auraslip wrote:IMHO it's the future!
bigmoose wrote:auraslip wrote:IMHO it's the future!
You know I am biased and feel this way also. The motors that were referenced in the paper I cited, I have run my hands over, and not in virtual reality. This "technology" of oil cooling works, and works well. There is a bit of windage loss, (and it was measured on the motors in the paper) but whether it is relevant or not only matters if you have or don't have the electrical power to overcome it.
Partial oil filling is the wave of the future. It will be followed with limited circulation after batteries/controllers take another step. ... at least that is my prediction!
BTW: Stick with ATF Dextron III, or Honda ATF. It is the right oil to use, it's cheap and it works.
bigmoose wrote: (If you want real power dense, we (a contractor) designed a 300HP LH2 cooled motor the size of a 3# coffee can and a 50,000 HP motor the size of a trash can. The 300HP version was verified in test... now that is "power dense.")
Hillhater wrote:bigmoose wrote:.... So does anyone know a car that has had reasonable production volume that has very small planetaries in the transmission that could be repurposed?
Audi A4 starter planetary set being repurposed with a RC motor..
John in CR wrote:
WRT to Halls, I wasn't worried about them working in oil, but instead the 10-15mph river of oil eventually breaking off one of the 9 tiny wires going to them that will be exposed to the flow.
Magnets. Running them from the factory, they have an air gap of less than a millimeter. When the stator gets hot, the magnets will also get hot on the surface facing the stator. I'd bet it's above 80 celcius when your windings/stator are at 120+ which is what some people are running at. Mine runs at 75 pretty much constant with brief peaks to 90. I' be surprised if this was worse for the magnets- if they do start to fail I'll be the first to chime in and let people know. I'd also like to know where this magic figure of 80 celcius comes from. AFAIK the Curie Temp of Neo magnets is around 320 celcius. I believe the magnets may start to demagnetise a bit below that temperature, but surely not at 80? We are in the business of helping each other out on the forum which is a fantastic thing. Many minds to the problems and issues we face comes up with all sorts of clever solutions. Even with my oil cooling I'm just following on from others before me
As for water spraying- it might help but why would you? More complicated, you need temperature switches, pressure pump, water reservoir etc. You are also not taking the heat away from the source- the stator and windings. Not to mention getting water on your back tyre. Oh, that's another good reason for sealing the hub well if putting oil in it- oil on the rear tyre is worse!
As Bigmoose and others have said, why wouldn't you consider oil cooling. Car engines are water cooled. Commercial electric motors are liquid cooled. Heck, even Golden Motor sells liquid cooled electric motors! I think the advantages far outweigh the disadvantages.
...As Bigmoose and others have said, why wouldn't you consider oil cooling. Car engines are water cooled. Commercial electric motors are liquid cooled. Heck, even Golden Motor sells liquid cooled electric motors! I think the advantages far outweigh the disadvantages.
Hillhater wrote:...As Bigmoose and others have said, why wouldn't you consider oil cooling. Car engines are water cooled. Commercial electric motors are liquid cooled. Heck, even Golden Motor sells liquid cooled electric motors! I think the advantages far outweigh the disadvantages.
The oil in car/truck/bus IC engines plays a major part in transfering the heat from the internal components to the surrounding walls of the water jacket. Many vehicles now have oil coolers also to further help disperse the heat.
bigmoose wrote:Here is a good summary paper on the Liquid Hydrogen cooled "power dense" motor/generators that I referenced above. http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA537468 and a picture of a 600 Kw unit from that paper. Yes that ruler is in centimeters!
Grinhill wrote:Another idea for ventilation - the rubber plug could just have a small slit cut in the centre of it (e.g. with an exacto knife). Should only open slightly under pressure.
fechter wrote:I was thinking it would work well to drill and tap a hole in the side cover near the edge to use as a drain/fill hole. With the hole at the bottom, it could drain and with the hole about 1/3 up (just rotate the wheel), it would only take the right amount of fluid, then start coming out like a car differential. Something like a 1/8" NPT tapered pipe plug (which is really more like 10mm) would be a good size.
I was also thinking it might be good to use a piece of flexible tubing coming out of the axle along side the wires as a vent. The open end of the tube could be located higher than the axle to prevent oil from leaking out and it would be sealed at the axle.
The magnets weaken with heat which provides unintended flux weakening which actually will increase your top speed (less back emf)
As long as they cool down when you decelerate they will recover and you'll have full torque off the line
An irreversible but recoverable loss occurs when the output falls but does not return when the magnet cools down (e.g. the high temperature takes the Intrinsic working point beyond the knee of the Intrinsic curve, causing demagnetisation) but this would be recovered if the Neodymium magnet is remagnetised. For all extents and purposes, this output is lost because the magnet will not be remagnetised during practical application... When cooled, such a demagnetised magnet will have the original Hci but a lower Br (the Br will have increased by the reversible temperature coefficient amount applied to the reduced high temperature Br).
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