The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: mikeb on 13.12. 2014 08:41

Title: my '61 BSA super rocket is negative earth... really?
Post by: mikeb on 13.12. 2014 08:41
Hello
my first post...
I've just bought a 61 SR which is said to have been off the road for while and has a very old dead 6V exide battery (includes white lumps on the inside). Weird thing is the earth wire to frame (checked by my multimeter) is red but goes to the negative battery terminal. So i removed the battery and added a 6v power source and when the power negative goes to frame and the lights are on then the amp meter shows current drawn (like -ve amps, draining) - hence confirming its negative earth... right?
All I've seen on the forums is they are positive earth. but there are wiring diagrams around also showing negative earth. would someone actually bother to change the polarity from +ve to -ve earth? before I put in the new battery I'd like to be sure i get it in the right way around.

BTW is it safe to run without a battery? Its not running yet tho maybe soon i could test polarity by getting it running and measuring with a volt meter

Any advice? 

thanks

Mike
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: duTch on 13.12. 2014 09:36

 G'day Mike, yeah could well be positive earth to frame- I'm actually in the midst of a battery issue, and seriously considering a change to -ve Earth to frame (or otherwise)...not that I care if it's + or -, but personally to save confusion.

  So long as you know what is going on, and everything is connected appropriately I think it's nothing other than a matter of choice and polarizing- but allow those more knowledgeable (geez that spellin' took a few goes), than I to get it right....

 Where you at..??
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: Triton Thrasher on 13.12. 2014 13:54
Polarity is up to you.

+ earth is original, some people change it to -.

You can run without a battery, if you want. Some say it burns the regulator contacts, but I've never seen that happen.
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: muskrat on 13.12. 2014 22:49
G'day Mike,  *welcome* to the forum.
As both duTch and TT said it doesn't matter much ass long ass you flash the dynamo. Use the search on the left, next to Home Help Search for flash dynamo. Also the same for battery, there's a few discussions going on.
Go to Bikes Pictures & Members start a new post and tell us about yourself and bike.
Cheers
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: duTch on 14.12. 2014 00:16

 I'm also having another thought as to whether or not the brushes /'D'/'F' configuration changes.....for change of polarity...?? I'm sure I can find that with some research .......or think about it..??

 I think I want to change to -ve earth, just for simplicity, and uhoh-I just realized I already said that..... *conf*
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: Triton Thrasher on 14.12. 2014 02:30
Wires don't change for change of polarity.

Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: mikeb on 14.12. 2014 03:29
thanks for the replies.
ok so increasingly looking like negative earth.
I've got the bike running (!!) without a battery but its not generating any voltage at the battery leads. So I can't test polarity this way and may have other problems.
is this likely to be the revs are too low? is there a cut-it point for the regulator?
looks like i may be reading up some other threads re the generator or regulator

any tips appreciated!

cheers

Mike
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: beezermacc on 14.12. 2014 09:19
The first thing to do is check what is coming out of your dynamo, i.e. voltage and +/- earth. The two leads connected to the dynamo are usually yellow (D) and green (F). If you twist these two leads together so that you are connecting the two terminals together and connect a 12v bulb to the joint where the leads are twisted together and the other side of the bulb to earth, start the bike you should get a healthy glow from the bulb. The dynamo can deliver 20v. so don't rev the bike. If the dynamo is producing a charge you can test the output with a multimeter to find if it is +ve or -ve earth or you can determine which way you want the dynamo to deliver by 'flashing' the 'F' terminal with your selected live lead off a battery.
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: duTch on 14.12. 2014 10:00

 
Quote
Wires don't change for change of polarity.

 TT, if that's for my benefit, I'm not that friggin' dumb- I said ...'...brushes /'D'/'F' configuration changes'...maybe I just had a moment, but at least I gave it consideration....didn't think my English was that bad, sorry!

 I think B-Macc has answered the call- so it's that simple as I would've otherwise expected, just change the polarity of the FLASH,(software) but not any wiring 'configuration' (hardware).?? how about the amps guage- no, I'm ok to work that out myself...if I get stuck, I'll holla.....!!

 My dumb sounding questions are as much for the benefit of any future similar inquisitions (FAQ's).....*beer*

Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: Triton Thrasher on 14.12. 2014 13:24
OK brush and field connections don't change when you change polarity.

Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: bsa-bill on 14.12. 2014 13:49
Strange old day today
I just read a Dutch fella from New Zealand and a Scot discussing the intricacies of the English language, now me being a pretty died in the wool adopted Geordie like (like is obligatory at the end of any Geordie speak like) I don't feel I could add much of use but as I look out my living room window for inspiration a double decker red bus passes by, we are four miles from the nearest bus service, (the last bus service that passed anywhere near here was phased out in the sixties).
This has little to do with  mikeb's problem (sorry Mike) unless Red double deckers had positive earth systems, but it's is email so careful how you read it

Sandwich and a cuppa then off back to the shed where sanity will be restored
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: RichardL on 14.12. 2014 16:34
If you were also curious...

From separate research and through the forum, I've known about flashing a non-working dynamo, or one in need of polarity change, for some time. What I just admitted to myself was that I didn't understand what magnet was being magnetized, since the dynamo doesn't really have a dedicated permanent magnet. After more research, I now see that the soft iron pole pieces in the centers of the field coils (which also hold the field coils in place) serve as weak permanent magnets that control the direction of the very small current flow from the armature just as the dynamo begins to spin. Once spinning, part (I think it's just "part") of the generated current is sent back through the field coil. This intensifies the strength of the magnetic field through the field pole piece, hence increasing the current generated through the armature until equilibrium is reached for a given engine speed. The routing of generated current through the field coils keeps their iron pole pieces weakly magnetized after the dynamo stops spinning, therefore, maintaining polarization for + or - earth.

More specialized forum members (I could name a few, including posters to this thread) could probably explain this better or in more depth. I just hadn't seen this magnet issue explained, so I thought I'd throw it out there.

Finally, just for reference, in case someone is about to flash their dynamo, I thought this was a really clear set of instructions: http://www.dynamoregulatorconversions.com/polarising-a-dynamo.php

Richard L.
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: bsa-bill on 14.12. 2014 16:53
Thanks for that Richard, one of those things I just accepted without wondering too much about how a coil held a residual charge, just assumed it was kind of like those can things
(scuse the techno talk)
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: groily on 14.12. 2014 17:50
This is also regarded as a useful and 'bookmarkable' place by many people in the parallel universe of AMC machinery  . . . http://matchlessclueless.com/electrical/lucas/testing-lucas-dynamo/#reading

and this is my simplified  take on it  . . . with apologies to those who know this stuff better than I do anyway. An important point being that D gives everything (rather than part of itself) to F at pre-cut-in rpm.

There are five stages in a system comprising a (two brush) dynamo and voltage regulator: Static (ie dynamo at rest); excitation; avalanche; unregulated charging; and regulated charging.

With the engine stopped (static stage)
1. The cut-out is open.
The battery can not permanently be connected to the dynamo. If it were, it would try to make it turn like a motor.  So, in ‘FADE’ terminology, wire A (to ammeter, switch and battery) is only connected to D when the cut-out is shut. A and D are never connected at rest or at low dynamo rpm.
2. The contacts on the voltage regulator are closed. So D is connected to F through the voltage regulator contacts. Their default position is ‘Shut’. When the revs are high enough for voltage regulation to be required the connection switches off and on rapidly - but at rest and low- to mid-rpm the contacts are closed firmly.

The ammeter shows nothing because Nothing’s Happening unless you've left the lights on.

From Start-up to Cut-in (excitation and avalanche stages)
The dynamo starts by turning slowly.
The dynamo’s body contains a small amount of residual or remanent magnetism from the last time it ran (Richard's point). The armature is therefore turning in a very  weak magnetic field.
The armature uses that weak field in the initial ‘excitation’ phase to produce a very small amount (like ½ a volt) between D and E.
This very small amount is fed from the D terminal straight back to F the field through the closed points on the voltage regulator.
With the extra electro-magnetism now available in the field, power builds up fast at D. This is the ‘avalanche’ phase.
 
The dynamo is working away now, but nothing’s yet showing on the ammeter. That happens when the voltage being supplied from D becomes greater than the battery voltage already present at A. At that moment, the cut-out closes. D and A are now connected. Power from D is now allowed out to play.
So D, F and A are now connected – F  to D through the still-closed regulator contacts, D to A through the now-closed cut-out. Because the ammeter is in the A line to the battery, we can now start to see what’s happening for real. This is the end of the ‘avalanche’ and the start of a phase of unregulated charging.

As Dynamo rpm gradually increase in this unregulated stage, so does the power generated by the armature.
D is connected to A as we’ve seen ( via the cut-out) and always has been to F (voltage regulator contacts).
The system voltage rises a little but not much – the battery, a chunky resistor now in play, prevents that (even when it’s state of charge is low) - so the voltage into the field doesn’t increase much and nor does the power it is consuming.
The system’s working fine, but at this intermediate stage the voltage is still not being regulated (D is connected to F solidly by those points on the regulator).
But it gets closer to needing to be regulated with every extra engine/dynamo rpm, as the voltage rises.

