Generator polarizing with magneto ignition

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Re: Generator polarizing with magneto ignition

Postby jOe » Sat May 14, 2016 11:24 pm

I had a Klystron tube go bad,-- really bad, in a radar van. I still remember that smell.
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Re: Generator polarizing with magneto ignition

Postby hennesse » Sun May 15, 2016 9:08 pm

jOe wrote:Moving on to that big capacitor off the regulator , which I recall is 450 picofarads/24V, if the relay is manually triggered, and however much is stored in it was put back into the system, would that be enough to flash the fields?
But if there's no output from the generator it wouldn't recharge anyway.


jOe - microfarad NOT picofarad !!!

The 32727-63 capacitor was used on 1963 - 1969 XLCH (above engine 63 XL[ch] 3015). I believe it was added to help either the headlight or the horn (or both) at low rpm. At idle, my 1962 headlight dims and brightens, and the horn works not at all. I think the generator output is right at the cutout relay setting. I don't know if it helps smooth out the headlight, but I'll bet it gives you something out of the horn. Not stock for my bike, but it might be a nice-to-have.

Magneto Sportster wrote:
posted some photos over on XLforum showing the mounting location.

For 1963-1964, it connects to the + (red wires) side of the horn. For 1966-1969, it connects to the "61" terminal of the Bosch regulator. For some odd reason, Harley put it in the "Circuit Breaker" section of the Parts Catalog.

Vtwin sells a "Country of Origin: Imported" repro for $36 here.
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Re: Generator polarizing with magneto ignition

Postby hennesse » Sun May 15, 2016 9:15 pm

hennesse wrote:We instill the instruction in the pole shoes of a "new" generator by polarizing the generator. On a battery equipped bike, this is accomplished by momentarily (like 1 second) connecting a wire between the "BAT" and the "ARM" terminals of the regulator. On a magneto-equipped XLCH, you have to supply an external battery, but it need not be any bigger than the battery in an XLH. Connect the negative terminal of the external battery to ground, and touch the positive terminal of the battery to the regulator's ARM terminal for 1 second.


For the Bosch regulator on 1965-1969 (and to around 1976) models, "BAT" is called "B+" and "ARM" is called "D+".
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Re: Generator polarizing with magneto ignition

Postby jOe » Sun May 15, 2016 10:20 pm

[quote]jOe - microfarad NOT picofarad !!!

Are you sure? I saw the pico farad symbol (or though I did--I wrote it down in my manual) which is sort of like a U with a tail associated with the cap. The microfarad symbol is more mike an M.
The voice of experience would probably say that the originals are probably pretty much dead by now anyway. Back in the day they worked ok. No surprise that lights dim and horns are quite much below 1700 rpm.
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Re: Generator polarizing with magneto ignition

Postby sportsterpaul » Sun May 15, 2016 10:53 pm

Nope, I spent 35 years in Silicon Valley-- the little u with a tail (µ) is the Greek mu, and stands for micro, that is, one-millionth. The small m is milli, one-thousandths, like mA. The capital M in mega, as in a million. Computer jocks like Dave get to use either the micro,
http://www.fileformat.info/info/unicode ... /index.htm
or the Greek letter:
http://www.fileformat.info/info/unicode ... /index.htm

In factors of 1000, its F, mF, nF, µF, pF, fF
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Re: Generator polarizing with magneto ignition

Postby jOe » Sun May 15, 2016 11:09 pm

Thanks for the clarification! I learned something today.
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Re: Generator polarizing with magneto ignition

Postby hennesse » Mon May 16, 2016 2:18 pm

sportsterpaul wrote:Nope, I spent 35 years in Silicon Valley-- the little u with a tail (µ) is the Greek mu, and stands for micro, that is, one-millionth. The small m is milli, one-thousandths, like mA. The capital M in mega, as in a million. Computer jocks like Dave get to use either the micro,


Yeah, us computer jocks understand that the greek letter mu often does not display correctly in web pages, so we say "micro".

AEI sells .3 and .2 microfarad condensors for FM magnetos. For grins, I just tested a condensor from a K circuit breaker with my $15 capacitor tester - guess what - it's .24 microfarad, about the same as the one for the magneto.

