Power Transister or Relays?? (correction)
 

Your power requirement is pretty close to what I got for Rutu. Now you
will find that there are so many alternatives that your brain will start
fogging over.

You have a starting point but the cylinder is going to be pretty big and
heavy and the tiller arm will have to be 18 to 19" long. You have
plenty of room to work with the pressure. With 700 lb. on a 12" throw
you can get by with a much smaller rod diameter. Look for a 1.5" to 2"
cylinder with a 5/8 to 3/4" rod and 12 to 14" of throw. It will be a
lot lighter and you can use a shorter tiller. The displacement will be
less and the pressure will go up about the same so the required HP will
be about the same.

Also, small 12VDC motors develop HP with RPM more than torque and the
lower you gear it the less efficient it gets. Try to stay under 3:1.

For example a 2x12x.625 cylinder will take about 34 cu. in. for a full
throw or about 136 CI/minute for a 15 second hard over. Now say we
choose a 3600 RPM PM motor (Surplus Center #10-1779 would be close but a
little over powered) and start with a belt ratio of 2:1 so the pump is
running 1800 RPM. 136/1800 is .075 so we need a pump with about that
displacement. The Surplus Center #9-5567 is a little small so the belt
ratio would have to be more like 1.8:1

Admitedly that is not an ideal setup but it will be very hard to get the
perfect match with surplus parts. The thing is, when you add up the
cost of all the parts including the mounts, fittings, hoses etc, you
will come out spending $500-600 and many hours of thinking and labor and
still not be quite sure that it will work the way you want. That makes
the $1,200 price of a complete professionally designed unit seem a lot
more attractive. You would have to be a compulsive DIYer like me to
rationalize it. :-)

OTOH, if you go through the exercise of designing one you have a lot
better understanding of how they work and know more about how to select
the correct one for your boat.

Steve wrote:

Sorry, another typo..

"Steve" wrote in message
...

Seems I should be using about a 2"X20"X1.5" cylinder, 318psi @ .186gpm.



Should read .... 2"X20"X 1 1/8" cylinder, .......

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

Power Transister or Relays??
 

Steve,

15 second hard over time seems slow to me. May not be able to track well
in a seaway.

Doug
s/v Callista

"Steve" wrote in message
...
Thanks for the formulas Glenn.

I ran the numbers to get some idea of what I might be looking for.

Seems I should be using about a 2"X20"X1.5" cylinder, 318psi @ .186gpm.

Using a slightly oversize pump at a lower RPM, I would need a 1/4hp motor
to
achieve the 15 sec. hard over time.

Seems do-able on paper. I just don't know what the max current draw might
be
for this motor. I'm sure someone has a formula for this as well.

Steve
s/v Good Intentions

Power Transister or Relays??
 

15 seconds is a bit slow for a fin keel but you are spoiled. ;-) Will
likes the WH to run under 10 seconds with full load and usually closer
to 6 seconds.

Doug Dotson wrote:

Steve,

15 second hard over time seems slow to me. May not be able to track well
in a seaway.

Doug
s/v Callista

"Steve" wrote in message
...

Thanks for the formulas Glenn.

I ran the numbers to get some idea of what I might be looking for.

Seems I should be using about a 2"X20"X1.5" cylinder, 318psi @ .186gpm.

Using a slightly oversize pump at a lower RPM, I would need a 1/4hp motor

to

achieve the 15 sec. hard over time.

Seems do-able on paper. I just don't know what the max current draw might

be

for this motor. I'm sure someone has a formula for this as well.

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

Power Transister or Relays?? (correction)
 

Thanks again Glenn.. Makes sense, however (as always), as you can see in
this picture http://hood.hctc.com/~esteve/launch15.jpg
the rudder pintle line extends up and behind the head of the rudder. So this
would require a tiller arm of at least 20" and even that is awkward due to
the rudder angle of 37.5 degrees. The cylinder could be rail mounted and
reach over the tiller head but that wouldn't be very elegant.

Looking at this problem and the picture, I am thinking of a cylinder mount
on the boomkin and a tiller arm lower down and perpendicular to the rudder.

I could resolve this by installing the tiller arm though the stern post into
the lazarette, but I really hate to give up all that storage. And then there
is the engage/disengage problem and sealing up the opening for the tiller
arm

Just about anything that is behind the stern rail would require a method to
remotely engage, disengage from the helm position.

Strange how a serious cruiser would call it a problem while DIYer will see
this as a mental challenge.

The (mental) wheels are turning. I'll start a new topic in
Rec.boats.cruising when I get some ideas.

Oh Yah! before we abandon this Elex topic, I still need a 12vdc controller
design. Haven't actually found anything here that I could get my head
around.

