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Old 16-03-2009, 13:22   #1
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Auto Pilot Clutch question

Currently I am running a B&G Below Deck Auto Pilot. The ram is directly connected to the quadrant. This is on a catamaran with 2 rudders and all the associated cable and linkage and the helm pressure is higher than I want while hand steering. The current system has considerably more drag because of the always connected ram piston. When you manually disconnect the ram the steering is much lighter. I know on some race boats they use a clutch to remotely disconnect the ram for better feel when hand steering. Does anyone know of an off the shelf clutch that will work on B&G and how complicated the installation would be?

Thx, Jim
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Old 16-03-2009, 13:54   #2
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Hmm, we have about the same system on mono-hull: chain&wire from 2 wheels to quadrant and hydraulic ram to quadrant for AP. We disengage the AP with a manual valve that "shortcuts" the hydraulic circuit and are quite happy with it. I can't move the rudder by hand while this valve isn't opened.

I also see systems where the AP itself will control a solenoid-valve to do what our manual valve does. I guess that is what you have? You would want to check that the (solenoid)valve has at least the same internal diameter than the hoses for minimum resistance.

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Old 16-03-2009, 13:54   #3
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The Alpha Pilot used to come with a special quadrant that would disconnect. It used a Morse cable and T handle. They might still be around, they were a few years ago, although they dont advertise etc....
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Old 16-03-2009, 14:39   #4
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Thanks for the replies. B&G type 2 ram combines the motor, pump and hydraulic cylinder into one unit so there is no externally run hydraulic lines or other provision for installing a valve that I can think of. I was thinking it would require a mechanical disconnect either actuated manually like Cheechako was describing or automatically with a servo of some sort like some others I have heard of. The search continues...

Jim
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Old 16-03-2009, 16:56   #5
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Here ya go.....

It looks like Alpha Marine is still in business quietly selling the best AP ever made! My friends is something like 22 years old... Alpha Marine Systems - 3000 General Information
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Old 16-03-2009, 17:09   #6
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Are you sure that there is no clutch/solenoid built in to your unit? How many wires are connected to the ram unit? The motor drive wires will attach directly to the motor but there should be 2 wires going to a clutch assembly in front of the motor/pump assembly.
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Old 16-03-2009, 18:38   #7
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B&G has a solenoid on the hydraulic ram to bypass the pump and make the ram easier to move when the autopilot is disengaged. Try to move the steering with the solenoid energized and de-energized to see if it is doing its job.

See http://www.bandg.com/upload/B&G/Docu.../newhpilot.pdf
about p 89.
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Old 16-03-2009, 20:41   #8
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Jedi, Deep and Don you are correct. I was not clear in my description. There is a solenoid that allows the fluid to by-pass and the ram to move freely. Otherwise it would be impossible to hand steer. However this is different than the clutch. When the ram is connected there is a great deal of residual friction left over. I assume this is from the piston drag and viscous fluid squishing through the by-pass. When the ram arm is physically disconnected there is a huge reduction in the friction. I guess this is why some race boats I remember being on used clutches to disconnect the ram completely. There is better tactile feedback. It may seem trivial in my case but with twin rudders and all the associated linkage it is like driving a bus without power steering when the ram is connected. No fun. I rarely hand steer anymore because of it.
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Old 16-03-2009, 22:03   #9
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I believe the only Autopilots with an electric clutch on the ram are the Raymarine (formerly Autohelm). It may have expired, but I believe they had a patent on this function. The fact that it disengages almost completely (very little friction) when off without having to make a mechanical disconnect like with the Alpha.
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Old 16-03-2009, 22:08   #10
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Jim,

Okay, I agree about friction of the piston moving the fluid around but you obviously have much more of that than I. I don't think I would notice it when ram was taken off the quadrant. I have tried the difference during maintenance and did feel it.. I think, but only by comparing it within minutes. If you give the wheel a spin, will it keep turning when you let go or stop?

I think I have 3/8" ID lines so friction might be more if yours are smaller diameter? I can't tell you.

There might be something wrong with the unit, like bent piston/shaft, degraded fluid etc. I would suggest you drain the unit and try it empty with the lines open. Put new fluid in etc.

cheers,
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Old 16-03-2009, 22:10   #11
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Ray: I wouldn't know what you mean with electric clutch. Isn't a clutch something that allows/stops something from turning? What's turning?

ciao!
Nick.
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Old 16-03-2009, 22:22   #12
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You are right. I have had the unit apart a few times. It is a friction clutch that is engaged by an electromagnet when energized. This is in a mechanical linear drive unit. This thread seem to be about a hydraulic unit.
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Old 16-03-2009, 22:45   #13
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Ray: ah ;-) yep those are different and I know you had to open it up to replace the nylon gear, right? Replace it with a bronze one!

cheers,
Nick.
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