Stator Cooling - The Final Solution??

[Lucky]

My reasoning, and you may not agree & that's fine, is that the cooler, as i have it installed, is at the very beginning of the oil circuit, just after the pump. it just seems like a bad idea to tap off the oil before it's reached the critical areas of the engine. i'd rather change a stator than a set of bearings....

[Night Vision]

Hey...I can't argue with good reasoning... I'm just looking for an easy way to cool the top of the stator. It may end up be the crank bolt....

hmmmm..... what about some kind of oil turbulator? kinda like one of those tornadoes you put on a carb to swirl the air?

bolt it on the end of the crank and it could scoop up the cool oil from the bottom of the case and splash it all over the place?

Hey can't argue with bad reasoning  ;D  oh yeah, btw... patent is pending  ;)

edit - crud... L_D says Briggs and Straton already uses a plastic oil slinger... there goes free Visions for eveybody  :'( :'(

[Lucky]

ok, how about this:
if i remember right, the rotor spins around the outside of the stator. then how about machining some angular grooves inside the rotor, kind of turbine-ish. the groves need only be a couple of hundreths deep, but would pick up oil from the bottom of the case & kind of 'pump' it to the back of the rotor, where the stator is, & help keep it flowing to the top.  you'd have to be careful not to whip the oil up though..

[Cdnlouie]

Nice diagram. If we look at the oil level in relation to the flywheel I don't think it is close enough to pick up the oil, especially when it running. If we were able to get oil into the flywheel (and that is the current problem) then this would probably channel the oil out as it turns. I am not sure how the flywheel would work with a liquid running around inside.  We need some of the college guys to check this out for us.  Perhaps we may need a raised groove (this might not be possible because of clearance issues) in order to fling the oil while it is turning around the flywheel as it spins.

If the oil comes from the flywheel bolt it will most likely work back along the inside of the fywheel (as it enlarges) and run up the back and then outwards along the sides of the rotor to be flung against the engine case.

Getting the oil into the case is our problem as only vapor reaches it at the moment.  Distributing it evenly around the stator would be fine if it behaved as described although we cannot be sure it is still going to be contacting sufficiently the stator itself.  It would do a great job of cooling the flywheel, which no doubt would be a signficant source of radiant heat.

The idea of tapping off the oil pressure switch could supply oil to the top of the stator and then let it run down into the flywheel and be distributed around inside.  There is no difference in effect upon the engine oil pressure but the outside line would be more exposed to damage unless well protected. A feed from the oil cooler would be quite sweet for this application.  The bottom line is how much oil can we spare from the system and still maintain good oil pressure?

Pressure testing could be done to monitor the result and to see if the pump does keep up with sufficient supply.

I appreciate the viewpoint of dpequip as this is good background info on this situation.  I wonder who is actually building the best temperature resistant stator these days?  This is definitely the easiest solution if someone would actually do it.  It would kill the 'cash cow' that these bikes provide so most suppliers are not really incented to build a lifetime stator although the technology no doubt is around to do so.

Appreciate the good thoughts here,

Louie  :)

[Extent]

My first impression with the grooves would be to worry about the ballance of the flywheel.  With a smooth interior the oil that makes its way in can easily distribute it's way around the inside of the flywheel, but with grooves wouldn't there be a tendency for it to pool up in a "heavy spot"?

What about setting a squirter with a pressure valve that keeps it closed at anything but near peak pressure?  Then when you're at low pressure when idleing you're not sacrificing any pressure from the rest of the system, but when you're at speed and above the factory pressures anyway (I'm assuming a cooler here) the cooling circuit for the stator would open up.  If for some reason system pressure drops at all the extra line is automatically cut off to preserve pressure for the rest of the system.

[Superfly]

Right before the site crash, I was doing some research into the wiring & epoxy temp. ranges of the stators, and what I came up with is that they typically can withstand temps. of 320-400 degrees (F)  I am not sure how hot they get through their typical use, but I am starting to think that the oil is part of the problem.  I would actually like to figure a way to separate the stator from oil completely.

[Extent]

Well oils don't damage epoxies, and Lead_Deficiency reports external case temps of only ~180*.  Dosen't quite explain how they seem to burn up from the top down either.  Keeping the oil away from it wouldn't be too hard though, you could easily make a thin composite shield.  If you're worried about corrosion you could do it out of Vinyl Ester resin, but most datasheets I can come across list max temperature of only around 200*, so you're probably better off with a high temp epoxy.

[MotorPlow]

Well, how about this....
Is it possible that the more the bike sits without being ridden, the more chance that the epoxy gets dried out from not having oil on it. If the epoxy gets dried out, it would shrink and then crack, then cause it to fail and burn up. Most stators that I have seen that were fried, were more crispy on the top (less oil contact) than the bottom. My warped sense of reality would make me think that the top dried up and got brittle faster than the bottom. How often have you heard of someone bringing back a Vision from sitting for years and the 1st thing they need to do, after the starter clutch is the Stator?

~MP

[Extent]

Epoxy dosen't need to be oiled, and it dosen't dry out.  The R/R is actually encased in epoxy resin, it's really hard to break down.

[George R. Young]

The problem is not hot oil transferring heat to the stator and causing it to burn out.

The problem is the stator generates heat and doesn't transfer enough of it to the warm oil, the stator's temperature rises, and burns out.

[Cdnlouie]

I'm with you on that one George. The internal heat of the stator is the issue, and that is generated by the current flow induced by the rotor magnets.  Also, the higher the rpm the higher the AC voltage generated.  While it being bled off by the regulator it is still producing over 100 Volts AC at higher rpms.  I am not an electrical engineer but I am quite sure there is significant heat being generated by the stator that far exceeds what you can measure in the oil temp or the side cases. 

