how many agree that stator failure is caused by vibration ?

[admin]

ah kiwi you stole my idea...,   great minds think alike ?  :D
the idea is that you drill some cooling airflow holes in the flywheel, possibly replace the magnet
and lighten the flywheel at the same time.

I like the design idea of a heavy flywheel in the way that the vision was built but in the real
world, I think I prefer the rpms to rise and especially drop quicker and dump some of that effect.
years ago I didn't mind it but now I feel like it sometimes gets in the way.

I'm (Still) in the camp that says playing with cooling the stator via fins and oil coolers is a fun science project
but the real problem is electrical and needs to be addressed and ultimately solved that way.
I'm currently running a used honda vt500 stator and mosfet reg/rec hoping I'll get 10 years out of it... :-\

I have one of those virago stators that will fit if you really must do it but, if you have any crank thrust clearance
issues with your vision motor you will have a crankcase full of cast iron filings ( not good  )
btw I am selling my extra virago stator for 45 plus shipping if anyone is interested.   8)

to quote Doc Brown " This sucker is electrical"

And yes having the flywheel enclose the stator will definitely hold the heat in. This makes me wonder if cutting a diagonal slot between the magnets or even drilling holes through the flywheel to enable more air movement round the stator as it spins would help with cooling. Would lighten the flywheel a little which wouldn't be a big issue but it would have to be balanced correctly.

[kiwibum]

ah kiwi you stole my idea...,   great minds think alike ?  :D
the idea is that you drill some cooling airflow holes in the flywheel, possibly replace the magnet
and lighten the flywheel at the same time.

mmm... Maybe this would be a nice way of lightening a XZ400 flywheel that little be more and enabling some cooling for the stator as well. Lots of things to test and try.

[Lucky]

Wouldn't the magnets break? I've never tried to drill a magnet.


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[admin]

yes they would break, it would probably be a mess.
in my mind I envisioned (pun intended) pulling out the magnet and having
a machine shop drill and lighten the flywheel it along with finding a way to use those
new rare earth magnets that are super powerful.

I remember reading something about how they added weight to the flywheel intentionally
at some point in the process and so maybe along the way the engine builders got a
little too crazy with adding the extra flywheel weight and goofed up the original design
that allowed for more clearance or whatever.

of course at this point we are now in cost prohibitive land because the cost for re engineering
the flywheel wouldnt be too cheap.

but lets just say we wanted to do this on the cheap,  you could drill two or four opposing
holes in the flywheel, inside, away from the magnet, if you were careful enough and measured
pretty accurately you could probably do it well enough to not upset the balance of the thing
you'd get some airflow in the process, possibly enough to make a difference. ( lots of if's here )


Supervision, very cool on the magnetti marelli stuff, man ya gotta love those Italians, a great idea
swapping the location of the rotor and stator for cooling. obviously why the Japanese are better at copying
than innovating but I digress.

if you could swap out the stator and flywheel locations then we probably wouldn't be here...   8)

[kiwibum]

but lets just say we wanted to do this on the cheap,  you could drill two or four opposing
holes in the flywheel, inside, away from the magnet, if you were careful enough and measured
pretty accurately you could probably do it well enough to not upset the balance of the thing
you'd get some airflow in the process, possibly enough to make a difference. ( lots of if's here )

That's what I had envisioned, carefully drilling to miss the magnets. Can't remember what the flywheel is like on inside now but there should be space between the magnets and enough to drill between. I assume the holes would want to be on an angle to help scoop air in or out (another issue which way to angle them) rather than perpendicular to the outside.

[Lucky]

If you could dry the rotor you might be able to set up an oil spray on the stator poles. You have an oil passage in the crank that feeds the starter clutch gear. The trick would be that it would need to be drilled vertically thought the side of the rotor (near where the clutch bolts go) lining up with the oil passage in the crank, then intercept that passage horizontally at the level of the poles.very exacting drilling

If there was a spot to do it.
If the resulting loss of oil pressure is ok.
If centrifugal force didn't just throw the oil onto the inside of the rotor...

