Does anyone know the peak output of the -67 750 alternator?
I installed an after market halogen headlight .its a 55-60w h4 . I also installed an ameter in the headlight housing .
The hook is correct ,gauge works fine . The problem is apparently the alternator does not put out enough to show a charge on the amp meter .at 2500to 3000 rpms the gauge still shows about 2amps discharge .
The gauge shows about 10 amp discharge at idle . the battery life would not be long in this situation. I know my sons headlight wattage is 40-50w [he has a 71 bsa firebird].
If i modify the socket and change to this bulb might this be enough of a reduction in current draw to maintain a charged battery and still have decent brightness of the headlight?
There was a small 4 3/4'' sealed beam on the bike [low brightness] that is why i changed to new headlight . Any ideas are welcomed . I understand there is a halogen hs-1 35-35w that is a cross match of the base on the h-4 but at the loss of britness . Thanks again for any suggestions . Ken in Penfield , New York

Lucas High Output 3 Phase

I recall that a few months ago, we were discussing the relative merits of the Lucas 3 phase RM24 vs the older RM19/21 single phase alternators.

Fortunately, tonight I found a graph from Lucas that puts proof to the discussion once and for all: it shows that as I'd stated, the 3 phase alternator produces much more useable power at any engine speed.

Click pic.to see the Full Graph

I've pulled off the following key numbers which tell the tale:

Comparison of RM 24 (3 phase) vs RM21 (single phase):
============ ===============

1. Output current at 1500 RPM - 7 amps vs 5.5 amps

2. Power output @ 2400 RPM - 157 watts vs 90 watts

3. Engine speed to produce 120 watts of output (ie Max output of RM21) - 1800 RPM vs 5000 RPM

4. Maximum alternator output @ required Engine speed
- 180 watts @ 4500 RPM vs 120 watts @ 5000RPM

The important fact is that especially at low engine speeds, the 3 phase system produces much more power, which is the main attribute of this type of system.

.. gREgg

GREGG !! Absolutely ELECTRIFYING !!!

Can anyone suggest a good supplier of a Lucas RM24. I am in Chicago. Pardon my ignorance of things British and Lucas, but what do I need? Do I just ask for an RM24 Alternator?

-Rick

Rick,

You need more than just the RM24 alternator and rotor, but there are some
options.

You will need the mating 3 phase rectifier, as well as a pair of matched
Zener diodes for regulation. In place of the special rectifier and Zeners ,
you could use the 3 phase Boyer Power Box. Alternately, you could use the 3
phase PODtronics box (which is an adaptation of a Japanese
rectifier/regulator box) that uses SCRs instead of Zeners.

However, before you go making the conversion, are you sure your RM21 is
really set up correctly? One of our club members (Bruce) was having
charging troubles with his Commando, and I advised him to check the
following simple details:

1. Ensure his rotor was fully magnetized (he subbed another rotor which
'felt' like it was more powerful). BTW, this is the most common problem
with low output, and is easily resolved by replacing with a new rotor.

2. Ensure the rotor is aligned with the stator. This means ensuring they
are concentric, as well as the rotor being centered axially with the
windings when viewed from above. This is the second most common problem and
easily solved with spacing the rotor and/or stator.

3. If you have one of the older 3-wire *single* phase alternators and you
are using it in a 12 volt system, two of its wires (green/yellow &
green/black) must be tied together. Make sure those two are tied together,
and that they are the correct ones are tied together ... you will cut the
output if the White-green wire is joined instead. Also, it is imperative
that the windings connected to both windings being joined are functional.
Testing each winding with an ohmmeter for continuity before joining the
wires is a good start, but even better is each of the windings for output
with the engine running,

With Bruce's Commando, correcting the above details completely cured his
charging problems.

.. gREgg

Coil operation

When the points close, current through the coil primary increases from zero to a maximum value (determined by circuit resistance) in an exponential manner, rapidly at first, then slowing as the current reaches it's maximum value.

The rate at which the current rises is determined by the coil inductance and the circuit resistance. At low engine speeds, the points are closed long enough to allow the current to reach a level limited only by the total
circuit resistance, ie, a DC value.

At higher speeds, the points open before the current has time to reach this maximum value. In fact, at
very high speeds, the current may not reach a value high enough to provide sufficient spark, and the engine will begin to miss.

This current through the coil builds a magnetic field around the coil. When the points open, The current through the coil is disrupted, and the field collapses. The collapsing field tries to maintain the current through the coil. Without the capacitor, the voltage will rise to a very high value at the points, and arcing will occur. The time for the field to collapse will also increase.

With the capacitor, the current provided by the collapsing field will discharge through it, limiting the voltage at the points, and the current/field will collapse very rapidly, having a discharge path to ground through the capacitor.
The coil, capacitor, and resister form a tuned, oscillator circuit.

When the coil is completely discharged, the capacitor is completely charged. Now, the capacitor will try to discharge to the coil. Without resistance, there is nothing to limit the coil or capacitor discharge current, and the cycle will repeat, ie, the coil will charge, then discharge to the capacitor, which will charge, then discharge to the coil, etc.

