OT: Diesel Motorcycle stator question

Hi doods,
I have a diesel Indian Enfield i imported from India in quite a state of 'fix and make do'. I am fixing the electrics at the mo in order to get her on the road for the spring. But the electrics have been moded somewhat.... the stator on the lombardini motor has been bugered about with, with what appears to be 2.5mm copper cable connecting the windings to each other. i have done some multi metering and discovered that 5 of the windings are daisy chained and connected to the 2 out put wires from the stator and the other 5 are again daisy chained connected between earth and the final third wire going to the 'rectifier'. Does this sound right? I have bought a bowden power box three phase rectifier/regulator to replace the bit of plastic with 9 diodes poking through it that was on the bike when it came from India... I don't want to blow the power box if the stator wiring doesn't sound right.
Any help appreciated,
Steve
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On 06/03/2014 21:19, Mr Sandman wrote:

Are you saying there are 10 stator segments?
Is the rotor a permanent magnet, or one driven by slip rings?
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uk.rec.motorcycles ?
I hear it can be a bit of a bunfight but it sounds like you need specialist knowledge.
--
fred
it's a ba-na-na . . . .
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On Thursday, March 6, 2014 10:41:47 PM UTC, fred wrote:

It does sound a bit beyond diy. I'd test the gen output without electronics on it.
NT
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wrote:

Congratulations! You've got yourself a Royal Enfield Taurus 'Super bike' (200mpg! no wonder you're keen to get this one running :-)
The nine diodes rather suggests a 3 phase generator (6 for the fullwave bridge rectifier and the other 3 to provide fullwave rectified sense/ exciter current to the VR unit).
However, the presence of a total of 10 poles with two banks of 5 coils suggest a single phase generator (probably with permanent magnet rotor) which would normally be connected to a single phase 4 diode rectifier bridge (where one of the sets of coils would be permanently connected to the rectifier and the other switched by auxiliary contacts in the headlamp switch to compensate for the extra loading by the lighting.
IOW the whole thing is a complete bodge. The 9 diode rectifier may simply have been canabalised from a 3 phase generator to replace the original single phase rectifier bridge.
The 'classic' PM alternator used on british motorbikes in the 60s and 70s typically used a 6 pole PM rotor mounted directly onto the crankshaft with a 6 pole stator usually with one pair of coils, wired in series, permanently connected to the rectifier pack and the two remaining coil pairs wired in parallel to the head lamp switch so that they could be paralleled up with the permanently wired coil pair to make up a total of 3 coil pairs in parallel to provide full output to compensate for the extra electrical loading from the lighting circuits.
In the 60s and very early 70's, the battery was used to 'regulate' the output voltage and suffered a shortened service life as a result of excess gassing which demanded frequent maintainance top ups with distilled water. Later designs used a power zenner diode to do the regulation and remove this extra strain on the hapless battery. It wasn't a very efficient way of stabilising the voltage but it did the job.
The ten pole stator is rather unusual though[1] but, provided the rotor has a matching number of permanent magnet poles, what you have is a single phase PM alternator intended to be wired to a 4 element bridge rectifier pack exactly as per the British bikes of the 60s and 70s and your Bowden Power Box will be totally unsuitable for this generator configuration.
If you beg borrow or steal a dual beam oscilloscope, you can compare the ac outputs from the sets of windings to confirm not only that the output is single phase but also their phasing relative to each other (extremely important that they're in phase when paralleled up).
Alternatively, a set of headphones and a 1 or 2K ohm series resistor could be used to do likewise and confirm wich way round is which to obtain an in phase parallel connection between the two sets of coils.
As it stands (one set of 5 coils connected (erroneously) to the frame and the rectifier with the end connections for the other 5 coils just dangling loose) you can connect the sleeve of the headphone jack plug to frame and the other, via the 1 or 2k resistor, to the connection going to the rectifier and listen for the hum when the engine is idling (or even just being cranked from the kick starter if the engine isn't yet in a running condition).
Assuming the engine can be started and set to a fast tickover, you can listen to the hum and compare with the other disconnected coils by temporaily connecting one end to frame and swap the headphone connection to the free end of the 'floating' coils.
If the hum sounds about the same from each coil set, you can then listen across the two 'hots' to check the phasing. If the hum doubles up in volume, they're out of phase and one set needs to have their connections reversed.
If the hum nulls out, they're in phase and the hot ends can be safely paralleled with the earthed ones disconnected from the frame and then joined back to each other at one of the rectifier AC input terminals. One of the remaining 'hots' can be directly connected to the other AC input terminal of the rectifier pack with the other connected to the same rectifier terminal via the auxiliary switch contacts on the headlight switch.
There may or may not be a power zenner diode mounted on a heatsink which would be connected across the output terminals of the rectifier pack (also effectively in parallel with the battery). Alternatively, you could utilise a more efficient switched regulator module between the rectifier output and the battery connection which would allow you to bypass the headlamp auxiliary switch and have both sets of coils permanentyl connected to the rectifier ac input terminals.
It's important to make sure there are no framing faults in the alternator stator windings otherwise you risk burning out the rectifier pack.
[1] I suspect a ten, rather than the more traditional six pole stator/rotor was chosen to compensate for the lowe rev range of the diesel compared to the more usual petrol engines used for motorcycle power plant.
Good luck and I hope this has proved helpful to you.
PS, Could you describe (or post a picture somewhere) more details about the alternator rotor and how it's driven? The Wiki article was rather light on detail.
--
Regards, J B Good