As Dynamo rpm rise further (regulated stage)  . . .
With D, A and F all still firmly connected, voltage has risen to the point where the voltage regulator says ‘Enough, I’m at my pre-set limit, and I’m going to start regulating’. We’ve arrived (probably around 1800-2000 engine rpm ) at the regulated phase.

(In reality it all happens darn fast – a mere blip of the throttle gets you through most of this in the blink of an eye.)
 
The voltage regulator is pre-set to prevent D from feeding the field with more current than is necessary for it to enable D to support it (the field) and the electrical needs of the machine at that moment (A). F’s feeding programme and other calls on the dynamo all depend on what’s switched on – and the state of charge of the battery.
If F isn’t overfed, then D can’t overproduce and fry itself or anything else; if F isn’t underfed, then D will produce enough to balance the load and maintain the battery.
The trick is in making sure that F is adequately fed when the electrical load requires lots of support and/or the battery needs a charge, and is not overfed when the load is light and the battery only needs a trickle to keep it up.

How does the regulator regulate?
When it cries ‘Enough’, those voltage regulator contact-breaker points open for the first time so far and F is disconnected from D (and therefore from A).
Immediately, the current to the field drops, so the armature’s output drops and so the current from A to the battery also obviously drops. So does the voltage. A split second later the control box decides the voltage is no longer excessive after all, countermands the order, and the regulator closes and reconnects F to D and A. Next instance the cycle repeats – too high a voltage - disconnection. Then, the voltage drops – reconnection. And so on and so forth, depending on revs and load. The contact-breaker is now in ‘trembling’ mode and we’re regulating.

It’s the relative amount of time the regulator points stay shut versus open that determines the average voltage at A. The higher the proportion of time the points are open the lower the voltage, and vice-versa. Thus the voltage at A is maintained at about what it should be to avoid overcharging the battery, to trickle-charge it once it’s fully-charged and to protect any electrical components that are in use from blowing.

As dynamo revs drop off (or as the electrical load increases to the point that the dynamo can’t sustain the prescribed regulation voltage) the regulator switch stops trembling and closes to let the full output from D go to F once again. D and A remain connected through the cut-out. The dynamo is running unregulated once more.

As the revs drop off even further, the point will be reached where the cut-out senses that the battery needs to be disconnected – and opens to prevent the battery trying to drive the dynamo as a motor.
A is disconnected from D, while D and F remain fully connected at the regulator.

This is precisely where we started.

Cheers, Bill
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: RichardL on 14.12. 2014 18:41
Groily (being one of those names I could think of),

Great post. I must confess that I plagiarized one sentence in my post from a different matchlessclueless page. Specifically, "equilibrium is reached for a given engine speed. " http://matchlessclueless.com/electrical/lucas/repolarising-lucas-dynamo/
I would have gotten away with it until you stepped in.  *smile* *smile*

Richard L.
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: bsa-bill on 14.12. 2014 19:07
I'll have to read that a time or two before it sticks groily but a great post

as old Joe had to invent something to do all that it's no wonder he advised us not to venture out after dark  ;)
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: duTch on 14.12. 2014 19:29

 Ok TT, thanks....um B-Bill       *whistle*

Quote
Strange old day today
I just read a Dutch fella from New Zealand and a Scot d

 Who's the Dutch guy frum UnZeelund.....???   *fight*.... maybe Mikeb..??.....my Granpa was a real Scott Scot (but not the GREAT Scott)who went there...

      TBC
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: bsa-bill on 14.12. 2014 20:16
Oh No !! I'm seeing more stars than I should now as well as big red buses.
Apologies to however many nations I've managed to insult
I do need to hang in to this thread though, I've just got the battery and wiring to sort on the Flash now and it's done, I've had trouble sorting this harness out previously and got to  do it again, beats me how such a simple wiring diagram can lead to a harness with so many surplus, additional and wrongly coloured wires, and the little paper labels I put on the last time have faded so I can't read them, no remarks re Specsavers please
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: RichardL on 14.12. 2014 20:25
B-Bill,

Not saying that I would automatically know any better how the harness goes in, but I'd enjoy helping to suss it out over, say, three beers. You just happen to be a bit far away to hop on over.

