I had considered hydraulic and if I already had hydraulic on the engine, I
probably would reconsider it.

Originally I had planned on hydraulic for the anchor windlass but found the
Lewmar 1000 vertical and I'm now happy with that.

Also any hydraulic cylinder and hoses would be right in the cockpit since my
rudder is 'outboard' and no provision for an inboard cylinder.

Additionally, I would have to find or build some kinda electrical to
hydraulic control valve for the AP control head to operate.

After reading Glenns comments regarding the operating speed of the screw
drive, I went to the boat and did a test to determine the rate of travel of
the OEM (AH3000) linear drive. It is exactly 1 inch per min. with no load.
The unit I'm considering is 3/4 inch per min.. 25% slower, however since the
this unit has 3 times the thrust I could move the tiller attachment pin aft
an appropriate amount to increase the rudder stop to stop travel time and
still have the advantage of the increased dynamic and static load.

I'm going to contact the fellows at Surplus Center and see if I can get some
more spec. info on this unit. They have been very help full in the past.

I am however taking Glenns warnings into consideration and thanks for the
heads up.

Steve
s/v Good Intentions

WOW! I am amazed that the AH3000 is that slow. How long does it take
to go hard over to hard over? I was thinking that 15 or 20 seconds
would be the bare minumum. 1" per minute on a 6" tiller arm would take
more than 3 minutes.

Steve wrote:

I had considered hydraulic and if I already had hydraulic on the engine, I
probably would reconsider it.

Originally I had planned on hydraulic for the anchor windlass but found the
Lewmar 1000 vertical and I'm now happy with that.

Also any hydraulic cylinder and hoses would be right in the cockpit since my
rudder is 'outboard' and no provision for an inboard cylinder.

Additionally, I would have to find or build some kinda electrical to
hydraulic control valve for the AP control head to operate.

After reading Glenns comments regarding the operating speed of the screw
drive, I went to the boat and did a test to determine the rate of travel of
the OEM (AH3000) linear drive. It is exactly 1 inch per min. with no load.
The unit I'm considering is 3/4 inch per min.. 25% slower, however since the
this unit has 3 times the thrust I could move the tiller attachment pin aft
an appropriate amount to increase the rudder stop to stop travel time and
still have the advantage of the increased dynamic and static load.

I'm going to contact the fellows at Surplus Center and see if I can get some
more spec. info on this unit. They have been very help full in the past.

I am however taking Glenns warnings into consideration and thanks for the
heads up.

Steve
s/v Good Intentions




--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Correction::

That was suppose to be 1"/sec. for the AH3000 linear drive.

The ram (if you wanna call it that) total travel is 10.5 inches and it take
a little over 10 sec from stop to stop.

Sorry about the error.

Steve
s/v Good Intentions

Wow, my WH moves the rudder from stop to stop in about
3 or 4 seconds!

Doug


"Glenn Ashmore" wrote in message
news:8_llb.85875$sp2.29546@lakeread04...
WOW! I am amazed that the AH3000 is that slow. How long does it take
to go hard over to hard over? I was thinking that 15 or 20 seconds
would be the bare minumum. 1" per minute on a 6" tiller arm would take
more than 3 minutes.

Steve wrote:

I had considered hydraulic and if I already had hydraulic on the
engine, I
probably would reconsider it.

Originally I had planned on hydraulic for the anchor windlass but found
the
Lewmar 1000 vertical and I'm now happy with that.

Also any hydraulic cylinder and hoses would be right in the cockpit
since my
rudder is 'outboard' and no provision for an inboard cylinder.

Additionally, I would have to find or build some kinda electrical to
hydraulic control valve for the AP control head to operate.

After reading Glenns comments regarding the operating speed of the screw
drive, I went to the boat and did a test to determine the rate of travel
of
the OEM (AH3000) linear drive. It is exactly 1 inch per min. with no
load.
The unit I'm considering is 3/4 inch per min.. 25% slower, however since
the
this unit has 3 times the thrust I could move the tiller attachment pin
aft
an appropriate amount to increase the rudder stop to stop travel time
and
still have the advantage of the increased dynamic and static load.