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"Johny B Good" wrote in message wrote:

Congratulations! You've got yourself a Royal Enfield Taurus 'Super bike' (200mpg! no wonder you're keen to get this one running :-)
The nine diodes rather suggests a 3 phase generator (6 for the fullwave bridge rectifier and the other 3 to provide fullwave rectified sense/ exciter current to the VR unit).
However, the presence of a total of 10 poles with two banks of 5 coils suggest a single phase generator (probably with permanent magnet rotor) which would normally be connected to a single phase 4 diode rectifier bridge (where one of the sets of coils would be permanently connected to the rectifier and the other switched by auxiliary contacts in the headlamp switch to compensate for the extra loading by the lighting.
IOW the whole thing is a complete bodge. The 9 diode rectifier may simply have been canabalised from a 3 phase generator to replace the original single phase rectifier bridge.
The 'classic' PM alternator used on british motorbikes in the 60s and 70s typically used a 6 pole PM rotor mounted directly onto the crankshaft with a 6 pole stator usually with one pair of coils, wired in series, permanently connected to the rectifier pack and the two remaining coil pairs wired in parallel to the head lamp switch so that they could be paralleled up with the permanently wired coil pair to make up a total of 3 coil pairs in parallel to provide full output to compensate for the extra electrical loading from the lighting circuits.
In the 60s and very early 70's, the battery was used to 'regulate' the output voltage and suffered a shortened service life as a result of excess gassing which demanded frequent maintainance top ups with distilled water. Later designs used a power zenner diode to do the regulation and remove this extra strain on the hapless battery. It wasn't a very efficient way of stabilising the voltage but it did the job.
The ten pole stator is rather unusual though[1] but, provided the rotor has a matching number of permanent magnet poles, what you have is a single phase PM alternator intended to be wired to a 4 element bridge rectifier pack exactly as per the British bikes of the 60s and 70s and your Bowden Power Box will be totally unsuitable for this generator configuration.
If you beg borrow or steal a dual beam oscilloscope, you can compare the ac outputs from the sets of windings to confirm not only that the output is single phase but also their phasing relative to each other (extremely important that they're in phase when paralleled up).
Alternatively, a set of headphones and a 1 or 2K ohm series resistor could be used to do likewise and confirm wich way round is which to obtain an in phase parallel connection between the two sets of coils.
As it stands (one set of 5 coils connected (erroneously) to the frame and the rectifier with the end connections for the other 5 coils just dangling loose) you can connect the sleeve of the headphone jack plug to frame and the other, via the 1 or 2k resistor, to the connection going to the rectifier and listen for the hum when the engine is idling (or even just being cranked from the kick starter if the engine isn't yet in a running condition).
Assuming the engine can be started and set to a fast tickover, you can listen to the hum and compare with the other disconnected coils by temporaily connecting one end to frame and swap the headphone connection to the free end of the 'floating' coils.
If the hum sounds about the same from each coil set, you can then listen across the two 'hots' to check the phasing. If the hum doubles up in volume, they're out of phase and one set needs to have their connections reversed.
If the hum nulls out, they're in phase and the hot ends can be safely paralleled with the earthed ones disconnected from the frame and then joined back to each other at one of the rectifier AC input terminals. One of the remaining 'hots' can be directly connected to the other AC input terminal of the rectifier pack with the other connected to the same rectifier terminal via the auxiliary switch contacts on the headlight switch.
There may or may not be a power zenner diode mounted on a heatsink which would be connected across the output terminals of the rectifier pack (also effectively in parallel with the battery). Alternatively, you could utilise a more efficient switched regulator module between the rectifier output and the battery connection which would allow you to bypass the headlamp auxiliary switch and have both sets of coils permanentyl connected to the rectifier ac input terminals.
It's important to make sure there are no framing faults in the alternator stator windings otherwise you risk burning out the rectifier pack.
[1] I suspect a ten, rather than the more traditional six pole stator/rotor was chosen to compensate for the lowe rev range of the diesel compared to the more usual petrol engines used for motorcycle power plant.
Good luck and I hope this has proved helpful to you.
PS, Could you describe (or post a picture somewhere) more details about the alternator rotor and how it's driven? The Wiki article was rather light on detail.
--
Regards, J B Good