Richard L.
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: bsa-bill on 14.12. 2014 20:34
Appreciate the thought Richard, think the three beers sounds good.
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: duTch on 14.12. 2014 23:25

 Well  *beer*(x3x2- each one comes as a pair ) all 'round I say, and especially for Groily for that epic story.... now that I had a chance to read it...a bit easier to take in than the explanation in the Lucas book. ...Richard your point was kinda what I was too lazy/didn't have time to make- well mainly just regarding the polarity of thefield magnet thanks
  Could be wrong, but I think I figured there's a couple of different configurations of connecting the brush wires to the 'F ' / 'D ' To produce the same result and same for opposite (think direction of motoring)....?
 Groily- ¿is 'remanent' the same as 'remnant'..?
 B-Bill, there's one of those buses truckin' 'round my area lately too. ... *beer*
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: groily on 15.12. 2014 06:51
Ha! Well same origin probably, but remanent just means residual in this case Dutch, a hangover from the last time it ran.

You're not wrong in raising the dynamo wiring configuration, but a standard Lucas will have one end of the field coil to earth, t'other to F terminal, one brush to earth and t'other brush to D. Which end of the field is to earth, which to F (and which brush to D and E), determines direction of rotation; swapping one or the other reverses it. Swapping field leads AND brushes would bring you back to where you started.

Miller dynamos and most 'continental' ones aren't the same (and also have an additional resistor winding that can be confused with the field coil), and some Lucas will have been modified to 'Miller' spec to accept some types of electronic regulators, JG in particular, which regulate on the opposite side. (Because you can regulate on the earth or the live side of things.)

But if a dynamo is wired as standard, no problem. You then just choose your direction of rotation and polarity, both of which I always confirm for myself by motoring them with a battery (for positive earth, batt negative to F and D joined together, positive battery terminal to dynamo body). And then away she should go, if she's going to that is! Cheers.
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: mikeb on 15.12. 2014 08:46
groily that was a helpful post and dutch thanks for defending the honour of our respective nations. side question - how do you get those little flags in your post's footers?

ok so but back to the first question: as the plot thickens maybe you can tell me this -
- if the regulator is really an easier place to disconnect the dynamo wires then I'm assuming i have to pry open the case - its an RB108 and from what I've read the wires are soldered in.... true?
- or can i just get the cover off the back of the dynamo and disconnect and test it there?

I'm hoping this is just a case of an unused bike's dynamo needing reflashing. new battery arrives tomorrow.

cheers

Mike
Mod edit: Like that one down there!
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: groily on 15.12. 2014 09:05
I'd have thought it would be easier to disconnect D and F at the dynamo. Have you got external plugs on a bakelite end cover and steel strap, or is there a one-piece metal cover with the wires plugged in on the inside? In the former case, undo the little screw on the kidney-shaped bit on the outsdie (if it's still there the way Lucas intended) and pull out the 2 wires; in the latter, just undo the central cover screw, remove the cover being careful with the wires and the grommet, and all will be revealed. Then you can do your tests.
Can't recall whether on RB108s things are soldered or plugged in (can't even remember the Lucas numbers for the different versions!) - as I haven't messed with a mechanical regulator for years, preferring ManorMike's DVR2, as do quite a lot of us. It's as likely the regulator is the cause of any problems as it is that the dynamo is misbehaving to be honest - but for setting up the regulator properly if that's the problem area, you need to wait until Trevinoz or some other resident mechanical regulator expert comes along! Cheers.
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: mikeb on 15.12. 2014 09:10
thanks groily. i'll have a look at that tomorrow and see how far i get
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: bsa-bill on 15.12. 2014 09:19
Quote
Have you got external plugs on a bakelite end cover and steel strap, or is there a one-piece metal cover with the wires plugged in on the inside?

Daft question coming

I don't suppose for 1 minute these are exchangeable, really don't like that strap affair, it's the type on my RGF so it doesn't really matter for originality just have had some issues with corrosion on the wires and so forth
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: duTch on 15.12. 2014 09:59
 Not so daft B-Bill, I have the latter one piece jobbie, but I have a feeling there is a minor difference to do with an 'O' ring and also a locating kind of lump/notch...I have one of each will have a looksee.....only thing is, with my recent dilemma, I did note that the bakelite/strap cover has a bit more room for wires to not engage with the cover and rub/wear/short-circuit/blowup.....and if the joint is at the bottom for drainage, is at least a step up...and I shall now recommend some rubber inside for wire protection

 Thanks Mikeb, but I was more making sure B-Bill wasn't calling me a Kiwi- no offense, but I went into a cold sweat when my Ma informed me at age about 30, that I was almost born such..... *eek*   she was a born Aussie but when they left UnZud to go to Scootlun, they left her Bro there (turned out, he later became my uncle) maybe they didn't like him or he missed the boat-dunno.....but when she married my Dad, wanted him to go live there- nuhuh noway getfar***f***off.....he was stayin' home after being in all the wartorn places.....
 

