On 07 Jun 2004 10:48:32 GMT, (JAXAshby) wrote:

ah, you just might wish to remember that the prop MUST push against the prop
shaft which pushes against the thrust bearing to push the boat forward. Got
to.

In other words, the thrust bearing takes 100% of the horsepower developed by
the engine. That is a lot. In forward.

There is also a thrust bearing needed for going in reverse as well. However,
as the horsepower used in reverse is much less and the time it is used is
hugely less the reverse thrust bearing need not be anywhere near as big.

Now, change the prop so the former reverse thrust bearing becomes the new
forward thrust bearing and operates at 100% power over extended time the
potential to trash that bearing becomes very real.

Most people forget that the prop has to push against something to push the boat
forward. That something is the thrust bearing.


Yes, all these things are right ones.

Question is: How has been designed (engineered) the Thrust Bearings Box ?

(sorry I don't know its English code-name)

Our ones are designed and manufactured with a couple of Heavy-Duty Taper Rolling Bearings, # 322xx, a couple of Rubber
Seals for Lube and Water Cooling devices.

Used in Clam Dredgers working in Reverse... they are tailored to be operating in both directions.

Heavy-Duty Bearings in Forward and Light-Dutry ones in Reverse were used times when Bearings were very expensive... but
actually it is a "poor" spare, requiring different machining on both sides, double the Stocks of spares on shelves and
aboard.

But they could be till existing...

Glad to have meet someone involved in Technical matter.

I'm a newcomer in this NG but I will visit it at least once a week.

I hope to have some interesting questions to put to NG attention.


Thank you for your time,

WinXP.

fair winds, guy. As you point out, if the tranny is designed to take a prop
going either direction things are fine.

ah, you just might wish to remember that the prop MUST push against the prop
shaft which pushes against the thrust bearing to push the boat forward. Got
to.

In other words, the thrust bearing takes 100% of the horsepower developed by
the engine. That is a lot. In forward.

There is also a thrust bearing needed for going in reverse as well.
However,
as the horsepower used in reverse is much less and the time it is used is
hugely less the reverse thrust bearing need not be anywhere near as big.

Now, change the prop so the former reverse thrust bearing becomes the new
forward thrust bearing and operates at 100% power over extended time the
potential to trash that bearing becomes very real.

Most people forget that the prop has to push against something to push the
boat
forward. That something is the thrust bearing.


Yes, all these things are right ones.

Question is: How has been designed (engineered) the Thrust Bearings Box ?

(sorry I don't know its English code-name)

Our ones are designed and manufactured with a couple of Heavy-Duty Taper
Rolling Bearings, # 322xx, a couple of Rubber
Seals for Lube and Water Cooling devices.

Used in Clam Dredgers working in Reverse... they are tailored to be operating
in both directions.

Heavy-Duty Bearings in Forward and Light-Dutry ones in Reverse were used
times when Bearings were very expensive... but
actually it is a "poor" spare, requiring different machining on both sides,
double the Stocks of spares on shelves and
aboard.

But they could be till existing...

Glad to have meet someone involved in Technical matter.

I'm a newcomer in this NG but I will visit it at least once a week.

I hope to have some interesting questions to put to NG attention.


Thank you for your time,

WinXP.

Thanks for all your replies.

I've cleared things up this much:

The transmission is designed to run equally fine in both directions. Ratios
are almost similar. The transmission has two "modes" - A and B. A is the
"normal" mode where the propeller-shaft runs in opposite direction of the
engine. B is normally reverse - the propeller-shaft runs same way as the
engine.

Here's the funny thing: From the factory, the boat is delivered with a LH
propeller - which means that the transmission has to run in the "B"-position
to have the boat move forward - i.e. reverse of "normal"!

I called the Norwegian factory to ask why. They replied that "the boat liked
the LH propeller the most"! (Don't know what that means.)

So it all narrows down to this: Assuming that transmission is not an issue -
are there any "hull-issues" that should imply that a given hull simply "runs
better" with a LH instead of a RH - or vice versa?