Our friends at VTwin call their repro 32727-63 a "500 MFD" - a non-standard terminology. Micro? Milli? Mega? Nobody uses millifarads, so I think it is most likely a 500 microfarad.

Let's try to reason this out. If your generator and battery die, you can run a XLH all day long on a 6v lantern battery. On the other hand, a headlight or horn will exhaust that battery in about a minute. So the "circuit breaker condensor" doesn't have to store a whole lot of 'lectrikity to do its job, but the "headlight/horn condensor" does. Would a capacitor 2500 times larger than a circuit breaker capacitor (500 microfarad = 2500 * .2 microfarad) do it? That sounds reasonable. 500 milli-farad is 1000 times larger than that, and that seems to be stretching it quite a bit.

Looking at electronics suppliers like Mouser, the typical 500 microfarads are similar (mostly larger) size as the 32767-63. They do show .5F and 500,000 micro-farads (equivalent to 500 milli-farad), but these approach beer can size. So 500 microfarad would seem to be the proper interpretation. Unfortunately, nothing comes in the same kind of package as the 32767-63.

Here's an interesting tidbit from Wikipedia about what an ignition system condensor does...


The first reliable battery operated ignition was developed by the Dayton Engineering Laboratories Co. (Delco) and introduced in the 1910 Cadillac. This ignition was developed by Charles Kettering and was a wonder in its day. It consisted of a single coil, points (the switch), a capacitor and a distributor set up to allocate the spark from the ignition coil timed to the correct cylinder.

The points allow the coil magnetic field to build. When the points open by a cam arrangement, the magnetic field collapses inducing an EMF in the primary that is much larger than the battery voltage and the transformer action produces a large output voltage (20 kV or greater) from the secondary.

The capacitor has two functions. Its main function is to form a parallel resonant circuit with the ignition coil.[2][3] During resonance, energy is repeatedly transferred to the secondary side until the energy is exhausted.[4] As a result of this resonance the duration of the spark is sustained and so implements a good flame front in the air/fuel mixture. The capacitor's second function and consequent on the first, is to minimise arcing at the contacts at the point of opening by providing an alternative destination for the coil's discharge current. This reduces contact burning and maximizes point life. The Kettering system became the primary ignition system for many years in the automotive industry due to its lower cost, and relative simplicity.
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Re: Generator polarizing with magneto ignition

Postby sportsterpaul » Mon May 16, 2016 6:00 pm

Fantastic logic Dave, comparing the times and capacities. This what my co-worker would call "back-of-envelope" calculations. The term was invented by Enrico Fermi, the A-bomb physicist. So many of my other co-workers would come up with computer simulation answers that were just absurd, but since they came from the computer, everybody would just trust the numbers. My pal would just run things down in his head, screw up his face and say "you better check that number."

And yeah, I have had great fun with symbols in websites. Just like µ, there is one unicode symbol for ohms, and a different one for Omega. I was pretty frustrated when having trouble, and one of the programmers said "Oh, it depends on the font, not all fonts have all the unicodes." Thus was born my program to round up all web programmers into internment camps, where they can be punished for doing stuff like this to their fellow earthlings. I don't know how you get the patience to struggle with this, when even a little letter is not really a letter, its a character encoding.

Back on topic, I spend a decade trying to design a Harley voltage regulator that could work on a magneto bike with no capacitor. That means either you use 120V parts to withstand the switching spics, or put a 32V clamp diode to cut the spikes down. The spikes only happen when you have no load connected. With the lights on, the spikes pretty much disappear. Thing is, if you wire the bike to leave the lights on, it also makes it harder for the generator to self-start. And when the light blows out, you get the 100-volt spikes again.

I might undertake re-visiting that regulator design, now that I am older and smarter, and that there are tiny ceramic capacitors of high value that I could work into the design. I tell you this, all that work did get me to respect the factory and the Accel designs. And it taught me that while transistors are great, there is a lot to love in that old Delco mechanical regulator.

Dave, you mentioned output wavering around the cutout voltage. On a magneto bike I would not be afraid to open the regulator up and bend the tab on the cut-out relay to lower the spring tension. Having the cut-out does help start up, but with no battery to back-flow, you don't have to worry if the cutout opens a little below 6V or 12V, whatever your generator voltage is.

BTW Dave, what is the correct answer to the choke capscha question? Its not pull.
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