Author Topic: Is my dynamo still not polarized right?  (Read 3007 times)

Offline roadrocket

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Is my dynamo still not polarized right?
« on: 13.07. 2012 19:13 »
Hello All!

I have at long last assembled my RR lookalike after a crash two years ago. I have even managed to get the carburettor right, which took a while. But I still have charging troubles. I rebuilt the dynamo with new armature and new brushes. I had the electronic charge control thingy checked. I had the dynamo checked. I put the dynamo on the bike, connected all the wires, and charged the battery. I have lights, and the ammeter shows disharge as it should. But when the bike is running no charge is seen on the ammeter. I have connected a multimeter on the voltmeter function directly on the battery poles - only a solid discharge when the lights are on and the bike running - nothing happens when revs are increased. I have checked the dynamo on the bike by connecting D and F wires, and putting the voltmeter between it and battery positive (earth). This shows an increasing output to over 20 volts (I put the meter on the 200 V scale and it went on to 25 volts). But this reading was negative! So am I right in concluding that the dynamo is not polarized right for positive earth? I put the probes on with red positive to red positive on the battery and black negative to the connected D and F wires. I have tried to polarise the dynamo as per the Lucas workshop instructions, by disconnecting the output wires on the dynamo, and briefly connecting F to positive on the battery. This changed nothing.

So, I'm afraid I have toasted yet another expensive charge regulator, or is it clear that my dynamo is still not polarized right, since I get the negative reading on the voltmeter? I assume that correct polarity is necessary to get a charge?

All answers welcomed with thanks!

Regards, Otto in Denmark

Otto in Denmark

Online chaterlea25

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Re: Is my dynamo still not polarized right?
« Reply #1 on: 13.07. 2012 20:18 »
Hi Otto,
Your post is somewhat confusing *conf*
To polarize the dynamo on a positive earth system you need to flash the field to the negative side of the battery
Yes your connection of the volt meter is correct, live is negative.
Connect a 20 watt 12 volt bulb from the D&F bridge connection to earth (+) it should light brightly, rev the engine and the bulb should blow,
The other day I wired up an electronic reg and found no charge , I polarised the dynamo again but still no joy ???? ????
Finally I flashed the F connection to the battery live (-) while the engine was running, and it started charging
 *smile* *smile* *smile*
I have no idea how this worked?? but it did *ex*

HTH
John O R
1961 Super Rocket
1963 RGS (ongoing)

Offline roadrocket

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Re: Is my dynamo still not polarized right?
« Reply #2 on: 13.07. 2012 20:45 »
Hi John

Thanks, but according to this Lucas instruction: http://classicrider.dk/dokuments/Lucas/1953%20Lucas%20Dynamos%20E3L%20E3LM%20E3N[2].pdf
you have to flash F to battery positive for a positive earth circuit. This is rather crucial, and both statements can't be right??? My hope is of course that my reg is still OK, and that I need to polarise the dynamo somehow, and all will be well.

Cheers, Otto
Otto in Denmark

Online bsa-bill

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Re: Is my dynamo still not polarized right?
« Reply #3 on: 13.07. 2012 22:07 »
John has it Otto, you have to impart a small charge into the dynamo, you can't do this from the positive side of the battery because that is the earthed side (same as dynamo body)
so from the live (negative) side of the battery connect a wire (or use existing lead) and momentarily touch the F connection
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline beezermacc

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Re: Is my dynamo still not polarized right?
« Reply #4 on: 13.07. 2012 23:51 »
You may have seen Beezageeza's thread about charging problems. The route to the solution is to run the charging system in isolation until you have sourced the problem. You definitely need to flash the negative lead of the battery onto the F terminal then test the dynamo in isolation. If it's charging correctly connect the regulator and battery and measure the voltage at the battery with the bike running at about 1500 - 2000 r.p.m. It should rise up to about 7.2v then hold steady.
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk

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Re: Is my dynamo still not polarized right?
« Reply #5 on: 14.07. 2012 01:10 »
Hi roadrocket, as per the previous posts the way to remember how to flash the field coil is that you want some "residual" magnetism left in the coils core, which is to say you want to pass some current through it in the same direction as current would flow if it was charging normally, this would then leave a residual magnetism in the right "polarity".

