Autopilot Hydraulic Ram Bypass

[Dockhead]

I'm having a bit of trouble with my autopilot.

I have just upgraded all my electronics to N2K, all B&G/Simrad. The only thing I left in place was the Raymarine autopilot drive, consisting of a reversible pump just replaced last year, and a big hydraulic ram on my quadrant, Raymarine Type III, if I'm not mistaken.

The new Simrad autopilot computer at first didn't want to play with the Raymarine stuff. When I tried to do the dockside commissioning, the computer puked. I called Simrad tech support, and they said I needed a relay for the "clutch" (actually, an electrohydraulic bypass valve). OoooKaaaaay -- although I only measured 2 amps of current, well within the specs. I duly installed the relay, and it all worked -- successfully commissioned, successful sea trials (so cool the way the Simrad pilot experiments and analyzes the rudder response), then successfully used for the first passage.

The second time out, the pilot flipped off -- "rudder response error". The bypass valve was not closing. The pilot would switch on, but the wheel would still turn freely. Multiple attempts; multiple failures.

The third time out, it all worked again, including wind vane steering. Exciting because the the Simrad pilot has a completely different style from the previous Raymarine -- seems to steer better with less rudder action, as if it can anticipate the motion of the boat. Very cool. It also has a very aggressive dodge function -- press +10 or -10, and the boat goes right over. I am anticipating that this is one really great pilot.

But -- the bypass valve is not working right. What can it be? It is 10 years old, after all, but it would really be a coincidence if it started to fail just at the same moment as I attempted to marry it to a new pilot computer.

How do these things work? Does anyone know? A small (2 amp) 24v current is applied which closes the bypass valve, thus locking the quadrant to the ram, right? Aren't they all the same? Or is there some inherent incompatibility between the Raymarine ram and bypass valve, and the Simrad computer, that no one in tech support of either company wants to talk about?

Anyone have any insight?

[colemj]

Are you sure the "rudder response error" is not due to an error in the rudder indicator reading and not the clutch? Is the ram moving, or otherwise engaged (clutched) when you get this error? Didn't you earlier have a problem with the rudder indicator?

Even 2 amps at 24V seems like a lot of current for a bypass valve engagement. Our B&G hydraulic ram took <1 amp at 9V to engage. Maybe the clutch solenoid is going bad? We had to replace ours on the B&G drive. The symptoms were randomly disengaging (or not engaging at all) and a rudder response error. Usually, this is an easy fix as the solenoid is external to the actual valve components - just pull off the solenoid coil and replace with new. I used a coil off a spare propane solenoid for a whole year until we were able to get a "proper" B&G solenoid.

Mark

[george123]

I installed the Simrad autopilot AC42,AP28,RF300 and the Raymarine type III M81202. The pump was connected directly to the pump connections on the AC42 computer. The clutch on the ram assembly was connected tot the clutch terminals on the AC42 computer. It worked fine. I did have a problem with adjusting the rudder reference. Make sure you install it per the instructions.

George

[Dockhead]

Originally Posted by colemj

Are you sure the "rudder response error" is not due to an error in the rudder indicator reading and not the clutch? Is the ram moving, or otherwise engaged (clutched) when you get this error? Didn't you earlier have a problem with the rudder indicator?

Even 2 amps at 24V seems like a lot of current for a bypass valve engagement. Our B&G hydraulic ram took <1 amp at 9V to engage. Maybe the clutch solenoid is going bad? We had to replace ours on the B&G drive. The symptoms were randomly disengaging (or not engaging at all) and a rudder response error. Usually, this is an easy fix as the solenoid is external to the actual valve components - just pull off the solenoid coil and replace with new. I used a coil off a spare propane solenoid for a whole year until we were able to get a "proper" B&G solenoid.

Mark

Yes, when I get the error, the "clutch" is not engaged and the wheel turns freely.

No, the rudder reference (a new Simrad unit) is working fine. I'm getting rudder order and angle data on the network with no problems. The problem is that the bypass valve is not closing and so the pilot cannot turn the quadrant by operating the pump.

If the bypass valve and/or solenoid are inexpensive, I might just change them out to be sure. It seems like an odd coincidence that it would have worked flawlessly all this time then suddenly fail just when I install a new pilot computer, but can't be excluded.

Meanwhile I have just added the diode and rewired everything carefully. I'll give it another try -- maybe it will be working ok now.

