Autopilot failure leading to jammed steering on "Standby"

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Autopilot failure leading to jammed steering on \"Standby\"

My Holman & Pye Super Sovereign has a new Raymarine S2G autopilot which was installed this spring (2006). At the end of a long passage, when switching from 'Auto' to 'Standby' the steeering locked up, ie. it was not possible to turn the wheel and steer the boat.

The immediate solution was to remove the access plate in the cockpit sole and physically disconnect the linear drive, which took several minutes in all.

Although the linear drive would work under autopilot control, it could not be back driven from the steering linkage.

After some time and cajoling on the bench, the linear drive freed itself, and a Raymarine agent who inspected the unit could find no fault with it.

The Linear drive is a Raymarine Type 1 unit, which had operated for approximately 200 hours in total from installation to first failure.

The problem recurred after another 60 hours of operation.

This type of failure could be extremely dangerous. Raymarine has been informed of the failures and I am waiting for their comments. However, I would like to hear from anyone who has had a similar problem.
 
Re: Autopilot failure leading to jammed steering on \"Standby\"

I am not familiar with the type of boat nor the type of autopilot. However, as a matter of principle I find it extraordinary that an autopilot could be installed that does not allow manual i.e. mechanical and immediate disconnection.

The only types I have ever used are the simple autohelm that can be just pulled off the tiller pin or the type that can be disconnected at the wheel steering position by opening a clutch. I would feel very uncomfortable not being able to disconnect in an emergency. Is this common?
Morgan
 
Re: Autopilot failure leading to jammed steering on \"Standby\"

I have a same type but I have not such problem. From my point of view problem is with CLUTCH and can be fault in Linear drive or computer not work properly.
But as it works few months without problems the best is to check it with Raymarine specialist.
 
Re: Autopilot failure leading to jammed steering on \"Standby\"

The linear drives are designed to fail safe, but like most things that does not discount the possibility of their not doing so.

However, have you discounted the possibility of improper installation causing it an internal jamb up. Both electrically (for example, preventing the clutch from disengaging) and mechanically (ensuring, for example, that when the wheel is in the mid position then the linear drive actuator is at right angles to the tiller arm it drives on the rudder stock).

John
 
Re: Autopilot failure leading to jammed steering on \"Standby\"

Not sure which model, but there was a thread about this problem with Raymarine pilots, where the cause was a broken piece of plastic lug, jamming when the drive unit was in freewheel - I'll try to recall where / when I read about it.
 
To answer your ?

"serious" autopilots for wheel-steered vessels all operate on a ram (hydraulic or linear electric) direct to the rudder quadrant. They're usually more reliable and far more powerful than the "occasional-use" ones that operate on a drum attached to the steering wheel.

It is, perhaps, a design flaw if you have to dismantle the boat to disconnect the actuator.
 
Re: Autopilot failure leading to jammed steering on \"Standby\"

Thanks all for your replies so far.

In reply to David Morgan ,The Super Sovereign is a 35ft fibreglass ketch with 26ft waterline. This type of undefloor autopilot is quite common. Your concern at not being able to disconnect it immediately is borne out by my own recent experience. Normally the only way to achieve manual control is to de-energise the clutch inside the linear drive, which is done automatically by switching to standby.

In common with Branko's experience, most people don't seem to have a problem and it is one reason I went down this route. My unit was inspected by a Raymarine specialist after the first failure occurence, and no fault was found. It has since failed again. Disconnecting the electrics makes no difference, the fault is definately in the linear drive.

'Ship's Cat's' suggestion is a fair one, but this installation was meticulously carried out and all angles and clearances are well within the tolerances specified in the installation instructions.

Rick's suggestion is promising, any further information would be appreciated.

I agree with charles_reed, and this is one reason I selected this type of autopilot. Disconnecting the actuator in my installation is not as tricky as it sounds, I have to lift the liferaft out of the way, lift out the floorboards, undo 5 quarter turn fasteners and lift out the inspection plate which reveals the actuator. This is disconnected by pulling out a simple spring clip. I've had a look at some other installations and they would all need more time to get access to the rudder quadrant.

Thanks again for all your responses.

Regards,
Alan
 
Re: Autopilot failure leading to jammed steering on \"Standby\"

Would be interested to hear what the problem turns out to be when solved.

Good luck with it.

John
 
I\'ve always found

a visit in person to Anchorage Way is an ideal way of sorting such problems.

Without bullying, Raymarine have proved most accomodating to me and about 5 others' problems, about which I've called.

I strongly suspect a problem in the control head rather than the linear drive (which is a laughably simple peice of kit).

I'm down at my daughter's place (in Soton) next 17 Aug. PM me if you think we can do anything to resolve the issue.
 
Re: Autopilot failure leading to jammed steering on \"Standby\"

Another thought - is the travel of the drive correctly set using the max helm setup on the pilot controller instrument so that the linear drive is not trying to power against the rudder stops at full helm?

If not it could be that such an event (which would only happen occasionally) might be jambing the clutch so's that when de-energised to standby it is not releasing leaving you with a jambed drive.