When charging normally in your case the regulator will provide (regulated) current from the negative terminal of the battery which will pass through the field coil to earth, your earth is of course connected to the positive terminal of the battery, which completes the circuit.

There are ways to check if your regulator is the probable source of the problem, without buying another one, you can for example bypass the regulator altogether and pass some current through the field coil and then check if the dynamo will charge the battery.
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Offline duTch

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Re: Is my dynamo still not polarized right?
« Reply #6 on: 14.07. 2012 10:02 »
Correct me if I'm wrong or missed something, but this is assuming that the field coil wires are properly connected, as are the armature/brush connections??
  cheers, duTch
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline roadrocket

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Re: Is my dynamo still not polarized right?
« Reply #7 on: 14.07. 2012 10:29 »
Hooray! I hooked everything up, preparing to flash the field coil as per John's syggetions, and when the bike was runinng the voltmeter showed charge! Revving the bike the charge rose to 15 volts and 12,34 at idle with no lights on. I hope cut-off at 15 volts are in order, but I guess the regulator is working, since it does cut off. Well I didn't do anything other than described above, which did not work initially, but I guess a bike can do with a good nights sleep as well as us...

Thanks for all input!

Otto in Denmark
Otto in Denmark

Offline duTch

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Re: Is my dynamo still not polarized right?
« Reply #8 on: 14.07. 2012 10:46 »
Again,and I'm no expert, but unless I'm mistaken doesn't 15 volts sound a bit high, unless you've had it wired for 12 Volts, to which I can't see a reference??

Cheers duTch
 
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline roadrocket

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Re: Is my dynamo still not polarized right?
« Reply #9 on: 14.07. 2012 21:45 »
Yes it's a 12 V conversion, armature and field coil suited for this.
Otto in Denmark

Offline sparx

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Re: Is my dynamo still not polarized right?
« Reply #10 on: 24.07. 2012 00:30 »
15v is a bit on the high side, it should be around the 14.2v to 14.4v mark with a charged battery and no loads switched on. That extra 0.6v may not sound much, but it's enough to cause battery problems.
Dave
Peterborough (UK)

Offline warmshed

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Re: Is my dynamo still not polarized right?
« Reply #11 on: 29.07. 2012 09:19 »
Roadrocket.  To clear up the discrepancy, the Lucas service sheet says that they supply dynamos ready polarized for +ve earth.  It goes on to say that if you need to repolarize for -ve earth.  It then tells you how to do this, ie flash F terminal to +ve side of the battery.   I think this is where you went wrong.  Its badly worded.

Offline duTch

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Re: Is my dynamo still not polarized right?
« Reply #12 on: 29.07. 2012 10:29 »
Yes Warmy,
            I agree it can get confusing, I've been reading those sheets forwards and backwards, and also the relevant posts, for the last few days and there's a few(minor but very important) things that need to be carefully read.
  As per my reply to your other post double check everything, as I'm still sussing this all out myself.
                Cheers, duTch
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline roadrocket

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Re: Is my dynamo still not polarized right?
« Reply #13 on: 29.07. 2012 12:45 »
I am running positive ground, and have done the polarizing as you suggest, but no real luck. I installed a new battery as the old one turned out to have lost a cell. I thought I had cracked it, but no - it was showing 8 v when I returned from the test ride, and the ammter did show discharge - except for a brief period where I had lots of charge showing on the ammeter. This has prompted me to order a new regulator. The dynamo motors fine ind the right direction, and delivers more than 20 v when bridging field and dynamo and connecting a voltmeter from here to ground.

Otto in Denmark
Otto in Denmark

Offline duTch

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Re: Is my dynamo still not polarized right?
« Reply #14 on: 29.07. 2012 14:26 »
Otto,
      I'm interested in the issue, but not the right person to comment, but have I think learned a few things over the last few days from different angles(enough to be a bit more dangerous than before), and as I've had a variety of results on mine- mostly ok I think- but I'm following progress intently(that doesn't mean I'm camping out either...!). What reg have you gone for this time? I'm a bit of a stickler for the mechanical rigs as I can see what's going on,
 Ciao fer now duTch
 
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia