On Tue, 25 May 2004 18:37:27 +0200, "Anders Lassen" anders.lassenNEJTILSPAM (at)adr.dk wrote:

Hi,

Recently my propeller threw off a blade. I ordered a new propeller from
Michigan and today it arrived.

BUT - my local dealer made a mistake: He ordered a right-hand propeller -
but the old one was a left hand rotation!

I just waited for four weeks - and really wouldn't like waiting another four
weeks for another to arrive. So here's my question: Is it possible to
reverse the direction of the transmission instead so I don't have to change
the propeller? The engine is a Yanmar 6LP-STE and the transmission is a
Hurth/ZF.

And: Should I do it? I mean - Is there any drawbacks in changing rotation?

Anders
Denmark






Hi Anders,

I hope it will be not too late for a reply to your question.

Rotation is not a your choice, but it is depending from the boat manufacturer designer.

You don't specify WHAT kind of transmission you are using, but presuming you own a classic one comprising an Engine, a
Marine Transmission, a Propeller Drive Shaft and a Propeller...

....you will have these problems...

It is depending from engine rotation (LH or RH), kind of transmission gear (LH or RH, Forward Ratio and Reverse Ratio,
Forward Torque and Reverse Torque, Internal Gears design etc.)

Some technical details:

Usually all engines are "LH" (seen from Flywheel side).

Usually Forward is "direct drive" meaning that there are only TWO gears engaged... so Rotation of Propeller Shaft is
inverted versus engine rotation ( LHRH=RH) ... so Propeller has to be RH .

Reverse is done by THREE Gears... so Engine and Transmission Shaft have same rotation ( LHRHLH=LH ) so a RH Propeller
rotates LH and does REVERSE.

Where is the matter?

You will have NEVER the same ratio Forward and Reverse:

Forward has TWO Gears coupled together and transfers a lot of power (direct drive).

Reverse has THREE Gears coupled together and the Second One is a small one rated (designed) for a limited Torque and
use.

So you cannot use "Transmission Reverse" for " Boat Forward".

So, if you wish to use a "Reverse Propeller" you have to replace ENGINE with a RH one!

Of course there are other options, but these are the most important ones.
+++

Otherwise... if you have another kind of transmission, and specifically the one with Forward and Reverse similar to the
one used on Outboards ( Three Bevel Gears Style with Cog Clutches ) there are no matters...

Forward and Reverse have same Ratio, same Torque, same Cog Clutch.... so RH or LH are optional choices and are not
involving any other part or performance...
+++

The answer is exclusively depending from the parts involved in.

I hope this could help you.

Regards,

WinXP


PS.- I don't know who-where is your Supplier... but any decent Supplier has "a lot" of used Propellers available for
speed tests or power test or saved or... so he "has to have" a decent one for emergency purpose...

Important is it has same HUB and same Rotation... Pitch, Outer Dia and number of Blades is relative...

By the way, it is a good idea to have a "replaceable" propeller on board...

the trust bearing is wrong.


anders.lassenNEJTILSPAM (at)adr.dk wrote:

Hi,

Recently my propeller threw off a blade. I ordered a new propeller from
Michigan and today it arrived.

BUT - my local dealer made a mistake: He ordered a right-hand propeller -
but the old one was a left hand rotation!

I just waited for four weeks - and really wouldn't like waiting another four
weeks for another to arrive. So here's my question: Is it possible to
reverse the direction of the transmission instead so I don't have to change
the propeller? The engine is a Yanmar 6LP-STE and the transmission is a
Hurth/ZF.

And: Should I do it? I mean - Is there any drawbacks in changing rotation?

Anders
Denmark






Hi Anders,

I hope it will be not too late for a reply to your question.

Rotation is not a your choice, but it is depending from the boat manufacturer
designer.

You don't specify WHAT kind of transmission you are using, but presuming you
own a classic one comprising an Engine, a
Marine Transmission, a Propeller Drive Shaft and a Propeller...

...you will have these problems...

It is depending from engine rotation (LH or RH), kind of transmission gear
(LH or RH, Forward Ratio and Reverse Ratio,
Forward Torque and Reverse Torque, Internal Gears design etc.)

Some technical details:

Usually all engines are "LH" (seen from Flywheel side).

Usually Forward is "direct drive" meaning that there are only TWO gears
engaged... so Rotation of Propeller Shaft is
inverted versus engine rotation ( LHRH=RH) ... so Propeller has to be RH .

Reverse is done by THREE Gears... so Engine and Transmission Shaft have same
rotation ( LHRHLH=LH ) so a RH Propeller
rotates LH and does REVERSE.

Where is the matter?

You will have NEVER the same ratio Forward and Reverse:

Forward has TWO Gears coupled together and transfers a lot of power (direct
drive).

Reverse has THREE Gears coupled together and the Second One is a small one
rated (designed) for a limited Torque and
use.

So you cannot use "Transmission Reverse" for " Boat Forward".

So, if you wish to use a "Reverse Propeller" you have to replace ENGINE with
a RH one!

Of course there are other options, but these are the most important ones.
+++

Otherwise... if you have another kind of transmission, and specifically the
one with Forward and Reverse similar to the
one used on Outboards ( Three Bevel Gears Style with Cog Clutches ) there are
no matters...

Forward and Reverse have same Ratio, same Torque, same Cog Clutch.... so RH
or LH are optional choices and are not
involving any other part or performance...
+++

The answer is exclusively depending from the parts involved in.

I hope this could help you.

Regards,

WinXP


PS.- I don't know who-where is your Supplier... but any decent Supplier has
"a lot" of used Propellers available for
speed tests or power test or saved or... so he "has to have" a decent one
for emergency purpose...

Important is it has same HUB and same Rotation... Pitch, Outer Dia and
number of Blades is relative...

By the way, it is a good idea to have a "replaceable" propeller on board...

On 07 Jun 2004 03:03:28 GMT, (JAXAshby) wrote:

the trust bearing is wrong.

snip


Hi.

It should be or should be not.

It is depending from "direction" not "rotation":

"Forward" is always forward so Propeller is always "pushing" the vessel.

Usually is the "Propeller Shaft" to be supporting the pushing efforts.

Gears and Clutches are supporting only the rotational torques.

But in any way has to be examined the specific Driveline, application and purpose.

Same thing for Gearbox engineering, drawing, performance and manufacturer technical choices...

By the way in North Adria Sea and Lagoon of Venice all Clam Dredgers are operating in Reverse !

So a lot of fishermen are replacing rotation of Propeller just to operate Gearbox in "Forward"...

.... other ones are "preferring" to operate in true Reverse as so the gear-ratio is wider than Forward one...

In any way it is a good thing don't operate DIY on ANY vital parts of any kind ofvessel...


Bye,


WinXP

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.

the trust bearing is wrong.

snip


Hi.

It should be or should be not.

It is depending from "direction" not "rotation":

"Forward" is always forward so Propeller is always "pushing" the vessel.

Usually is the "Propeller Shaft" to be supporting the pushing efforts.

Gears and Clutches are supporting only the rotational torques.

But in any way has to be examined the specific Driveline, application and
purpose.

Same thing for Gearbox engineering, drawing, performance and manufacturer
technical choices...

By the way in North Adria Sea and Lagoon of Venice all Clam Dredgers are
operating in Reverse !

So a lot of fishermen are replacing rotation of Propeller just to operate
Gearbox in "Forward"...

... other ones are "preferring" to operate in true Reverse as so the
gear-ratio is wider than Forward one...

In any way it is a good thing don't operate DIY on ANY vital parts of any
kind ofvessel...


Bye,


WinXP

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

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.