[Dockhead]

Originally Posted by george123

I installed the Simrad autopilot AC42,AP28,RF300 and the Raymarine type III M81202. The pump was connected directly to the pump connections on the AC42 computer. The clutch on the ram assembly was connected tot the clutch terminals on the AC42 computer. It worked fine. I did have a problem with adjusting the rudder reference. Make sure you install it per the instructions.

George

That's somewhat alarming. My setup, which is almost exactly like yours, would absolutely not work with the clutch connected directly to the AC42. Simrad tech support told me I needed a relay, which is what I installed, after which it started to work, mostly.

I wonder why the difference? Maybe really my solenoid is going bad?

I installed my RF300 precisely according to the instructions, and have had no trouble with it.

[colemj]

Originally Posted by Dockhead

It seems like an odd coincidence that it would have worked flawlessly all this time then suddenly fail just when I install a new pilot computer, but can't be excluded.

Ours worked flawlessly until I installed a new membrane in our watermaker, then it suddenly failed. Odd coincidence?

Actually, one key point that I didn't make clearly is that ours failed intermittently for quite a while until it failed completely. It would steer the boat for days, then suddenly drop out for a while (always at night in rougher weather), then work fine. Then it would go bad for a long period, but work flawlessly after I did things like reset and recommission the AP, change wiring, etc - leading me to believe I fixed it. It drove me nuts trying to troubleshoot the problem.

Try to find out what the solenoid clutch current should be. 2A at 24V (48W) seems high to me. Maybe measure the resistance through the coil?

Mark

[Dockhead]

Originally Posted by colemj

Ours worked flawlessly until I installed a new membrane in our watermaker, then it suddenly failed. Odd coincidence?

Actually, one key point that I didn't make clearly is that ours failed intermittently for quite a while until it failed completely. It would steer the boat for days, then suddenly drop out for a while (always at night in rougher weather), then work fine. Then it would go bad for a long period, but work flawlessly after I did things like reset and recommission the AP, change wiring, etc - leading me to believe I fixed it. It drove me nuts trying to troubleshoot the problem.

Try to find out what the solenoid clutch current should be. 2A at 24V (48W) seems high to me. Maybe measure the resistance through the coil?

Mark

So it was your bypass valve, or solenoid, which failed?

I didn't know they were prone to failure; sounds like it would be prudent to acquire spares in any case.

I have just redone all of the wiring, and have installed the diode. I have engaged and disengaged it a couple of dozen times, and it seems to be working now.

But I think I'll order spares, in case I've got the same situation you had.

Thanks a lot for the advice.

P.S. can't check the current now, since I dropped my lovely Radio Shack (Sinometer) DC clamp meter into the Medina River from the masthead last week . I'll do it when the replacement arrives.

I guess excess current could be a sign that it is failing.

[colemj]

The problem was the solenoid coil. The bypass valve is simply an internal..uh..valve, that is actuated electromechanically by an external energized solenoid coil. Just like that on propane tank installations. The coil is replaceable - takes 3 minutes - a bit longer if you need to recrimp wires.

Yours could be different. The only picture I have of what I think is your unit is a line drawing that seems to indicate that the solenoid coil is external and removable.

The coil itself can fail, although it is not "prone to failure". A spare could be carried, but they do last a decade or more between failures. Like I said, ours failed after 13 years and we got by for almost a year using a coil off a spare propane solenoid valve.

I think your solenoid is drawing too much current and may be failing. It is less likely that Simrad's AP provides less clutch current than Raymarine's, and unlikely that Raymarine sells their gear unable to work together without aftermarket, user-installed kludges like relays, etc. The Simrad AP will provide 3A of clutch current and even this amount for a solenoid clutch is a whopper amount of power - it would be red-hot drawing that (touch your engaged <1A draw propane solenoid to see what I mean). If you are drawing more than this, something is wrong with the solenoid/bypass.

Mark

[Dockhead]

Originally Posted by colemj

The problem was the solenoid coil. The bypass valve is simply an internal..uh..valve, that is actuated electromechanically by an external energized solenoid coil. Just like that on propane tank installations. The coil is replaceable - takes 3 minutes - a bit longer if you need to recrimp wires.

Yours could be different. The only picture I have of what I think is your unit is a line drawing that seems to indicate that the solenoid coil is external and removable.

The coil itself can fail, although it is not "prone to failure". A spare could be carried, but they do last a decade or more between failures. Like I said, ours failed after 13 years and we got by for almost a year using a coil off a spare propane solenoid valve.

