Powering Hydraulics

sunchaser said:

With our hydraulic pump off the fins do not move in a seaway nor do we pin them. I assume this is the case as liquids are incompressible. That said I will mark them accurately next time to be sure my statement is accurate to the nearest millimeter.

As far as what keeps the cylinder rams from moving when the system is off, I have never torn mine down, but I can only assume the system's valving or internal glands require pressure differential to allow piston travel which is the case in my industrial experience. A leaky or failed hydraulic cylinder requires a rebuild. Air actuated cylinders are a different story as pressure bleeds off under rest.

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Tom, I presume the reason they don't move is the same reason the bucket on a front loader will stay raised when the hydraulics on the tractor are off. In that case, the position of the manual levers on the flow manifold (correct term?) aren't allowing any fluid flow. On stabilizers a three position servo valve with solenoids determine ram movement. Extend, retract and no flow are the options. The solenoids are normally closed so when you power down there is no flow and no movement for the reason you state. On our ABTs hitting the Center button moves the fins to the centered position and 3 way servo valve settles in the no flow position so the ram and the fins don't move. Go into reverse and if you haven't centered already a reverse sensor puts the servo valve into the no flow after centering the fins. If you hit "Restart" you hear a positive pin lock which is held normally open when the system is powered, and that solenoid depowers after centering so the fins cannot move, period.

The only reason I can think of for the fins to be able to move is if the seals in the ram cylinder are allowing bypass, just as the bucket on a front loader will settle with its hydraulic cylinder seals are shot.

Hollywood, how old was the system on the 57 you said would move when depowered and if not pin locked?

Capt.Bill11 said:

Apparently I'm not making myself clear enough for some of you. Of course they auto center when the hydraulics are working. My point was that they have to be manually pinned if the hydralic system is off or if it fails. So you couldn't just turn your Genset off if it powered your fins and be on your merry way.

And no in most cases they will not destroy them selves if you are in reverse if not centered unless you were really backing down hard and fast perhaps.

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Why doesn't the bucket on a front loader fall to the ground when you stop the tractor?

Regarding reverse, I only relate what ABT told me, which I suppose would explain why all systems sold provide for centering driven off a reverse sensor. It's there for some reason I guess.

To answer Delfin: Electric over Hydraulic valves. My tractors all have a brace or stop pin that allows you to lock the bucket in place if you are removing hoses or servicing the hydraulics. If you have a leaking hose the bucket will lower by itself - the fluid must have a way of leaving one side of the ram to move.

Capt.Bill11 said:

The reason fins don't have check valves in them to hydraulic lock them like a davit is because its a safety feature. There can be a tremendous amount of force on the fins if the system is off for what ever reason and the boat is moving through the water or maneuvering.

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Could be wrong, but I thought that eventuality was handled by a small bypass that allowed equalization of the pressure on both sides of the cylinder in the event of unplanned depowering, but was small enough it didn't diminish movement force enough to worry about. Since the fins only move a few inches it's hard to see how pressure could build on a cylinder to cause a blown seal when the cylinder is designed to withstand 3,000 psi as a normal state in any case.

ulysses said:

To answer Delfin: Electric over Hydraulic valves. My tractors all have a brace or stop pin that allows you to lock the bucket in place if you are removing hoses or servicing the hydraulics. If you have a leaking hose the bucket will lower by itself - the fluid must have a way of leaving one side of the ram to move.

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Perhaps, but electric merely does what the manual lever does on the tractor - allows flow from one side of the cylinder to the other.

Delfin said:

Perhaps, but electric merely does what the manual lever does on the tractor - allows flow from one side of the cylinder to the other.

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Yes our ABT's will stay centered with the engine off, the trick is to leave the power on to the system. We used to leave it on at the dock so they were always centered, but one day I touched one of the hydro valves and it was warmer then I liked so we just turn them off once settled into to dock. Although at anchor we leave them one.

Exactly, actually the lever will not even work if there is not electric behind it. The actuator is electrically driven which then operates the valves. There are tractors though where its all manual but those are mostly older. My excavators, back-hoes and doziers are all post 1995. The point being is that unless the fluid has somewhere to go the ram or cylinder will not move. Of course if extreme external pressures (backing full in the case of the stabilizers) are applied they may.
Personally I put up the steadying sail and not worry about the stabilizers.

N4712 said:

Yes our ABT's will stay centered with the engine off, the trick is to leave the power on to the system. We used to leave it on at the dock so they were always centered, but one day I touched one of the hydro valves and it was warmer then I liked so we just turn them off once settled into to dock. Although at anchor we leave them one.

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Do yours have a positive lock, normally held open but which auto closes when power is removed? I think that is the new system as of a few years ago.