With the resistance, however, the current is "dampened," and the amplitude of the oscillating current is
reduced rapidly, dropping to negligible within 3-4 cycles. When the magnetic field of the primary coil collapses, it cuts through the windings of the secondary coil, producing an output voltage.

The magnitude of the output voltage is determined primarily by the windings ratio and by the speed at which the primary field collapses. A slow collapse will produce a lower output than a rapid collapse. Until the arc occurs at the plugs, the output of the secondary is nearly an open circuit, allowing the voltage to reach a peak before current is produced.

As soon as the spark occurs, the resistance is reduced, and current flows through the plug gap, maintaining the arc. The primary and secondary windings are isolated from each other, so that no current in one flows through the other.

However, the secondary is connected to the primary at the point where the primary connects to the points and capacitor, and there is no direct path for the return of the secondary current other than through the capacitor. As a result, the capacitor is part of the secondary as well as the primary. There is an oscillation in the secondary, just as there is in the primary, for the same reasons.

By properly selecting the coil/capacitor parameters, the designer can "tune" the circuit to provide the most effective output voltage, as described below.

Capacitor (Condenser)
The capacitor performs several functions. It prevents the points from arcing and prevents coil insulation
breakdown by limiting the rate of voltage rise at the points. It's primary function is to provide for a rapid decay of the primary coil current. The capacitor also "third-harmonic" tunes the coil, raising the peak output voltage and increasing the secondary voltage rise time.

This increases the efficiency and the amount of energy transferred to the spark plugs. If the coil secondary voltage rises too quickly, excessive high frequency energy is produced. This energy is then lost into the air-waves by electro-magnetic radiation from the ignition wiring instead of going to the spark plugs where we
would like it to go.

Voltage rise time should be more than 10 microseconds; a 50-microsecond rise time is OK. Conventional systems have a typical rise time of about 100 microseconds. but mostly, the condenser protects the points.

Here I'm assuming that we're talking about a Series 1 or II Interceptor.

Basically, you have to reverse the polarity of every component that has a
polarity. The simplest way is to replace them with their negative-ground
(earth) counterparts. These would be: the rectifier, and the Zener diode.
The, you have to reverse the wires going to the blue can capacitor, and to
the battery.

It is possible to reverse teh connections to the Zener and the rectifier,
but it is a little trickier if you are not perfectly clear on what you are
doing: the trick is that the body of the component has to be isolated from
the frame, and a connection added to it in order to reverse the connections
to it. In the case of the Zener, it means having to insulate it from its
heatsink ... there are standard kits available for this in the electronics
world, but its a matter of tracking them down if you don't have industry
contact.

.. gREgg

Once again I seek the help of the collective. This question is in two parts. First, does anyone have experience installing the Boyer Bransden electronic ignition on their Mk1A or Interceptors in general?

Second, does anyone know if the Boyer Bransden unit can be installed with a "negative" ground instead of the positive ground that is prevelant on most British machines? I'm looking into converting my Mk1A to a negative ground unit. Thanks in advance.
Rick

I use Boyer Bransden on my Series II; it runs fine and was easy to instal, but has the drawback that when starting, it often will "kick back" when the kickstarter is swung for the first time. BB don't seem to have an answer for this.

Nevertheless it is very easy to time, and has proved reliable. I reckon the engine is a little smoother at high revs, ie comfortable cruising has gone from 75 to 80 mph.
Your best bet to convert to neg. ground (why?) is to ask BB as they probably can supply a neg. unit.
Dave Hollyman

I've never tried one on an Interceptor, but I have one on my Bonneville, and the unit comes with instructions on how to connect it up to a negative ground machine. I'm not sure it is wise to make the conversion though. Anyway, familiar with Brit
machines will assume it is positive ground. If the polarity is accidentally reversed for any reason, it will blow the Boyer, so converting an Interceptor to negative ground and adding a Boyer may be asking for trouble unless the owner can be absolutely
certain that he will be the only one to work on the bike.

Bob Cram

I have a Lucas Rita for a Commando on my Series II and had to make a spacer so the eluctor would clear the points cover (this cured all my hot starting woes, period) if I had to do it over again I would look into a Boyer as this might clear the points cover without the 1/4" spacer.

I also have a Boyer micro digital on my Matchless 650 twin and wired it up negative ground, Podtronics, 3 phase power base alternator as per the instructions and it works just fine showing 14.8 volts across the battery with the lights on.

Mechanics now-a-days are schooled in negative ground machinery and have to wrap their heads around positive ground so IMHO I would think that the chances of a mishap are far greater with a positive ground than with the norm.
Cheers
Rick Fisher

Thanks to you all. The information will be put to good use. The reason for my query is the desire to install a system that conforms to most "on the road" bikes today. One of the items I am installing is an LED tail light unit for both my brakes and tail lights.

This unit is brighter, (added safety factor), and uses much less electricity than the
standard double filament bulb leaving more wattage and amps for my headlight, (hopefully a brighter light than the kerosene lamp that Lucas installed!). And, since diodes are very particular about how the positive and negative lines are hooked up, (has to be a negative ground), the more info I have about a conversion, the better to make an informed decision before I move to the assembly phase.

