2
SV Flying Pig KI4MPC
http://tinyurl.com/384p2 The vessel as Tehamana, as we bought her

"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail
away from the safe harbor. Catch the trade winds in your sails. Explore.
Dream. Discover." - Mark Twain

"Skip Gundlach" skipgundlach at gmail dotcom wrote

I understand and "get" what you are saying about the drivesavers -
but years of use by others, successfully, makes me wonder why the
problems you cite/project don't make it so nobody uses them?

They aren't really a problem by themselves but sort of a band aid
solution for not doing it right in the first place. Of course, most
pleasure boaters, and plenty of boatbuilders, don't want to do it
right. They just want to take stuff out of boxes and bolt it
together. A drivesaver probably won't make things any worse in that
situation, it may even help a little bit with a boost from the placebo
effect.

In the commercial world, the flange on the gear is trued up so that
the outside edge is exactly concentric and the face exactly
perpendicular to the shaft. That flange is then mated to the
propeller shaft flange which is trued up after being installed on the
shaft with the whole thing being turned in a lathe or other fixture.
A male/female pilot or disk; not the bolts, keeps the two halves
concentric.

If you're not going to do this stuff, maybe a drivesaver will help but
it won't be as good as doing it right.

If you do it right, you won't need the drivesaver and it just makes
things more likely to slip.

Still, I wouldn't bother taking the one out of my shaft system except
to make it less of a pain to repack the stuffing box.

--

Roger Long

"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."

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."