Thanks again.

Steve
s/v Good Intentions

Power Transister or Relays??
 

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

Power Transister or Relays?? (correction)
 

oh,oh,oh, I forgot you have an outboard rudder. 15 seconds is probably
a pretty good rate. That ol' girl should keep her head pretty well with
no help and probably will not want to turn any faster than that anyway.

Don't ask me about the control box. The electronic side of my brain
overheated on that remote control light switch and blew out completely
after figuring out the automatic flush/backwash circuit for the
watermaker. :-)

Steve wrote:

Thanks again Glenn.. Makes sense, however (as always), as you can see in
this picture http://hood.hctc.com/~esteve/launch15.jpg
the rudder pintle line extends up and behind the head of the rudder. So this
would require a tiller arm of at least 20" and even that is awkward due to
the rudder angle of 37.5 degrees. The cylinder could be rail mounted and
reach over the tiller head but that wouldn't be very elegant.

Looking at this problem and the picture, I am thinking of a cylinder mount
on the boomkin and a tiller arm lower down and perpendicular to the rudder.

I could resolve this by installing the tiller arm though the stern post into
the lazarette, but I really hate to give up all that storage. And then there
is the engage/disengage problem and sealing up the opening for the tiller
arm

Just about anything that is behind the stern rail would require a method to
remotely engage, disengage from the helm position.

Strange how a serious cruiser would call it a problem while DIYer will see
this as a mental challenge.

The (mental) wheels are turning. I'll start a new topic in
Rec.boats.cruising when I get some ideas.

Oh Yah! before we abandon this Elex topic, I still need a 12vdc controller
design. Haven't actually found anything here that I could get my head
around.

Thanks again.

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

Power Transister or Relays??
 

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

Power Transister or Relays??
 

In article XDElb.87781$sp2.47416@lakeread04,
Glenn Ashmore wrote:

That is fine if you are designing from scratch and can program the
controller for PWM to run the motor faster in one direction than the
other but for a home brew match up it would be close to impossible.

Bruce in Alaska wrote:

In article k9elb.83730$sp2.44153@lakeread04,
Glenn Ashmore wrote:


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.


The above is NOT a correct statement considering that most AutoPilots use
an Electonic Feedback Loop for Rudder Position. This is accomplished by
having a Rudder Position Encoder mounted to the Rudder System that then
feeds back to the Pilot Logic directly. In this type of system, the
travel time of the Piston isn't even considered, unless the Hydrolic
Pump that feeds the system is so underrated that the movement of the
piston is slower than the Pulsewidth Modulation of the Feedback Loop.
All the AutoPilot OEM's I am familiar with take this into account when
designing the Feedback Loop in the first place, and therefor it is a
NONISSUE for the end user.

Bruce in alaska

You missed the point entirely with the above. The PWM for the rudder
position is set in the controller design and does not care what mechanism
is moving the rudder, andlong as it has postive control over that
mechanism. (ie move right, oir move left) The rest is already designed
into the controller feedback loop, and a nonissue for the user. It
could be an issue if you were designing an AP controller from scratch,
but that is not the case in this thread.

Bruce in alaska
--
add a 2 before @

Power Transister or Relays??
 

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

Power Transister or Relays??
 

How big is Good Intentions, Steve? 1/4 horse is bigger than the
autopilot pump on Swee****er (Swan 57, actual weight about 60,000
pounds in round-the-world trim). I don't remember how strong it was,
but both physical size and power consumption suggest around 1/10hp.

As an extremely rough check on the sensibility of your numbers from
Glenn's formulas, the motor driving Fintry's hydraulic steering was a
2hp 220VDC. She was designed to be bulletproof -- Lloyds 100A1
Maltese, for navigation on the North Sea -- so I suspect that half
that would have done fine. Since rudder area varies as displacement
to the 2/3 power and speeds are probably similar (under 10 knots), 1/4
horse should be good up to around 1/4 of Fintry's displacement, say 37
tons.

1/4 horse is 186 watts, so a perfect motor would draw 15 amps at
12VDC. Your results will vary with reality, maybe double -- small DC
motors aren't very efficient.


Jim Woodward
www.mvFintry.com


"Steve" wrote in message ...
Thanks for the formulas Glenn.

I ran the numbers to get some idea of what I might be looking for.

Seems I should be using about a 2"X20"X1.5" cylinder, 318psi @ .186gpm.

Using a slightly oversize pump at a lower RPM, I would need a 1/4hp motor to
achieve the 15 sec. hard over time.

Seems do-able on paper. I just don't know what the max current draw might be
for this motor. I'm sure someone has a formula for this as well.

Steve
s/v Good Intentions