Delfin said:

Do yours have a positive lock, normally held open but which auto closes when power is removed? I think that is the new system as of a few years ago.

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Not sure what you mean by a positive lock. Ours also have pins if we want to center them for extended period of time.

N4712 said:

Not sure what you mean by a positive lock. Ours also have pins if we want to center them for extended period of time.

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Do they engage automatically when you power down the system? That is how mine work.

Delfin said:

Do they engage automatically when you power down the system? That is how mine work.

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The first thing that pops up on the little ABT display is Fin Control- All, Port, or STB. If the engine is off the solenoids will open and close accordingly but nothing will happen then a little alarm will display and sound on the controller display.

N4712 said:

The first thing that pops up on the little ABT display is Fin Control- All, Port, or STB. If the engine is off the solenoids will open and close accordingly but nothing will happen then a little alarm will display and sound on the controller display.

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Apparently different than mine. I have Activate, which powers the port and starboard 3 way servo valves, Center, which puts the 3 way into equal pressure on both A and B ports on the cylinder, and Restart, which turns off power to a normally open solenoid that when de-powered, releases a spring loaded locking pin that then engages the fin shaft. So, in a power failure, the locking pin isn't held back and when the fins center, they are locked into place.

As I mentioned above, my understanding is that in a power failure, there is a small port bypass that allows the fins to center by themselves slowly if power is lost. The locking pin will slide into place and the fins will then be positively locked into the centered position. Could be wrong about the bypass, although I think that is how they work.

Delfin said:

Apparently different than mine. I have Activate, which powers the port and starboard 3 way servo valves, Center, which puts the 3 way into equal pressure on both A and B ports on the cylinder, and Restart, which turns off power to a normally open solenoid that when de-powered, releases a spring loaded locking pin that then engages the fin shaft. So, in a power failure, the locking pin isn't held back and when the fins center, they are locked into place.



As I mentioned above, my understanding is that in a power failure, there is a small port bypass that allows the fins to center by themselves slowly if power is lost. The locking pin will slide into place and the fins will then be positively locked into the centered position. Could be wrong about the bypass, although I think that is how they work.

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I have the Activate and center display that also shows the fin travel, but that's after the initial display that asks All, Port, or STB. I don't think I have the restart feature, although I will check the next time I go out. When were your's installed?

My stabilizer pins remain in their drawer awaiting a hydraulic pump failure, removal/disconnect of the ram, a failure of the ram seals or leakage around the external valve block so they can lock the fins in the centered position until repairs are facilitated.

One of the most sophisticated fin setups is what Twisted has on his new vessel. If per chance he is reading this thread a few words on how the fins are doing would be interesting.

Last but not least a comment from the poor worn out OP may be forthcoming.

Delfin said:

Apparently different than mine. I have Activate, which powers the port and starboard 3 way servo valves, Center, which puts the 3 way into equal pressure on both A and B ports on the cylinder, and Restart, which turns off power to a normally open solenoid that when de-powered, releases a spring loaded locking pin that then engages the fin shaft. So, in a power failure, the locking pin isn't held back and when the fins center, they are locked into place.

As I mentioned above, my understanding is that in a power failure, there is a small port bypass that allows the fins to center by themselves slowly if power is lost. The locking pin will slide into place and the fins will then be positively locked into the centered position. Could be wrong about the bypass, although I think that is how they work.

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That is my whole point. When the system is powered down and you are underway or manuvering the fins should/must get locked in center position some how mechanically.

Also if you are underway and the vessel is say rolling how would the fins find center on there own? I guess maybe they would pass center sooner or later and the pin would drop. But they could just get forced over into one offset position and get stuck there.

sunchaser said:

My stabilizer pins remain in their drawer awaiting a hydraulic pump failure, removal/disconnect of the ram, a failure of the ram seals or leakage around the external valve block so they can lock the fins in the centered position until repairs are facilitated.

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Again, that was my point. In the event of a hydraulic failure or if you have to shut the system down while underway the fins should be mechanically pinned in place. I never said you had to pin them under normal operating conditions.

I'm not the OP, but you guys are wearing me out on this topic.

My system works like Delfin's - both the Nordhavn and the Grand Banks. It's no surprise since they are all ABT, and relatively late generation. When I put the stabilizers on my Grand Banks in 2011, the hydraulic locking pins were an option, but all systems were being specified with them. As Delfin has described, it's a spring loaded locking pin that requires hydraulic power to retract/disengage the lock. So the fail-safe state is locked.

As for hydraulic centering/locking vs pin locking, I don't know all the nuances of the designs, but I do know that leak down on hydraulics is quite common. Going back to the loader bucket example, most all buckets will drift down over time. The amount of time varies a lot (look, look, I said "a lot" and not "alot").

