AC/DC Lucas electrics

[BriMor]

Hello all, first posting.
My '78 Bonneville is currently apart @ the drive side to address a sloppy primary chain among other issues.
My concern here is with the 3 decades old RM21 alternator and the desire to develop a component system to use with a recently purchased Tri-Spark for Twins E.I. system.
I'm no electrical wizard but i have been studying this subject in regards to whats available, the choices are somewhat confusing; Single phase vs. three phase AC alternators, rectifying to DC using zeners, regulating to DC without zeners, etc.
My studies indicate the use of a Lucas setup RM24 (3 phase)as the last of a series intended for the electric start bikes circa 1982.
Looking thru Paul Goffs electrical website for instance, he offers a single phase 2 wire 190 watt RM27 pattern, and which must be used with a regulator/rectifier.
He also states that the RM21 original setup for points will not perform with electronic ignition systems.
One question would be where did the RM27 pattern evolve from, but, back to the Tri-Spark system, their website offers a voltage regulator but no mention is made to what alternator it's designed for, other than that it's rated for 18 Amps,max.
Ultimately i would like to establish a game plan for updating my system and would welcome all and any advise in this regard and remain,
Sincerely

[L.A.B.]

My studies indicate the use of a Lucas setup RM24 (3 phase)as the last of a series intended for the electric start bikes circa 1982.

The RM24 was used in its lower output form on Triumphs (T140D/E)from 1979, along with a new Lucas three-phase rectifier and single Zener diode, the electrical system was also changed at that time to negative earth/ground.

In 1981, the higher output version RM24 alternator was fitted because of the extra charging capacity required due to the fitting of electric starters, although a single phase 180W RM23 was used on the electric start Norton Commando (1975).

    

Looking thru Paul Goffs electrical website for instance, he offers a single phase 2 wire 190 watt RM27 pattern, and which must be used with a regulator/rectifier.

A modern reg/rec box is normally the preferred option these days, over the separate rectifier and Zener, and a single Zener will be overloaded @190W which is why a triple Zener pack was used with the 1981-on high output RM24 system.

He also states that the RM21 original setup for points will not perform with electronic ignition systems.

Electronic ignitions (especially the Rita) tend to use more power than points ignitions, and they do not function as well as points if the battery becomes drained and the available voltage drops below a certain level, although the Tri-Spark system supposedly has a lower power consumption than either a Rita or Boyer, and it also works better at reduced voltage however, running for long periods at low speed with the headlight on, as is required in many countries (not the UK) as the 120W alternator won't be making enough output at low RPM to keep the battery fully charged.  

[L.A.B.]

Part 2 (as I ran out of space - 2000 characters max. per message)

One question would be where did the RM27 pattern evolve from,

- I've no idea! Possibly the RM23, or maybe from a special Police high-output version stator?

but, back to the Tri-Spark system, their website offers a voltage regulator but no mention is made to what alternator it's designed for, other than that it's rated for 18 Amps,max.

[Edit]:That's a single phase box, as it says - use the Podtronic  single-phase box for over 150W output

Ultimately i would like to establish a game plan for updating my system and would welcome all and any advise in this regard and remain,
 

I suggest that you fit a three-phase alternator and suitable reg/rec box, as that's the normal upgrade which will give much higher output, especially at low RPM.

[BriMor]

[Edit]:That's a single phase box, as it says - use the Podtronic  single-phase box for over 150W output

LAB, Thanks for your help. Can you clarify your edit as quoted above as i don't understand where on the Tri-Spark website this info was gleaned?
When fitted, the Tri-Spark unit provided a good idle,but wouldn't "pull" over approx. 15 mph.
I now have the electronic stator from the company owners bike but have yet to re-fit in light of these issues.

[L.A.B.]

LAB, Thanks for your help. Can you clarify your edit as quoted above as i don't understand where on the Tri-Spark website this info was gleaned?

