Rotor Winding Tooling

Hey, Jim. Found this during some mindless surfing. Some trivia for your files.

Screenshot_20190504-230508_Chrome.jpg


From here: https://www.240turbo.com/AdjustableVoltage.html

I used to "flash the field" on ol' Harley 6 volt generators, after a rebuild/rewind. Quite necessary on those.

First I've heard of this being done on alternator rotor/armatures. Our XSs can have the brush polarity either way, depending on which system, and a used type "A" rotor refitted to a type "B" alternator would certainly experience current reversal.

We probably don't have this issue since our alternators aren't self-energizing, and get full current immediately when the bike is switched "on"...
 
More mindless surfing, researching about type "A" and type "B" regulators, and came across an interesting failure scenario.

First, consider our two alternator types.
RegulatorTypes.jpg


Evidently, each type has it's own strengths and weaknesses.
But, the type "A" can have a unique failure mode, causing "alternator runaway".
Also known as an "N" type, here's the scenario.
RunawayAlternator01.jpg


This is how it would look on our XS650 system.
RunawayAlternator02.jpg


I believe that we suspect that many of our shorted/grounded rotors are shorting at the critical point where the inner winding wire passes from the inside to the outside. An area that you have specifically addressed with your localized double-wrap procedure where the wire emerges from the coil inner.

I don't know what procedure specifics or quality controls were/are applied to the existing rotors, but I could presume that there's a 50/50 chance of the emerging inner wire being attached to the outer slipring. If that shorts to ground, there'll be a "runaway alternator" event.

If the emerging inner wire is attached to the inner slipring, and shorts to ground, it'll simply blow a fuse.

Just stuff to contemplate...
 
but I could presume that there's a 50/50 chance of the emerging inner wire being attached to the outer slipring.
I set my winding tooling up so that positioning of the leads is consistent. I'd guess the factory did too.... although I honestly can't say what my positioning is. I'll check it and make sure it's positioned for the "blow the fuse" scenario. Thanks for the info Steve.
 
I used to "flash the field" on ol' Harley 6 volt generators, after a rebuild/rewind. Quite necessary on those.
Funny story.... about 15 yrs ago we had a huge ice storm here. We lost power for over a week. Before the storm hit, I bought a generator. It didn't work. Flashed the field and it still works to this day. The day after I bought it, I went back to the tool store for sumpin' else and there were dozens of angry folk there wantin' their money back for the generators they bought that didn't work. Turns out they bought in a truck full (100's) of generators that had sat in a warehouse for years. I showed the guys there how to flash the field on 'em and left. Went back a few weeks later and they gave me a gift card for 200 bucks. Apparently I saved the day. These young guys never heard of magnets losing magnetism and flashing the field to re-magnetize it.:rolleyes:
 
Last edited:
Aaaarrrrg......More Tooling.
The old style (non-TCI) rotors have their balance holes drilld on the edges.... which are angled. Made a ramp to set the drilling fixture on.....

IMG_20190515_192150.jpg


IMG_20190515_192051.jpg


Need to clean it up and varnish it, but it works.... no drill bit walking. :)
Last piece of tooling.... maybe. :umm:
 
The Never Ending Tooling Saga. :rolleyes:
A forum member contacted me about rewinding a Honda CB big 4 rotor. I reckon it's worth a shot. Here's the Honda rotor next to an XS rotor...

diff.jpg


As you can see, diameter's roughly the same, but the bottom of the CB rotor's full round without the cutouts the XS has. Means my XS tooling to separate the halves won't work. So I cut out 4 pieces of 2X3/16" angle and welded some 1/2" rod on top to fit inside the 2 halves. Ground flat spots on the end of the rods and welded 2 of them to a 10ga flat plate.

splitter tooling 1.jpg


Set the rotor in place and clamped the other 2 angles with C clamps.... and into the press we go.

splitter tooling 2.jpg


Worked a treat.:D
It even separated leaving the winding pretty much intact. Now I get to do the tedious task of counting the number of turns. The guys over on the Honda site gave me a number that looks correct, but since I can count 'em, I will just to verify.

rotor split.jpg


Then on to measuring and making the winding form.
 
Last edited:
Well this is an interesting project. You enjoy the challenge don’t you...the puzzle to be solved. Keeps the mind sharp! :geek:
 
Well that took a minute or two... phew... :er:
The Honda boys said 500 turns. I came out with 529 turns. I'm wondering if Honda (or Hitachi... or whoever) wound them to a diameter range instead of a specific number of turns? Dunno. Original wire is off standard. Between 21 and 22 AWG. I'm going with 21AWG, so I think I'll stick with 500 turns. Shooting for about 3.8-4Ω. we'll see. On to the measuring. One thing I noticed, Honda wrapped their coils with fiberglass tape, which is what I'm doing with my coils. The XS coils aren't wrapped.

counting.jpg
 
I showed the guys there how to flash the field on 'em and left.
Jim,
Can you please explain this process (when you have some spare time, of course!)? I have an old Coleman PowerMate generator I horse-traded with a friend of mine. It purrs (Briggs & Straton engine, 'natch), but doesn't make any volts. Brushes are fine, breaker's closed. I'm thinking this is another situation where it's been sitting for so long it needs to be "flashed". Friend used it to build, then power his camp. When I got it, replaced the air filter, spark plug, oil, and fuel. Like I said, it purrs... Thank you in advance,
Tebo

P.S. Your work on these generators is brilliant! You are a treasure! t
 
Most, not all generators use an early system that's basically a hybrid of a electrically controlled alternator (such as our XS) and a PMA (permanent magnet alternator). It electrically controls the field to control the output, whereas a PMA relies strictly on a strong permanent magnet to produce a strong (but fixed... at maximum at that) output. But since most generators have no battery, where does the initial voltage to control them come from? The answer is a magnet... Not the strong magnet like the PMA, just a weak magnet. It creates just enough electricity for the regulator to send to the field coils to start the process. And without getting too deep into the weeds, it's not really a magnet. The iron core of the field has what's called "residual magnetism." It ain't much, just enough to jump start the whole process. When that residual magnetism disappears (as it does over time), there's nothing there to create electricity. We have to have magnetism to create electricity.
So... if your eyes haven't glazed over yet, you have to restore that residual magnetism. Inside the generator is a wire between the field winding and the regulator, usually just marked with an "F." It's usually green. Take a battery... it can even be your 12-18V drill battery... it don't take much. and touch the positive side to the "F" wire and ground the negative side of the battery to the generator cases. Hold it there for a second or two and it will re-magnetize the field. Then start the generator. Once it's generating it will build up a good amount of magnetism in the field core and there ya go.. you're in business. If it's an old generator, it's good practice to run it every month or so to keep the residual magnetism alive.
 
Last edited:
That is invaluable information, Jim! My eyes haven't glazed over!... I'll give it a shot when time permits. If I can re-energize that generator, I have many, many options open to me. If I can make that PowerMate make volts again, I'll keep it maintained for many future uses. Thanks again and again!
 
Back
Top