Another alternator hits the dust and not under warranty

I have far more questions then answers, but here are the few I have:

Flying.moto, the stator on our bikes is a 3 phase Y configuration.

I found my notes from tests a long time ago, no easy feat lol, 213 volts RMS was the open circuit voltage at 6,000 RPM, but 1ms averaged peaks were 394 volts. I did not test at higher RPM because It was my stator I was testing and I was concerned about going higher but most certainly that voltage will climb somewhat linear to increases in RPM.

A few additional notes: I measured the temperature of engine oil in my sump after a hard ride on a hot day and it was 124 C which is another reason that thermal image way above makes no sense. Our thermostat isn't full open till about 100c and the oil is always going to be hotter then the coolant. I would suspect we are going to have to work with stator temperatures south of 140c at the very least. Also, my normal knowledge of induction wire is in air or pure oil. Our oil contains a lot of carbon and often also contains water. Combustion byproducts include water and engine oil may contain quite a bit of water, especially when it's cold and even more so if the bike makes regular short trips. This is to say nothing of bikes that are submerged in water which happens to mine occasionally.

In an oil cooled transformer, the addition of just a little water really drives the insulation resistance down.

I am very leery of greatly raising stator voltages under these conditions. Further, experience with other stators will only tell so much. A stator that say honda uses may be built to withstand voltage better then ours, or it may not. I simply do not know.

JR, I can't see the crank being hotter then oil. Normally the oil runs hotter then the crank owing to heat absorbed from the head. Also I just can't see aluminum or even magnesium, whatever the cover is made out of, having that sharp of temperature differences. What I suspect we were seeing is a change in emissivity. Perhaps there was a sticker or flat painted graphic in the center and the surrounding area was shiny. In any case, that thermal image means nothing to me.

In any case, I don't dispute and can absolutely confirm that a series voltage regulator will run the stator cooler any time demand is less then 100%.

There are actually two common types of series regulators. "series resistive" and "series switching". Series resistive regulators would not allow the stator voltages to go nearly as high, would be less efficient at reducing stator loads, have huge heat sinks and double as a waffle iron. Series switching will be noisy as hell, run very cool, be efficient and allow stator voltages to go through the roof.

What would be really nice is a hybrid voltage regulator. Actually I could design it and even get components, but I don't have any resources for a custom board and heat sink.

A schematic would be better, but I have no apps for generating such on this computer. 2 zener circuits for precision reference voltages, say 14.18 volts and 14.22 volts. 1 op amp triggered by the lower voltage zener for driving 3 FET's through a 10 ohm resistor to ground. the higher reference zener driving an op amp to 3 more FET's that break the series. You would need a feedback circuit to compensate line voltage fluctuation to the zeners but these are simple, and since were going all out, 3 SCR's set up to avalanche at 15 volts as a redundant safety. I'd build it 6 wire so regulation was done by a sensing wire straight to the battery that carried no current to cancel out the annoying loss in voltage as load went up. Heck, for a few pennies more we could add a circuit to flash an LED green yellow or red for system voltage. Leave the avalanche diodes on load sensing so loss of the sensor wire wouldn't cook the bike. Perhaps $50 retail for the components less the custom board and heat sink and that assumes we used over spec'd components.

The results would be that the stator was never completely disconnected from load, RMS would still go pretty high but insulation piercing spikes would be halved, yet the system would go into series regulation to run the stator cooler and improve fuel economy. I'd probably also get sued for violating someones patent unless someone else already thought of this so long ago that the patent is up which is likely :)

P.S. Larger gauge wire will fit on the stator with the same number of turns but this isn't everything. The magnetic field is only close to or at saturation with max back EMF at redline. Increasing winding size will also up current nullifying some of the I*R heat reduction. In addition to that, I don't know how much additional current if any our stock regulators could handle.

As to oil feed to the stator. I don't know that there is any though I would sure hope there is. The crank is charged so theres either a nozzle at the end of the crank inside the rotor, or there is not. Assuming there is a nozzle. perhaps varnish buildup is causing a reduction? If there is no oil nozzle directed on the stator, well I know why they are failing lol. I would shutter to add a nozzle if none currently exist. Drilling on the crank and tapping a finite oil supply is beyond my engineering skills and testicle size.

Thanks Joel!

I have no clue on the IR readings either ... seems screwy...

I thought I understood that the current created in the stator would be proportional (on a first order basis anyway) only to 1) the number of turns of wire, 2) the strength of the magnetic field, and 3) the speed at which the field was changing ... So it was on that basis I was thinking that heavier/lower resistance wire would be our friend...but I'm not 100% on that ...

I'll not be drilling any holes in my crankshaft either .... If the motor design has some provision for sending oil in to cool the stator I've seen no evidence of that ...