Its, not a Taurus, but it is related. It has an electric kicker too.
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wrote:

Thanks for the pics Steve.
I think we can safely assume that the flywheel rotor has ten magnetic poles. The stator seems to be keyed (presumably to suit a petrol engine's ignition timing requirements when an AC only system is used with no battery in sight - the combination of direct ac feed to an ignition coil making it the equivilent of a 'magneto ignition' system).
In this case, keying the stator is rather redundent with a diesel engine (or a petrol engine with battery and coil ignition).
All that aside, the answer to your question is that the "bowden power box three phase rectifier/regulator" is of no use whatsoever with the generator used on this bike.
I did notice that the rectifier pack actually consists of 12 rectifier diodes which I suspect are arranged in a standard single phase fullwave bridge using 3 diodes in parallel per rectifier element. The diodes look like they're unlikely to have a max average current rating beyond 3A each, hence the tripling up.
You might be better off replacing this with the type of rectifier pack that was typical of 60s / 70's British motorbike electrical equipment ( usually four silicon 8 or 10A diodes each on their own heatsink plate (looking like a blob under the protective coating with a wire poking out), suitably polarised and mounted on a threaded spindle with spacers to keep the plates seperated so that cooling airflow could remove the heat generated by the forward volt drops, effectively an average dissipation at 8 amps output of 2v per conducting pair times that 8 amps giving a total of 16 watts).
Alternatively, you could employ a 10A rated bridge recifier pack designed to be mounted on a suitable heatsink if there's a suitable location to mount it to or room for a seperate heatsink. I think one with a PIV rating of 200v would do the job but I'd be inclined to select one with a 400v PIV rating if I was going to use a switching regulator module (but it's a slow revving diesel so 200v PIV may be more than sufficient even in this case).
The max unloaded output voltage from such PM alternators can reach surprisingly high voltages at the red line limit. It's the leakage inductance of the alternator windings that helps regulate the maximum current output due to speed variations but this effect only applies when connected to a load.
If the rectifier output terminal is disconnected from the battery, this moderating effect all but vanishes and excessive voltages can be generated at max rpms which may exceed the PIV rating of the rectifier which often means instant burnout.
The best way to test the actual peak voltage output at max rpms is to use a small 1N4008 diode as a simple half wave rectifier feeding a 400v or higher rated 1 or 2 microfard capacitor and measure the cap voltage with a cheap DMM. This will give you worst case maximum peak voltage and the rectifier needs to be rated to at least twice this value if a series switching regulator is going to be used to control the output voltage. You could get away with a lower PIV when using the battery and/or a power zenner diode to provide 'shunt regulation' perhaps just 50% higher providing sufficient safety margin in this case.
BTW, can I assume that the battery is a 12v lead acid type?
Also, btw, I see you're posting to usenet using LiveMail which has horribly mangled the quotage and created a new 'thread' entitled "Re: Diesel Motorcycle stator question" seperate from the original. I had to copy your reply and paste as quoted text.. twice! before the quotage formatting was restored to normal.
I'm not sure whether Livemail can be configured to make less of a hash of usenet posting than it's currently doing (even OE does a better job, ignoring the misplaced sig seperator issue which also seems to plague LiveMail).
If you're going to remain subscribed to news groups and make further postings, you might want to consider using a better news client. There are plenty of free news clients available and even a few payware ones.
I'm using Free Agent which is really a cutdown free version of a payware news client known as "Agent". The free version does the job ok, it simply lacks the luxury features of the payware version. I'm a tight fisted sod so I'm prepared to forgo such luxuries. :-)
--
Regards, J B Good