Might work.


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[Lucky]

Drill the rotor, not dry it lol


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[Rick G]

That's a hoot about the Magnetti Marreli  electrical equipment. it looks great ! Its afar cry from their stuff used in 60's Duc's it was awful back then!

[fret not]

 I think that drawing heat away from the stator is better accomplished with direct heat conduction through the case and to the heat sink idea on the outside of the case.  Probably better contact of the stator to the case could be fashioned for more efficiency in conducting the heat to a sink.   

Of the three stators I have one is crispy and crumbly with some loose outer winds on a few coils because the epoxy has crumbled away.  The other two have smooth epoxy but one is black and the other is slightly more brown but still rather dark color.  The smooth epoxy stators test good but are on the way out judging by their coloration.  I'll use them as long as they don't become crumbly.  It seems obvious to me that heat has done the crumbly one in and is working on the other two, and that the windings becoming loose as the epoxy crumbles away allows the windings to vibrate and move about, which in turn can cause metal fatigue of the windings.  That's the open and short of it, I think. ;)

So, MOSFET or other efficient regulator to help prevent heat build up, plus heat dissipation to keep the epoxy from falling apart should go a long way toward prolonging stator life.

[dingleberry]

Sorry to dredge up an old post, but someone said it's good to flog a dead horse for new perspectives etc.
A question I have regarding stator failures is what climate are most of the failed stators being ridden in, style of riding, duration. I suppose in most cases it's difficult to answer  as many of our bikes have changed hands numerous times.
There has been talk of heat sinks and air cooling, oil cooling as well. I would like to add my theory.
What if a breather hole was drilled in the crankcase in a suitable position to catch a lot of oil splash from the crank. A hose routed to the stator cover with a fitting aimed at the top of the stator (where many think is lacking in cooling) providing at the least an oil mist/drip?
Would be a simple mod for only a couple of dollars.   

[jefferson]

A big part of the problem is that the stator is enclosed inside the flywheel and there isn't really a good way to get oil to it. Another problem is the oil that does get to it is already going to 200 degrees or there abouts. It would be alot better if the stator was in a sealed compartment from the engine. I also have an xs750 and the stator is sealed off from the engine and I don't see near as many stator problems with that model. The other thing is they run a demand system on those bikes and that has a lot to do with less stator burn ups. If our system could be converted over to a demand system then I think we would see alot better life out of the stators. I know it would take a different reg/rec, but not sure what else as electrical is not my forte. One thing that I think would help our stators is to use some of that heat sink paste that helps to conduct heat. If that was used between the stator and the sidecover it might help some with the heat. Whatever was used would have to be able to withstand the oily environment.

Jeff

[The Prophet of Doom]

I would like to add my theory.

If we have to have a theory - here is mine

My feeling is the stator's working temperature thing is a bit of a red herring. 

While it is impossible to know the heat rating of the wire used, the engine shouldn't be getting anywhere near as hot as the insulation rating - often 180^oC or 200^oC .  If it was, we would be getting stator burnouts after a single hard ride, not after thousands or even tens of thousands of kilometers.

I've seen a whole bunch of XZ stators.  They seem to be either uncharred (not to be confused with oil blackening) and working fine, or charred and failed - no in between.  Yes, obviously heat cycles and vibration will cause degradation and damage, but these would show as localised black spots where mostly we are talking sudden and violent failure of the entire stator.  I think we need to look elsewhere for the majority of failures.

I think the problem is the R/R.
When the R/R determines it is producing too much, then the SCR, dumps it back to earth.  This stops the battery from boiling and bulbs from blowing, but the excess energy has to go somewhere, and that somewhere is the stator - which will heat up.
If there is a lot of current switching the SCR will overheat and fail.  SCRs can fail while they are over temperature and return to being perfectly normal afterwards.

When the SCR fails, it will stop latching.  It can do so in one of two ways - it will either send all current to the battery (and so it will boil, and bulbs will pop, or it will dump it ALL to the stator.  The stator is not designed to handle this and will turn into a crispy critter.

