Recharging 250 MK1/MK3 Magneto

[Desmoto-M.3]

Bob, can you tell me the auction number of the advancer you're talking about?

You didn't say how the power diode should be connected, forward or backward?
And my only other question for now is,
is the shape of the lobe for the pionts cam, the only reason for why Ducati didn't also use 28 degrees of advance, instead of just 18 like on the models like my Mark 3 has?

Thanks,
Ken

[captpaul]

To all who are wondering if your magnets in your fly wheel are good or in fairly normal working condition.
My son who rewinds the brass fly wheeled narrow case stator coils,told me from all the alt testing he has performed,
If the coils are in proper working order, and if you put the flywheel in question on the steel side of a car door or refrigerator,and it sticks like crazy , it should work as it was designed.
But if it slides down or isn't really sticking it won't charge very good at all.
I found a man in Kentucky, who re-magnetizes cushman flywheels. he told me he could re-magnetise my ducati flywheels
for me but I would have to pay a fee for the jig for the first one to fit the ducati flywheels then the rest would be a standard price, I don't remember how much but as I recall it wasn't much plus both way shipping, I have 8 brass wheels 4 are weak
Now that I just retired and will soon have all my wife's honey doo list about caught up.I'll have to dig throuh all my phone numbers and find this mr.Tucker in kentuckey!

[DewCatTea-Bob]

By Desmoto-M.3 : ...
" can you tell me the auction number of the advancer you're talking about? "

____ It was eBay# 180453094568 .


" You didn't say how the power diode should be connected, forward or backward? "

____ I had thought of including that info but figured since I had recently covered the subject already in greater detail (within another thread), that I might as well not bother to explain again so soon afterwords.
But now I guess that since this particular modification is actually in itself a unique operation which may be separately done solely by itself, I'll use different and accordingly simpler wording -(than I had used for the conversion to battery-powered brake-light).
So without getting into as great of detail,, I'd suggest just connecting the power-diode (between the alternator's YELLOW-wirelead & the ign.coil's ign.points-terminal), with the diode 'pointing' in which-ever direction that you happen to pick,, and if you then find that you no longer have any spark, THEN flip-it-over & reconnect it pointing the other way.


" is the shape of the lobe for the pionts cam, the only reason for why Ducati didn't also use 28 degrees of advance, instead of just 18 like on the models like my Mark 3 has? "

_____ While the difference (in how long the two different types of cam-lobes make the points stay open) actually has nothing to do with the 10-degrees difference (of auto-advance) between the two advancer-unit models,, the reason (of why Ducati did not also choose to have that full 28-degrees of ign.advance on their models which don't employ battery-powered ignition), most likely had to do with the limited duration of the power-pulse which the ignition-system (on the non-battery powered models) requires to make it's spark...
___ You see, each power-pulse of the 6-pole alternator of the battery-powered models, lasts 60-degrees of crankshaft-rotation,, and that model of alt.rotor is 'timed' to the crankshaft so that the peak of it's power-pulse will occur 10 degrees BTDC - just ever so slightly BEFORE the time when the ign.points open at kickstarting-RPM, (so as to help fully assist a battery [which may be low on charge] ).
Even though THE pertinent power-pulse's peak is just 30-degrees away from ZER0 energy-output, and the associated 28-degree advancer-unit will, (at higher RPM), cause the spark to occur as soon as just only 4 rotational-degrees after it's birth, (thus at a relatively week stage in the life of that power-pulse),,
since, (on-the-other-hand), the FASTER an alternator spins - the MORE power-juice it produces, this ADVANTAGE obviously tends to compensate for the (previously mentioned) DISADVANTAGE which the auto-advancer promotes, (however so, not at an exact reciprocal rate.). ...
So anyway, as RPMs climb higher & higher and the advancer-unit auto-advances the ignition-spark further & further towards points-in-time when that alternator power-pulse is then weaker & weaker,, then the ignition-system will tend to draw more & more from the battery to supplement it's required demand, (until after the auto-advance has maxed-out -[@ 3k-RPM], of course, [after which point, increasing-RPM will then only increase alternator-output, (for helping the ign.system!)] ).
Therefore, the 28-degrees of advance is no problem what-so-ever for the battery-powered models (with the shorter-duration power-pulses)!.
___ Now in the case of the 4-pole alternator (of the 40 & 28-watt) models,, each power pulse lasts 90-degrees, and it's 4-pole flywheel-rotor is 'timed' to the crankshaft so that the peak of it's power-pulse will occur 20-degrees BTDC - just ever so slightly AFTER the time when the ign.points open at kickstarting-RPM. - Thus making sure that not only will the ign.coil be subjected to a sudden-jolt of MAXimum power-juice, but also the collapsing-flux of the power-coil will insure to help super-force the juice through the ign.coil !! - (Side-Note: Now you can understand why a battery-powered ign.system doesn't produce it's spark at the instant when the ign.points make contact & then allow juice to enter the ign.coil... as a battery just doesn't have any collapsing-flux to "super-force" it's juice through the ign.coil !)
__ Since in this case, the pertinent power-pulse's peak is 45-degrees away from ZER0 energy-output, and the associated 18-degree advancer-unit will cause the spark to still occur at least 25-degrees after the birth of the power-pulse,,
you can now understand how there's still more than enough power-juice to satisfy the ignition's requirements at full-advance -(@ 3k-RPM).
And since it's possible to run a motor which has the 28-degree auto-advance & the 6-pole alternator -(with short 60-degree power-pulses), without need for a battery,, then you can understand how there would still be plenty of power-juice for a motor to certainly run with the 28-degree auto-advancer & a 4-pole alternator -(with long 90-degree power-pulses)! _ (Since it would have the advantage of being about 20 rotational-degrees further past the birth of the related power-pulse! - [As compared to the 6-pole's shorter-duration power-pulse].)
Therefore the 28-degree advancer-unit can also easily complete it's function, in place of the 18-degree unit. _ It's just simply a matter of being even more certain that the flywheel-rotor is indeed accurately 'timed' to the crankshaft. ...
__ Now since the new static-timing (with the use of the 28-degree unit), will require it's pre-set to be retarded from 22 (+/- 1) degrees, back to 11 (+/-2) degrees BTDC,, the flywheel-rotor ought to also be retarded about the same 10-degrees, so that the required power-pulse will still be just about peaked when the ign.points open at kicking-RPM.
I would not suggest resetting the rotor before installing the 28-degree advancer-unit and trying-it-out first, cuz the rotor's pre-set timing (to the crankshaft) is possibly not exactly set optimally anyhow, and so there's a fair chance that it's existing phase-timing may still be close enough for the spark to be sufficient anyway.
(More about flywheel-rotor phase-timing later.)


