Another Thead for Discussing Conversion from 6 to 12 Volts

[StewartD]

Mach 1 wiring.jpg

Bob,

A revised diagram of my proposed conversion is attached. Having the full alternator details shown has made things clearer to me. Am I correct to assume that I should have no connection to the rectifier negative terminal?

Hans,

Yes, the diagram of the alternator is for the Mach 1. This is my project at the moment. Regarding the 450, my memory could be wrong - it is 34 years since I did that conversion. Your diagram is for 1968 points ignition models though. My 450 was a 1974 model with electronic ignition. In the early 1980s I wrote an article for the Ducati Owners Club of Victoria (Australia), about the conversion. I will try and get the wiring diagram I did at the time to confirm my memory of the two wires exiting the crankcase. My experience with Ducatis over many years is that the factory tend to throw whatever is in the parts bin onto a machine, if it is convenient.

Cheers,

Stewart D

[DewCatTea-Bob]

[quote=StewartD ...
" Am I correct to assume that I should have no connection to the rectifier negative terminal? "

____ Well, that's indeed as I had just-previously indicated. ...
Your charging-system project retains the stock negative-ground standard, so therefore your system can only direct just the alternator's rectified positive-type power-pulses to the battery & load-system,, whilst leaving any negative power-pulses ignored, as a normal manner of course.
__ If you wish, you could possibly also employ a positive-ground system as well, for obtaining two SEPARATE electrical-systems on your Duke. _ But I wouldn't recommend that it also be used for powering any high-draw load, such-as a regular headlight.
If your planned neg.ground-system turns-out to be a bit deficient for your needs, you may wish to consider converting your normal battery-powered ign.system over-to a positive-ground system with a Brit.bike battery-eliminator setup. _ That way, your engine could always be started (with a fairly independent power-system), regardless of the charge-state of your (neg.ground) battery.
This is a dual-system which I first came-up with in the late-60s, as it was otherwise always a disappointing-downer to expect going-out for a ride on a hot-day and instead become faced with an engine that wouldn't easily start-up because the battery had become run-down (for any of several probable reasons).
__ Anyhow, such alternative-system considerations are possible options which you may take advantage-of sometime down the road with your Duke-project.


Enlightened-Cheers,
-Bob

[StewartD]

DOCV_1978-02 p1.jpg

DOCV_1978-02 p2.jpg

DOCV_1978-02 p3.jpg

Bob,

Thanks again, for all your guidance. I will not use a dual circuit, but just disconnect the negative terminal of the rectifier as you say.

Peter Shearman, a past President and now life member of the Ducati Owners Club of Victoria (Australia), has given me access to an article written in 1978 for the club newsletter 'Desmoto' issue #2. It is by Stewart Marshall; I think it is quite a good article and I hope it is of interest to forum members. It is for a 1972 model with the 3 wires from the alternator. The page 3 raves are quite humorous too.

Enjoy,

Stewart D

[ducwiz]

Stewart,

thanks for the informaive article. It shows a different approach, called "half wave shunt regulation", whereas the DUCATI w/c regulators use the "dual half wave series regulation" principle, shown in the fig. below.

My point of view:
As mentioned in the article, in the shunt regulator the SCR fires instantly if the system (battery) voltage exceeds a preset limit. This causes a short circuitacross the corresponding stator winding, and the electric power of the actual voltage half-wave is dumped into the stator coil and the SCR. In the electronic world, the circuit is generally known as "voltage crowbar". The other half-winding stays unaffected, so always delivers it's power into the system. So, this regulator can never switch into zero-power output, it roughly regulates between 60 and 100% output.
The series regulator has two SCRs in series between winding and ground, and disconnect both half-windings alternatly from the system, if the preset voltage is exceeded. By this, the alternator idles, delivers no power into the system, but builds up a high AC voltage. This equals the open circuit voltage measured between the red and a yellow wire, which may exceed 35Volts at 5000 rpm. I suppose, each SCR has to block up to 100 Volt under this condition. This regulator type covers 0 to 100% power output.

From the "12V conversion" point of view there is only marginal difference between the two circuits. The series regulator uses the (red) center terminal of the stator as the positive output, in the shunt regulator the red terminal is the negativ (grounded) output. There is no difference in power output, and for both battery charging current sets in at the same engine rpm.

cheers Hans

[DewCatTea-Bob]

[quote= ducwiz ...
" It shows a different approach, called "half wave shunt regulation", whereas the DUCATI w/c regulators use the "dual half wave series regulation" principle, shown in the fig. below. "