If I am correct the problem can be addressed in a few ways.
1.  Reduce failure of the R/R by increased ventilation and/or heat sink area OR switching to a less failure prone R/R (eg Mosfet)
2.  Reduce R/R switching by consuming more power - ie High wattage lights always on - note that racers have real issues with burning stators as they typically only power the TCI - many will switch to series regulators which burn excess power rather than deliver back to stator
3.  Place a power consuming device (ie high power bulb  or large wire wound resistor and heat sink between the R/R and earth)

[Rikugun]

Do the SCR's ground stator windings to reduce rectifier output to a prescribed DC threshold? If so, what produces more heat in the R/R: 3(?) SCR's working hard with minimal load on the system or 6 diodes working hard with the addition of mega watt bulbs and/or resistors etc.

Jefferson -  while the costly and complex excitable field alternators are a thing of the past (for bikes), the "make only what you need" scheme does offer some advantages. Unfortunately, converting an XZ to this charging system would be quite an engineering project. It would make fitting alternate carbs look like a walk in the park.  :)

[The Prophet of Doom]

Do the SCR's ground stator windings to reduce rectifier output to a prescribed DC threshold? If so, what produces more heat in the R/R: 3(?) SCR's working hard with minimal load on the system or 6 diodes working hard with the addition of mega watt bulbs and/or resistors etc.

As far as I can tell the 6 diodes will be busy generating heat regardless of the path the electricity is taking
The 1 or 3 SCRs (I should crack open one of my failed units) generating heat (mostly) only when they switch

[Rikugun]

As far as I can tell the 6 diodes will be busy generating heat regardless of the path the electricity is taking
The 1 or 3 SCRs (I should crack open one of my failed units) generating heat (mostly) only when they switch

if you say so  :)

[fret not]

Excited field alternators do not produce any current if the battery is dead (needs voltage to excite the field).  They were not bad if the battery was in good health.  My Honda 750s had them. 

[The Prophet of Doom]

if you say so  :)

Well not because I say so, but because every schematic I've seen has the diodes on the stator side of the SCR  :P

[Cdnlouie]

It's definitely heat. I recently refreshed my Venture Royale which has the drilled crank and while it lasts much longer than the Vision (about 100000km) it stills wears out (eventually).  And the interesting thing is that it wears out in the same top high heat zone.  I have gone through two original Venture stators and they were both toasting up in the upper 1/3 of the stator.  All my Vision stators (3 now) toasted in the upper zone, so lower in the crankcase is definitely better for stators.

The Venture not only drills the crank but it has a tin cover (inserted in the sidecover) that allows the oil to fill it up and then it spills out onto the flywheel as an oil feed that baths the stator inside the flywheel.  This can only be a cooling effect on the stator which is really isolated from the crankcase oil.  When smaller flywheels were the norm and stators were on the outside they lasted forever.  It's an unhealthy engine design for stators.  Great for throttle roll-ons but bad for electrical.

Now if you could rotate your stator you could get a lot more use out of it.  This is kind of tough though because of the wires that exit from the windings needing to move (never tried it).  I have a Mosfet on an OEM stator for the last 10K and it should be due anytime so if I get another season it will be the most likely reason for doing so.

This is an oldie but goldie topic!  Thanks Ron!

[dingleberry]

If I am correct the problem can be addressed in a few ways.
1.  Reduce failure of the R/R by increased ventilation and/or heat sink area OR switching to a less failure prone R/R (eg Mosfet)
2.  Reduce R/R switching by consuming more power - ie High wattage lights always on - note that racers have real issues with burning stators as they typically only power the TCI - many will switch to series regulators which burn excess power rather than deliver back to stator
3.  Place a power consuming device (ie high power bulb  or large wire wound resistor and heat sink between the R/R and earth)

Maybe a zener diode like on the old brit bikes? Would that work as number 3 above?

[Rikugun]

I wonder how some stators in dry covers last so long?

Does anyone know the claimed OEM alternator wattage?