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On 08/03/2014 00:50, Johny B Good wrote:

Old bikes use to have resistors to match loads such as headlands when they weren't used, to limit charging current.
Personally I feel that is a disastrous system leading to short battery life and blown bulbs, but given the lack of control of field through having permanent magnets, the only way is to short windings based on terminal voltage. I'm not aware of any system that would be suitable for a bike. These sort of methods are used on narrow boat alternators that produce mains via a control hardware.
Without knowing the output current, it would be difficult to advise on diode sizing. There is no need to have high PIV diodes as long as the alternator remains connected to the battery through these diodes. If the windings are connected in a star formation then it is prudent to add another pair of diodes to the star point, as done on high output automotive alternators.
Diode current could be measured by passing the rectified output current directly into an ammeter. The leakage inductance of the winding will limit current to an asymptotic value with increasing revs.

I use Mozilla Thunderbird and I have to say the message is correctly "threaded" and not at all mangled.
Far better that some of the posts via Google Groups!
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====snip===
I have a theory that the 'new thread syndrome' arises when a colon is used after OT, TOT RTOT in the OP as in "OT: Diesel Motorcycle stator question" so that when a follow up is made, either the sending client _replaces_ the OT: bit with Re: creating a mismatched topic name or else the recieving client does the same and then lists it as a new topic.
I've seen this phenonema before where I've just assumed it was the other poster's news client getting it wrong so I can now imagine that FreeAgent might well be the real culprit for mangling the threading (time to make use of the alt.uk.test NG methinks).
However, I can't see how the quoting got mangled the way it did other than by LiveMail itself. It looked like Livemail didn't know to prepend the extra set of chevrons on the quoted text. It made my text look like it was authored by Steve himself (no prepended chevrons) and it failed to snip my sig lines so that Steve's actual reply followed on below, indistinguishable in appearance to my text (but for the sig line clue).
The only bit of quoted text was the bit my follow up had quoted to which he was responding.
Anyway, I'm off to alt.uk.test to check my theory out.
--
Regards, J B Good

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On Sun, 09 Mar 2014 00:50:47 +0000, Johny B Good

And the result is in. It looks like FreeAgent is innocent of 'thread mangling' so it must be a problem with LiveMail (and just possibly other clients that mangle the threading as well).
--
Regards, J B Good

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Thanks for the pics Steve.
I think we can safely assume that the flywheel rotor has ten magnetic poles. The stator seems to be keyed (presumably to suit a petrol engine's ignition timing requirements when an AC only system is used with no battery in sight - the combination of direct ac feed to an ignition coil making it the equivilent of a 'magneto ignition' system).
In this case, keying the stator is rather redundent with a diesel engine (or a petrol engine with battery and coil ignition).
All that aside, the answer to your question is that the "bowden power box three phase rectifier/regulator" is of no use whatsoever with the generator used on this bike.
I did notice that the rectifier pack actually consists of 12 rectifier diodes which I suspect are arranged in a standard single phase fullwave bridge using 3 diodes in parallel per rectifier element. The diodes look like they're unlikely to have a max average current rating beyond 3A each, hence the tripling up.
You might be better off replacing this with the type of rectifier pack that was typical of 60s / 70's British motorbike electrical equipment ( usually four silicon 8 or 10A diodes each on their own heatsink plate (looking like a blob under the protective coating with a wire poking out), suitably polarised and mounted on a threaded spindle with spacers to keep the plates seperated so that cooling airflow could remove the heat generated by the forward volt drops, effectively an average dissipation at 8 amps output of 2v per conducting pair times that 8 amps giving a total of 16 watts).
Alternatively, you could employ a 10A rated bridge recifier pack designed to be mounted on a suitable heatsink if there's a suitable location to mount it to or room for a seperate heatsink. I think one with a PIV rating of 200v would do the job but I'd be inclined to select one with a 400v PIV rating if I was going to use a switching regulator module (but it's a slow revving diesel so 200v PIV may be more than sufficient even in this case).
The max unloaded output voltage from such PM alternators can reach surprisingly high voltages at the red line limit. It's the leakage inductance of the alternator windings that helps regulate the maximum current output due to speed variations but this effect only applies when connected to a load.
If the rectifier output terminal is disconnected from the battery, this moderating effect all but vanishes and excessive voltages can be generated at max rpms which may exceed the PIV rating of the rectifier which often means instant burnout.
The best way to test the actual peak voltage output at max rpms is to use a small 1N4008 diode as a simple half wave rectifier feeding a 400v or higher rated 1 or 2 microfard capacitor and measure the cap voltage with a cheap DMM. This will give you worst case maximum peak voltage and the rectifier needs to be rated to at least twice this value if a series switching regulator is going to be used to control the output voltage. You could get away with a lower PIV when using the battery and/or a power zenner diode to provide 'shunt regulation' perhaps just 50% higher providing sufficient safety margin in this case.
BTW, can I assume that the battery is a 12v lead acid type?
Also, btw, I see you're posting to usenet using LiveMail which has horribly mangled the quotage and created a new 'thread' entitled "Re: Diesel Motorcycle stator question" seperate from the original. I had to copy your reply and paste as quoted text.. twice! before the quotage formatting was restored to normal.
I'm not sure whether Livemail can be configured to make less of a hash of usenet posting than it's currently doing (even OE does a better job, ignoring the misplaced sig seperator issue which also seems to plague LiveMail).
If you're going to remain subscribed to news groups and make further postings, you might want to consider using a better news client. There are plenty of free news clients available and even a few payware ones.
I'm using Free Agent which is really a cutdown free version of a payware news client known as "Agent". The free version does the job ok, it simply lacks the luxury features of the payware version. I'm a tight fisted sod so I'm prepared to forgo such luxuries. :-)
--
Regards, J B Good

