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Discussion in 'Parallel Universe' started by C5!, Jul 11, 2011.
When you get it, let's see some pics on how you installed this heat shield.
I think this is a neat solution. Why bmw didn't think about a vented rotor:
from the compufire website: The precision balanced vented rotor keeps the stator cooler in closed primary systems to maintain maximum output under all high current draw conditions. http://www.compufire.com/index.php?option=com_content&view=category&layout=blog&id=2&Itemid=6
Cush suggested that 4 ties would make for neater job - one at each end and one on each side of the dog-leg ... I agree 4 ties is better, I'll kit it out that way.
At $20 this is likely the cheapest farkle I'll have on the bike ...
I need to get 10 - 12 folks interested to make it work, I've got three so far... If you want one let me know,
the stuff is a bit cheaper than I thought, if first class USA postage is OK with everyone I can include that in the $20 kit price. What you would get is 4 stainless steel ties 3/16" x 8" long and an ~ 12" x 3" piece of the 1/4" think heatshield material which will give you about a 2/3 wrap around the pipe or you can trim it narrower if you wish...
I'll play with it when I get it....
Honestly I don't know how much it will help, there may be something else going on here...
shut style regulators are quite common so root cause might be some design flaw.......but a rise of 10 degrees celcius doubles the rate of most chemical reactions, likely including the heat-related aging of the stator insulation, so while the root cause may lie elsewhere I think this is a good idea for $20....
If you want in PM me, and if I get enough interest y'all can PayPal me the money and I'll get us set up, it really doesn't seem cost effective without about 10 folks ...
Shit - i'd do it.
As I said the Austrian company which did the stator rewinding does not exist any more. So I asked a few guys I know, about the problem and possible solutions. After a hint I read a zillion posts in German and even Italian forums. Most things are not new but I think worth to mention even if there is no demystification.
At least we are not alone and there are hundreds of Aprilias having the same problem. There are similarities, no doubt. The F8 engine and the Aprilia V2 are both manufactured in Austria at Rotax (lets see if I can get them on the phone, maybe I will try). This allows to speculate about which supplier Rotax uses for the stators of both engines. I'd guess the same one (Denso). Many, many Triumphs and Buells (Rotax engine!) have the same problem, but thats another story.
Now it is getting complicated as I have to talk about things I am not really familiar with nor do I fully understand them or have more than basic knowledge necessary to see the potential relationships. Additionally my English isn't the best. So please forgive me if I explain or describe technical things a bit odd.
Before I write anything else, the German Prilia riders have for their understanding solved the problem. More or less.
Many Aprilia stators may have died due to a loose conncetor or cables which have been crimped too loose. If I understood correctly the loose conncector/crimps leads to a power interruption and that - so was said - leads in DC systems to an arch (spark) which can create superhigh voltage for the fraction of a second leading to a electrical discharge between the windings of the stator.They named it Tesla - effect. Changing the lenght and the connector sitting in the engine cover cured this and less alternators died. But this was not the major problem as further rotors burned and - guess - with higher mileage affected the far most Aprilias.
For most bikes the problem is heat.
And no the problem is not heat from the exhaust! I am pretty sure you can forget that as the Aprilias exhaust isnt close to the engine cover where the stator sits. Aprilia uses the same type of regulator as BMW does, so it is in fact that system you (or somebody else) described in that way that the alternator is always working with full output whether the produced electrical power is needed or not. Maybe not the best of descriptions but the way I understood it.
Well, the Germans went exactly the same way and even contacted the same companies like CARMO in the Netherlands for rewinding and for different types of regulators.
However, if I translate correctly it was said that the Aprilia (like the BMW) uses a cross regulator with shunt and with such a system the excess energy produced is converted into heat. Heat which affects the rotor. So the guys talked to Carmo and tried different regulators, like MOSFET cross regulators, Harley Davidson regulators and other stuff.
They ended with regulator rectifiers they got from Cycle Electric Inc (Series E 600) or Compu-Fire (55402). At the end a long term solution was to install a Carmo rotor (with different insulating) together with the Compu-Fire regulator. Some guys did only install the Carmo rotor but they soon were roasted too, it was said that some of them died between 700 and 5000mls. Most guys who installed both, Camro rotor and CF regulator had no problems, one reported that everything works fine since 5000mls and he checks current, voltage and other values regularly but did not find the slightest problem.
Its for sure that the regulator alone is not the problem! The Germans also assumed that when magnetism of the permanent magnets is set to high ex factory the electric power is too high resulting in a higher temperature of the stator coil.
One guy posted an image showing the differences of a MOSFET regulator (Yamaha R1) and the Compu-Fire 55402)
Last and maybe most intersting is, that the Italian Aprila riders started some kind of protest action with forms one could fill on a website and send directly to the Aprilia factory. The Italians reported that Aprilia started slow but then further investigated resulting in a reduced price for the stator and after a while in changing the output power from 500W (watt) to 300!!!
Needless to say that Aprilia never made an official statement, they see no problem at all!