I think your solenoid is drawing too much current and may be failing. It is less likely that Simrad's AP provides less clutch current than Raymarine's, and unlikely that Raymarine sells their gear unable to work together without aftermarket, user-installed kludges like relays, etc. The Simrad AP will provide 3A of clutch current and even this amount for a solenoid clutch is a whopper amount of power - it would be red-hot drawing that (touch your engaged <1A draw propane solenoid to see what I mean). If you are drawing more than this, something is wrong with the solenoid/bypass.

Mark

OK, thanks for that. Sounds logical. The ram and bypass valve/solenoid are the LAST remaining parts of the original installation, and so 11 or 12 years old. I changed the pump last year.

Would be a shame if all the time and money I spent on installing that relay (as per Simrad tech support instructions) turns out to have been a waste.

I'll order one of those solenoids to have on board.

At the moment, everything seems to be working ok.

[donradcliffe]

If it makes you feel any better, I installed a new Simrad linear hydraulic drive in Hawaii and it came with a dodgy solenoid. It worked well enough on my shakedown sail from Oahu to Kauai, but crapped out the first night of my sail back to California. Fortunately I had the old drive aboard and was able to change the solenoid and valve at sea.

[Dockhead]

Originally Posted by donradcliffe

If it makes you feel any better, I installed a new Simrad linear hydraulic drive in Hawaii and it came with a dodgy solenoid. It worked well enough on my shakedown sail from Oahu to Kauai, but crapped out the first night of my sail back to California. Fortunately I had the old drive aboard and was able to change the solenoid and valve at sea.

Misery loves company, but . . .

Yet another failure-prone component on board Where does it end?

[brianb00]

Hi Dockhead,
I design & use autopilots. Most of the recent AP's clutch circuit use a technique that reduces the clutch current & power once it is engaged. They essentially lower the voltage to the clutch coil (they use a PWM signal). You have used a relay with the RM clutch. It is possible, and your symptoms seem to fit, that the relay drop out voltage is above the level that Simrad circuit was designed for. One symptom that may show up, does the failure occur when the engine is running, IE when batteries are charging ? If so this would tend to confirm the problem as during charging, from any charge source, your 12 volt system is propbably at 14 volts. Also, it could be excited when the AP is dealing with more aggressive conditions as the AP motor will pull the system voltage down during hard steering. Lets assume this is the case. Try running very heavy wire directly to the AP from the battery and eliminate all intermediate things like breakers/switch's/fuses(with exception of AP internal fuse). [this is a temporary measure].

If you have an oscilloscope you could look at the system voltage (12V) at the AP terminals and see how much voltage drop you get in use pushing large loads.

Other fixes could involve a large capacitor, say 20,000 uf, installed right at the AP power terminals.

Then again maybe my guess it totally off but I have seen similar issues on an NKE unit and this really was not the NKE but the less than adequate drive to the clutch due to a misunderstanding of operation.

BB

[fchurtic]

Thank you Brian for your response to the previous post. I have a slightly different problem. I upgraded my Autopilot pilot unit from a B&G ACP2 to an H5000 sysyem. I kept my Hydraulic unit in place, an original B&G blue ram at 24v All works well but I feel that the resistance on the wheel has become stronger, And therefore sailing a bit less natural. I was wondering whether the clutch system is actually different between the two pilots. Is the clutch system just an on and off switch, or is it a gradual system? Could this be the cause of the extra resistance ?

Another possible culprit could be the rudder feedback unit. The new one is the simrad 300, but this will sound strange to me

Thank you for your help

[brianb00]

Originally Posted by fchurtic

Thank you Brian for your response to the previous post. I have a slightly different problem. I upgraded my Autopilot pilot unit from a B&G ACP2 to an H5000 sysyem. I kept my Hydraulic unit in place, an original B&G blue ram at 24v All works well but I feel that the resistance on the wheel has become stronger, And therefore sailing a bit less natural. I was wondering whether the clutch system is actually different between the two pilots. Is the clutch system just an on and off switch, or is it a gradual system? Could this be the cause of the extra resistance ?

Another possible culprit could be the rudder feedback unit. The new one is the simrad 300, but this will sound strange to me

Thank you for your help

The clutch is all or nothing. A valve is opened all the way. The rudder sensor makes no sense. It has no load. It is a simple variable resistor. Is it possible something else, like something in the link from your wheel ?
Brian

[fchurtic]

Will check, Thanks