Stator part 2: the WRECKONING!

[Night Vision]

I not sure the ying-yang magnetism has a major role in the failure....

I have had the same rotor through three stators (orig, electrosux, Virago) and all three failed at different intervals 6k, 3k, 9k.

It is unusal that H₂O's stators (mostly) failed at 1,000 miles... no one else's have.

I told him long ago to unhook his odometer....

The few stators here that have lasted (Kenny, Jason) get just as hot and backened as a short term fryer...
I think it has more to do with the vibration and the quality of the materials...

as far as I know, no one has kilt a Tim Parrot stator yet (ha! 'yall better knock the wood)

[funkamongus]

unhook the odometer? What does that do?

[QBS]

In the case of H2o, it might render peace of mind or at least blissful ignorance.

[funkamongus]

hahahahahahahahahah   cough cough..  ..    .. hhahahhhahahhaahahahahahhahhahahahhahaa

[Walt_M.]

I have been trying to stay out of the stator discussions because I know the answer but no one seems to care. The stators fail because the repeated heating and cooling of the epoxy coating by the heat of the engine causes the epoxy to become brittle. As the copper windings heat and cool they open spaces in the coating that allow the windings to vibrate. This destroys the remaining insulation in short order leading to a ground and stator failure.
The key to stator survival is to keep the epoxy intact. Either use a stator that will withstand the engine heat or find a way to reduce the engine heat.
The stator can not produce enough electrical energy to heat itself to the point of failure.

[George R. Young]

Tried the drilled bolt, inconclusive.

One suggestion if you're winding yourself, use teflon-coated high-temp wire.

Good luck.

[Rick G]

Maybe the answer is to install a competition stator , that mounts on the out side of the case. There are used on many bikes used in the Baja 1000. Even if they crap out just as often , they would be easy to change. :D :D :D :D :D :D :D :D

[Kid Jedi]

the funny thing is that I will probably do everything that everyone has mentioned, improved cooling, better materials, better stator,and use everyone's theorys. so we will still be with out conclusive proof.

by the way, has any one else installed a heat sink or relocated the R/R to a better location, ya know... NOT 5 INCHES FROM THE FREAKING EXHAUST!

I mean C'MON Yamaha!

some of the things that the engineers did when designing this bike make me hurt.  :'(

[Tiger]

 :) Quite a number have made/bought a bracket that comes off of the left rear foot rest and mounted the R/R there. The bracket I have on "The Mistress", comes off of the screw that holds the lower fender in place (left side again). These two ways ensure that the R/R gets sufficient air circulation...

                   8).......TIGER....... 8)

[Night Vision]

by the way, has any one else installed a heat sink ....

if you study toasted stators, you'll find most of them are toastier on the top than the bottom.
we did a sidecase temperature comparison with an infra red thermometer and noticed a significant difference between the top and bottom.

I sawed a heatsink from a 386 processor in half and was going to use the thermo epoxy to attach it above the crank bolt cover, but never followed through  :P

[Rick G]

While I have moved the RR to the left passenger foot rest / muffler bracket , a Visionary did some testing and found it did not run hot, in its roaster position.

[Walt_M.]

N-V, I have been thinking about putting one of the liquid cooled CPU coolers on my stator cover but haven't gotten into details yet. I'm not sure an air cooler would make enough of a difference. I do think Lucky's oil cooler must help some but I don't want to get into the oil system.

[Blake]

I have been trying to stay out of the stator discussions because I know the answer but no one seems to care. The stators fail because the repeated heating and cooling of the epoxy coating by the heat of the engine causes the epoxy to become brittle. As the copper windings heat and cool they open spaces in the coating that allow the windings to vibrate. This destroys the remaining insulation in short order leading to a ground and stator failure.
The key to stator survival is to keep the epoxy intact. Either use a stator that will withstand the engine heat or find a way to reduce the engine heat.
The stator can not produce enough electrical energy to heat itself to the point of failure.