(I have not taken a Raymarine drive apart so whether such a jamb up of the clutch internally is possible or not I don't know)

John
 
Re: Autopilot failure leading to jammed steering on \"Standby\"

Thanks John,

It is an interesting idea, so I just checked it. Setting the 'software' end stops was part of the original dockside calibration, and hasn't changed.

With the autopilot in 'AUTO' the ram doesn't reach the rudder's endstops on either lock.

Also, as required, the ram reaches the rudder's endstops before its own internal stops.

So no apparent problem there.

Incidentally, the second time the actuator jammed up was after motoring in a flat calm at 3.5 knots for a few hours, so we could make a dawn landfall. The unit was therefore very lightly loaded at the time.

Regards,
Alan
 
Re: Autopilot failure leading to jammed steering on \"Standby\"

There are a few possibilities:

1. The drive has some crap in it that is causing the ball screw to jam. We used o see this from time to time and is not always easy to find. Can sometimes be felt by pulling the ram in and out slowly.

2. The ball screw has a damaged ball(s) and is causing a lock up. Usually recurs regularly and easy to find. Not normal on a low usage unit unless it has been abused.

3. The clutch is dragging or not releasing properly. Can usually be heard catching is you run the drive in and out by hand.

4. The clutch output from the computer is faulty and did drop the voltage when it went to standby.

5. Not sure about the current (your) model course computers, but the earlier ones used to switch the 0Volt line and leave the clutch coil at 12 (24) Volts. If the clutch and the drive have a short to ground then the clutch will stay in. Unusual and will result in a live rudder and severe electrolysis!!

6. The drive is not running straight when mounted, can be caused by a frozen joint at either end of the unit, it should articulat freely left/right/up/down at the back and the ball joint should be free.

Be very wary until you find the fault!!

There are probably a few other posibilities, but these were the favourite ones when I worked at R.......e some years ago (ex service manager).
 
Re: Autopilot failure leading to jammed steering on \"Standby\"

There are a few possibilities:

1. The drive has some crap in it that is causing the ball screw to jam. We used o see this from time to time and is not always easy to find. Can sometimes be felt by pulling the ram in and out slowly.

2. The ball screw has a damaged ball(s) and is causing a lock up. Usually recurs regularly and easy to find. Not normal on a low usage unit unless it has been abused.

3. The clutch is dragging or not releasing properly. Can usually be heard catching is you run the drive in and out by hand.

4. The clutch output from the computer is faulty and did drop the voltage when it went to standby.

5. Not sure about the current (your) model course computers, but the earlier ones used to switch the 0Volt line and leave the clutch coil at 12 (24) Volts. If the clutch and the drive have a short to ground then the clutch will stay in. Unusual and will result in a live rudder and severe electrolysis!!

6. The drive is not running straight when mounted, can be caused by a frozen joint at either end of the unit, it should articulat freely left/right/up/down at the back and the ball joint should be free. Also check it is not touching anything else!!

Be very wary until you find the fault!!

There are probably a few other posibilities, but these were the favourite ones when I worked at R.......e some years ago (ex service manager).
 
Re: Autopilot failure leading to jammed steering on \"Standby\"

I had a similar problem with my type-1 linear drive a few weeks ago.

Our delivery passage from Cornwall to S. Holland had been almost entirely under engine (5 hrs sailing in 5 days) in flat seas and almost entirely under autopilot. At the beginning of our cruise through the Dutch canals and waterways, the steering was felt to be stiff but still usable. I was unable to find any obvious cause so I lubricated a few places and kept my eye on it. SWMBO was especially critical of how stiff it felt.

Before venturing out into the North Sea, it was clear that I needed to get a better idea of the cause of the problem. A more thorough investigation quickly identified the drive unit as the culprit. I called Raymarine in Portsmouth before dismantling it, to get some idea of the options and possible problems. They emailed me (via the KJMC harbourmaster in Den Helder) a copy of the service manual.

With the unit dismantled, the problem was less obvious that it might have been. The clutch coil is fitted on a central shaft arrangement (a sort of barrel) that is spring loaded. When energised, the clutch coil part is attracted to the plate and thus pulls out from the casing against the spring. It is guided, and prevented from turning, by two pins in the casting which locate in grooves in the body of the coil part. When de-energised, the clutch unit (should) spring back towards the casing and away from the clutch plate. In my case it was stuck in the operating position.

I found two possible causes: (1) friction on the locating pins – there was some sign of wear/unfairness; (2) the coil coming away from the central, spring-loaded shaft.

Concerning (2), let me explain that I was able, without too much force, to pull the clutch coil unit completely off this (brass-looking) shaft. There did not appear to be anything to stop this from being possible. The unit was disassembled very carefully and I'm sure that there was no worn part, such as a lip on the shaft, which had come off. The exploded diagram in the service manual does not make it clear how this barrel is supposed to be attached to the coil unit. I plan to have a really good look at it this winter.

Anyway, after cleaning up and lubricating the locating pins, the unit seemed to function properly and I could not induce it to fail again. It worked fine for the rest of our cruise, both in operation and on standby.

Note that in our case this failure only made the steering heavy, not unusable. Being a long-keeler, Tadorna does not need lots of rudder input so it was less of an issue than it might be in some boats.

Hope this helps,
Alan.
 
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