Aprilia Italy reduced the price for the rotor dramatically and stated that the warranty for replaced stators is valid and extended if full service documentation is existing. Germany followed this procedure described in Aprilia Service Bulletin #006/2011.
Well no really new findings, but maybe good as food for thoughts.
PS. I had technician from Bosch on the phone a minute ago and he said if you measure 100°C (dunno what Farenheits that is) on the engine cover the stator itself will most likely have over 100°C which he thinks is the treshold between normal and too hot. Exceeding 100° he said, will damage the insulating of the wires. Not if this happens once or twice or even ten times. The insulating is killed by the cool/hot/cool cycle. The insulating coat (similar to some kinds of paint) gets softer when hot and when cooling down gets hard again. This cycle, in his words, lead to microscopically small cracks in the insulating. It gets brittle (hope that is the correct term, am not sure).
PPS. Hope this helps, at least it took me two hours to write this sittiung between 10 different dictionaries
That is great input and seems to show clearly that this is a design problem from Rotax. Here in the U.S. we have lemon laws that force the Car/Motorcycle manufacture to correct the problem or is the worst case end give the customer an new motorcycle. BMW is clearly side stepping their responsibility...to this point. Maybe there should be some type of coordinated protest to BMW?
On the charts you provide. Looking at those the fix is cutting the power of the system in about half. That will certainly cut the waste heat dissipation down...but for those of us who use a good portion of the F800 400W output for heated grips, heated vests, lights etc....dropping the out put to 15amps x 12 volts = 180 watts is just not acceptable.
We need BMW/Rotax to face and fix this problem for us.
Thank you - your English is better than mine ... and I only know English
100C would be 212F and I can easily see the stator exceeding that temperature.
"Thermal cycling" of the stator from a high-side temperature that is too high seems a very likely explaination.
I wonder - Is there a better grade of insulation available?
VTBob: I see your point on not wanting a de-tuned stator as the solution ... you Vermont-riders likely need all 400W from time to time. The good news is that when you need the 400W the outside temp. is so low the stator may not care?
My hope for insulating the exhaust header was not that it was a real CURE, but only that it would help things a bit ... esp. during low speed operation in hot environment....
Looks like you read many of the same forums as I did a few months ago, that is where my recommendation for the Compufire regulator comes from.
I am pretty sure the whole "generator" assembly (stator + flywheel) is indeed made by Denso (as for most other bikes), so the problem is probably unrelated to Rotax.
Is there much "history" to look at when it comes to non-shunt regulators installed on fuel-injected CAN-bus bikes?
Maybe I'm just being a crybaby.... I'm certainly won't be an "early adopter" but it does seem that non-shunt designs have the "potential" to add undesirable electrial noise to the system...
This is turning into a very interesting thread....with awesome information. Thank you to all that has contributed to this.
First.... I am a little weary regarding replacing the stator/rr combo...... Since a misstep could fry the onboard chips.....
But I will ring my supplier of epoxy. He is a superior alchemist..... And..... A rider. We have discussed thermal heat dip epochs before..... But not in great lengths. I do seem to think that his mix threshold was far greater than 100c/212f though. After a conversation with him..... I will post it here. Set aside the R/R.......the materials from the dip would be about $10.......but I know not much about the dipping of stators........epoxys....a bit more...
As I said my knowledge concerning motorcycle electrics is very limited, but yes it seems very logical. BMW could sure fix that but I am not convinced that they will do anything.
Although I am not convinced maybe a heatshield as JRWooden suggested is worth a try, it does not cost a lot and if it only keeps a few degrees of heat off the darn rotor it may extend lifetime.
*lol* Thank you for being tolerant I promise that I'll try to improve
Thats exactly what I asked the Bosch worker and he said that he does not know for sure but he also said that he is very sure that if the coat is too thick it will quickly crumble and the stator will die even quicker.
Frankly speaking, I am happy that I know about this issue but I am also sad cuase I dont have a clue how we could fix this
I can tell ya it took me hours and I had a massive headache as I also tried to look through some literature explaining what is going on inside an alternator, especially the part with the regulators. There is also a British (?) Aprilia forum where you can find 30 pages of discussion about exactly the same issue. Some guys really postet something like a doctoral research study. Similar with Triumphs and Buells.
Possibly he's right, the Bosch guy said he thinks that about 100C is close to the upper operation limit but he did not know for sure. Maybe someone can figure out the proper values. That may help to find out how far we are away from -let's say - an acceptable temperature window....
The speculation that the upper temp for the stator / insulation is at 100C / 212 F seem way to low to me.