Exactly.  Ideally there would be a flexible epoxy that can withstand the high temperatures/repeated expanding/contracting experienced.

[Night Vision]

N-V, I have been thinking about putting one of the liquid cooled CPU coolers on my stator cover but haven't gotten into details yet. I'm not sure an air cooler would make enough of a difference. I do think Lucky's oil cooler must help some but I don't want to get into the oil system.

I have the oil cooler mod and still smoked two stators  :-\

[Kid Jedi]

Talked to a motor tech today with 25 years experience in the field. I askedif it was vibration. he said no way. if it was vibration then we would see windings coming off. that stator overheated to the point of failure.
at least that's how mine failed

I have been trying to stay out of the stator discussions because I know the answer but no one seems to care. The stators fail because the repeated heating and cooling of the epoxy coating by the heat of the engine causes the epoxy to become brittle. As the copper windings heat and cool they open spaces in the coating that allow the windings to vibrate. This destroys the remaining insulation in short order leading to a ground and stator failure. 

basically Walt summed up what we have been discussing for the last couple of days! we do care!  ;D

I said the stator was overheating, here is my proof.

The stator is rated to produce 20A at 14v(Haynes manual pg141) assuming a 75% efficiency you can say that the stator is actual producing 26.6 amps, so 6.6 is lost to heat. (because it isn't lost to light emission!   :P)

6.6 amps. What is that in a unit of power?

OHMS law
*= multiply
Voltage (volts) * Current (amps)= Power in watts
14v * 6.6A =92.4 watts of energy lost to heat
But we need that in Joules per second
which is, conveniently 92.4 joules per sec

Waste energy: 92.4 Joules per sec

What temp is the case where the stator sitting? I am going to assume its the coolant temp, and I have had my fan come on in traffic, that's 98c plus or minus 3 c (pg 180 Yamaha service manual) and we sure as hell know the oil isn't touching the stator, when siting the oil level is below the stator and when running its even lower.

so lets call it 100c

Ambient temp 100c

Next question- how much material is heating up?

the stator with winding weigh about 2.6 lbs( bathroom scale, me with stator, me without)   *Note: go on diet*

2.6 lbs = 1179 grams

now for the real science!  :D
we need the change in heat formula ( we are attempting Calorimetry Kids!  http://en.wikipedia.org/wiki/Calorimetry)
*= multiply
Q= M*C* Delta T

Q=  energy or heat
M= mass of object to undergo thermal change
C= it the heat capacity of the object ( a number that describes the relationship between energy and temp)
Delta T= the change in temperature that the object undergoes in Kelvins but since we are working in numbers higher than zero c can be used
Do some simple algebra to get

Delta T= (M*C) divided by Q

Delta T= what we want
Q=energy  in joules 92.4
M= mass of the stator in grams 1179g
C= heat capacity of the stator in Joules per gram per kelvin
Since the stator is steel, and copper with a small percentage (by mass) of insulation, we can negate the mass of the insulation. also because the heat capacity of steel and copper are also very close to the same .38 and .42 lets call it .42 since there is about 6 times more steel than copper  C=.42

now for the answer:

Delta T=(1197*.42)/92.4


5.5 degrees c per SECOND


So the stator generates enough energy to increase 5 degrees c per second. and without cooling that can get out of hand VERY fast

I remember some article on the forums saying that the stator case was reaching 160 c,  any one remember who figured this out?

If i can improve the surface connection between the cover and stator that would effectively double the mass of the stator, so half the rate of temp increase, so that would hit ~ 137 degrees c

Wile i was at the motor shop picking out wire I am using for the rewind, I identified the old wire, by the color of the insulation, to be rated for 80c. what a joke.  I picked up some "thermaleze" Qs wire, 17 gauge. the catalog says 200c and the insulating paper has the same rating. I have a good feeling about this.

the total at the motor store for the super high grade wire and paper? $13.63  ;D
the wire has a low friction coating  ;D


P.S. Thanks for all of your input guys. But especially to inane cathode, he is keeping me honest!

