Clutched 12v alternator

[Speedwheel]

Does such a thing exist with a manual clutch?

 

Thanks

[Bee]

Not that I know of but probably not too difficult to set up with a loose belt and a tensioning wheel on a lever, should be some useful bits down the scrapyard, timing belt tensioners and the like.

[Timleech]

Does such a thing exist with a manual clutch?

 

Thanks

 

Never heard of such a thing.

Best bet would be to fit an electric clutch from a car aircon compressor. Lots of those secondhand on fleabay. I might have a spare one if you want one.

 

 

Edit - why?

 

Tim

Edited March 15, 2014 by Timleech

[MoominPapa]

Why do you want to clutch it? If it's to unload the engine for starting or similar, then just interrupting the field circuit will have the same effect.

 

MP.

[Speedwheel]

Edit - why?

 

Well, I've had a (probably stupid) idea.

 

Currently on Tycho there is a Dynamo system which does work but only puts out 5-10 amps max, usually less and I have a couple of quite big batteries on there.

 

Also I've been looking at how I can attach that Parsons pump today and there doesn't appear to be space.

 

I would like to have something that can push a bit more power into the batteries, but I don't want to remove the dynamo, and also run the pump. In one of the barns here there is an old saw bench rusting away with an old lister in it (about 4hp I think). You can see where this is going........

 

The main problem is where I would put such a contraption. Do I really need a bed?

[by'eck]

Why do you want to clutch it? If it's to unload the engine for starting or similar, then just interrupting the field circuit will have the same effect.

 

MP.

 

Piston engined aircraft work on that principle since there is no ignition switch (magneto ignition). There is often a split rocker switch controlling Battery Master isolator on the left and Alternator field on the right. After starting engine you operate the latter to bring the alternator on line whilst checking for charge current on the ammeter (times two if its a twin).

 

 

Well, I've had a (probably stupid) idea.

 

Currently on Tycho there is a Dynamo system which does work but only puts out 5-10 amps max, usually less and I have a couple of quite big batteries on there.

 

Also I've been looking at how I can attach that Parsons pump today and there doesn't appear to be space.

 

I would like to have something that can push a bit more power into the batteries, but I don't want to remove the dynamo, and also run the pump. In one of the barns here there is an old saw bench rusting away with an old lister in it (about 4hp I think). You can see where this is going........

 

The main problem is where I would put such a contraption. Do I really need a bed?

 

Not sure why you would want a mechanical clutch since an engine alternator already has an electrical one - its own regulator. When there is no current demand from the batteries it effectively shuts down the field. This happens one one of my two when the main bank is fully charged to the extent that its warning light comes on.

Edited March 16, 2014 by by'eck

[kris88]

I've got a little lister with an alternator on (brilliant thing.) Anyway I start this with no load,then connect the load (batteries to charge.)

[Speedwheel]

Ahh right. So can I run it with no batteries attached without doing damage to the alternator? My concern was that if I ran it without a load then I might damage it but maybe I misunderstood?

 

Thanks

[Timleech]

Ahh right. So can I run it with no batteries attached without doing damage to the alternator? My concern was that if I ran it without a load then I might damage it but maybe I misunderstood?

 

Thanks

 

The biggest danger is disconnecting the load when charging. There's little risk in connecting when running, but as has been said having the field disconnected, and connecting when ready, is a much better solution.

 

Tim

[by'eck]

Ahh right. So can I run it with no batteries attached without doing damage to the alternator? My concern was that if I ran it without a load then I might damage it but maybe I misunderstood?

 

Thanks

 

As long as there was no field current yes.

[Speedwheel]

 

As long as there was no field current yes.

 

Many thanks.

[ditchcrawler]

 

As long as there was no field current yes.

And the only way I can see that you ensure that is the case is to open the end of the alternator and put a a witch in the field connection wire. Even with no battery connected you can still get self excitation with an inbuilt regulator.

My 24 volt alternator relies on self excitation and only starts charging at about 600rpm engine speed, so I can start the engine on no load and take it up to fast tick over if required before hitting it with the charging load in the morning.

[Timleech]

And the only way I can see that you ensure that is the case is to open the end of the alternator and put a witch in the field connection wire. Even with no battery connected you can still get self excitation with an inbuilt regulator.

My 24 volt alternator relies on self excitation and only starts charging at about 600rpm engine speed, so I can start the engine on no load and take it up to fast tick over if required before hitting it with the charging load in the morning.

 

I know some people reckon anything electrical is akin to sorcery...

 

Tim

[ditchcrawler]

 

I know some people reckon anything electrical is akin to sorcery...

 

Tim

Well I ant going back to correct the spell

[kris88]

Electrickery in fact

[BEngo]

Fortunately it doesn't much matter. If a totally open circuit alternator is run-up and does self excite the process is, in electronic terms, very slow and the regulator will regulate fast enough to maintain the terminal voltage pretty much at the regulated setting. If the alternator is the subsequently connected to a load the regulator can manage that too, albeit there is likely to be a bit of a dip in the output voltage till it catches up. If however an on-load alternator has the main output open-circuited the regulator is rarely able to shut down fast enough and the resulting voltage spike will probably seriously upset the alternator diodes.

 

 

N

[Sir Nibble]

Put a switch from alternator D+ to negative and the field will be collapsed to unload the alternator.