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Old 16-05-2018, 05:29   #1
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B&G course computer with old Alpha ram

So I bought a new B&G Nac-3 course computer when my Alpha control box (calling it a computer would be too generous) died, and have finally gotten around to installing it. I'm having a dealer install it so that I get the warranty (they said they had to at least review the install for B&G to honor the warranty), but they are balking at using the Alpha mechanical ram drive and trying to sell me a B&G T2 drive.

Their reasoning is that the Alpha is a low power unit, using a small motor, which was connected with to power with 18 gauge wire (looked more like 14 to me, need to check it again). I'm not sure why this is an issue unless the Nac-3 could somehow supply too much juice to the ram. They also maintain that if the ram jams that it could "burn up the transistors in the computer." This seems like a bunch of hooey to me. There must be some fault protection that would prevent this as otherwise it would be a risk with any ram, since the only connection between them is +/-.

While I'd like to have some of the features of a new ram (a clutch instead of manual tiller arm engagement, etc.) and expect to update it at some point, the T2 is around $2k and it's going to take considerable modification of the mount and the tiller arm to fit it.

Alpha rams are famously efficient and robust. I know others have used this combination successfully. if it works I'd like to use it in the short term, but I don't want to "blow up" the Nac-2 along the way.

So my questions comes down to this. Is there any risk to the B&G Nac-2 in using it with the Alpha ram? Is there risk to the ram? There is a B&G (Simrad) rudder feedback unit installed.

Thanks to anyone with some expertise on this.
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Old 16-05-2018, 08:07   #2
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Re: B&G course computer with old Alpha ram

You would need to know the locked rotor amperage of the Alpha Ram to know if it will overload the transistors. But your fuse should be sized below the locked rotor amperage.

Do you have a NAC-2 or NAC-3?
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Old 16-05-2018, 10:02   #3
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Re: B&G course computer with old Alpha ram

Oops I see I said Nac-2 and Nac-3 in my post. It's a NAC-3 with a 30amp fuse. Thank you KeelMe that is very useful information.

This is data on the entire Alpha system from the specs:

POWER REQUIREMENTS

Input Voltage 12-14.5VDC

Input Current 15amps max. 2-3amps typical cruising on a well balanced, well sailed vessel.


So sounds like a 12 amp fuse would be prudent and would protect the NAC-3? Are there any other considerations/concerns if I go down this route?
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Old 16-05-2018, 10:48   #4
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Re: B&G course computer with old Alpha ram

If the installers are stating that there are limits to the output current of the controller ask them to put an inline fuse on the output circuit between controller and linear actuator to protect the controller and see what they say.
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Old 16-05-2018, 11:30   #5
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Re: B&G course computer with old Alpha ram

I have no personal experience, but I don’t see a problem using the Alpha drive.

A more powerful course computer should not cause a problem with a smaller drive.

Manufacturers tend to get very defensive when mixing and matching equipment. It is a common problem.

There is a view that just want to sell their products, and I think there is element of truth in this statement, but in their defence they have no idea what the requirement of third party products may be. Therefore, it is reasonable they state it is up to consumer to check suitability.
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Old 16-05-2018, 12:01   #6
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Re: B&G course computer with old Alpha ram

I purchased an NAC-3 (Simrad version but identical) for my boat and am using it with the old Raymarine linear drive. I spoke with Simrad tech support several times to get information on the max current output from the NAC-3 clutch output and in the course of the discussion mentioned using the Raymarine drive. That drew no comment at all about any potential problem with the NAC-3 drive output but they wanted me to use a relay between the clutch output of the NAC and the clutch of the Raymarine drive, supposedly to protech the NAC clutch output from overload which I did but think it's totally unnecessary.

Also no mention about the warranty and I did the entire install myself.
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Old 16-05-2018, 17:40   #7
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Re: B&G course computer with old Alpha ram

OK thanks guys. I'm on the fence right now about just swapping it out or putting the old ram back in. The modifications for the new one are not insignificant (need to cut a new keyway in the tiller arm, build a new platform etc.) and make a crowded space even more of a tangle. That said, the convenience of having an electric push button clutch does have it's attractions.

And while I know I'm getting the upsell I do think he's concerned about what he doesn't know and putting his name on it. He also had a good point, which is Alpha is slowly going out of business and they are not the most pleasant people to deal with, so why not bite the bullet and install gear that is compatible with increased functionality.
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Old 17-05-2018, 07:49   #8
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Re: B&G course computer with old Alpha ram

I use a Ray course computer with an Alpha ram. Works great.

Main issue is that the CC does not "know" where the ram is, only where the tiller arm is. This is because of the mechanical disconnect of the Alpha ram. If the ram is disconnected and the CC energized, it can drive the ram to (and past) its limits.

Solution is to add a switch to the mechanical disconnect dog that disconnects the electrical to the ram when it is disconnected from the tiller arm. Very easy to do, and saves lots of angst.

The Ray CC has a Sleep mode circuit that does a similar function, but it takes a looong time for the CC to wake up, so not a perfect solution. Perhaps your CC has a similar feature you can use.
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