A clever regulator that both keeps electrical noise away from the DME, and keeps the stator from running at 100% duty cycle seems like the easiest way out ... I'd hate to install an aftermarket regulator in an effort to save a $150 stator and end up frying the computer ................

Thank you, Joel, for digging up your notes! With 400+ volt spikes i'm not sure i'd go further up in RPM either.
It does make sense that we have a Y configuration stator. It leaves me to wonder if it was connected in Delta config. how would it behave at low rpm...

Regarding oil temps in the sump at 124 degrees, i am amazed. Seems a bit on the red line so to speak. What this bike could really use then is an external oil cooler. It should not be hard to hook up by replacing existing oil/coolant heat exchanger with a machined block with some fittings on it. I will look at my manual CD when i get home to see if that part is easily removable. Maybe with cooler engine temps we will not need to screw with stators/RRs to begin with. Or maybe can getaway with the use of FET shunt type if its that more efficient, although the stator would probably heat up the same... Still, seems like an easier solution. Rotax probably was onto something designing that heat exchanger to begin with - a bandaid fix for hot running oil system? I can't say i have seen such a part on any bikes i've dealt with.

Be careful trying to adjust engine temps. On some stationary CAT engines if the coolant and oil temperature are not at the correct ratio the pistons will sieze. I don't think that will happen here as the clearences between the piston and liner are probably larger, but the engine was designed to run at a specific temperature and messing with that could cause unintended consequences.

If Rotax is like most companies, the electrical guys and the mechanical guys don't speak with each other and the stator might not be designed for the temperatures the mechanical were shooting for in thier design. However, I would think that there are ways to get a stator to live in hot enviroments.

As far as thermal properties of oil in the crankcase, I'm sure most models use clean oil and then a fouling factor is added for the impurites and coking. The only sure way is to devise a test and measure the results of clean oil vs dirty engine oil. However a model and some luck may get us close enough for this project.

I think your comments on the thermal image of the Aprilla are spot on Joel. Without knowing the details of the surface and who was taking the image, interpretation of the results are a crapshoot.

There's a huge write up about this issue on the F800S bikes failing stators in this month's BMW ON (owner's news) magazine. It's a good read. Sorry I dont have a way to scan it in.

Did they offer any solutions?

synopsis??

Interesting! I do believe current members can access it online, who's got it?

If you mean the December issue, tain't up on the MOA site, yet.

The Dec issue showed up in the mailbox, today.

Synopsis of the article:

Voni's bike (F800S) displayed charging problems while on a trip. Paul noted the DC measurements he made. They managed to get the bike home.
He described the difference between the F bike alternator and the ones on the rest of the BMW lineup.
He went through the logic of troubleshooting the problem.
Then he described the tests he ran.
He decided to order a stator from Rick's Motorsports Electrics.
The article ended with the bike on the lift waiting for the part.

Nothing that hasn't already been talked about on this forum. He checked continuity of the windings, measured AC output of each winding and discovered that one was lower than the others, 50v compared to 75v. The article will be informative for anyone who hasn't paid attention to the issue, but there's as much or more info on this forum.

Edit: Paul has also written about the rear drive failure Voni's bike suffered and the cam chain tensioner failure of one of their F bikes (that may have been his F650).

There was no real definitive anwser other than the Stator wiring is suspect. The author noted that a call to BMW for parts yielded a cost of over $900 large as it was a complete charging system... but all that is needed is a Stator.

The good news is that he found a Stator only at Ricks Motorsports Electrics for $165 !!!

http://www.ricksmotorsportelectrics.com/

Hope this helps!

That part from Ricks is available from Parts Unlimited too. Same price. Read the article and agree, nothing not discussed here.

Not sure where the $900 comes from. There may be some parts you need besides the two mentioned. Both the gasket for the cover and the generator comes to just under $800. The warranty from BMW is 2 years. Not sure about the Ricks warranty. Probably at least 1 year. I would bet that the stator will be available soon from BMW as a single part.

