View Single Post
Old 01-06-2012, 08:51 AM   #241
Joined: Jun 2009
Location: Western Vermont
Oddometer: 603
Originally Posted by JoelWisman View Post
I suspect you are waiting for a horse that isn't going to come with BMW, and Rotax and Denso has nothing to do with this. BMW designed this engine including the charging system from the ground up except for parts they bought of the shelf. Rotax just put it together to their specifications and occasionally not to lol. Plenty of stators fail on plenty of bikes, my guess would be if BMW addresses it at all it will be in a silent rolling production change.

I have a an F8 coming by for other reasons. I have a 4 channel 200MHZ DSO 2.5GS/S 400pS resolution, A reluctance meter and a 30MHZ 3 phase harmonics analyzer as well as a 2MHZ octopus and I'm quite proficient in all of their use. What is it you wish to see?

Somewhere I have video of the output waveform on one leg at a resolution of 4.2nS a division and the transient induced by unhooking the R/R at 3,000 RPM but I can tell you right now the transient was milk and toast.
Unfortunately, I agree it is unlikely we will get any public response. Eventually BMW will do some thing as this is costing them warrantee expense. The result will likely be a subtle change to the stator design and /or the regulator....likely evan still the same part number...just a mod/revision we will never know about.

So we are on our own. You have an impressive and expensive set of equipment (toys!). Well done!

I'll admit I have no clue at this point. My suspicion is either poor stator insulation materials that degrade and fail with age or poor stator design or materials so that the self limiting function of saturation occurs too too much self heating.

Insulation materials...I know of no way can find out what they are. see if there is enough design margin to survive the worst case heat in operation and life of the engine. Our only hope is some replacement mfg or re winder will come up with a to better high temp retrofit part and sell it as say...a 550F certified part Some type of post mortum diagnosis may..just may give some insights...but that would be a science project.

Stator saturation yep a bit of a long shot. If we could determine/ find out the core material and the winding parameters we could come up with with some predictive saturation curves. This also could be tested with a new stator. One of the earlier posts did indicate current limiting. This would help predict eddy current heating. We already know that the heat dissipation environment in the installed engine is pretty poor.

Transient damage to regulator. due to diode effect of corroded connections or noisy/failing components is essential impossible for us to do. We can not replicate corrosion. dead end. We do not have a real schematic or part list so we do not know what type of on board filtering/decoupling is done in the regulator...nor do we know the main switching can not determine either switching transient noise or susceptibility.
Putting your scope on a good bike and putting it on a failed or failing bike may...may give some in looking into a black box....but another long shot science project.

I'm not a motor/ power guy so my knowledge is pretty ad hoc/ poor. Any one on this list have better ideas?
vtbob is offline   Reply With Quote