The internal stator heat can only be radiated away by cooling from the oil or oil/vapour environment of the engine.  The top of the stator is probably the area that has the least oil contact and therefore tends to become toast first.  Someone suggested that some of the epoxies used can withstand 400F well that is a pretty good indicator of how hot the stator can become over time with the gradual build up of wire resistance due to high voltage running through it.  These stators have to get so hot they eventually burn through the epoxy insulation and then short out internally.

Therefore, using a wire insulator (epoxy, etc.) that is also a good conductor of heat is part of the solution. I am not certain if anyone is doing a good job with that aspect to specifically meet the needs of our Vision. Enabling cooling of the stator through oil bath is another. This is an engine design issue that at the moment does have an immediate solution.

Louie  :(

[Night Vision]

until an easy solution is found to internally cool the stator, I'm going to try or consider some other methods.

switch to semi or full synthetic to lower oil temps.
research cooling paste?
maybe try to add some fins near the top of the case?
paint the case black?

I have done all the other reccomended mods (new electrosport stator,soldered connections, moved R&R, cleaned connections, added oil cooler)

honestly, I don't even know if my stator is in danger. If it weren't for that pesky oil leak coming and going (I think I gave it to Squid  :o ) I would have pulled the case by now and had a look see.

I will be doing that this winter (unless the case starts leaking again  >:( )

[NewVisionGuy]

Just  a shot in the dark  here   but  Night Vision  mentionned  painting the case  black...    I was thinking along the same  lines  sort of  when  this  topic opened.    Laws in Thermo  Physics   say that  lighter colors  and  dull  surfaces  will  radiate  heat  better.  A  thin  flat  white  layer  of  HighTemp  paint  my  give us a few  degrees  in the  case.   I haven't  started  with  any of the mods  yet,  but I'm  planning on moving the R/R  ASAP. (The apartment  won't let me work on the bike  so I'm looking for a good  Butane soldering iron to do the job  in the parking lot at the parts  store)     As for the paint,  my only  concern  would be this...  A layer of paint  could possibly insulate the case  even more no matter what color it is, flat or gloss.   Should this  be a concern.  I don't know how much  gain  could come out of a different color case either. 

BTW  This is a great topic that  all of us want resolved.   Thanks  guys  for  all the  suggestions and  possibilities.  Now  we just need some  ginea pigs!!  :o

[Extent]

I had always heard that flat black actually helps cooling the most, that's why you'll never see a radiator painted white.  But that aside I think we're looking for way more than a few degrees here and I don't think any kind of coating on the case is going to significantly impact the problem.

[haunter]

a little more oil in the case might help?

[Night Vision]

I had always heard that flat black actually helps cooling the most, that's why you'll never see a radiator painted white..... 

I'm thinking flat black wrinkle / or golf ball texture   ::) would be best for the case 

..... I don't think any kind of coating on the case is going to significantly impact the problem.

agreed: after some quick web topic searching...seems that the "cooling paste" [thermal grease] would not be a good idea.

.....But that aside I think we're looking for way more than a few degrees here [and there]

I think all mods combined would add up to a significant decrease in stator temp and maybe premature failure.

... cool what little oil bathes the top of the stator, turn the side case into a heat sink, reduce as much resistance in the electrical system (resistance=heat right?)
as possible....

Who knows?.... I'm only at 3k on a new stator.... (and about 600 miles on the starter solenoid fix btw  ;D) and the other mods I've done.... not a long term analysis by any means

[Extent]

Well any kind of paste on the inside on the stator itsself is a bad idea, and it wouldn't be any use on the outside of the case unless you're using it to mount a heatsink.  Whether a heatsink (or any other sort of heat dissapator) on the case would be any use shouldn't be too hard to determine.  If the case temperature around the stator is hotter than other areas of the case (either farther away on that side or on the right engine case) then we could assume that the stator is contributing that extra heat, and helping to cool the case would then help to cool the stator.  If the case isn't much hotter there then it's probably not getting a significant heat contribution, and any additional cooling on the outside isn't going to help any.

As far as coatings go powercoat is the way to go :D.  Can you get textured powdercoats?

[Night Vision]

If the case temperature around the stator is hotter than other areas of the case (either farther away on that side or on the right engine case) then we could assume that the stator is contributing that extra heat, and helping to cool the case would then help to cool the stator. 

that's exactly what Lead _Def's readings showed... hottest  just above the YICS plate... look at Walt's avatar too.
I wonder if the plate could be replaced with a finned cover? again, not the total solution, just a contribution

[paste would have gone on out side of case, not inside. the thermal paste I found was mainly for computer heat sinking, not the magic cream I was looking for  :D ]

[Night Vision]

ok, I'm starting to like the heat sink idea.... seems cheap and easy..
just gotta find the right size to fit the YICS plate and get some thermal epoxy.

just might end up getting a large piece of extruded sink, cut it to length, throw in a tube of epoxy and sell them to you guys  ;D  the epoxy would be the expensive part. nice winter project

[Extent]

that's exactly what Lead _Def's readings showed... hottest  just above the YICS plate... look at Walt's avatar too.
I wonder if the plate could be replaced with a finned cover? again, not the total solution, just a contribution

Well those readings show that it was hotter than the bottom of the engine casing which gets a lot better oil coverage.  I'm not sure how much of that heat is from the stator directly, and how much is just soak from the engine in general. 

The YICS plate is actually probably the worst place you could put a heat sink, it's loose fitting and right in the middle of the ring of the stator.  You'ld get better performance if you mount the sinks around the plate, and closer to the ring the stator slips over.