The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: roadrocket on 13.07. 2012 19:13

Title: Is my dynamo still not polarized right?
Post by: roadrocket 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

Title: Re: Is my dynamo still not polarized right?
Post by: chaterlea25 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
Title: Re: Is my dynamo still not polarized right?
Post by: roadrocket 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
Title: Re: Is my dynamo still not polarized right?
Post by: bsa-bill 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
Title: Re: Is my dynamo still not polarized right?
Post by: beezermacc 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.
Title: Re: Is my dynamo still not polarized right?
Post by: KiwiGF 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.
Title: Re: Is my dynamo still not polarized right?
Post by: duTch 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
Title: Re: Is my dynamo still not polarized right?
Post by: roadrocket 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
Title: Re: Is my dynamo still not polarized right?
Post by: duTch 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
 
Title: Re: Is my dynamo still not polarized right?
Post by: roadrocket on 14.07. 2012 21:45
Yes it's a 12 V conversion, armature and field coil suited for this.
Title: Re: Is my dynamo still not polarized right?
Post by: sparx 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.
Title: Re: Is my dynamo still not polarized right?
Post by: warmshed 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.
Title: Re: Is my dynamo still not polarized right?
Post by: duTch 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
Title: Re: Is my dynamo still not polarized right?
Post by: roadrocket 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
Title: Re: Is my dynamo still not polarized right?
Post by: duTch 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
 
Title: Re: Is my dynamo still not polarized right?
Post by: roadrocket on 29.07. 2012 20:46
Hi Dutch
I ordered a Dyno Tech from Sean Hawker. I have had two Danish ones, one which I fried out of stupidity (switching field and dynamo...), and the current one which act up, though I have been very careful not make the same mistake again.

Cheers, Otto
Title: Re: Is my dynamo still not polarized right?
Post by: duTch on 30.07. 2012 00:19
Ok Otto,good luck with it cheers

  Afterthought here, correct me if I read it wrong, you said you had the volt meter connected to the D+F bridged, and I may be guessing a bit here, but the way I see it, 'D' output is not regulated, so maybe that's why your output is high.
Playing with mine yesterday, I had 2 Volt meters, one on the battery which gave I think about 7+, and another on the 'D' which went to over 9v, but  the literature suggests 'don't go over 10v', so am thinking this is acceptable as it's unregulated, as opposed to the 'A' terminal ...??
Maybe someone already covered all that though??


 
Title: Re: Is my dynamo still not polarized right?
Post by: KiwiGF on 30.07. 2012 12:53
Hi Dutch, I'm pretty certain the reg controls the field current not armature current and by controlling the field current it controls the armature voltage and current. If the voltage on the battery gets too high the reg reduces the volts/power it's supplying to the field and so on.

Bridging the armature and field connections and spinning the armature as a test causes the armature to pass current through the field (assuming there is some residual magnetism in the field to start things off) and this increases the magnetism in the field to abive its residual level which increase the power generated by the armature which further increases the magnetism in the field and so on, so this test will lead to spiralling up voltages  - if you see what I mean!

Title: Re: Is my dynamo still not polarized right?
Post by: duTch on 31.07. 2012 00:50
Hi Kiwi,
           You're probably right there, but first let me reiterate that I'm fairly much a novice at regulators, and what I say is as much a question as otherwise.
             I'm sure you're right in what you say, but I did say " 'A' terminal' meaning the ammeter (not armature), and with the volt meter on 'D'  was with the reg in circuit,(as opposed to voltage on D+F bridged, reg out of circuit).  (sorry just re-read your post )
       I understand as you say the 'D' feeds 'F' feeds 'D'..., in a continuing upward voltage spiral till melting point(hence- 'don't go over 10v')?
 So if I have a slightly higher voltage at 'D' I'm imagining that the regulator needs to be adjusted down a bit with the spring adjusting screw to (? 7.2v~?)...?
     Regulator is a new ~replica RB107, sold as a MCR2, and all my testing is on the bench with drill drive, so am trying to wait till it's in place before adjusting anything.

  Hope I'm not Hijacking Ottos' thread, but it is related.

   Cheers and thanks for the input, hope I got all that in right perspective?, duTch
 
Title: Re: Is my dynamo still not polarized right?
Post by: warmshed on 31.07. 2012 08:48
The voltage at D (output from the dynamo) should be the same or very close to the voltage at the A (ammeter) that you are measuring, once the dynamo output exceeds the battery voltage.   The voltage form the D terminal passes through the regulator contacts ( which should be closed once the voltage exceeds the battery voltage) and the series winding which should be low resistance and therefore no give any significant voltdrop.
Title: Re: Is my dynamo still not polarized right?
Post by: duTch on 31.07. 2012 12:47
Thanks Warmshed, appreciate that, I think we're on the same page, but'll have to process that again a little later, will have to get back in regulator mode, my Thunder'nLightning conrods turned up today , so am in that phase for now..cheers,duTch