[inanecathode]

Talked to a motor tech today with 25 years experience in the field. I askedif it was vibration. he said no way. if it was vibration then we would see windings coming off. So, this super motor tech. Has he ever worked on the charging system of a v-twin with a permanent magnet charging system? Does he even know what a vision is? that stator overheated to the point of failure. at least that's how mine failed Once again you havent actually determined the actual source of initial failure, all you've determined is that at some point it had gotten hot

I have been trying to stay out of the stator discussions because I know the answer but no one seems to care. The stators fail because the repeated heating and cooling of the epoxy coating by the heat of the engine causes the epoxy to become brittle. As the copper windings heat and cool they open spaces in the coating that allow the windings to vibrate. This destroys the remaining insulation in short order leading to a ground and stator failure. 

basically Walt summed up what we have been discussing for the last couple of days! we do care!  ;D

I said the stator was overheating, here is my proof.

The stator is rated to produce 20A at 14v(Haynes manual pg141) assuming a 75% efficiency you can say that the stator is actual producing 26.6 amps, so 6.6 is lost to heat. (because it isn't lost to light emission!   :P) Where do you get 75% efficiency from? This makes no sense whatsoever, the stator is not a lightbulb or a heating element, its a long piece of wire wrapped around and around. You're doing the waste heat calculation wrong, its not a cumulative effect of lost electrical power through arbitrary efficiency numbers, its a function of electrical current put through a finite diameter wire. Find the resistance per foot of the particular alloy of copper yamaha used and you'll have a much closer number.

6.6 amps. What is that in a unit of power?

OHMS law
*= multiply
Voltage (volts) * Current (amps)= Power in watts
14v * 6.6A =92.4 watts of energy lost to heat
But we need that in Joules per second
which is, conveniently 92.4 joules per sec

Waste energy: 92.4 Joules per sec

What temp is the case where the stator sitting? I am going to assume its the coolant temp, and I have had my fan come on in traffic, that's 98c plus or minus 3 c (pg 180 Yamaha service manual) and we sure as hell know the oil isn't touching the stator, when siting the oil level is below the stator and when running its even lower. 240F is as hot as the oil will get according to multiple forum posters

so lets call it 100c

Ambient temp 100c

Next question- how much material is heating up?

the stator with winding weigh about 2.6 lbs( bathroom scale, me with stator, me without)   *Note: go on diet*

2.6 lbs = 1179 grams

now for the real science!  :D
we need the change in heat formula ( we are attempting Calorimetry Kids!  http://en.wikipedia.org/wiki/Calorimetry)
*= multiply
Q= M*C* Delta T

Q=  energy or heat
M= mass of object to undergo thermal change
C= it the heat capacity of the object ( a number that describes the relationship between energy and temp)
Delta T= the change in temperature that the object undergoes in Kelvins but since we are working in numbers higher than zero c can be used
Do some simple algebra to get

Delta T= (M*C) divided by Q

Delta T= what we want
Q=energy  in joules 92.4
M= mass of the stator in grams 1179g
C= heat capacity of the stator in Joules per gram per kelvin
Since the stator is steel, and copper with a small percentage (by mass) of insulation, we can negate the mass of the insulation. also because the heat capacity of steel and copper are also very close to the same .38 and .42 lets call it .42 since there is about 6 times more steel than copper  C=.42 You can't discard numbers if you're doing finite calculations because they're complicated or disagree with your premise

now for the answer:

Delta T=(1197*.42)/92.4


5.5 degrees c per SECOND


So the stator generates enough energy to increase 5 degrees c per second. and without cooling that can get out of hand VERY fast To suggest that theres absolutely ZERO cooling (absolutely no thermal losses to ANYTHING in your equation) either through convection to the air thats whirling around the stator from the magnet, or from the stator core to the case itself is absurd at best

I remember some article on the forums saying that the stator case was reaching 160 c,  any one remember who figured this out?

