Alternator clutch

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Gunfleet

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Anyone tried fitting a clutch to a boat engine's alternator? I have a 1GM10 and a Lucas alternator, controleld by an adverc. It would be convenient to be able to cut the alternator out mechanically until the engine is warmed up.
 
You could install a switch so that the field is not energized untill you want it. In that case the alternator spins freely, no need for a clutch. Ask Adverc.
Good luck
Theo
 
with a lucas alt you can fit a switch in the warning light circuit to stop it energising if you switch this off when on load nothing will be damaged.Cheap,easy to fit,not much to go wrong and idiot proof. Many small engines are controlled through the oil pressure switch such as in the Perkins engine, this requires a special switch with one contact normally open and a normally closed contact. I trust that this sulution will help solve your suituation.
 
Why would it be convenient to disengage the alternator?
For years I have been starting a 14.5 hp engine on a (2 x 110Ah) battery-bank, with its 70Ah alternator re-charging them under Adverc control: no problems!
Perhaps your set-up has a problem : dying batteries? ; Adverc not correctly wired-in? ; engine compression shot?
Whatever it is, I suggest it would be better to address the problem, rather than resort to a 'solution' which adds complexity and is likely to be temporary because it is not really a solution at all.
I'm sure others in the forum could come up with suggestions for diagnosis.
 
I don\'t think that a clutch is the right way to go...

..since there are now charge controllers that offer a late cut-in facility. A switch COULD be rigged, but there is always the strong possibility of forgetting to switch the energising current back on again when the engine can cope. There are also different sorts of "Smart" controllers on the market which could offer far more features than the one you mention.

Steve Cronin
 
It's a similar set up but the Yanmar is of course slightly under 10HP. I think that's the difference. I just want the choice, charge or not.
 
I have a 1GM (original 7hp version of 1GM10) with a sterling regulator. I have a switch on the regulator bost function so I can select if and when to be charging at high rate. This helps when cold, or when I want all 7hp for moving the boat forward.

This setup is detailed in sterling instructions, maybe ask Adverc if you can do the same?
 
I would certainly avoid installing any sort of mechanical system to isolate the alternator since this is likely to be a future source of problems. A simple switch that cuts out power through the field windings would unload the alternator. As already said by others, Sterling describe just such a system in their installation instructions. If a simple switch is too simple(??!), it would be very easy to design a switching relay with a set time delay.
Morgan
 
Yes, they suggested a switch in the field side. I did that, but then realised the field was fed by the 'ignition' switch too. I don't want to join them up (god knows what effect that would have on the adverc) and I don't want two switches in the field side. Perhaps I'll just have to do that.
 
Depowering the field should remove the looad on the engine however..
in answer to your question I had a friend way back who fitted a 250VAC alternator to his engine which was driven via an airconditioning compressor clutch. Actually again I don't know why he thought it desirable to mechanically disconnect unless he had a drive gear ratio which gave 50 hertz at low engine RPM so when the engine was run at full RPM the alternator would be running at several times its design speed.
The aircon clutch draws about 8 amps so not practical for your installation given that that would waste much of your generated power. good luck olewilll
 
Simple solution...

Assuming you have separate starting and domestic batteries, just start your engine with only the start battery in circuit. Once it's warmed up, switch the domestic battery on too. Starting an engine consumes very little power, so the charging load immediately after starting is low.

Incidentally, most Adverc regulators don't start boosting the charge current until the charge voltage at the battery reaches about 13.5V. That means if your domestic battery is low, the Adverc won't start boosting immediately.
 
Could I suggest a simpler solution? I am not familiar wit the Ardverc wiring details, but I would asssume that, like most smart controllers, it has a main power feed which, if disconnected, allows the alternator to revert to machine sensed mode. If this is the case then insertion of a simple on/off switch in the power feed would allow you to switch off the alternator boost if engine power is urgently needed for something else, e.g. a rapid departure with a cold engine.

I fitted such a switch to my smart controller and, while I haven't yet had to use it in anger, it's reassuring to know that the option is there.
 
I used to (a long time ago) have a second alt mounted to take over if the primary should fail rather than try and get into a hot engine to change stuff. I used an air con clutch to allow the back-up alt to free-wheel when not used. I used to run it periodically to ensure it's continued health.

I had endless trouble with the back-up alt when I ran it.

I was told by a boffin that the magnetic field created by the aircon clutch electromagnet was interfering with the magnetic field created by the stator or rotor (forget which) and that was why it kept packing up.

Is there any merit in that statement, do you think?
 
That\'s not a solution...

That's not a solution, because a heavily discharged domestic battery could still place quite a load on the alternator - with or without the Adverc in operation. The only easy way to reduce the load on the alternator is to take the domestic battery out of circuit.
 
I think it highly unlikely the alternator would be affected by the magnetic field from the clutch. The usual trick is to make the magnetic field a closed circuit ie with the smallest of gaps so it is unlikely the field would be strong external to the clutch. I doubt also becuase of the relatively closed magnetic circuit of the alternaor that any strong field could affect it. No I reckon your problems where just coincidental or from lack of use. The large current requirement for the clutch would have made the standby alternaor value a bit doubtful. ie 8 amps wasted before you start.
Perhaps that drain on the battery caused the problems.
(some alternaors will not get up and charge without a decent charge from the battery providing an initial field. Thhe clutch current coiuld have pulled the battery down to that point. olewill
 
Thanks for your replies, one and all. I think the consensus is my solution ignores the KISS principle! You've given me stuff to think about.
 
Re: That\'s not a solution...

I don't think that's entirely right. I recall an earlier discussion on methods of charging a remote windlass battery, which eventually concluded that charging current with the windlass running would probably not be embarrassingly high provided the engine was kept down to idle speed and a smart controller was not in use. Incidentally, VP recommend 1300 to 1500 (engine) rpm for battery charging with an engine that idles at around 800 rpm.

A machine sensed alternator's output current varies more or less linearly with speed until a maximum value is reached, which is then maintained at all higher speeds. (Incidentally, it is at the "knee point" speed that the cooling fan design is most critical: at higher speeds there is the same heating effect but more cooling air, at lower speeds the heating is reduced, being proportional to the square of the current and hence the square of the speed - unless, of course, you upset the calculations by fitting a smart regulator...)

Of course if the batteries are wired up using a VSR it becomes largely academic, since the domestic battery will be kept disconnected from the alternator until the cranking battery is well charged.
 
Re: That\'s not a solution...

The alternator output curves I've seen certainly aren't linear. During warm-up, a boat engine will typically be running at about 1000rpm, a fast idle. Remember that most alternators are driven at 2 to 3 times crankshaft speed, so at an engine speed of 1000rpm the alternator may be spinning at around 2500rpm. This is well up the output curve on most alternators. As an example, my Prestolite 90A alternator produces 55A at 2500 alternator rpm, and absorbs 2hp. The Prestolite 65A alternator produces 50A at 2500 alternator rpm, and will also absorb about 2hp. With Gunfleet's 9hp engine, disconnecting the domestic battery until the engine's warmed up is the simplest and most effective solution.

Incidentally, you seem to misunderstand the function of a VSR. The purpose of a VSR isn't to prioritise charging of the starting battery, it's to ensure that the domestic loads can't discharge the starting battery when the engine isn't running. A VSR won't keep the domestic battery "disconnected from the alternator until the cranking battery is well charged" - it will connect very quickly because so little power is used to start an engine that the cranking battery will exceed the VSR operating voltage almost immediately. Once connected, the batteries will share the available charging current according to their needs.
 
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