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Old 13-06-2021, 08:29   #1
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Join Date: Jan 2019
Location: New York, USA
Boat: Freedom 39 PHS
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Ancient AP Drive + New AP Computer

Hello,
Last year the control head to our W-H Autopilot died. While I'm frankly glad to be rid of the eyesore factor, there is a "robust" hydraulic setup below I'd prefer to re-use with our new NAC-3 computer. Based on previous help from here, I know it's possible at a basic level, I'm just working out the details.

The questions:
-There's a "plunger" in the cockpit that actuates the hydraulic bypass valve below allowing manual steering, is it possible to install a solenoid to switch this instead? It's ugly as sin and if a solenoid fails I can go below in <60s and manually throw the bypass valve.
-Do these solenoids just actuate the existing bypass valve, or do they usually come with their own full valve body and solenoid integrated?
-Or (as I fear) are the bypass solenoids typically integral to the motor itself, which means I'm screwed because every single component in my hydraulic setup is separated out?
-Just to sanity check, as this isn't a typical neat and tidy integrated pump/ram/solenoid combo, this is in fact a "Hydraulic Linear Drive" right? As in not a "Reversible Pump" as shown in the NAC-3 installation guide? Or is it technically both? I assume reversible pump in the diagram below refers to something that would act directly on a fully hydraulic steering system, rather than using a ram. In which case, I would love the NAC-3 to be able to switch the pictured "Drive Engage" device with the Autopilot Standby button, by throwing the bypass valve down below.

The facts:
-Steering is chain and cable, edson pedestal
-AP power unit is a PacSci DC motor connected by a small belt to a standalone hydraulic pump (I think..).
-Hynautic hydraulic cylinder directly acts on rudder quadrant
-New computer is a B&G/Simrad NAC-3

The pictures:
plotter1.jpg - The manual cable that currently switches the hydraulic bypass (big ugly flex conduit protruding from cockpit floor)
plotter2.jpg - The motor drive unit (a small belt below the blue plate connects it to the black pump body on the right)
plotter3.jpg - Full system overview
plotter4.jpg - Detail view of the bypass valve and cable coming from cockpit
simrad.png - Simrad/BG Installation diagram


As ever, very grateful for any clues as most electronics outfits have gone radio silent when I've sent them these photos...
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Old 13-06-2021, 09:08   #2
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Re: Ancient AP Drive + New AP Computer

If those were a new install it would probably use electrically operated valves. But the system you have looks in decent condition and it works. You could use an electrical solenoid to actuate the existing lever. The key parameters are throw distance (how far do you move the current cable to switch from one mode to the other) and throw force (how hard it is to move). The first is pretty easy to measure, the second a bit more difficult, and should be tested by removing the existing cable and testing at the actual lever (the cable probably adds significant friction that will not be there if you add an actuator below deck).

You have some flexibility there, you can decrease force by increasing throw (going further out the lever) and vice versa. Another option to a linear solenoid would be an electric rotary valve actuator. You’d need limit switches to turn off the power once the valve is actuated (possibly same with a linear device, depends on what kind of actuator, maintained power, spring return, etc.).

I’d be talking with an industrial valve supplier rather than a marine place. 12V will be a bit of a challenge (24V would be dead easy), but should be available. Out here I’d be talking with the fishing boat suppliers and the heavy equipment vendors.

Can’t read the model # on the PacSci pump (very nice BTW) but it appears to be a reversing pump, and the overall installation looks that way, but can’t say definitively.

[Edit]absolutely not a recommendation, but here’s a linear actuator of the type that could be used to replace the pull cable. Would have to look at how it returns, etc. Just an example of the kind of things out there.
https://www.amazon.com/dp/B07ZJ4B3WW...ing=UTF8&psc=1

https://www.adafruit.com/product/413...SABEgJ5Y_D_BwE
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Old 13-06-2021, 12:34   #3
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Re: Ancient AP Drive + New AP Computer

Thank you for the advice, I'm guessing the variables here are why most marine installers might not want to take a stab at it. The more I look into this and other setups the more I realize how overengineered mine is. All the rigid hydraulic lines and reservoirs and the belt-driven pump would normally be fully integrated into a simple cylinder+pump combo now, but yeah I think this qualifies as a reversible pump. The PacSci model is BA3614-2827-2. Unfortunately like most things in the AP the company that made it is no longer around.

Quote:
Originally Posted by Dsanduril View Post
Canít read the model # on the PacSci pump (very nice BTW) but it appears to be a reversing pump, and the overall installation looks that way, but canít say definitively.