Anders
Denmark



"JAXAshby" skrev i en meddelelse
...
fair winds, guy. As you point out, if the tranny is designed to take a
prop
going either direction things are fine.

ah, you just might wish to remember that the prop MUST push against the
prop
shaft which pushes against the thrust bearing to push the boat forward.
Got
to.

In other words, the thrust bearing takes 100% of the horsepower
developed by
the engine. That is a lot. In forward.

There is also a thrust bearing needed for going in reverse as well.
However,
as the horsepower used in reverse is much less and the time it is used
is
hugely less the reverse thrust bearing need not be anywhere near as big.

Now, change the prop so the former reverse thrust bearing becomes the
new
forward thrust bearing and operates at 100% power over extended time the
potential to trash that bearing becomes very real.

Most people forget that the prop has to push against something to push
the
boat
forward. That something is the thrust bearing.


Yes, all these things are right ones.

Question is: How has been designed (engineered) the Thrust Bearings Box ?

(sorry I don't know its English code-name)

Our ones are designed and manufactured with a couple of Heavy-Duty Taper
Rolling Bearings, # 322xx, a couple of Rubber
Seals for Lube and Water Cooling devices.

Used in Clam Dredgers working in Reverse... they are tailored to be
operating
in both directions.

Heavy-Duty Bearings in Forward and Light-Dutry ones in Reverse were used
times when Bearings were very expensive... but
actually it is a "poor" spare, requiring different machining on both
sides,
double the Stocks of spares on shelves and
aboard.

But they could be till existing...

Glad to have meet someone involved in Technical matter.

I'm a newcomer in this NG but I will visit it at least once a week.

I hope to have some interesting questions to put to NG attention.


Thank you for your time,

WinXP.

"JAXAshby" wrote in message
...

There is also a thrust bearing needed for going in reverse as well.
However,
as the horsepower used in reverse is much less and the time it is used is
hugely less the reverse thrust bearing need not be anywhere near as big.

Now, change the prop so the former reverse thrust bearing becomes the new
forward thrust bearing and operates at 100% power over extended time the
potential to trash that bearing becomes very real.


Either I am not following what you are saying or I am envisioning something
totally different.

As you said, the thrust on the shaft must be countered someplace, and that
someplace is the thrust bearing(s). The thrust will either "push" or
"pull", it shouldn't matter which direction the shaft is rotating.

If you attempted to drive the boat by having the propeller in front, like an
airplane, then the shaft will be pulling and the thrust bearing surface
associated with "pull" will bear the brunt of the load. But I didn't think
this is what we were talking about.

I know that several models of Velvet Drive transmissions don't care which
direction the input and output shafts turn, as long as they turn the same
direction in "forward". You can have a Left Hand and Right Hand rotating
engine turning Left Hand and Right Hand props and the transmissions don't
care. If you attempted to have the Left Hand engine turn the Right Hand
prop, however, then the transmission would be using the "reverse" clutch for
forward which is not nearly as robust as the "forward" clutch and you would
likely have reliability issues.

The web page for the Hurth transmissions indicated that many of their models
were capable of full engine horsepower in either "forward" or "reverse"
operation. I don't know if that really means you can use them for reversing
the rotation for counter rotation or not.

There are many outdrive designs that has the drive shaft come down and drive
two gears, one towards the front and one towards the rear. A "dog" or cone
clutch will engage one gear or the other, which will make the prop shaft
turn one way or the other. The clutches are identical and the thrust is
carried on the shaft bearing (not the gears) so it doesn't matter if the
gear more towards the front is considered "forward" or not.

Rod

Assuming that transmission is not an issue -
are there any "hull-issues" that should imply that a given hull simply "runs
better" with a LH instead of a RH - or vice versa?

Anders
Denmark

I've lost track of the boat in question. The issue could well involve
"operator" ease or senses such as the steering station location to the side,
which can be a factor when docking.
Some people just have a "feel" that a particular rotation works better or feels
better to them

On Mon, 7 Jun 2004 23:03:19 +0200, "Anders Lassen" anders.lassenNEJTILSPAM (at)adr.dk wrote:

Thanks for all your replies.

I've cleared things up this much:

The transmission is designed to run equally fine in both directions. Ratios
are almost similar. The transmission has two "modes" - A and B. A is the
"normal" mode where the propeller-shaft runs in opposite direction of the
engine. B is normally reverse - the propeller-shaft runs same way as the
engine.