Good Cheers,
DCT-Bob

[dsmess]

You've got some good ideas there Bob (and incredible energy). It sounds like it will work, except you will have voltage drop (0.7V) due to the diode. I'm not sure what the peak voltage of the sinusoidal waveform is....10V maybe? This will reduce your charge energy to the coil. If I remember my trig, I think the voltage is about 86% of peak when 30 degrees off from the peak. You could probably rephase the rotor clockwise 15 degrees or so if you want to optimize things. The change in advance would be welcome. My Mark 3 (40W alt) is pretty snappish. I had a problem with this bike flooding very easily if you tickled the carb and turned the throttle too much while kicking, it would not start...or start and die. I would remove the plug...seeing it was wet..dry it and try again. It was tricky. I switched to a Japanese coil. I think it is the one used for the older 90 or 110CC singles...no more flooding, and it starts pretty easy now. I had a scrambler years ago with the same problem.

As far as drag on the engine with the alternator. I vaguely remember a number from Physics...740 watts per horsepower.
I don't think the puny Ducati alternator will slow the bike down much!

Regards,

Scott (the new guy)

[DewCatTea-Bob]

By dsmess : ...
" except you will have voltage drop (0.7V) due to the diode. I'm not sure what the peak voltage of the sinusoidal waveform is....10V maybe? This will reduce your charge energy to the coil. "

____ The amplitude of the sine-wave varies depending on RPM, and I have measured it to climb as high as over 70-volts (with no load). _ The insignificant loss of a half-volt is no concern since it's rather more-so the 'sudden-jolt' of current-juice through the ign.coil, which creates the spark-strength ! - (The ign.coil is not exactly used as a voltage-transformer.)


" If I remember my trig, I think the voltage is about 86% of peak when 30 degrees off from the peak. "

____ That seems about right but, lets keep in mind that THAT "30 degrees" is in reference to the center-peak of a 'power-pulse' which is in itself 180-degrees long of the 360-degree long [single] sine-wave cycle),, and those type of 'WAVEFORM'-degrees should not be confused with the "ROTATIONAL-degrees" of the crankshaft, (which I have been solely referring with).


" You could probably rephase the rotor clockwise 15 degrees or so if you want to optimize things. "

____ That statement seems to indicate that you're actually aware of & have a decent grasp of whats going-on! ...
I agree that the timing of the flywheel-rotor could be retarded a few degrees (more than the 10-degrees of difference between the two advancer-units), so long as the rotor's magnets are not too weak of course.
(And I had intended to cover such details about rotor-phasing, later!)
Pulling-off the rotor & rotating it clockwise 15-degrees and then pressing it back onto the crankshaft, (thus retarding the power-pulses), would then have it (theoretically) set to produce the peak of the power-pulse about 4-degrees after the newly-reset static-timing would have the ign.coil fired-up.
That would no doubt be okay, since I'm sure that there were many n-c Mark-3 & Scrambler models which ran well even with the alt.rotor 'timed' less optimally phased.