<TABLE style="MARGIN-TOP: 3px; WIDTH: 756px; HEIGHT: 153px" border=0 cellSpacing=2 cellPadding=2><TBODY><TR><TD class=Heading align=left></TD></TR><TR><TD class=Content align=center><TABLE style="BORDER-BOTTOM: rgb(102,102,102) 1px solid; BORDER-LEFT: rgb(102,102,102) 1px solid; BORDER-TOP: rgb(102,102,102) 1px solid; BORDER-RIGHT: rgb(102,102,102) 1px solid" cellSpacing=0 cellPadding=0><TBODY><TR style="BACKGROUND-COLOR: rgb(102,102,102); FONT-FAMILY: Arial; COLOR: rgb(255,255,255); FONT-SIZE: 11px; FONT-WEIGHT: bold"><TD style="BORDER-BOTTOM: rgb(102,102,102) 1px solid; BORDER-LEFT: rgb(102,102,102) 1px solid; WIDTH: 75px; BORDER-TOP: rgb(102,102,102) 1px solid; BORDER-RIGHT: rgb(102,102,102) 1px solid" align=center>Part Number</TD><TD style="BORDER-BOTTOM: rgb(102,102,102) 1px solid; BORDER-LEFT: rgb(102,102,102) 1px solid; WIDTH: 420px; BORDER-TOP: rgb(102,102,102) 1px solid; BORDER-RIGHT: rgb(102,102,102) 1px solid" align=left>Description</TD><TD style="BORDER-BOTTOM: rgb(102,102,102) 1px solid; BORDER-LEFT: rgb(102,102,102) 1px solid; WIDTH: 30px; BORDER-TOP: rgb(102,102,102) 1px solid; CURSOR: help; BORDER-RIGHT: rgb(102,102,102) 1px solid" title="Weight in Pounds" align=center>lb</TD><TD style="BORDER-BOTTOM: rgb(102,102,102) 1px solid; BORDER-LEFT: rgb(102,102,102) 1px solid; WIDTH: 70px; BORDER-TOP: rgb(102,102,102) 1px solid; CURSOR: help; BORDER-RIGHT: rgb(102,102,102) 1px solid" title="Recomended quantity. Price is for each one." align=center>Qty</TD><TD style="BORDER-BOTTOM: rgb(102,102,102) 1px solid; BORDER-LEFT: rgb(102,102,102) 1px solid; WIDTH: 60px; BORDER-TOP: rgb(102,102,102) 1px solid; BORDER-RIGHT: rgb(102,102,102) 1px solid" align=center>Each</TD><TD style="BORDER-BOTTOM: rgb(102,102,102) 1px solid; BORDER-LEFT: rgb(102,102,102) 1px solid; WIDTH: 65px; BORDER-TOP: rgb(102,102,102) 1px solid; BORDER-RIGHT: rgb(102,102,102) 1px solid" align=center>Total</TD></TR><TR style="BACKGROUND-COLOR: rgb(221,221,221); FONT-FAMILY: Arial; FONT-SIZE: 11px; VERTICAL-ALIGN: middle"><TD style="BORDER-LEFT: rgb(102,102,102) 1px solid; FONT-WEIGHT: bold" align=left>11147670688</TD><TD style="BORDER-LEFT: rgb(102,102,102) 1px solid; FONT-FAMILY: Arial Narrow" align=left>GASKET RIGHT</TD><TD style="BORDER-LEFT: rgb(102,102,102) 1px solid" align=right>0.01 </TD><TD style="BORDER-LEFT: rgb(102,102,102) 1px solid; WIDTH: 70px" align=center><INPUT style="TEXT-ALIGN: center; BACKGROUND-COLOR: transparent; WIDTH: 33px; FONT-FAMILY: Arial; FONT-SIZE: 8pt" id=Q_1 name=Q_1 readOnly value=1></TD><TD style="BORDER-LEFT: rgb(102,102,102) 1px solid" align=right></TD><TD style="BORDER-LEFT: rgb(102,102,102) 1px solid" align=right><INPUT style="TEXT-ALIGN: right; BACKGROUND-COLOR: transparent; WIDTH: 63px; FONT-FAMILY: Arial; FONT-SIZE: 8pt" id=TP_1 readOnly value=$15.00><INPUT id=AS_1 value=$0.00 type=hidden><INPUT id=DIM_1 type=hidden><INPUT id=W_1 value=0.01 type=hidden></TD></TR><TR style="BACKGROUND-COLOR: rgb(249,249,249); FONT-FAMILY: Arial; FONT-SIZE: 11px; VERTICAL-ALIGN: middle"><TD style="BORDER-LEFT: rgb(102,102,102) 1px solid; FONT-WEIGHT: bold" align=left>12317690427</TD><TD style="BORDER-LEFT: rgb(102,102,102) 1px solid; FONT-FAMILY: Arial Narrow" align=left>GENERATOR</TD><TD style="BORDER-LEFT: rgb(102,102,102) 1px solid" align=right>10.24 </TD><TD style="BORDER-LEFT: rgb(102,102,102) 1px solid; WIDTH: 70px" align=center><INPUT style="TEXT-ALIGN: center; BACKGROUND-COLOR: transparent; WIDTH: 33px; FONT-FAMILY: Arial; FONT-SIZE: 8pt" id=Q_2 name=Q_2 readOnly value=1></TD><TD style="BORDER-LEFT: rgb(102,102,102) 1px solid" align=right><INPUT style="TEXT-ALIGN: right; BACKGROUND-COLOR: transparent; WIDTH: 58px; FONT-FAMILY: Arial; FONT-SIZE: 8pt" id=UP_2 readOnly value=$778.66></TD><TD style="BORDER-LEFT: rgb(102,102,102) 1px solid" align=right><INPUT style="TEXT-ALIGN: right; BACKGROUND-COLOR: transparent; WIDTH: 63px; FONT-FAMILY: Arial; FONT-SIZE: 8pt" id=TP_2 readOnly value=$778.66><INPUT id=AS_2 value=$0.00 type=hidden><INPUT id=DIM_2 type=hidden><INPUT id=W_2 value=10.24 type=hidden></TD></TR><TR style="BACKGROUND-COLOR: rgb(102,102,102); FONT-FAMILY: Arial; COLOR: rgb(255,255,255); FONT-SIZE: 11px; FONT-WEIGHT: bold"><TD colSpan=3 align=right>Total Weight:<INPUT style="TEXT-ALIGN: right; BACKGROUND-COLOR: transparent; FONT-FAMILY: Arial; COLOR: rgb(255,255,255); FONT-SIZE: 8pt; FONT-WEIGHT: bold" id=TotalWeight name=TotalWeight readOnly value=0.0 size=3>lbs</TD><TD colSpan=3 align=right>ub Total:<INPUT style="TEXT-ALIGN: right; BACKGROUND-COLOR: transparent; FONT-FAMILY: Arial; COLOR: rgb(255,255,255); FONT-SIZE: 8pt; FONT-WEIGHT: bold" id=SubTotal name=SubTotal readOnly value=$0.0 size=6></TD></TR><TR style="BACKGROUND-COLOR: rgb(102,102,102); DISPLAY: none; FONT-FAMILY: Arial; COLOR: rgb(255,255,255); FONT-SIZE: 11px; FONT-WEIGHT: bold" id=TR_ADDITIONALSHIPPING><TD colSpan=6 align=right>Additional Shipping Charges:<INPUT style="TEXT-ALIGN: right; BACKGROUND-COLOR: transparent; FONT-FAMILY: Arial; COLOR: rgb(255,255,255); FONT-SIZE: 8pt; FONT-WEIGHT: bold" id=AdditionalShipping name=AdditionalShipping readOnly value=-$0.0 size=6></TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>


