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Old 25-03-2019, 18:36   #1
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Hydraulic autopilot below deck: How does the tiller arm disengage?

Hi all,

I am trying to figure out how works my autopilot because I haven't install myself. So before, re-calibrating it, I'd like to have an understanding how it works.

Here is my system;
1- It's an hydraulic arm which moves the tiller lever. The tiller lever is itself attached directly to the rudder stock.
2- I have also a steering wheel with cable and quadrant

So with the quadrant/steering wheel, I can pivot by rudder from 70 degrees port to 70 degrees starboard.
Considering the course of hydraulic arm and the length of my tiller lever, it could be from 40 degrees port to 40 degrees port.

So my first question is; If I use my steering wheel and goes beyond 40 degrees, how can my tiller lever disengage to let it go?

Therefore I went below deck (Not fun...), and when I retract the hydraulic arm to its minimum position, I noticed that the arm can pivot up and down, and also that the tiller lever can also pivot up and down around the rudder stock.

So my second question is; Is there some sort of mechanism at the attachment of the tiller lever to the rudder stock which allow the disengagement of it? If yes, do you have an example?

Thanks.
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Old 26-03-2019, 16:58   #2
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

To your 1st question, your hydraulic ram will limit the rudder travel to 40 degrees port and stbd. On my boat it's 30. To your 2nd question, you can get around this by removing the pin that attaches the ram to the rudder stock arm. This will disengage the ram from the rudder. Mine is an elaborate bolt with a nut, but I've also seen them as just a pin.



The ram will have a clutch that engages when you push "Auto" on the controller. It disengages when you push "Standby". Note with the ram in place you will experience a little hydraulic friction when in standby, and the pilot takes over in Auto. With the pin removed and the rudder free, you will experience more "feel" on the wheel when sailing.
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Old 26-03-2019, 17:03   #3
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

It's more likely the autopilot ram is engaged and disengaged by a solenoid activated valve which opens to allow hydraulic fluid to freeflow from one end of the ram to the other when the pilot is switched off.
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Old 26-03-2019, 17:04   #4
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

Thanks Mal. Can you describe what do you mean by Ram and how looks like a clutch?
(Just trying to figure out the terminologies at the moment used by knowledgeable people )
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Old 26-03-2019, 17:20   #5
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

Are you absolutely sure it's not a 12VDC linear drive rather than a hydraulic ram ?
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Old 26-03-2019, 18:13   #6
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

A picture might help
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Old 26-03-2019, 18:28   #7
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

I noticed something funny yesterday and I filmed it. See .mp4 attached.

As you can see, I used the Autopilot to turn the rudder. When I turn the rudder port side (First 36 seconds), it works just fine.
But if I turn towards starboard side the rudder (From the 36th second), then there is some sort of game. The rudder stock is not turning and you can see that the tiller arm is moving from down to up, then it finally turns.

This is happening regardless the position of the hydraulic arm. There is some game when starting to turn the rudder towards port side. And I can't explain this...
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Old 26-03-2019, 18:29   #8
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

Its better to have rudder stops installed so the hydraulic ram isn't taking the stress of stopping the rudder. I can't imagine what is happening when you say the tiller arm is pivoting. The only drives I have seen are attached to solid tiller arms mounted solidly to the rudder post. Pictures would help, video might help even more.
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Old 26-03-2019, 18:31   #9
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

Are you certain your wheel and quadrant are able to turn the rudder 70 degrees to both port and starboard? This means the rudder could swing a total of 140 degrees, and that is very unusual. Usually it is a combined ( port & starboard)
total of 70 or 80 degrees.

As stated, electrical/mechanical linear drives have an electric clutch which disengages the mechanism and allows the linear drive to free wheel, and hydraulic linear drives have bypass valves which let the fluid bypass from one side of the cylinder to the opposite side of the cylinder.
In neither case does the linear drive actually mechanically disconnect from the tiller arm.
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Old 26-03-2019, 18:39   #10
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

I'm not sure what you mean by pivot - the photo would be helpful.