I'm going to contact the fellows at Surplus Center and see if I can get
some
more spec. info on this unit. They have been very help full in the past.

I am however taking Glenns warnings into consideration and thanks for
the
heads up.

Steve
s/v Good Intentions




--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

I think you misunderstand the typical hydraulic auto-pilot for
mid-size boats where the manual steering is not hydraulic. They
typically have a dedicated reversible hydraulic pump driving (as Glenn
points out) a balanced cylinder. The AP electronics turns the electric
motor driving the pump on and off in the required direction.

Larger vessels, including Fintry, have a setup like the one you
describe below, where an hydraulic pump runs continuously with
hydraulic servos (fluid operated relays) supplying the fluid to the
ram(s) as required. This is similar to automotive power steering.

I think I'd rather have an hydraulic cylinder and hoses back there
rather than an electrically driven screw about the same size. The
hoses would be bigger than the wires, but the Surplus Center drive is
not designed for your environment.

Finally, think harder about the broader design issues here. In
particular, what happens when a big wave pushes the rudder harder than
the AP can push back? This is the touchy area for screw drive APs, as
the drive has to stall safely, and then go on pushing as soon as it's
able. An hydraulic unit does this easily, but a direct electric drive
has problems -- electric motors don't like to stop and you can't just
un-clutch the thing, as it has to stop, not backdrive.

Also think about duty cycle and design life. An AP is working all the
time, back and forth. Very few applications require this kind of
activity, so it may be an area where adapting something from elsewhere
is difficult.

As a complete aside, I wonder about the need for a balanced cylinder
in a hydraulic drive. As Glenn says, with an ordinary single ended
cylinder, you have different thrust in the two directions. But,
modern autopilots are pretty sophisticated and adjusting for that in
software might be cheaper than the extra cost and maintenance (two
seals rather than one) of a balanced cylinder.

Jim Woodward
www.mvFintry.com

"Steve" wrote in message ...
I had considered hydraulic and if I already had hydraulic on the engine, I
probably would reconsider it.

Originally I had planned on hydraulic for the anchor windlass but found the
Lewmar 1000 vertical and I'm now happy with that.

Also any hydraulic cylinder and hoses would be right in the cockpit since my
rudder is 'outboard' and no provision for an inboard cylinder.

Additionally, I would have to find or build some kinda electrical to
hydraulic control valve for the AP control head to operate.

After reading Glenns comments regarding the operating speed of the screw
drive, I went to the boat and did a test to determine the rate of travel of
the OEM (AH3000) linear drive. It is exactly 1 inch per min. with no load.
The unit I'm considering is 3/4 inch per min.. 25% slower, however since the
this unit has 3 times the thrust I could move the tiller attachment pin aft
an appropriate amount to increase the rudder stop to stop travel time and
still have the advantage of the increased dynamic and static load.

I'm going to contact the fellows at Surplus Center and see if I can get some
more spec. info on this unit. They have been very help full in the past.

I am however taking Glenns warnings into consideration and thanks for the
heads up.

Steve
s/v Good Intentions

I think you misunderstand the typical hydraulic auto-pilot for
mid-size boats where the manual steering is not hydraulic. They
typically have a dedicated reversible hydraulic pump driving (as Glenn
points out) a balanced cylinder. The AP electronics turns the electric
motor driving the pump on and off in the required direction.

I was kinda thinking the same thing. Infact, at first, I thought this unit
was a electro-hydraulic unit.

Since I'm not going to drive the hydraulics off the engine I really need to
find a compact efficient 12vdc power unit.

I don't think I need to get into a continious running pump since the boat
has a full keel and maintains it's course very well. 90% of the time, the AP
linear drive is just holding the tiller in position (static load). Something
that a hydrualic cylinder it very good at. The main reason the AH3000 linear
isn't satisfactory, is because in heavy weather, the rudder tiller exerts
enough force against the linear drive to force the motor to turn in reverse.
I'm afraid of what this is doing to the planetary gear reduction.

