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#462417 - 11/08/12 5:26 pm 2 / 3 wire stator testing, help needed again.....  
Joined: Aug 2001
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KC in S.B. Online content
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Santa Barbara, California
I know this topic has been run into the ground, but I can never get the search function to work.
The bike is a '69 A65L, Boyer, and Podtronics Rectifier / Regulator in one unit. Lead Acid battery, at the moment...
All stators mentioned here are the later encapsulated type, not open wire wound units.
I know the intent of the 3 wire stator on older bikes, was to control excess over charging the battery, due to poor regulation equipment, using the headlight switch to add the 3rd wire only when lights were on. The later 2 wire stators came along matched with the zener diode, that simply dumps excess voltage to ground. Worked OK, but inefficent use of generated voltage. Then along come aftermarket "HI OUTPUT" parts, some of these called "3 phase", having 3 wires. Are all Lucas 3 wire stators also "3 phase? I would assume yes.

The question comes from this: I have a bike that was using the Sparks 3 wire stator, along with a Podtronics regulator that has 3 yellow wires to connect to the stator wires. The Pod instructions are clear, just hook up the 3 Pod wires to the 3 stator wires, don't worry about what order or colors. It worked fine.
Then, I removed that motor, along with the stator, and installed a motor I want to run in after rebuild. The motor runs fine, but the 3 wire Lucas stator connected to that 3 wire Podtronics seems to give random voltage. Riding around with a Fluke Meter attached to the gauges showed the following.
With headlight OFF, Voltage will slowly climb up past 14V, and with the headlight ON it is a nice steady 12.9 at cruise. In stop and go traffic, it starts to degrade untill I take action, and turn off the Light.
The most likely and simple answer is the Lucas and Sparks output are not the same, which is why Sparks was invented.
What is the output of the Lucas 2 wire, and 3 wire Stators?
The parts books list many stator Part Numbers, but so far I don't see an explaination of why so many. Also, some stators do not seem to have a P/N on them that I can see. Since Triumph and BSA stators will fit either bike, this makes trying to match a stator to a year and make of bike difficult. So, 2 and 3 wire seems to be the only real change. Does anyone have some experience with this? It is a pain to get the motor all together, and then find out the charging is poor. It would be great to have a way to test stators before mounting, but that takes mounting the stator on some kind of rig most of us are not going to build. BTW, I do have the perfect large wire wound 1 Ohm 300w resistor to use for testing, but cannot identify the wire colors out of the stator, so don't know how to connect it for the A,B,C, tests mentioned in the shop book. So much for Fettling........


Last edited by KC in S.B.; 11/08/12 5:31 pm. Reason: added more

Down to 1 BSA, 2 Triumphs, 2 '56 Chevys
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#462470 - 11/08/12 11:42 pm Re: 2 / 3 wire stator testing, help needed again..... [Re: KC in S.B.]  
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Hi KC,

Originally Posted By: KC in S.B.
Are all Lucas 3 wire stators also "3 phase? I would assume yes.
I know the intent of the 3 wire stator on older bikes, was to control excess over charging the battery,

Neither statement would be correct.

I suspect the "3 wire stator on older bikes" to which you refer is the RM19, fitted from the early to the late 1960's. There is also its high-output equivalent, the RM20, but this tended to be fitted only on bikes for the police and military, where there was a requirement to power radios, additional lights and/or horns, etc.

Unlike the specifically 3-phase stators Lucas produced from 1978, the 3-wire RM19 and RM20 are not 3-phase, they are single-phase. The significant difference between Lucas (and pattern) 3-phase stators and single-phase stators (including the later 2-wire ones) is 3-phase have nine coils connected in three groups of three while single-phase have only six coils, wired differently depending ...

The RM19 (and RM20) have the six stator coils connected two-together and four-together. As you've noted, the output of just the 'two-together' is used when just the ignition is in use, with the "headlight" switch connecting in the output of the 'four-together' when the lights were on, or the switch was turned to the 'emergency' position.

The "regulation equipment" at this time wasn't "poor", it's simply that there wasn't (and still isn't afaik) a 6V Zener diode. However, that's why, if you fit a 12V Zener diode to regulate the charging, you can connect the Green/Yellow and Green/Black wires together to one side of the rectifier, leaving the White/Green connected to the other side of the rectifier - White/Green is common to all six stator coils while Green/Yellow and Green/Black are connected either to the 'two-together' or the 'four-together', so you are then connecting all six coils together.

Around '68/'69, the RM19 and high-output RM20 were superseded by the RM21 and high-output RM23 - still six stator coils but all connected together internally, hence still single-phase but just two wires coming out.