Here's the funny thing: From the factory, the boat is delivered with a LH
propeller - which means that the transmission has to run in the "B"-position
to have the boat move forward - i.e. reverse of "normal"!

I called the Norwegian factory to ask why. They replied that "the boat liked
the LH propeller the most"! (Don't know what that means.)

So it all narrows down to this: Assuming that transmission is not an issue -
are there any "hull-issues" that should imply that a given hull simply "runs
better" with a LH instead of a RH - or vice versa?

Anders
Denmark


Yes, it is.

Venetian Gondola is operated by a "single" oar in the RH side: to go straight it is shaped asymmetrical.

The LH side is more curved than the RH side.

Oar turns to left... shaped side turns to right... = straight line.

Same thing happens to a single propeller boat: the reaction to propeller rotation tries to turn boat to right or to lift
direction.

To go straight forward you have to compensate time by time.

To avoid this any Boat Designer has an its own "trick"... maybe a different shape of the hull... maybe a slight
"off-center" centerline... maybe a different tank in one side... maybe battery pack.. maybe something else...

It could be "calculated" or it could have been found during the first tests of the boat...

Right now we are "blueprinting" several propellers for an all new power boat that doesn't wish to plane...

Of course for the Boat Manufacturer is cheaper to replace several propellers than get away a full set of boat moulds...

This is the way: Test... no good... modify... test... no good... replace... test... maybe... adjust a bit.. test... go!

Cheer!

WinXP

On Mon, 7 Jun 2004 14:52:14 -0700, "Rod McInnis" wrote:


"JAXAshby" wrote in message
...

There is also a thrust bearing needed for going in reverse as well.
However,
as the horsepower used in reverse is much less and the time it is used is
hugely less the reverse thrust bearing need not be anywhere near as big.

Now, change the prop so the former reverse thrust bearing becomes the new
forward thrust bearing and operates at 100% power over extended time the
potential to trash that bearing becomes very real.


Either I am not following what you are saying or I am envisioning something
totally different.

As you said, the thrust on the shaft must be countered someplace, and that
someplace is the thrust bearing(s). The thrust will either "push" or
"pull", it shouldn't matter which direction the shaft is rotating.

If you attempted to drive the boat by having the propeller in front, like an
airplane, then the shaft will be pulling and the thrust bearing surface
associated with "pull" will bear the brunt of the load. But I didn't think
this is what we were talking about.

I know that several models of Velvet Drive transmissions don't care which
direction the input and output shafts turn, as long as they turn the same
direction in "forward". You can have a Left Hand and Right Hand rotating
engine turning Left Hand and Right Hand props and the transmissions don't
care. If you attempted to have the Left Hand engine turn the Right Hand
prop, however, then the transmission would be using the "reverse" clutch for
forward which is not nearly as robust as the "forward" clutch and you would
likely have reliability issues.

The web page for the Hurth transmissions indicated that many of their models
were capable of full engine horsepower in either "forward" or "reverse"
operation. I don't know if that really means you can use them for reversing
the rotation for counter rotation or not.

There are many outdrive designs that has the drive shaft come down and drive
two gears, one towards the front and one towards the rear. A "dog" or cone
clutch will engage one gear or the other, which will make the prop shaft
turn one way or the other. The clutches are identical and the thrust is
carried on the shaft bearing (not the gears) so it doesn't matter if the
gear more towards the front is considered "forward" or not.

Rod


Hi Rod.

You are right... we are right else.

All problems are regarding: what kind of Transmission you are reversing.

Clutches and Gearbox::

Good HD ones have same clutch for Forward and Reverse.
Some ones have not... so Forward has to be forward, engaging only two gears.
So it requires a propeller rotating reverse than engine.

Reverse has Three Gears and the central one (idler) is a very small one, rotating on a small Roller Bearing or
equivalent one.
Gear Ratio between Driven Gear and Idler Gear (the small one) is usually in the ratio of 3:1

This is meaning that with boat engine rotating at 2,000 rpm the Idler Gear is rotating at 6.000 rpm!
With boat engine rotating at 4.000 rpm... Idle Gear is rotating at 12,000 rpm !