Sorry my mistake (= brain slipped into neutral!) , I was looking at the 150W reg/rec box info on the Paul Goff website and mixed it up with the Tri-Spark, - but they're not the same, as the Tri-Spark reg/rec box is rated up to 18 amps (V x A = W) which should be capable of handling the output of any known (to me) single-phase Lucas type alternator.

When fitted, the Tri-Spark unit provided a good idle,but wouldn't "pull" over approx. 15 mph.

I don't see how a reg/rec box could be causing that problem, if it is wired up correctly and the bike starts well? It sounds as if it's not advancing?

Did you strobe it?

What battery voltage readings are you getting, at: engine off/idle/above idle lights off/above idle with lights on?

[BriMor]

I don't see how a reg/rec box could be causing that problem, if it is wired up correctly and the bike starts well? It sounds as if it's not advancing?

Sorry for the mis-communication, the EI was running with the standard rectifier and zener setup.

It sounds as if it's not advancing?

Well, it felt like it too!
....no it wasn't strobed but according to Tri-Spark the static led arrangement is very close.
Unfortunately i didn't take note of the battery voltage.  

[L.A.B.]

Well, it felt like it too!
....no it wasn't strobed but according to Tri-Spark the static led arrangement is very close.

Yes the static setting should be fairly close to correct, that's assuming that the Tri-Spark rotor was set accurately with the crankshaft at the 38 degrees BTDC position and as yours is a '78 model, there's normally a timing access plug in the primary cover instead of the removable cover as shown in the Tri-Spark instructions so the opposite alternator rotor mark needs to be used to the one shown.

Personally, I'd want to put a strobe on it, to check that it was actually advancing, as well as being set accurately.  

[BriMor]

Hi LAB,
Yes the initial setup included indexing 38*BTDC using the flywheel locating plunger tool 61-7022.
I swear i could perform this with my eyes closed!
Your recommendation regarding a 3 phase alternator is interesting in conjunction with Paul Goff's statement:"I don't sell 3 phase rotors.", although he does sell 3 phase reg/rectifiers.
I know the weekend is here so i'll say thanks for your help.

[L.A.B.]

Your recommendation regarding a 3 phase alternator is interesting in conjunction with Paul Goff's statement:"I don't sell 3 phase rotors.", although he does sell 3 phase reg/rectifiers.

But please note that he says he doesn't sell three-phase ROTORS and as far as I know no-one else does either?

As the latest 54202298 type rotor is the one recommended for all RM21-on stators, both single and three-phase:

http://www.oldbritts.com/11_068100.html

"Three Phase, 180 watts Alternator:
This consists of the Lucas rotor (part # 54202298, which is the same rotor as used in both the 130 watts and 180 watts single phase alternators)"

[BriMor]

Thanks again LAB,
I've now got a  clearer understanding of this issue.
BTW, i like to run with headlights on, for the sake of safety.
Cheers!

[L.A.B.]

Some parts suppliers appear to sell a 54202299 number rotor, and I must admit I don't know what the difference is, - as the -98 one is supposed to be the welded type? And both seem to be around the same price...

There's also the Sparx (Tri-Cor England) SPX003 high-output three-phase kits, if you wanted to buy the complete setup?:  
http://www.tri-corengland.com/acatalog/Alternators.html

 



  

[BriMor]

Thanks for the link info. . .

VERY important to fit spark plug caps of the 5000ohm resisted type.
Failure to do so will cause overloading.

Per Tri-Spark website:SPL - 0003 Single suppressor cap $6.00 ,
these were supplied with my kit although i didn't order them.

My growing database of elec. knowledge suggests the use of one type of supressor only, spark plug or supressor cap,but not both.

Thoughts?

[L.A.B.]

My growing database of elec. knowledge suggests the use of one type of supressor only, spark plug or supressor cap,but not both.

Yes, use one or the other, but not both, preferably using copper HT  leads (plug wires), as standard carbon leads normally have an inbuilt resistance of around 3000 Ohms (3kOhm) per foot.