If i can improve the surface connection between the cover and stator that would effectively double the mass of the stator, so half the rate of temp increase, so that would hit ~ 137 degrees c You're assuming a hypothetical totally homologous heated mass with no consideration to thermal lag between your assumed hot spots and the rest of the mass. Have you done any calculations for how quickly heat could actually dissipate under full charging load?

Wile i was at the motor shop picking out wire I am using for the rewind, I identified the old wire, by the color of the insulation Dyes used in insulation batches, especially 25 years ago, have no bearing on what is actually in the insulation. Have you had the insulation analysed to find out what exactly its composed of?, to be rated for 80c. what a joke.  I picked up some "thermaleze" Qs wire, 17 gauge. the catalog says 200c and the insulating paper has the same rating. I have a good feeling about this. Is this wire oil safe? What's it actually made out of?

the total at the motor store for the super high grade wire and paper? $13.63  ;D
the wire has a low friction coating  ;D


P.S. Thanks for all of your input guys. But especially to inane cathode, he is keeping me honest!

There's some stuff to think about. I'd invite the mystery super mechanic to explain how he thinks the wire from the stator poles would somehow come loose. I'd also like an explanation from you why you're totally discounting the fact that the stock stator wires rest, with no extra insulation or holding fixtures, against sharp steel corners and how after thousands of hours of operation and vibrations this would have no impact on the insulation integrity. Instead entirely speculative overheating is the root cause.

[vadasz1]

Looks like the Kid Jedi is the new Coil........  ;)

[Kid Jedi]

i am not trying to produce a very accurate calculation, I am trying to point out the failure.

Mainly i wanted a theoretical number that would be harsher than the environment, so if i designed a solution rugged enough to solve the horribly overkill numbers i found, then the real problem will be far within tolerances.

cooling was not taken in to account in the math, only energy generated

and yes the wire is oil proof.

the stator i identified was not oem, but a supposed heavy duty replacement I put in 2 years ago

I fully disassembled my stator and nothing was loose. the insulation came off in strips. If the insulation wasn't burnt, then vibration would have had no effect.with my vision running I feel almost no vibration on my case. footpegs buzz more than my side cases.

there were no sharp corners on my stator, the wire had welded itself to the inside upper edge on the arms in 3 spots, one for each phase. each corner was smoothed out and coated with epoxy.


For cooling calculations, I plan on finding those through experiment, using actual engine components, when I have some results I will share them here

As for my waste calculation..  that was a great idea inane, and I should have calculated that way!

[inanecathode]

The reason the wire was welded is because it shorted out and burned the stator.
Your feet arent inside the engine, and i doubt you'd be able to feel the frequency thats short enough to cause the inner wires to vibrate. Remember we're not talking about taking a file to the wire, all it has to do is move 1/10th of a milimeter and its enough to take the insulation off the wire. Understand its not robust insulation AT ALL. Its ONLY design is to prevent two touching wires to conduct NOT to withstand ANY abrasion of ANY kind.
The thing i dont get, is if its really heat, why doesnt it fail the instant the bike gets to operating temperature? The stator is under full load constantly, all it would take is the engine reaching operating temperature ONCE and the insulation would fail. Its barely a thousandth thick, its not thick enough to sustain any heat spikes. Theres plenty of room between stator wires for the insulation to run out. If it was truely a wire insulation problem it would fail the very first time you would run it up to operating temperature.
If you're really concerned about heat you need to focus on a better way of soaking the entire stator windings and all in epoxy. Not that shitty assembly epoxy they put in fan motors, but a high temperature flexible type. Its the JB weld problem. Its super strong, but its super brittle and inflexible. Nothing can withstand constant agitation, they'll fail eventually you just need to find one thats flexible enough to deal with it.
One thing i noticed, if you're trying to make some super heat conductive stator setup, it wont work with the mylar board (i saw the instructable too ;)) you'll essentially insulate the windings from the core and actually increase the heat it develops.

[Kid Jedi]

epoxy is ductile till it is burnt....