____ Thanks a lot for your contribution-input, Hans ! _ I've read your posts on such matters and so-far (in my opinion) YOU've displayed the most advanced understanding of Ducati's charging-systems. _ However, I believe you have yet to conceive everything as I-myself do. ...
I presume that you-yourself drew-up the schematic-diagram that you've posted, is that not true ?
The detail within that drawing which most raises my eyebrow, is that it indicates the alt.stator-winding as-if it's merely a single/continuous-winding with an actual 'center-tap',, which I find to be somewhat misleading. _ And that's because the pair of stator-windings are rather two separate (but physically combined) stator-windings, (which are both EACH continuously-wound TOGETHER around the core-fingers in the same-manor as-like a SINGLE-winding would normally be done -[EXCEPT-that there's TWO instead of just one winding !]), of-which both are terminated-together (only at ONE-end) with a single 'common' circuit-path (rather than tapped-into as-like a standard 'center-tap' into ONE continuous-winding) !
Of-course I would agree that the 'common' & a 'center-tap' would be exactly the same electrically providing the two stator-windings were BOTH actually wound-connected the very-same (as-if like just one/single winding which has happened to have had it's physical-pathway interrupted and joined back-together at their common-connection). _
__ If you comprehend my chosen-wording, then you now ought-to understand why I find your posted representation of the alt-stator-winding as "misleading".
When I find it, I'll post my-own drawing/representation of the alt.stator-winding's electrical-relationship,, (as their physical-relationship isn't as easy to draw).
But hopefully you'll grasp the concept of what I'm trying to convey, without needing to see my drawing.
- UPDATE, I've since found one of my old-drawings (which I use-to think was fairly correct) and have now posted it (center pic). _ But I have NOW recalled that it's also somewhat flawed*, and-so I really need to make another drawing that's even MORE representative of the actual stator-winding arrangement. -(* Which is why that posted-pic's file-comment says what it does.)
__ I've also added a pic.diagram (which I found on the net) that depicts a std.regular center-tapped transformer, for comparing it's normal secondary center-tapped circuit-arrangement with Ducati's dual stator-winding arrangement.



" in the shunt regulator the SCR fires instantly if the system (battery) voltage exceeds a preset limit. This causes a short circuitacross the corresponding stator winding, and the electric power of the actual voltage half-wave is dumped into the stator coil and the SCR. In the electronic world, the circuit is generally known as "voltage crowbar". "

____ I really don't care-for that ZenerDiode-like effect, as it seems fairly wasteful.
__ Also, that process (of shorting-out one of the stator-windings) tends to work-AGAINST it's-own intended regulation-effect, cuz that creates increased flux-field strength which thus-then induces MORE power into the OPPOSITE-winding (that's still providing it's power) !


" The other half-winding stays unaffected, "

____ I'm hoping that you'll come to agree that rather than: "The other half-winding",
it's actually: 'the OTHER whole-winding'.


" this regulator can never switch into zero-power output, it roughly regulates between 60 and 100% output. "

____ I think you may likely reconsider your stated-percentages after I've finally convinced you of what's all actually what, with the Ducati-alternator's scheme-of-things.



" The series regulator has two SCRs in series between winding and ground, and disconnect both half-windings alternatly from the system,
the alternator
delivers no power into the system, "

____ Ducati's stock w-c.regulator-circuit is certainly the most SUPERIOR method for 'taming' the power-output of Ducati's uniquely-arranged alt.stator-windings (which make-use of the 'mutual-induction effect') !
__ The use of a Zener-diode regulator-circuit not-only shorts-out the excess-power that's available from the alternator, it ALSO can then cause the alternator to create still MORE power ! _ So-thus once the Z.diode begins to come-into effect, it then becomes it's-own enemy (by creating still more work for itself) !



" From the "12V conversion" point of view there is only marginal difference between the two circuits.
There is no difference in power output, and for both battery charging current sets in at the same engine rpm. "

____ I'm afraid I can't agree with all of this, since the amount of current-load on the two stator-windings will also effect alt.power-output (along with RPM) !

____ Hans, I'm really hoping that you will at-least entertain the concept which I'd like you to adopt, and after you've come to understand it all (as I do), I'm sure you will then see the-light & FULLY realize how Ducati actually expected their charging-system to function (in the rather 'Green' manor in which it does).
So if you don't fully comprehend the "mutual-induction effect", then please ask a related question,, and I will then explain & convince you of how it MUST work.
__ I've included a pic.diagram of Ducati's regulator-circuit... I don't know who originally drew-up that scheme-layout just as it is, but I-myself added all the coloring to it.
While it's representation of the two alt.stator winding-circuits is somewhat MORE representative of the actual-case than YOUR depiction of the entire stator-winding scheme-layout, I STILL don't find IT to be a fully-accurate representation of the ACTUAL scheme-layout, EITHER.
____ Your thoughtful-comments are looked forward to ! _ (And I hope you'll think it over well, before going-ahead & committing yourself to whatever you first/initially jump-into thinking.)