<LABEL style="COLOR: rgb(255,51,51); FONT-SIZE: 10px; FONT-WEIGHT: normal">11147670688 Gasket $15.00</LABEL>
<LABEL style="COLOR: rgb(255,51,51); FONT-SIZE: 10px; FONT-WEIGHT: normal">12317690427 Generator $778.66 </LABEL>

Total $793.66
<LABEL style="COLOR: rgb(255,51,51); FONT-SIZE: 10px; FONT-WEIGHT: normal"></LABEL>

I'm pretty sure that included in the $900 price you get a new flywheel that you don't need

Somewhere recently it was rumored that BMW would start selling the stator separately in the near future....

Yeah in post #67 of this thread...

I am not an engineer, just a dumb shade tree mechanic who looks at stuff without counting the binary numbers. When I pulled my dead stator at 50,000 miles all the windings were black and it smelled like fried electrics. I had it re-wound... and that didn't work (bad winding job or somthing). Bought Ricks stator and am using it now. Look at the placement of the exhaust tubes.... too damn close to the alternator for my taste. You know that exhaust tube gets MIGHTY damn hot.... tell me it does not effect the alternator. I suggested heat wrap on the exhaust around the alternator area - but have been too busy to try it.... it might be a simple fix.

TheCowboy

Damn good idea Cowboy... damn good observation.

It sure as hell can't hurt ....
I was in O'Reilly auto parts the other day and they had the stuff hanging on the shelf ...
I think I'll go back and get some...

It looks like it will require removing the headers to do the wrapping....
We'll need a pair of new gaskets P/N: 18217672804 to go between the pipes and the cylinder head?

If I was going to go that far I'd get mine jet-hot coated.
http://www.jet-hot.com/coatings/

Reduces heat, looks good & comes in various colors. Looks better than a wrapping.

Jet hot sounds like a good idea. I had been wrapping my header pipe on the dirtbike and it's been great! No burned leg/pants when i get pinned to it. BUT it clogs up with mud too easy and the mud soaks right through, not to mention moisture/water. Some said it will breed corrosion. At the end of it all i took it off and learned to ride better. It may be a solution for those who don't venture in a lot of mud/water... But then, caked on mud... Bad idea or just bad looks+weight?

What about a simple exhaust pipe heat shield of SS on the upper (closer) pipe to deflect the heat away from the cover. Won't absorb water like the wraps. Besides, there is not enough room to wrap only the upper pipe. You would have to wrap both. The distance between the pipes is not large enough to get the wrap between.

A Ti cover would look good but CF would disipate heat better.