 And TT...for the record, what you suggested about wires changing polarity is usually the kinda crap thing I'd say.....!! *smile*


Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: Triton Thrasher on 15.12. 2014 12:04

And TT...for the record, what you suggested about wires changing polarity is usually the kinda crap thing I'd say.....!! *smile*

This?

Wires don't change for change of polarity.

I find it to be true. Changing a dynamo's polarity doesn't involve changes to wiring.
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: u28909z on 15.12. 2014 12:21
It is possible to swap the strap type end cover for the one piece metal one. Just need to file down a small locating boss from the end housing, and replace or modify the brush plate, as the wires should now plug into this internally. The later brush plates are available but cost £20-30 to buy new.

I have modified one myself, altering the old brush plate was the tricky bit.

There are pictures of the brush plates on some of the dynamo specialists sites.

Arthur 
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: bsa-bill on 15.12. 2014 12:28
Thanks for that Arthur

got it copied to my "bike bits and bobs" document
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: trevinoz on 15.12. 2014 20:20
Actually the whole end is different, cover, brush plate and end bracket.
The end bracket has a groove around the circumference for an O ring.
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: duTch on 15.12. 2014 21:39
 *red* *red*
  Geez TT-  My Apologies. ...I must've had another dyslexic moment. ...I read that as something like 'Wire polarity doesn't change for change of polarity.'...Now I'll just pull both feet outta my gob and put them back in my boots but leave the socks in place+ Richards green 'Cone of Silence'...

       *shh*
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: Triton Thrasher on 15.12. 2014 22:09

Is it fixed yet?
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: mikeb on 18.12. 2014 08:29
not fixed yet. its a metal end cap. i flashed the dynamo field coil (F=green, both F and D disconnected from the wiring) and now when joining F and D there's about 0.25v coming out at about 1500rpm engine speed.
I'm now reading up the threads on dynamos (which is turning).

mike
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: Triton Thrasher on 18.12. 2014 10:46
Something that has worked for me is to run the engine at about 2,000 rpm with F and D connected together on the terminal of a headlight bulb and the base of the bulb earthed to frame. If they do not light the bulb, then briefly connect battery live to your F and D.

Battery earth side must, of course be connected to frame.

That wakes up a dynamo that has forgotten its polarity.

Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: wilko on 18.12. 2014 20:31
Are you double sure you're spinning it the right way? Also I did this test recently and got about 2volts.After much headscratching I tried another drill with a faster speed and suddenly lots of volts.
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: duTch on 18.12. 2014 21:30

 
Quote
It is possible to swap the strap type end cover for the one piece metal one. Just need to file down a small locating boss from the end housing, 

  Haven't got around to looking at the different bits yet, work's interfering with life- but maybe I've hybridized one with a lug/boss and 'O' ring, and I seem to recall rather than grinding a lug off, I decided it better to carve a corresponding notch in the cover with the dremel. ..
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: mikeb on 19.12. 2014 04:08
ok so flashing the dynamo the 'usual' way achieved nothing for me. What did work is  triton thrasher's trick of wiring a 12v bulb between (1) D+F and (2) earth, then touching live battery to the D+F while the engine is running. this started the dynamo (I guess energized the field) and it produced variable voltage (6 to 12+ V) according to revs (as it should). its a 6v system.
but when the engine is stopped and then restarted I need to repeat this live flashing.

is this normal? does the battery via the regulator essentially prime the field in this way when its all assembled/working? is this when people say put it together and take it for a long ride?

thanks

Mike
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: Triton Thrasher on 19.12. 2014 11:22
The casing is supposed to retain enough magnetism to start charging.

I have little electrical knowledge. I've heard excess distance between armature and pole shoe blamed for this needing a boost from the battery to start charging, but I don't know.

In the past, with a lazy dynamo like yours and with an electromechanical regulator, I have fitted a car-type charge warning lamp between dynamo D and a switched battery live. With regulator points closed, that let a little current into the field, or something like that and the dynamo behaved itself.

Maybe doesn't apply to solid state regulators. Anyone know?

Sometimes a dynamo just needs a few miles of riding, to start working.
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: wilko on 19.12. 2014 21:11
A new field coil on ebay fixed one of mine with similar symptoms.
Title: Re: my '61 BSA super rocket is negative earth... really?
Post by: trevinoz on 20.12. 2014 20:05
Mike,
              This can be caused by a film on the brush rubbing surface. Try cleaning the commutator and give the face of the brushes a rub with abrasive cloth and see what happens.