Edited-Post,
-Bob

[ducwiz]

Bob,

thanks for your friendly invitation to contribute, and the explicit praise of my input here. Just now, i'll give a rather brief response to your elaborated post, because I'm about to leave for a few days of vacation, but I promise to resume this posting later.

I presume that you-yourself drew-up the schematic-diagram that you've posted, is that not true ?

No, this schematic was not drawn by me, it was copied from a german specialist book from the early 1990ies, author: Juergen Kasedorf, title: "a service primer for automotive electronics" (as far as I remember, title translated by me). Kasedorf wass an engineer of high standing, also working as a college lecturer. He published numerous books about different areas of automotive technology.
Btw: If you carefully compare his circuit and the one you posted here, you'll recognize them as practically identic.

cheers/bye Hans

p.s. as english is not my native tongue, it may happen that occasionally I "get your wires crossed " here, and vice versa ...

[DewCatTea-Bob]

[quote= ducwiz ...
" thanks for your friendly invitation to contribute, and the explicit praise of my input here. "

____ Well Hans, considering my minimal wording pertaining to those notions, I didn't expect that my intent was quite so obvious,, so that indeed makes you extra-perceptive (on-top of your other attributes), as well.



" I'm about to leave for a few days of vacation, "

____ Well-then I sure hope that you don't then bother yourself with thoughts inspired by certain statements I had made in my previous post, cuz they were at-least misleading if not out-rightly incorrect. _ So I've since removed/deleted them and have now replaced them with truer statements. _ However, while those (now removed) associated-statements were actually-not really correct, they still none-the-less should've helped to inspire mind-opening thought-work which ought-to have helped achieve acceptance of the 'mutual-induction process',, which is WHAT I really want to get understood (by everyone possible).


" I promise to resume this posting later. "

____ That's fine & well enough ! _ I, for one, look-forward to your further input.
__ For the meantime,, I'll help to get the ball rolling in the expected direction, by mentioning that that-which I mean by "mutual-induction effect", is a concept which anyone who already comprehends & understands how similar inductive-circuits (such as transformers & ignition-coils) are able to perform their function,, could also just as well grasp the operating-function of, as well !
__ I've been waiting for ANYone to ask about such effect within a Ducati-alternator but, it's seeming that I shouldn't keep-on doing-so, or-else it may never come to happen, (before I'm no-longer able-to).



" this schematic was not drawn by me, it was copied from a german specialist book from the early 1990ies, author: Juergen Kasedorf, "

____ I had never-before seen THAT-particular schematic-diagram pic.drawing before you came-up with it, so I'm afraid I allowed myself to jump-to-conclusion that it was your-own work.



" Kasedorf wass an engineer of high standing, also working as a college lecturer. "

____ It fairly-much disappoints me that anyone of such high-standing would allow any of their work to be simplified towards lower-standards in any way... For example in the case of J.K's circuit-representation (with regards-to it's technical-accuracy), of Ducati's depicted stator-winding circuit-arrangement,, obviously seems to have been presumed as a mere std.center-tapped arrangement. - (I've now posted drawings of both the rather more ACTUAL circuit-arrangement, as well as an altered-version which better matches J.K's unrealistic & simpler arrangement,, which when compared, quite clearly clarifies the ACTUAL-difference between the 'REAL' & the 'wrong'.)
__ However I do find the rest of HIS drawing's layout to be superior in that it manages to keep the component-relationships better represented BOTH electrically AND physically.



" If you carefully compare his circuit and the one you posted here, you'll recognize them as practically identic. "

____ Yes, at-least electrically so,, as expected...
I-myself have always preferred such schematic-diagrams to be laid-out so as to be more physically recognizable, (as is J.K's).



" as english is not my native tongue, "

____ I've long been wondering about that...
Back when you first began posting here, I had then been kept away (due to extended family-issues),, and when I finally got to read one of your first posts, claiming to be located in Germany, I've ever since wanted to ask if you were of an English-family which happened to-be stationed in that Land (rather than an actual German yourself),, because your written-English has always seemed to-be TOO-good to-be that of any non-Englishman !
So that's still-another FINE attribute you have.



____ I've added a couple pic.diagrams, depicting Ducati's chosen alt.stator-winding arrangement for their dual winding-circuits, as well as an altered-version showing how the alt.stator would have-to be wound & connected-up in-order for it's winding-circuit to be rightfully considered as an ACTUAL 'center-tap' arrangement.
__ Now with the two DIFFERENT stator-winding arrangements, (top-pic = REAL ; and bottom-pic = wrong),, it should be quite clear, (even to those who're untrained), that there's certainly a SUBSTANTIAL-difference between Ducati's actual stator-winding arrangement and that which so many have ASSUMED as being a rather ordinary 'center-tap' type of arrangement.


Hopeful-Cheers,
dct.Bob