I do think there is a mode in the hydraulic control valves where both sides of the cylinder are open so the fin can self-tail as the boat moves forward. I don't know if it's a normal condition or a failure condition, but it's how the fins find center and lock if there has been a failure. For all I know, the valves are all open when de-powered.

What I do know is that I've seen a lot of boats on the hard with droopy fins. When I was putting mine together on the grand banks, at one point I had the lock pins removed and I'm pretty sure I was able to move the fins.

I also think that on the most recent ABTs, there is "Centered" which is hydraulically centered, and "Locked" which had the lock pin engaged. Assuming you have the system tied into your gear shifter, which you are supposed to have, I'm pretty sure the fins actually lock and pin when you go into reverse. I'm pretty sure the ABT application engineer told be that was to protect against the back pressure on the fins causing the relief valve to open allowing the fins to deflect. Because most of the fin is aft of the pivot point, they want to tail when moving forward, and defect when moving backwards, so they need to be locked down pretty tight.

Our Vickers vane pump is direct-coupled to the crankshaft pulley (balancer) on the main and has run like that for the last 34 years.
So I wouldn't be to fussed on the additional complication of a clutch.

We can run the thruster and the windlass simultaneously with the main at idle (700rpm).

Admittedly, the Cat 3406 has a lot of torque, even at idle, but it comes down to getting the design right.

We only installed the hydraulic thruster and windlass because the pump was already there - ex fishing boat. But it still cost a lot (design, Danfoss valve control system, as well as the actual windlass and thruster) and going with 24 volt systems would have been much cheaper.


But having 10hp to pull up the anchor when you've got 80m of chain out is very reassuring and it doesn't get tired. Similarly, using the 10hp thruster for as long as you like without overheating is nice too.

I reckon hydraulics cost about 3 times as much as electrics.

n4712 said:

i have the activate and center display that also shows the fin travel, but that's after the initial display that asks all, port, or stb. I don't think i have the restart feature, although i will check the next time i go out. When were your's installed?

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2007.

twistedtree said:

I'm not the OP, but you guys are wearing me out on this topic.

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I am the OP, and my question was answered long ago. But I have enjoyed the ongoing discussion.

Delfin said:

2007.

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Oh okay, yours are a bit newer. Here's some shots I took today.
First pic is when they are first powered up, second is after I choose which fin/or fins I want to take control of.

N4712 said:

Oh okay, yours are a bit newer. Here's some shots I took today.
First pic is when they are first powered up, second is after I choose which fin/or fins I want to take control of.
View attachment 33785
View attachment 33786

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You have 'Restart' as well. When I hit mine, you can hear the hydraulics deload and the locking pin releasing.

Delfin said:

You have 'Restart' as well. When I hit mine, you can hear the hydraulics deload and the locking pin releasing.

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You have automatic locking pins? Ours locking pins are in a little built in hole meant for them directly next to where the hole is to lock them.

N4712 said:

You have automatic locking pins? Ours locking pins are in a little built in hole meant for them directly next to where the hole is to lock them.

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Right, so you have the older style without the hydraulic/automatic locking pin.

What a great technical thread for those of us with active stabilizers. Some of us, misguided as we may be, enjoy this aspect of TF and keeps us coming back.

It appears that there are some fundamental design differences in stabilizer brands and build year that is causing some confusion, me for one. So with my Wesmar book in hand I will be talking to some of the systems designers at the next Seattle boat show. Fun stuff.

N4712 said:

You have automatic locking pins? Ours locking pins are in a little built in hole meant for them directly next to where the hole is to lock them.

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Yes. I think ours were purchased right after they changed from manual to automatic. Can you adjust the default boat speed to reduce response rate? I find that to be a nice feature. In calm waters I set it at 20 knots and in slop 10 knots. This affects the degree of deflection in response to certain rate of roll.

Delfin said:

Yes. I think ours were purchased right after they changed from manual to automatic. Can you adjust the default boat speed to reduce response rate? I find that to be a nice feature. In calm waters I set it at 20 knots and in slop 10 knots. This affects the degree of deflection in response to certain rate of roll.

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Not sure haven't really played with them. I'll have to go through the menus and see if there is.

N4712 said:

Not sure haven't really played with them. I'll have to go through the menus and see if there is.

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Menu - Speed - up and down arrows to change speed.

Delfin said:

Menu - Speed - up and down arrows to change speed.

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Thanks, going to write that down and check if we have the option.

Delfin said:

Menu - Speed - up and down arrows to change speed.

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I have the same controls as Oliver and you can adjust the speed. I use the speed adjustment like a "gain" control. If you reduce the speed (aka boat's speed), the controller makes the stabilizers work harder.

Very useful when the waves get large enough to be uncomfortable (unless they are following seas, then it makes it worse).