The linear drive I finally located (haven't purchased yet) is non-marine.
Rather commercial, industrial for gates, wheel chair lifts and positioning
appliactions.

I is presently available from Surplus Center
http://www.surpluscenter.com/item.as...&item= 5-1474

I'm anticipating that I will have to give some attention to marinizing the
unit, but that's what DIYs do.

Steve
s/v Good Intentions

"Steve" wrote in message
...
The linear drive I finally located (haven't purchased yet) is non-marine.
Rather commercial, industrial for gates, wheel chair lifts and positioning
appliactions.

I is presently available from Surplus Center

http://www.surpluscenter.com/item.as...&item= 5-1474

I'm anticipating that I will have to give some attention to marinizing the
unit, but that's what DIYs do.


The other thing you may need is some sort of a clutch to decouple it
whenever the autopilot is not in use.
I know that the raymarine use a sort of a magnetic affair that energises and
locks (by friction) two plates together whenever the autopilot is switched
on.
God knows how you will build that into it!!

garry

The tiller pilots are engaged by simply lifting the end of the linear drive
piston off the tiller pin. With my OEM linear drive, when not engaged on the
tiller pin, it swings out of the way to a storage clip on the stern rail.

BTW. The AH or ST wheel pilot, have internal belt drives with idler rollers
on a clutch lever. Not magnetic (couldn't/shouldn't have mag. around the
cockpit) or friction clutches in these. Trust me, I've had one apart for
voyage repairs in my last boat.

Steve
s/v Good Intentions

"Steve" wrote in message
...
The tiller pilots are engaged by simply lifting the end of the linear
drive
piston off the tiller pin. With my OEM linear drive, when not engaged on
the
tiller pin, it swings out of the way to a storage clip on the stern rail.

O.K I understand, I was thinking that you were going to use it below deck
directly attached to the quadrant.
In that situation you would need some sort of a clutch.
The marinising aspect might take a lot of work, that is usually the bit
where the manufactured models fall down, hence the desire to mount them
below decks if possible


BTW. The AH or ST wheel pilot, have internal belt drives with idler
rollers
on a clutch lever. Not magnetic (couldn't/shouldn't have mag. around the
cockpit) or friction clutches in these. Trust me, I've had one apart for
voyage repairs in my last boat.

Yeah, I know, have had to strip down those friction clutches myself, a real
PITA.
The one on the ST4000 is attached via two tiny roll pins that have a
tendency to shear off at awkward moments.

Re the magnetic clutch, I have seen them on the linear drive of the ST7000
ST6000 and havent noticed any problem with them affecting the compass.
But then I suppose it is fairly minimal, compared to the magnetism created
within the actuator motor itself.


good luck
garry

Regarding marinizing: if the cylinder ram plain steel, I will replace it
with stainless. (I have a machine shop) Pack and seal the gear case. And
epoxy coat the exterior.

Have to wait and see how well it's built.. If I don't like what I see, I'll
return it before I modify it.

Steve
s/v Good Intentions

Keep us posted on how you get on....
That ram sure is a lot cheaper that equivalent marine models

garry

"Steve" wrote in message
...
Regarding marinizing: if the cylinder ram plain steel, I will replace it
with stainless. (I have a machine shop) Pack and seal the gear case. And
epoxy coat the exterior.

Have to wait and see how well it's built.. If I don't like what I see,
I'll
return it before I modify it.

Steve
s/v Good Intentions

VERY bad idea. That drive is not going to be any where near fast enough
for an autopilot. It is a screw drive. A LOT slower than a hydraulic.

Also a hydraulic cylinder needs to be a "balanced" type with the rod
going all the way through so the displacement is the same in both
directions. Regular single ended double action cylinders have less
displacement on the rod side because of the volume of the rod. With a
constant pump speed it retracts faster than it extends and with less
force. You would never get an autopilot logic unit to control it properly.

These are more what you will need:
http://www.surpluscenter.com/sort.as...ke yword=HCP1

and the pump has to be reversable like these:
http://www.surpluscenter.com/sort.as...ke yword=HPSD

Steve wrote:
The linear drive I finally located (haven't purchased yet) is non-marine.
Rather commercial, industrial for gates, wheel chair lifts and positioning
appliactions.

I is presently available from Surplus Center
http://www.surpluscenter.com/item.as...&item= 5-1474

I'm anticipating that I will have to give some attention to marinizing the
unit, but that's what DIYs do.

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 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

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