In '78, the RM21 and RM23 were superseded by 'low-' and 'high-output' versions of the RM24 3-phase stators, although the rated outputs (10.5A and 14.5A @ 5,000 rpm) are the same as the RM21 and RM23 respectively.

As I say the RM24 stators have nine coils connected together in three groups of three. I'm assuming you're aware of how the magnetised rotor induces electron movement in the stator coils and, depending whether the magnet's north or south pole is nearest, the electron movement will be in one of the two different directions, hence 'alternating current'? Thus, with three groups of coils, each group is generating one of the three phases, and they are 120 degrees apart.

Originally Posted By: KC in S.B.
The later 2 wire stators came along matched with the zener diode, that simply dumps excess voltage to ground. Worked OK, but inefficent use of generated voltage.

As I say, you can connect a Zener to the earlier 3-wire, single-phase RM19 and RM20 stators.

Also, it is not correct to say that Zener diode regulation is "inefficient"; Lucas alternators are 'permanent magnet', it is possible to be debatably 'more efficient' with a separately-excited electro-magnet but, given a single horsepower is some 760 Watts, even if the entire 180W of a RM23 or high-output RM24 were being turned into heat (which it isn't, or the engine wouldn't run), any slight gain in 'efficiency' using a separately-excited electro-magnet alternator is far outweighed by the complexity and consequent additional cost.

Originally Posted By: KC in S.B.
Then along come aftermarket "HI OUTPUT" parts, some of these called "3 phase",

Again, this isn't correct. The after-market alternators - whether 3- or single-phase - are copies of Lucas products. The after-market producers claim 'higher' outputs but, as I've detailed innumerable times for years and years on this and other websites:- cry

. Watts are a product of multiplying Amps and Volts; Sparx uses higher (roughly 14.5) Volts than the (roughly) 12V used by Lucas when rating the originals of all the alternators available today.

. Lucas rated the original alternators by Amps produced @ 5,000 rpm; however, the Amps produced are a function of the rotational speed of the rotor - although it isn't linear, any given alternator produces less Amps at lower rpm and more Amps at greater rpm; if you spin a Lucas RM23 alternator (14.5A @ 5,000 rpm) at about 8,000 rpm, it too will produce the 16A claimed by the likes of Wassell for their pattern.

Originally Posted By: KC in S.B.
I have a bike that was using the Sparks 3 wire stator, along with a Podtronics regulator that has 3 yellow wires to connect to the stator wires.
just hook up the 3 Pod wires to the 3 stator wires, don't worry about what order or colors. It worked fine.
installed a motor I want to run in after rebuild. The motor runs fine, but the 3 wire LUCAS stator connected to that 3 wire Podtronics seems to give random voltage.

If you have assumed that both 3-wire alternators are 3-phase, that could be your error; "just hook up the 3 Pod wires to the 3 stator wires, don't worry about what order or colors" works fine for 3-phase (nine stator coils connected in three groups of three, remember) but not for a single-phase (six coils connected two-together and four-together). If Lucas made one big cock-up, it was re-using the Green/Yellow-Green/Black-White/Green colour combos. on the 3-phase stators when there wasn't any need for differentiation.

Originally Posted By: KC in S.B.
The most likely and simple answer is the Lucas and Sparks output are not the same, which is why Sparks was invented.
So, 2 and 3 wire seems to be the only real change.

But now you know that's nonsense? wink

Originally Posted By: KC in S.B.
What is the output of the Lucas 2 wire, and 3 wire Stators?

Ok now?

Originally Posted By: KC in S.B.
The parts books list many stator Part Numbers, but so far I don't see an explaination of why so many.

Errrm ... because they're different? Also, rather too often, Meriden and Small Heath gave different part numbers to the same part. mad Senior executives could and should have stamped on such stupidity at the time. frown

Originally Posted By: KC in S.B.
Also, some stators do not seem to have a P/N on them that I can see.

Sometimes they seem to have been numbered with some sort of ink stamp, which is washed off by oil.

Originally Posted By: KC in S.B.
Since Triumph and BSA stators will fit either bike, this makes trying to match a stator to a year and make of bike difficult.

Now that I've laid it all out for you, is that less difficult? You can tell 3- and single-phase stators apart by looking at the inner circumference, where the ends of the coil cores are visible. Ime, then the only difficulty left, if the five-figure part number isn't visible, is telling a given 'high-output' stator from its corresponding 'low-output' one.

Hth.