Not saying it is wrong...because I have no hard info
Just thinking ....the engine water temp is regulated at around 190F, most oil temp is regulated around 270F (so the water boils off and does not accumulate). So the normal running ambient temp in the stator housing is certainly above 150F...maybe as high as 200F.... Then there is the stator waste heat to dissipate. Think of a 400W light bulb in that inclosed area...how hot would it get? 300F? higher?. There iss minimal oil cooling it seems... so the only cooling is heat transfer via the aluminum engine cases...and the exhaust pipe are close to help keep them hot.
my guess the stator/armature should be designed to withstand 400F or 500F 195C to 250C.
again these speculations are just trying to use logic to come up with a guess.
there is no direct thermal conductivity between the stator and the aluminum cover, as the stator touches the casing only along the fins you see here:
As mentioned previously, I don't know if that stator (no.3) died for the same reason as the other ones, but if the fault is electrical, it appears it comes from the connection between the end of the stator wiring and the external wires, and if it would be overheating I would assume that the wiring should be turning black all around the stator, not only one side !!
Because if you look at the 2 following pictures you see that the wiring is ok on the outside side, and starting to chip on the inside side. So it appears that the heat is coming from the flywheel. (and thus not from the exhaust either)
here is the picture from the outside side, the side facing the cover.
and here is the side facing the flywheel. We don't see very well for the quality of the picture (it's an iphone and not a camera sorry) but the varnish is turning black and chipping away.
Now the exhaust cannot be eliminated either because what is actually completely charred is the connection between the ending of the winding and the external wire. This part passes below a bracket in the cover and thus is in contact with the aluminum cover. Now hopefully we'll see when we unwind this part if the fault was electric or itjust melted and generated the fault.
You might be right...... But I find it strange though...... As that is an easy reached limit...... Even for room temp cured epoxys. The epoxy I use that require post heat cure has a upper temp limit of about 250 deg C. And wont break down until 325deg C. That same epoxy is in fact used in potting.....
Ok, finally heard back from someone thats been helpful in the past.
Polyester-imide is what the F twin rotax stators are insulated with.
"Polyester-imide magnet wire is insulated with a Class H modified polyester resin. It has excellent thermal endurance, solvent resistance and exhibits a low coefficient of friction to improve windability. It requires mechanical or chemical stripping."
It is rated for a maximum temperature of 180C
Since theres some reference to Aprilia here, and it's something I have some new connections with, their 650 single and 1000 CC Rotax V twin stators are insulated with Polyester A / I Topcoat.
"Polyester-amide-imide magnet wire is a two-part insulation consisting of a modified polyester basecoat with a superimposed amide-imide outer coating. This wire exhibits exceptional windability, heat shock resistance, and ability to withstand overloads. Chemical resistance to most solvents and insulating varnishes is extremely good. It is not softened by refrigerants and extractions are essentially zero."
It is rated for a maximum temperature of 200C
On A side note, I don't remember seeing many charging system problems on old BMW F singles, which were actually built by Aprilia and rebadged by BMW.
I have never had any education specific to Parallel PM regulators (shunt type, stock for all of these) Or series PM regulators. Most of my education came from the automotive industry which does not use PM alternators.
That said, as an industrial electrician I had plenty of training with PWM motor controls, which seem to me to be similar to series PM regulators, and the problem is the large voltage spikes causing Partial Discharges (PD) in the coils or complete flashover and burn out.
Maybe theres some sort of new control technology, but any time we used PWM's, we wanted a motor with a magnet wire that said something like this "Polyamideimide For inverter duty applications, this insulation is designated for use in motors that may be subject to voltage spikes".
Neither the stator insulation BMW or Aprilia uses is known for spike resistance but particularly NEMA NW30, or Polyester-imide, what the F twin uses, is just plain bad at dealing with voltage spikes.
This may not be relevant. Perhaps series regulators some how avoid spikes, or maybe they aren't high enough to offset the benefits of lower heat. I simply don't know.
I do know that for me it wouldn't have mattered cause I use nearly all 400 available watts the F8 had to deliver either way.
Also 180 and 200C magnet wire is upper end to begin with and may explain why rebuilds aren't lasting long as 155C class is the usual to rewind car alternators with.
Without going too exotic...
Temperature Class: 240° C
Insulation Type: Polyimide-ML
NEMA Specification: MW 16C
Federal Specification: JW1177/15
IEC Specification: 317-7
ML is a film coated magnet wire made with polyimide resin. It is a Class 240° C thermal life insulation with exceptional resistance to chemical solvents and burnout. It will operate at a temperature up to 240° C. The outstanding cut-thru of over 400°C and its ability to withstand excessive overloads extends the use of magnet wire in extreme conditions. ML is unaffected by prolonged exposure to varnish solvents and it's compatible with virtually all systems
But I can say from experience, winding the above shit without cracking or bunching it is a PITA.
Sorry, still no answers, but more information.
P.S. Potting and varnishing are not the same thing. Once the varnish fails and causes shorts, the resultant short will cause the stator magnet wire to exceed 800C and sometimes even melts the copper so like 1100C. Potting just keeps the magnet wire from moving around and abrading.
P.P.S. Denso makes the PM rotor and stator of these and many many other motorcycles, but they are a goliath company with a tun of off the shelf products and ability to cater to any buyers design. In quality control and design, Denso makes Bosch look like a bunch of fools.