I happen to have a handful of 2 wire alternators kicking around that would have done the job nicely. Perhaps I'm doing it to amuse myself. I like the look of those coils and copper. Are you saying that the result in joining two wires is inferior to a 2 wire alternator? Or are you implying I'm a fool with my money? If so it looks like I'm in good company here.
I like the old style (unpotted coils) alternators like you have, because the exposed coils make it possible to resolder a connection if it fails. Unfortunately, the lack of potting means it is more likely to fail.
The problem is the AC current set up in each coil by the rotor also exerts a small AC force on the wires. This isn't (necessarily) a problem if the windings are completely tight, so individual windings cannot move with respect to each other, but it is a problem if a couple of the wires are even a little bit loose. The force reverses six times each revolution of the rotor, so even only 0.001" of looseness lets the wires rub that much against each other many hundreds of times a second. If this happens, eventually, the ~0.002"-thick insulation rubs through. If an electrical problem does develop, internal chafing within the coils isn't necessarily the most likely source of it. Wherever connecting wires are close to the stator core there is the potential for shorting to earth.
I lost one alternator to exactly this problem. I subsequently discovered a BSA (U.S.) racing bulletin issued in the early 1960s advising racers to dip their stators in glyptol to make them more reliable. Anyway, it would be ironic if you installed a new electronic voltage regulator with the goal of achieving greater reliability from your electrical system, but your old unpotted alternator let you down...
The alternator is new. I have one like it on my 1959 B33 and another on a 1965 BSA SS80. Both are working fine so I know they can last a long time. I'll take my chances. Also I'm using a Podtronics simply because I have one and don't have an old style rectifier. This will end up on a 1960 B40 that probably won't get all that many night miles on it. It can't be worse than the 6 volt system that the bike came with.
The one on my Royal Star lasted for forty years...should be good enough I think.
The fact both BSA and Triumph issued issued service bulletins about these armatures, and discontinued the bare wire version, suggests that it was a problem with enough of them that it was an issue at the time. However, age isn't what brought on the failures (in the percentage of cases where there were failures), miles did, so the fact yours still works after 40 years (as do many others) isn't evidence they are reliable.
I couldn't find the BSA bulletin this morning, but a Johnson Motors Service Note from 1963, number 17-63 says "For competition purposes, we have found it advisable to dip the stator in heavy red protective sealer... Dipping of the stator in this manner protects the windings against vibrations and short circuits from metal particles in the primary case."
The OP subsequently said that he will be using a bare wire stator because he has it on hand, not because he is trying for higher reliability. That's fine, and there's a very good chance he never will have a problem in the way he intends to use that bike. However, my suggestion is that if anyone were interested in reducing the probability of failure from the present fairly low number to something even lower, they should use an encapsulator stator for the reasons in the JoMo bulletin and in my earlier post.
Joined: Sep 2002 Posts: 7,812Alex
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Joined: Sep 2002
I don't think anybody is arguing that the potted stators aren't more rugged. But I think peter will be just fine with alternator, particularly if it isn't going to be on his daily ride or road racer. I'm just trying to counter the notion that EVERY part has to be upgraded ASAP on our old machines. Yea...stuff fails on occasion...and we deal with it, Peter, I think knows that and is willing to deal with it.
Incidentally, the one that eventually did fail on my Royal Star (I have no idea how many miles it had on it, but it was a lot) failed because the insulation paper got brittle and started to disintegrate. Once it stopped holding the coils in place, they started to rub through the insulation and charging gradually got weaker until it couldn't support the halogen headlamp and Boyer in traffic any more. A nice, gradual decline...I like failures you can procrastinate on...
A smattering: '53 Gold Flash '67 Royal Star '71 Rickman Metisse '40 Silver Star '37 Rudge Special sixtyseventy Lightboltrocket road racer...and many more.
I'm just trying to counter the notion that EVERY part has to be upgraded ASAP on our old machines.
I completely agree. This is why it usually is important to know an intended application in order to make a good recommendation. Preparing a bike to make a cross-country ride suggests a solution that increases reliability, while preparing a bike that will be used around town a small number of weekends each year suggests making do with existing components.
Originally Posted By: Alex
Incidentally, the one that eventually did fail on my Royal Star (I have no idea how many miles it had on it, but it was a lot) failed because the insulation paper got brittle and started to disintegrate.
The one that failed on me was because I deliberately used a bare wire alternator so that I could repair it if it failed. I put several thousand miles on the bike before the stator failed, but when it did it was a big headache because of where it happened. I should have used the encapsulated stator the first time...
Originally Posted By: Alex
A nice, gradual decline...I like failures you can procrastinate on...
Old tube electronics were ideal for giving you plenty of warning as they very slowly got worse. This is also why I prefer points to electronic ignitions (except for my Trident, where dealing with three sets of points is just too much to contemplate).
Seems alternator (or is that generator) threads are becoming like oil threads and best avoided)
Unlike oil threads, where everybody gets to have an opinion, alternator (and generator) posts either are based on the laws of physics and on commonly used terminology, or they're not. This current thread has been completely civil and based on facts. No one has even objected when opinions were offered on under what circumstances one stator might be more reasonbly used than another. But, that said, it doesn't change the fact that Castrol is indisputabily better than...
Are you saying that the result in joining two wires is inferior to a 2 wire alternator?
Very definitely, but only because the Lucas 3-wire single-phase alternators pre-date the 2-wire single-phase alternators, each succeeding 'generation' developed more power than the previous ones, and the 3-wire alternator you have is an early one.
Afaict, Lucas seems to have produced two versions of each 'generation' of alternator - a 'high-power' version for bikes presumably intended for the police/military/government customers with extra electrical consumers (e.g. radio, flashing lights, two-tone horns) and a 'low-power' version for Joe Public's bikes.
The most powerful 3-wire single-phase was the 'high-power' RM20, supplied from the early to the late 1960's; it was rated the same (10.5A @ 5,000 rpm) as the 'low-power' RM21 2-wire single-phase supplied from the late 1960's 'til 1978.
However, from the cable colours, you appear to have a late 1950's RM13 or RM15, which pre-dates the RM20 and related 'low-power' RM19. Unfortunately, I don't have an rpm vs. Amps curve for either but Triumph's "Instruction manual No.4" that covers the early unit 350 and 500 that had these alternators states, "The alternator is designed for use with headlamp bulbs not exceeding 30 watts (sic) rating".
Originally Posted By: Allan Gill
apparently when connected for 12v these units will give you more power
If, by "power" you mean Watts, obviously; if you're doubling the regulated Voltage, as long as you don't halve the Amps, by definition, you're going to have more Watts.