Hydraulic systems

[Selidster]

I’m close to a new to me KK42 with Naiad stabilization. I’ve worked with a lot of hydraulic equipment in my life and am wondering why if there is hydraulics on the boat why wouldn’t the thrusters and windlass utilize the hydraulics as well? Seems the hard part is done with the pump mounted and oil tank.

 

[twistedtree]

I’m close to a new to me KK42 with Naiad stabilization. I’ve worked with a lot of hydraulic equipment in my life and am wondering why if there is hydraulics on the boat why wouldn’t the thrusters and windlass utilize the hydraulics as well? Seems the hard part is done with the pump mounted and oil tank.

It's typically about the power requirements. It takes much less power to run stabilizers than to run a thruster or windlass. Stabilizers also typically run at about 1500 psi, and thrusters & windlasses at 3000 psi. So it ends up being a much higher capacity hydraulic system.

 

[Comodave]

And when you would be using thrusters the engine is usually about idle speed so not as much fluid being pumped.

 

[lwarden]

My thruster is hydraulic and is supplied by a flow compensating pump on the Stbd engine. The pump has variable displacement pistons which are controlled by a demand line feeding from the valve system. When any item (thruster, windlass, pot puller, steering, etc.) is activated, the volume and pressure increase to supply the needed function. Even at idle the pump can supply enough volume to run the thruster or windlass. This setup ensures that when no demand is put on the system there is also very little load on the engine, so it's more efficient as well.

 

[Selidster]

Nice to hear someone has a variable flow pump working. I have used variable flow pumps in the past. Swash plate piston pumps in conjunction with accumulators. They can run a lot of items without issue. And the variable pumps are amazing. I didn’t realize the pressure differences between the Naiad stabilizers and the windlass and thrusters. But that could be handled with pressure control valves. It’s still interesting to me I’ll continue to look into it. Thanks for the responses.

 

[lwarden]

Here is a picture of the Eaton variable displacement pump attached to the PTO on the TwinDisc transmission. I'm a mechanical engineer but pretty new to hydraulics. I'm really enjoying learning all about these systems and tinkering with them a bit. Whomever setup this system on my boat really knew their stuff.

 

[Selidster]

That’s a really nice install. I won’t have a pto on the transmission. The current pump is mounted on the front of the crankshaft. But it’s an A mount so changing the pump is the least of the challenges.

 

[Greg QS]

My boat is set up with westmar fins. I have 2 pumps one on each engine. I do have Thrusters stern and aft and windlass that work on the system. My system has a pressure gauge and it only seems to be 400 psi. system. Plenty of thruster power. The thrusters are even proportional. The system is tied into a joystick so maneuvering at the dock is simplified. Its been a learning curve but much easier than working sticks, throttles, and thrusters individually.

 

[twistedtree]

My boat is set up with westmar fins. I have 2 pumps one on each engine. I do have Thrusters stern and aft and windlass that work on the system. My system has a pressure gauge and it only seems to be 400 psi. system. Plenty of thruster power. The thrusters are even proportional. The system is tied into a joystick so maneuvering at the dock is simplified. Its been a learning curve but much easier than working sticks, throttles, and thrusters individually.

I suspect that gauge is reading the pilot pressure, or perhaps it's broken?


And I think fixed displacement pumps are only used with smaller, stabilizer-only hydraulic system. Otherwise the pumps are variable displacement.

 

[Arthurc]

I went through this on my k54 which had two pumps, a main pump for the bow thruster and a second pump for the stabilizers. Depending on your setup you might not have enough room to get a large variable pump in front of the engine, I did not. The other consideration as I talked to folks was new dc bow thrusters are much much better than past ones, I’ve now put sidepower proportional control thrusters bow and stern in and love them. I’ve tested for 3 minutes at full power and neither cut out. The down side is you need two more battery banks but it allowed me to rip a lot of hydraulics out that were taking up a lot of space.
I’m glad I moved to DC thrusters and kept my stabilizers as a dedicated small system, it simplified things mechanically and in case of a failure everything is isolated. Not to mention having to turn on the engine to adjust the chain would make a hydraulic windlass irritating imo (but I’ve never had one).

 

[sunchaser]

Yes AC

On anything less than say 15 kW DC power works great and is less a maintenance issue. You’ve never enjoyed boat cleanup until you’ve swamped out the aftermath of a bow thruster hydraulic hose rupture.