Burtie wrote:Hi parabellum, any updates on how this is working out with use ?
Burtie wrote:At 400ml fill, the oil level is just below the axle, where the filler hole is in the above photo,
electr0n wrote:So what is the verdict on oil cooling a hub motor? This is much easier than installing fans, drilling side covers and using liquid cooling.
bigmoose wrote:Thanks for the great data on oil cooling Burtie! I think this will become standard practice for high performance motors as we go forward. I saw how much this improved the "Power Dense" motor system developed at Bowling Green State University about 10 years ago, and strongly felt it was applicable to hub motors. Your data now proves the point.
This should now end any lamination/magnet corrosion issues, and bump power handling a bunch. I will also bet thermal soak hall failures are a thing of the past also.
Arlo1 wrote:WHat about drag at hi rpm??
itchynackers wrote:I still don't quite understand whether the oil is just delaying thermal soak (by the oil storing the heat), or if the oil is allowing the hub to dissipate more heat.
Edit: After re-reading the thread, it seems as though the oil transfers the heat quicker to the covers (making them hotter) so more heat is carried away with the same amount of windage. Is this correct?
andynogo wrote:Try a little bit less oil and drill a small (1mm) hole in the cover near the axle. Angle it so that it traverses from the central axis towards the outer circumference as you go from outside to inside. That way, when the wheel spins, any oil that happens to splash into the hole will be flung back inside the hub
andynogo wrote:I wondered about that too as the planetary gears will be spinning through the oil as well- but it didn't seem to make much difference during testing. Not that valid a test though as the windings are damaged- I'm putting a new 10 turn stator in it soon so will do thorough dry and wet tests with a set route, amps etc.
Reid Welch wrote:WHAT: running geared transmissions in light oil is a universal practice...except in these new, geared-type hub motors.
WHY: light oil cushions gear teeth, actually preventing contact of the pressure surfaces, through a phenomenon known as
hydrodynamic lubrication: the parts surf upon each other, oil as the separating agent. This form of lubrication prevents all wear
((think of your auto's automatic transmission, how quiet its helical gears run, and with no wear-out))
IS THERE LONG TERM HARM? Ans: No, not unless the oil were to somehow degrade hall sensor adhesive (unlikely, it seems)
Q: How much oil to be installed? A: Enough to fill the motor about one third full. Then, when running, centrifugal force
throws the oil at the perifery of the gear casing, bathing the soft steel ring gear and the plastic planets. Plus, oil contantly
washes all the bearings and constantly wets the lip seals of the axle. Some slight weepage at the axle "seals" is inevitable.
About heat and expansion: when the motor warms up, its contained air expands, and will push out a minute amount of oil.
Upon cooling down, the motor will slightly inhale some of this weeped oil.
Now, consider the stock (dry, not oiled) run in the rain: it will gradually ingest small amounts of water, eventually rusting internal parts to some small extent.
Oil is dielectric and has no effect on nylon gears nor synthetic rubber seals, which are DESIGNED to run in oil.
Oil, sloshing around the inside of the hub motor, is not of sufficient quantity to drown the rapidly spinning central rotor
of the motor, itself, so no fluid spray/strain/churn on the copper windings.
The oil will all be at the ring gear, surfing the planet gears, dampening noise, and fluid polishing the parts over time (perhaps)
to make, in time (thousands of running miles) a super quiet motor, with each planet gear tooth of the three planets, shoulder exactly the same amount of the load.
Benefit accrued: maximum robustness of the geared motor: it should never "peanut butter" any teeth, until some long-away day, when plastic fatique finally breaks off a tooth, which then spells instant destruction for all the remaining planet gear teeth.
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