B & G Autopilot computer with Alpha 3000 RAM?

[ScottMeilicke]

Long story, but I have a new B&G autopilot computer and compass with chart plotter, and a bad Alpha 3000. I was hoping the drive unit was OK, but after working with Alpha, I think it is dead. The B&G recommendation is a two part hydraulic, and a new mount will need to be constructed. Alpha sells a drop in replacement for my drive unit, and is linear, not hydraulic.

Ideally I would like to buy the Alpha drive unit, a few bolts later and it is installed, then drive it with the B&G computer. Alpha did not recommend it, but that is what I expected them to say. They cannot verify their drive unit will work with all of the computers out there.

My question - 1) will it work to drive a new Alpha 3000 drive unit with the B&G computer? 2) Is this a good idea?

Did I mention we are hoping to get out of here in a week? <sigh>

Thanks for any advice!


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[donradcliffe]

The alpha 3000 drive unit has a rudder position potentiometer installed, which you will have to abandon. If you use the B&G computer you will need to install a B&G rudder feedback unit (if required) and preferably a rate compass. Otherwise, the Alpha drive is just another 12v reversible motor and should work fine with the B&G brain. You will save about an amp over the other drives if you are used to putting up with the Alpha engagement/disengagement system instead of a solenoid valve.

The B&G brain is way smarter than the Alpha 3000, and will drive your boat a lot better.

[colemj]

Do yourself a favor and go the extra bit to install a drive different from the Alpha.

The Raymarine Type 2 linear is very close to the same dimensions as the Alpha, and it costs the same.

You have a very nice AP, and you will regret having to constantly line up the rudder and set/release a mechanical stop every time you want to engage/disengage the AP. Particularly if you plan to use some of the chart plotter control. Yes, this will cost you up to an amp, but you will find it worth that. Otherwise, there is a good chance you will be constantly turning off alarms when the AP detects that it no longer has control of the drive if you don't perfectly synchronize your engage/disengage.

Don is correct that you will need a rudder feedback sensor either way.

Mark

[ScottMeilicke]

Well after doing some research, the Ray marine will not fit in the space that I have. So alpha it is. Spoke with the sales rep, and he offered the caution about burning up the motor if you drive the AP with the mechanical linkage disconnected. I'll have to tie a procedure card around the release mechanism. Or wire it to a mild electrical shock.

I do have the rate compass and rudder feedback unit. Now I just have to figure out how to mount the feedback unit...

Thanks for both of your replies.


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[colemj]

Originally Posted by ScottMeilicke

Spoke with the sales rep, and he offered the caution about burning up the motor if you drive the AP with the mechanical linkage disconnected.

I'm not sure how this is possible. If the linkage was disconnected, the B&G AP will attempt to move the drive unit, not get any feedback that the rudder has turned and immediately fault out with an alarm.

And even if it was possible, I don't see how powering the drive unit without the mechanical linkage connected is any different than powering it with the linkage connected. The drive unit doesn't care if it is under load.

Mark

[ScottMeilicke]

Ah, right. I had forgotten about the rudder feedback. I'll have to see if there is a way to ensure the AP will stop prior to hitting the extension limits of the ram. Limit to -30/+30, when the ram can do -35/+35, for example.


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[skipmac]

Originally Posted by colemj

I don't see how powering the drive unit without the mechanical linkage connected is any different than powering it with the linkage connected. The drive unit doesn't care if it is under load.

Actually, I would speculate the drive would be happier without a load. A lot less work moving the drive rod in and out without a rudder attached.

Originally Posted by colemj

Do yourself a favor and go the extra bit to install a drive different from the Alpha.

The Raymarine Type 2 linear is very close to the same dimensions as the Alpha, and it costs the same.

You have a very nice AP, and you will regret having to constantly line up the rudder and set/release a mechanical stop every time you want to engage/disengage the AP. Particularly if you plan to use some of the chart plotter control. Yes, this will cost you up to an amp, but you will find it worth that. Otherwise, there is a good chance you will be constantly turning off alarms when the AP detects that it no longer has control of the drive if you don't perfectly synchronize your engage/disengage.

Don is correct that you will need a rudder feedback sensor either way.

Mark

I confess I have thought about using the Alpha linear drive just for the power savings. Back when I was cruising my typical AP usage was on a passage where I might not engage/disengage the drive for days. Even coastal cruising usually a few times per day at most so how annoyed would I be with a tedious procedure?