[Edit]absolutely not a recommendation, but hereís a linear actuator of the type that could be used to replace the pull cable.
The linear actuators are interesting, but as you mentioned I'd be most concerned with driving them from the clutch control terminals on the AP computer because I don't know about their power requirements (The NAC-3 supports a 3amp load natively), and I don't know if the clutch control just applies 12v when the AP is on, and relies on spring return when it's on standby. I'd also want the power failure mode to return the valve to the bypass position. This just kind of sucks because I'd hoped there would be a common marine part for this problem that wouldn't be such a kludge. Ideally I'd like this to be a pretty reliable mechanism, not something I gin up with some stuff from mcmaster-carr
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Old 22-06-2021, 14:39   #4
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Re: Ancient AP Drive + New AP Computer

I just went thru a similar situation with a non-working WH system.


Mine also has the unattractive lever at the helm and uses a Morse cable to open and close the bypass valve to allow the boat’s cable steering system to move the rudder when the AP isn’t running. I’ve got the same valve setup and don’t much care for it either but I’m leaving mine in place for now.


To try and answer your questions-
As DsandDuril suggested - Yes it should be straightforward to replace the cable with a small 12VDC linear actuator or solenoid to actuate the existing lever shown in Pic 4. Its also possible to use the NAC-3’s “Engage or Clutch output” to switch this valve automatically when you engage/disengage the AP. Worst case you could install a simple switch to accomplish this and lose the lever and cable. The valve underneath the lever in pic 4 is the bypass valve, it could easily be replaced with an electrically operated solenoid valve but without seeing exactly what’s under the aluminum plate its hard to suggest what might be involved. It should be straight forward, it allows the hyd fluid to flow unrestricted in a loop when the AP is not being used. The bypass on these WH systems is that valve, its not integral to the pump or motor.


The Pacific Scientific motor and belt driven pump are reversible so nearly any new AP motor controller should be capable of running it, the motor may draw as much as 22 amps so you should be okay with the NAC-3 (30 amps). The WH system operated it as a reversible motor so nothing will change there. If the Pac Sci motor ever fails it can easily be replaced with another 12V reversible motor.


As to your sanity check question – the beauty of a WH system is they are more or less a self contained backup steering system much like normal hydraulic steering systems. If your Edson chain or cables break you’ll still have something that can steer the boat albeit electronically. From your pictures – it should be treated as a complete Drive System with a reversible pump, not a hydraulic linear drive. If you wanted a 2nd fully independent steering system simply add a jog lever and you could easily steer the boat like most commercial vessels do.


The NAC-3 should be able to switch the pictured "Drive Engage" device if you add either a DC valve or small linear actuator. The NAC-3 has that capability but its limited to 3 amps. You should keep the added electrical drain in mind and consider maybe moving the lever or living with it.


For valves try a Parker normally open solenoid valve, I’d lean towards one that required 12V to hold it closed so that it would fail to bypass. As the other poster suggested a 12V valve may also be difficult to source. You could maybe add a step-up transformer somewhere to alleviate that issue.


To his credit Will Hamm ginned up these autopilots with parts from places exactly like McMaster and they’ve served most of their owners very well. Many WH pilots have crossed oceans repeatedly including mine. I left his mechanical bits just as they were installed and simply replaced the electronics that drive it with off the shelf parts.
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Old 06-07-2021, 10:57   #5
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Re: Ancient AP Drive + New AP Computer

All makes sense. Immediately we're going to keep the plunger and just make sure it's engaged to hydraulic mode before taking the AP off standby. One of the quirks with going from a separate motor control to an integrated computer + controller is we have fat 6a cable for the old motor control box. This is run to a 30A fuse, but I'd really like it to be an on/off function like the sailing instruments or anything else (phantom fused loads killed our battery bank this past winter). When you made this switch did you use a separate breaker or run a 25/30A fuse from your main panel? I'd be concerned with running the large 6a wire from the AP drive to the wimpy Blue sea terminal, and voltage drop across that breaker buss bar when the pilot kicks on / off. But currently the AP fuse for the 6ga run is hidden in the battery compartment.

I might run a short 10ga jumper from where the fuse is currently to a 30a breaker, as it's <10ft. Curious what others have done electrically.
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Old 09-07-2021, 05:37   #6
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Re: Ancient AP Drive + New AP Computer

I've also got a 30 Amp Buss lever type breaker hidden away near the batteries.


I've considered adding a small relay with a switch somewhere closer to the helm. Something similar to this-


https://www.amazon.com/PACK-AMP-Wate.../dp/B074FSZWVT
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