Regards,

#462482 - 11/09/12 1:38 am Re: 2 / 3 wire stator testing, help needed again..... [Re: KC in S.B.]  
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Wow Stuart !! That was some lesson!! I'm going to save it in my Shop manual for future reference since I am sure to forget at least some of it later on.
I am quite sure that when I bought that Sparks stator, the vendor made a point of telling me I would also need a 3 phase regulator. He may have been blowing smoke for all I know, but now I can just count the coils and if 6, then I'll know that was wrong. Assuming it WAS wrong, then it would be OK to continue using that regulator with a Lucas 3 wire stator.
Thanks for all the time you put into that, Regards KC


Down to 1 BSA, 2 Triumphs, 2 '56 Chevys
#465384 - 11/29/12 3:50 am Re: 2 / 3 wire stator testing, help needed again..... [Re: KC in S.B.]  
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OK, results I can SEE,........... finally. My retired machinist friend likes to have a project, and he spent the time to make this great adapter to test the Lucas alternators. I had been complaining they are hard to prove good, before actually installing in the motor............ and if they are junk, it's such a pain to open up the primary again, and replace parts. Not to mention the frustration and confusion that always accompanies any electrical issue... Is it the rectifier? The stator? The Regulator? The rotor?, who knows??? So now I will at least know the stuff in the primary is OK. WHOOPPEE !!!
Intersting to see how much variation was shown, using different rotors in the same stator. Oddly, the highest output came from the rotors without the timing mark on them. (early parts I think?)




Last edited by KC in S.B.; 11/29/12 3:47 pm.

Down to 1 BSA, 2 Triumphs, 2 '56 Chevys
#465396 - 11/29/12 6:56 am Re: 2 / 3 wire stator testing, help needed again..... [Re: KC in S.B.]  
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I LIKE that testing machine!!!!!!!!!!!!!!!

#465434 - 11/29/12 3:50 pm Re: 2 / 3 wire stator testing, help needed again..... [Re: KC in S.B.]  
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Another curiousity........ Does anyone know, or even have a theory on what the 3 small holes on the back of a rotor were for? They are marked with a letter, R,S,M if I recall correct.


Down to 1 BSA, 2 Triumphs, 2 '56 Chevys
#465446 - 11/29/12 5:27 pm Re: 2 / 3 wire stator testing, help needed again..... [Re: KC in S.B.]  
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The holes are for use with ET ignition,where the rotor is driven by a pin.
They allow you to time the rotor position exactly to suit the ignition timing.

#465447 - 11/29/12 5:28 pm Re: 2 / 3 wire stator testing, help needed again..... [Re: KC in S.B.]  
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They are for setting the rotor in the correct position when using an Energy Transfer Ignition. R= 41, M=39 and S=37 Before Top Dead Center.

If you are setting your points for open at 39 BTDC then you use the M hole to locate the rotor. There is a special engine sprocket and rotor spacer that has provisions for a dowel. The dowel aligns the rotor to the sprocket, and thus the crankshaft.


#465528 - 11/30/12 5:24 am Re: 2 / 3 wire stator testing, help needed again..... [Re: KC in S.B.]  
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Thanks. I've not had the pleasure of an ET bike. I wonder if those rotors are of stronger magnetism by design. It was certainly noticable that they produced a higher voltage as compared to the coil Ignition rotors. Probably just a coincidence.


Down to 1 BSA, 2 Triumphs, 2 '56 Chevys
#466015 - 12/03/12 4:33 pm Re: 2 / 3 wire stator testing, help needed again..... [Re: KC in S.B.]  
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Very nice machine. I can suspect the lower output rotors have less magnetism.
You can check with a screw driver hooked to a fish scale to measure each flat on the rotor. They can be revitalized at Joe Hunt Magneto.
In the ET system strong magnetism is essential especially in start up, but I think the rotors all come from the factory magnetized the same. ET's get less use so perhaps that is why they record stronger.

#466019 - 12/03/12 4:41 pm Re: 2 / 3 wire stator testing, help needed again..... [Re: KC in S.B.]  
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I had the same thought. Most people are not comfortable with the ET learning curve, so I suspect maybe those rotors saw less use / abuse ?? Of course they can still be used on coil Ignition bikes....... But then, you have to be "comfortable" working with no timing mark! We explored that some awhile back I recall.


Down to 1 BSA, 2 Triumphs, 2 '56 Chevys
#466039 - 12/03/12 6:38 pm Re: 2 / 3 wire stator testing, help needed again..... [Re: KC in S.B.]  
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Actually the ET rotors have timing marks 1967 on. Funny I have even found an ET rotor in two none Hornet bikes. A Spitfire and a Firebird scrambler.

#466132 - 12/04/12 5:01 am Re: 2 / 3 wire stator testing, help needed again..... [Re: KC in S.B.]  
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So my ET rotors aren't worth a bunch of $$ then as rare parts ???? Rats! ;-)


Down to 1 BSA, 2 Triumphs, 2 '56 Chevys

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