(By the way: Why Transmission Gearboxes are using Oil Coolers?)

So best solution for twin engines boat is to have one engine RH and one LH.

So best solution to "reverse" propeller... is to replace Engine !!!

Bevel Gear Gearbox has no problem to rotate Forward or Reverse... but they are on Outboards...

Thrust Bearing:

Old ones or cheap ones are assembled with two different Thrust Bearings: Heavy Duty for Forward, Light Duty for
Reverse...

Good new ones have Two identical HD Thrust Bearings both for Forward and for Reverse... so no matter in which direction
they are mainly operated (not rotating)..

You are right else: Forward is always Forward... no matter is RH or LH...

There has been a bit of confusing details. Sorry for this.

Bye,

WinXP

The thrust will either "push" or
"pull", it shouldn't matter which direction the shaft is rotating.

what happens is this. if the driven gear (the prop gear) in the lower unit is
in the foward part of the unit it has a large, easy to use surface to be put to
use as the thurst bearing.

One the other hand, if the driven gear is in the back (i.e. closer to the prop
than the driving gear/drive shaft). This means both gears get in the way of
providing a large, easy-to-use bearing surface.

All of which means unless the design engineers have some compelling reason to
make the tranny drive in either direction they will otherwise just use the
available thurst bearing surfaces as is, using the easiest for forward.

The boat in question is a 33 feet semiplaning motorboat. Controls/rudder to
the starboard as well as seating arrangment. Engine Yanmar 6LP-STE,
transmission Hurth HWS 630 A

Anders

I've lost track of the boat in question. The issue could well involve
"operator" ease or senses such as the steering station location to the
side,
which can be a factor when docking.
Some people just have a "feel" that a particular rotation works better or
feels
better to them

"JAXAshby" wrote in message
...


what happens is this. if the driven gear (the prop gear) in the lower
unit is
in the foward part of the unit it has a large, easy to use surface to be
put to
use as the thurst bearing.

I am not sure I am following: are you saying that the thrust is transfered
from the output shaft to the gear, and then from the gear to the housing?


I am having a hard time picturing that design. I have only had one lower
unit (a Volvo Penta from about 30 years ago) completely apart enough to
become intimately familiar with it, but the exploded views of other lower
units, including my 2000 Mercury outboards, appear to be very similar.

On the lower units I am familiar with, the prop shaft enters the lower unit
housing through an oil seal and fairly good sized bearing. This bearing is
also the thrust bearing for forward. I had thought that it was also the
thrust bearing for reverse, but I would not swear to that (memory is a
little foggy).

The shaft continues into the housing, passing through a beveled gear. This
gear uses the prop shaft as a bearing surface, it does NOT attach to or
drive the shaft directly. Continuing on the shaft passes through the "dog
clutch", which IS splined to the shaft. The clutch can slide easily forward
and back but turns with the shaft. Continuing on the shaft passes through
the other gear (which spins on the shaft, just like the first gear) then
continues on to the second bearing.

The two gears MUST be the same size, at least in diameter and number of
teeth because they both have the same center (the prop shaft) and both must
engage the same gear. Therefore, forward and reverse ratios are always the
same.

When the engine is running, the three bevel gears (one on the main drive
shaft, two on the prop shaft) are all turning. When in neutral, the clutch
is positioned between the two bevel gears, not engaging either one. To
engage a gear, the clutch is moved either forward or aft, engaging one of
the bevel gears that is rotating about the prop shaft, forcing the prop
shaft to turn in that direction.

Ideally, I would think that the two bevel gears would be totally "floating"
on the prop shaft so that there would be no movement at all with respect to
the driving gear. If the thrust was transferred through the shaft to the
forward gear when the boat was in "forward" then there would be some amount
of movement of the gear forward. As the thrust surface wore, this gear
would move farther and farther forward. As it moves it will change the
engagement with the gear on the driveshaft and before long you would end up
with a stripped gear.

As I said, I can't say if all outdrives are built this way, but the Volvo
Penta I/O I had 30 years ago was, and I am pretty sure my Mercury outboard
is like this as well.

Rod