Yep, its a chunky 12v LA battery. Is this good as a rectifier? -
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wrote:

It's a little OTT but should do the trick ok (better safe than sorry and it's cheap enough). You'll have to bolt it onto some sort of heatsink to stop it overheating. Either a suitable panel out of the way of any warm airflow or else a seperate heatsink bolted onto the frame somewhere out of the way.

Normally, the alternator will use only 3 wires, a common wire joined to the 'cold end' of the two sets of coils and a seperate wire for each of the two 'hot ends'. You simply cannot (and must not) connect _any_ of these wires to the frame.
The common wire is connected to one of the ac input tags and one of the other remaining 'hot ends' connected directly to the other ac input terminal. The remaining 'hot end' goes to the headlamp auxiliary switch contacts with an additional wire from the other contact going back to the ac input terminal to join up with the other 'hot end' connection.
Note I'm using the expressions 'hot' and cold' for the sake of phase polarity. Both ends are floating wrt the frame. You also need to make sure you don't connect the battery to the rectifier with reversed polarity lest you burn out the rectifier (you can use a 12v test lamp to check this before commiting yourself).
As long as the battery is of the flooded cell type that requires regular top up maintenance, you can safely subject it to a gassing charge for the relatively short periods required to test for overvoltage. I wouldn't subject any SLA to such abuse, no matter how briefly.
As I said earlier upthread, it was common practice with 60's british motorbikes to use the 6v battery to limit the voltage by absorbing some excess charging current, unfortunately to the detriment of battery life in spite of regular top up maintenance.
The later 70's bikes were converted to 12v by the simple expedient of fitting a 12v battery along with 12v lamps and a 12v ignition coil without changing the existing alternator. Some attempt at regulation was made by fitting a 14v power zenner diode (75W rating on the supplied heatsink afaicr) to shunt any excess current away from the battery. Switching extra coils in and out of the generator circuit to control its output was still essential in this case.
If you can't track down such a zenner diode, it's entire possible to use a 1 watt 13.2 volt zenner with a suitable power transistor to effectively emulate the original power zenner diode ( the power transistor will need to be suitably rated and mounted on a heatsink).
There may be series buck/boost switching regulator modules available to do away with a crude zenner shunt regulator and obviate the need to switch generator coils in and out of circuit. It's not something I've researched so can't advise on this.
BTW, I meant to reply sooner but had too many distractions to deal with so apologies for the delay.
--
Regards, J B Good

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"Johny B Good" wrote in message wrote:

It's a little OTT but should do the trick ok (better safe than sorry and it's cheap enough). You'll have to bolt it onto some sort of heatsink to stop it overheating. Either a suitable panel out of the way of any warm airflow or else a seperate heatsink bolted onto the frame somewhere out of the way.