My ram has pillow blocks that allow for changing geometries as the system moves.

The ram does not disengage from the rudder stock. And thus the limits of the rudder movement must be such that the ram is not run too far in our out. You can damage an internal seal that way if there is not a hard stop in the ram.

The AP can (usually) be set to limit the ram movements.

As was noted in an earlier post the AP when not engaged has a solenoid that allows the hydraulic fluid to bypass the AP pump. This means that the ram forces the fluid to run through all of the hoses tot eh AP pump and adds some "stiffness" to the steering.

On my AP there is a bypass valve at the ram that allows the hydraulic fluid to bypass the pump and almost all the hoses. Much less force required on the steering wheel when steering by hand. Of course you need to disengage the bypass to get the AP to work.

The valve (with the red handle) in the photo is the bypass.

The quadrant sets the limits of rudder angle on my boat and the ram is a long throw one. I also have cable/chain steering.

Hope that helps.
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Old 26-03-2019, 18:55   #11
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

Ok the video can be downloaded from my pro OneDrive:
https://landeskinc-my.sharepoint.com...CIRaw?e=1i3ZDE

I couldn't find a way to upload a video on the forum though.
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Old 26-03-2019, 19:02   #12
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

Quote:
Originally Posted by zeseb View Post
Ok the video can be downloaded from my pro OneDrive:
https://landeskinc-my.sharepoint.com...CIRaw?e=1i3ZDE

I couldn't find a way to upload a video on the forum though.
That's a poor video and tough to see the ram but I don't think that's hydraulic.
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Old 26-03-2019, 19:16   #13
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

I will try to make a better video this evening, but it's impossible to have one from the top or bottom, it's too small. Yes it's hydraulic ram with some ATF fluid involved.
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Old 26-03-2019, 19:30   #14
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

Quote:
Originally Posted by DougR View Post
As stated, electrical/mechanical linear drives have an electric clutch which disengages the mechanism and allows the linear drive to free wheel, and hydraulic linear drives have bypass valves which let the fluid bypass from one side of the cylinder to the opposite side of the cylinder.
In neither case does the linear drive actually mechanically disconnect from the tiller arm.
DougR
the old pilots disconnect from the tiller. with a mechanical cable in the cockpit to pull / push. (kind of like an engine shut down) seen a few. awkward to use as you have to steer the wheel back and forth to find the point where the pilot locks back into the tiller. but very nicely built for it's time. I reused one with a new Garmin pilot recently
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Old 26-03-2019, 20:12   #15
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Re: Hydraulic autopilot below deck: How does the tiller arm disengage?

First, I don’t see why you would EVER want to turn your rudder 70 degrees, unless you are using it as a parachute. Doing so at any kind of speed would severely stress the entire boat, and bring the boat to a rapid stop. You should have stops built into your system to prevent oversteering.

Second, 70 degree rudder throw would make for horrible geometry - at maximum extension, the ram(cylinder arm) would practically be wrapping around your rudder stock, and you would have minimal torque, as you are pushing or pulling the rudder more than turning it.

See my horrible drawings attached.....


Pull up the instructions from any autopilot system - you want an exact 90 degree angle (tiller straight back, arm mounted exactly perpendicular to the arm.

This allows for maximum torque out of the linkage. The ram will have a “proper tiller length” specified which will give you approximately 45 degrees of rotation each way from center, given the amount of travel the ram moves.
You also should then set the ‘endpoints’ of throw in your autopilot’s setup menu so you don’t quite hit your mechanical stops

All that being said, there are quick release linkages available to disconnect an aitopilot ram from the tiller.

Next the video isn’t quite close enough to see well, but it looks like the tiller arm is not FIRMLY attached to your rudder shaft. Lock the auto pilot so it’s not moving by hand, and you probably can turn the wheel (and rudder) by hand through that play - you shouldn’t be able to move it AT ALL.

Matt
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