Even if it is a bit of a pain that one amp saving adds up to 24 amp hours per day on a passage. For my current charging setup and capacity that is interesting.

[Saltyhog]

Originally Posted by skipmac

Actually, I would speculate the drive would be happier without a load. A lot less work moving the drive rod in and out without a rudder attached.





I confess I have thought about using the Alpha linear drive just for the power savings. Back when I was cruising my typical AP usage was on a passage where I might not engage/disengage the drive for days. Even coastal cruising usually a few times per day at most so how annoyed would I be with a tedious procedure?

Even if it is a bit of a pain that one amp saving adds up to 24 amp hours per day on a passage. For my current charging setup and capacity that is interesting.

Or you could use an L&S drive with the Ecopilot option. Reduces the daily engagement power from 30AH to 5AH. See here.

[skipmac]

Originally Posted by Saltyhog

Or you could use an L&S drive with the Ecopilot option. Reduces the daily engagement power from 30AH to 5AH. See here.

Hi Salty and thanks for this. Looks interesting but it's for hydraulic drives and I am very strongly leaning towards a mechanical drive. Before this starts an uproar my reasons are:

1. First and more important, the rudder post and area where the AP drive will be installed is directly under the mattress where I will sleep. I have never had a hydraulic drive on any of my APs but I have read numerous comments that the hydraulic drives are noisy.

2. My steering is all mechanical so hydraulic wouldn't integrate into an existing system, eliminating one of the advantages of hydraulic.

3. I have read a number of opinions that hydraulic is more reliable but don't understand how that could be. Hydraulic and mechanical both have motors. Hydraulic adds pump, hoses, valves, etc. Mechanical a couple of gears. Seems like more failure modes possible in hydraulic.

4. Even with a bypass valve on hydraulic I think there will be some additional resistance added to the steering when the hydraulic drive is disengaged.

[colemj]

Originally Posted by skipmac

how annoyed would I be with a tedious procedure?

I don't know, you would have to ask yourself that question.

Originally Posted by skipmac

Looks interesting but it's for hydraulic drives

If I understand it, it is only an electrical device sitting between the AP clutch output and the clutch itself. In effect, a latching relay that pulls the clutch closed and then drops the current to just enough enough to keep the clutch activated.

So it could be connected to any drive unit that uses a clutch. I don't know if that clutch needs to be a solenoid or not.

Our old B&G AP had a similar system built into it, but our new one does not. I think Jeffa also does something similar with their drive clutches.

Mark

[Saltyhog]

Originally Posted by colemj

I don't know, you would have to ask yourself that question.



If I understand it, it is only an electrical device sitting between the AP clutch output and the clutch itself. In effect, a latching relay that pulls the clutch closed and then drops the current to just enough enough to keep the clutch activated.

So it could be connected to any drive unit that uses a clutch. I don't know if that clutch needs to be a solenoid or not.

Our old B&G AP had a similar system built into it, but our new one does not. I think Jeffa also does something similar with their drive clutches.

Mark

I think it's mechanically connected to the bypass valve in the cylinder. IE, I think it interacts with the valve itself. It's not just a latching relay. I think a latching clutch would make sense for electro-mechanical drives like your Raymarine. I guess there is a fail-safe issue however. I believe the L&S part sits inline (electrically) with the solenoid that drives the bypass valve. It switches full on to engage the valve, but then adds resistance once engaged to provide just enough coil current to keep it engaged. They (L&S) used to make another version which was a full on mechanical latch, however they discontinued it because many autopilots would error out when they sensed no current to the engage circuit.

[Suijin]

I'm reviving this thread to get any information from those that have used an Alpha linear drive with a different AP computer. Specifically, I'm installing a B&G NAC-3, with rudder feedback unit and Precision 9 compass.

There are a number of settings in the commissioning procedure (drive engage, transition speed) that I'm wondering how to address as the drive does not have a clutch.

[jamhass]

I drive an Alpha 3000 linear drive with a Ray course computer, no problem. One mod I did do was to add a microswitch to the mechanical disconnect which disables (via relay) the drive motor when it is mechanically disconnected from the tiller arm. Otherwise, the course computer will drive the motor past its stops and damage it, as the computer only knows where the tiller is, not where the drive is.