As of right now it looks like the entire tail unit will have to be floated, (ungrounded
or isolated from the frame). The bike will also sport an RM23 alternator, controlled by a Podtronics regulator, to boost total power availability. I also came into osession of an older installation sheet from Boyer Bransden that explains the hook up of it's MkIII unit in a negative ground environment so that problem is solved. Wiring the
bike will be interesting. If anyone has any tips in this area please don't
hesitate to post it to the web site.

Once again, thanks to you all. I hope the finished product lives up to level of help you've all given.

Rick

I've just returned from travel, and note Rick has been having difficulty in adapting a negative earth replacement LED light to his bike. Here's some insight ...

Rick,
If you are using the stock Lucas tail light unit, take the red lens off and have a look inside. You will note that the bulb socket is actually isolated from earth, because it is held by the molded rubber base of the light unit. The actual connection from the socket to earth is made by a thin piece of braid from the bulb socket to the metal bracket inside the light unit.

So, if you sever that braid, you break the earth connection. Now, you can connect a separate wire directly to the socket, and not have to have it go directly to earth. (This achieves the same thing as floating the subframe, with far fewer complications).

However, I do not think that this is going to help you, since the brake and tail light circuits are both sourcing current, and the common lead from the LED tail light has to sink the current to earth. So, if you have an LED light that's made for negative earth, floating its common (cathode, or negative) lead in order to go positive earth will do you no good, since the polarity is still wrong. If you float this common connection and earth the other leads instead, you cannot connect the common lead to both the brake and tail light circuits at the same time and have the functions remain separate .... (hope this is clear). To do what you need, you must actually reverse the polarity of how the actual LEDs are connected inside the light.

To reverse the polarity of the LED lights, you will have to sever the connection tying the two common (cathode) leads together, and run each to separate wires to act as the connections to the brake and tail light circuits. The other end of the LEDs - the anode (or positive) ends - will then need to be tied together to act as the new earth connection .. bearing in mind that there will be a resistor in series with each of the LEDs, and those *must* remain in-circuit.

Hope this has helped,
.. gREgg

I changed my old Boyer mk 3 to the later digital type of Boyer electronic ignition. The old one is not very sophisticated as it advances in a straight line, while the digital one makes a real curve .
It proved money well spend.. acceleration is better, but more important the idle is very much improved thanks to a electronic stabiliser. Because Enfield (like Norton) has a chain driven ignition mounted on the camshaft the idle is very difficult.. at least it was on my Interceptor.. But now it is a delight.. going very slow and stable. But.. an unstable idle can also be the result of an idle jet that is dirty. On the captain Norton site you'll find advice how to clean this microscopic little thing which is hidden deep in the inner parts
of your Concentric.

Paulus

Got the '65 Interceptor running today, I set it up with a Lucas SR2 magneto from a Super Meteor. Spark is very so so, not exactly fat which made starting hard.
Still, not bad for a 50 year old piece of electrical equipment!

Always liked the SR2 mags but can anyone recommend someone in the USA where I can get it re-magnetised and new capacitor fitted?
Roger.

The SR2s always give an excellent spark, especially at low speeds, and its not hard to keep them that way. I'd find it hard to believe that it needs magnetizing.

Clean and gap the points (standard Lucas fare), and replace the capacitor. The capacitor is a standard Lucas can type, of the type you often find in British car applications. You may even find one at your local Pep Boys store. Its easily accessible inside the housing, and is about a 10 minute job to replace.

.. Gregg

I don't remember where you are located, but I have had good results dealing with two people in the US. Mark Seibert did 2 K2F Mags for me includeing the one on my 65 Interceptor. he does remaging and he is located here in So Cal. E-mail Address mseibert@adelphia.net. The other is Bob Kizer
Cypress Ignition Ltd.
Oak Plaza Dr.
Cypress, TX. 77429
281-955-6100

Email PODtronics@aol.com

Hope this helps
Orlan

I somehow missed this discussion earlier. Anyway, I just wanted to bring to
everyone's attention that there's a guy in the U.S. who rides Triumphs, BSAs
etc. who has developed an LED light that is a straight drop into the standard
Lucas signal light and, he says, draws only 1 watt instead of 21. Anyway, he is
now working on a similar replacement for the stop/taillight unit.

His website is:
http://www.freewebs.com/rtetetet1/index2.html

The problem of installing LED tail lights and brake lights on my MkIA has been solved. The trick is to isolate, (or float as Nathaniel called it), the tail light assembly and run seperate lines to each LED and ground hook up.

Since the bike has a positive ground I used the brake light switch hook up, (two wire), as an isolated switch with one end going to the LED and the to ground. When the switch is activated to ground positive flows to the LED.

The Negative is fused through a fuse block and is constant at the tail light. Since the tail light is isolated, (not grounded), problem is solved. Actually, only the LED board is isolated. The whole unit works beautifully.

Rick