" I had a problem with this bike flooding very easily if you tickled the carb and turned the throttle too much while kicking, it would not start...or start and die. I would remove the plug...seeing it was wet..dry it and try again. It was tricky. I switched to a Japanese coil. , and it starts pretty easy now. I had a scrambler years ago with the same problem. "

____ Well Scott, the stock SSI-carb along with the stock ignition-setup on those models is a fairly-poor combo! - I suggest switching to a Dellorto 'square-slide' carb (for better starting)!


" As far as drag on the engine with the alternator. I vaguely remember a number from Physics...740 watts per horsepower.
I don't think the puny Ducati alternator will slow the bike down much! "

____ I quite agree! ... It won't slow it down, "much!" .
It's quite true that the percentage of saved waste is not real significant but, the rest of the world is now supposed to finally be thinking "GREEN" these days, (just as I've always tended to do anyhow, without any such nudging) !
It's also very much the same as choosing the other gas-station across the street solely because their price is 2-cents cheaper per gallon!


Green-Cheers,
-Bob

[dsmess]

Bob,

You are definitely the King of Ducati single electrics!

Do you have the parts to test out your idea? Give it a try. The manuals describe the AC voltage of the battery type alternator, but I see no reference to the
40W Yellow-White coil voltage. It's a little hard to measure on a running bike with the points breaking. I expect you must have built some kind of a mechanical jig to turn the alternator, or used a digital scope.

Believe it or not, the SS1 works pretty well on this bike. It actually idles smoothly, and also looks a lot nicer than the square carb. I had a pair on an old Guzzi V7. One carb intermittently backfired at idle. I never did get it working right.

Regards,

Scott

[DewCatTea-Bob]

" Do you have the parts to test out your idea? Give it a try. The manuals describe the AC voltage of the battery type alternator, but I see no reference to the
40W Yellow-White coil voltage. It's a little hard to measure on a running bike with the points breaking. I expect you must have built some kind of a mechanical jig to turn the alternator, or used a digital scope. "

_____ I've already tried everything I know about on DUCATIs long ago back in the early '70s -(when I got my Tech.degree from O.I.T.)!
While in the process of converting the entire electrical-system of my favorite Mark-3 so as to incorporate every electrical-type of advantage that could possibly be done to it, I simply connected it's stock alt.leads to a volt-meter while the engine ran on a battery ('total-loss' at the time). _ (Nothing so fancy as you expected! - Although I had always wanted to do such extensive testing!)
__ I should point-out that while all the Ducati-alternators that I ever tested would easily send the volt-meter's needle well past 50-volts (during high-RPM!),, when connected to a load like a headlight-bulb, the output-voltage would then always drop way-down! - The measured voltage very much depends on the resistance of whatever (real) load is also connected!
So while the ign.coil is also a high-load electrical-component, it's the surge of CURRENT (not voltage), which creates magnetic-flux around the ign.coil to then instantly cause the high-tension for making a spark!


" looks a lot nicer than the square carb. I had a pair on an old Guzzi V7. One carb intermittently backfired at idle. I never did get it working right. "

____ I'm quite familiar with that regular 'snapping' that most all those GUZZIs always seem to expel from their intakes!
While I never came to be a GUZZI-guy, (like I am a DUKE-man!), I suspect that common snapping has it's roots somewhere within the valve-train, or perhaps it's due to spark-jumping within it's distributor,, NOT the carbs! ...
That same snapping-issue also existed when those V-twins came stock with SSI model carbs!
__ I sure understand what you mean about the looks of the SSI-carbs, of course,, and while it's doubtful that the 'square-slide' carbs 'flow' as well as the SSI models, I do suspect that the square-slides 'atomize' the fuel a bit better.
Plus the square-slide models sure do make starting a heck of a lot nicer!!


DUKE-Cheers,
DCT-Bob

[dsmess]

Bob,

Total loss...of course. I was fixating on some web info I saw awhile back. You may have seen it. This guy modified a Ducati single case. He had an electric motor driving the crank...rod removed I think. He was using this rig to test Stators. I believe he had a speed control on the thing.
Did you see my posting on the Electrex setup?

Scott

[captpaul]

Scott;

Was the guy with the alternator (mcy shop made)testing machine, you're talking about,madduck from msducati forum?
I saw that very same machine at Syd's Cycles in St Petersburg Fl, 10 years ago. It worked with a bare n/case motor,crankshaft balanced to work without a rod. it only had a set of points and coil and spark gap tester, worked like a champ.
Washing machine type motor spun the tester, they made alts of different volts and the one that interested me was the one
that they put on a endurance type single and it ran 2 super bright headlites tail and motor perfectly.

[dsmess]

I'm not sure.....but I think it is. I'll see if I can find the link in my bookmarks.

S