Thanks to your comments and that of Glenn, I will look farther for a 12vdc
(reversiable) PowerPack.. If anyone knows of something like this, please let
me know.. The pumps that Glenn referenced were just the pumps.. gotta be a
complete unit someplace, like truck power lifts, etc.

Steve
s/v Good Intentions

Steve,

You might contact WH. The power pack I have is a simple 1/4 HP
DC motor the drive a hydraulic pump via a belt. Pretty compact.
I suspect they would sell you a unit for a reasonable price. Motor
only runs when moving the runner. But that is a function of the
controller rather than the powerpack itself.

Doug
s/v Callista

"Steve" wrote in message
...

I think you misunderstand the typical hydraulic auto-pilot for
mid-size boats where the manual steering is not hydraulic. They
typically have a dedicated reversible hydraulic pump driving (as Glenn
points out) a balanced cylinder. The AP electronics turns the electric
motor driving the pump on and off in the required direction.

I was kinda thinking the same thing. Infact, at first, I thought this unit
was a electro-hydraulic unit.

Since I'm not going to drive the hydraulics off the engine I really need
to
find a compact efficient 12vdc power unit.

I don't think I need to get into a continious running pump since the boat
has a full keel and maintains it's course very well. 90% of the time, the
AP
linear drive is just holding the tiller in position (static load).
Something
that a hydrualic cylinder it very good at. The main reason the AH3000
linear
isn't satisfactory, is because in heavy weather, the rudder tiller exerts
enough force against the linear drive to force the motor to turn in
reverse.
I'm afraid of what this is doing to the planetary gear reduction.

Thanks to your comments and that of Glenn, I will look farther for a 12vdc
(reversiable) PowerPack.. If anyone knows of something like this, please
let
me know.. The pumps that Glenn referenced were just the pumps.. gotta be a
complete unit someplace, like truck power lifts, etc.

Steve
s/v Good Intentions

Doug,

Several metions of WH and I thought I saw it referred to as 'something'
Harris but I'm not familiar with WH. I assume he designs and provides
hydraulic packages.

Need a little help here..

Steve
s/v Good Intentions

WH autopilots. Will Ham makes an un-sexy, but elegant and bulletproof
autopilot system in a little shop out on Banbridge Island. Extremely
popular with serious cruisers and small commercial boats. The Dashews
love them if that means anything. It does not have some of the "smart"
and "learning" features of some fancier brands but you can set just
about everything for the best performance.

I think in a PS owner survey it was the only brand that reported no
failures and had the lowest failure rate in the SSCA survey.

Steve wrote:

Doug,

Several metions of WH and I thought I saw it referred to as 'something'
Harris but I'm not familiar with WH. I assume he designs and provides
hydraulic packages.

Need a little help here..

Steve
s/v Good Intentions



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

You can find them at www.whautopilots.com. One of the things
I really liked about it is the fact that the major controls come out
as knobs. Gain, Yaw, and Counter Rudder can be easily adjusted.
In all sorts of conditions I have rarely adjusted anything except
the Gain, and then not by much.

Doug
s/v Callista

"Glenn Ashmore" wrote in message
news:YZUlb.90635$sp2.28254@lakeread04...
WH autopilots. Will Ham makes an un-sexy, but elegant and bulletproof
autopilot system in a little shop out on Banbridge Island. Extremely
popular with serious cruisers and small commercial boats. The Dashews
love them if that means anything. It does not have some of the "smart"
and "learning" features of some fancier brands but you can set just
about everything for the best performance.

I think in a PS owner survey it was the only brand that reported no
failures and had the lowest failure rate in the SSCA survey.

Steve wrote:

Doug,

Several metions of WH and I thought I saw it referred to as 'something'
Harris but I'm not familiar with WH. I assume he designs and provides
hydraulic packages.

Need a little help here..

Steve
s/v Good Intentions



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com