Normally, the alternator will use only 3 wires, a common wire joined to the 'cold end' of the two sets of coils and a seperate wire for each of the two 'hot ends'. You simply cannot (and must not) connect _any_ of these wires to the frame.
The common wire is connected to one of the ac input tags and one of the other remaining 'hot ends' connected directly to the other ac input terminal. The remaining 'hot end' goes to the headlamp auxiliary switch contacts with an additional wire from the other contact going back to the ac input terminal to join up with the other 'hot end' connection.
Note I'm using the expressions 'hot' and cold' for the sake of phase polarity. Both ends are floating wrt the frame. You also need to make sure you don't connect the battery to the rectifier with reversed polarity lest you burn out the rectifier (you can use a 12v test lamp to check this before commiting yourself).
As long as the battery is of the flooded cell type that requires regular top up maintenance, you can safely subject it to a gassing charge for the relatively short periods required to test for overvoltage. I wouldn't subject any SLA to such abuse, no matter how briefly.
As I said earlier upthread, it was common practice with 60's british motorbikes to use the 6v battery to limit the voltage by absorbing some excess charging current, unfortunately to the detriment of battery life in spite of regular top up maintenance.
The later 70's bikes were converted to 12v by the simple expedient of fitting a 12v battery along with 12v lamps and a 12v ignition coil without changing the existing alternator. Some attempt at regulation was made by fitting a 14v power zenner diode (75W rating on the supplied heatsink afaicr) to shunt any excess current away from the battery. Switching extra coils in and out of the generator circuit to control its output was still essential in this case.
If you can't track down such a zenner diode, it's entire possible to use a 1 watt 13.2 volt zenner with a suitable power transistor to effectively emulate the original power zenner diode ( the power transistor will need to be suitably rated and mounted on a heatsink).
There may be series buck/boost switching regulator modules available to do away with a crude zenner shunt regulator and obviate the need to switch generator coils in and out of circuit. It's not something I've researched so can't advise on this.
BTW, I meant to reply sooner but had too many distractions to deal with so apologies for the delay.
--
Regards, J B Good

thanks JBG,
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wrote:

I've just had another look at the photos and I've now spotted the 'Earth Connection' that I missed the first time round. It looks to be a bodge with the bare end simply placed under a fixing bolt.
I'd be inclined to move that away from the fixing bolt and either use it as your 'second hot' or join it to the other cold, whichever is appropriate to get the two sets of 5 series connected coils commoned so the hots are in phase and all coils isolated from the frame.
You can start by isolating each coil set from each other _and_ any contact with the frame. You can use an ac voltmeter with the engine ticking over to first verify that you're getting equal voltage outputs from each coil set. Next, you can common one end of each coil set and then see whether there is zero or double voltage when measuring between the other free ends.
You need to arrange the common so that you see zero voltage between the free (two hot ends) before you're ready to wire it up to that rectifier pack (common wire directly connect to one of the ac tags with one of the two hots wired directly to the other ac tag. The remaining hot joins back to the other hot via the switch contact in the headlamp switch.
This will give you the 'classic' alternator wiring arrangement commonly used with such PM alternators on 60s and 70s British bikes. Usually, with 6v systems, the split would be a single pair of coils wired direct and the other two pairs wired in parallel via the headlamp switch.
The later 12v setups could use the same 33/67 split or else wire the coils into 2 sets of 3 coils to get a higher voltage output with a power zenner diode taking care of the greater imbalance between daylight and night time running load versus output mismatch that resulted from a 50/50 ratio.
Of course modern switch regulator/converter technology can nicely do away with the need to use the auxiliary headlamp switch to control the generator output (which would allow all the coils to be providing output using just a two wire circuit. I can't say whether or not such voltage regulator modules have ever been marketed for retro fit to old classic bikes to improve the electrics.
It just seems such a no-brainer mod that I can't see why a manufacturer hasn't spotted this niche in the vintage motorcycle accessories market. However, it might be a matter of picking a commercially made 'charge controller' intended for small 12v based PV systems and wire it up yourself.
It'd be rather like my adapting a Wireless World CD ignition 'add on' circuit for twin ignition coil use on my '72 T120V Triumph Bonneville so that I could use a harder grade plug and an even spottier leaner idling and mid range mixture to improve both performance and MPG (100mpg on open class A roads at speeds of 50 to 60 mph - that 200mpg of a bike with less performance than a 70s moped doesn't look quite so impressive now, does it? :-)
--
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