Sure sounds to me like that the planet gears are of thermoplastic, such as nylon,
and the heat caused some of the teeth to partially melt, deform, at shut-down time.
And the knock you hear now is that of one or more "clubbed" teeth gnashing the soft steel ring gear.
Cure: it may "fix itself" to a small extent. OR it may (I predict, I do not KNOW), strip all remaining teeth some day soon or far away, without the least prior warning.
Common sense: thermosetting plastics, other than those made for very high temperatures,
are not going to be ideal for geared hub motors.
Yet, there are plastics, thermosetting (google plastics, thermosetting) that can take 300F engine oil:
The well-beloved, time tested Honda 2000EU home/rv emergency power generator has a half time gear (cam gear, of a white, hard plastic, that takes the guff: MUCH more severe service than in your geared hub motor. The Honda is a "one lunger" as we say in the trade, and it, perforce, WHAMS and BAMS the silent, helical teeth of the cam gear at every explosive impulse.
Life span in running hours at full, electrical load? Apparently ten thousand hours, as timed by an engine hour meter.
WE SHOULD NOT be suffering planet gear failures, period.
There are super-duty plastics, and even INDESTRUCTABLE composites, phenolic-family, laminated fabric-impregnated, that can be hobbed and cut, just like cast iron or steel, but which will run nearly dead silent, and never "peanut butter due to excess heat in a hub motor. They would last for the life of ten burnt motors and more.
How hot is hot? 150F is about the limit of what a human hand can take, holding a hot plate, for instance.
Bright aluminum or dull aluminum or black anodized (black throws off heat!) motor casing, too hot to touch:
drop a drop of water on the hot motor. Does the water boil?
Then you can be sure that the internals have much gotten hotter yet than 100C!
Q: What is the softening point of nylon? I could google for the answer. It melts at a relatively low temperature,
first becoming like chewing gum, then turning to thick liquid, then, if hotter (a match flame), it actually will burn and sustain flame
(try this with some nylon twine sometime? Heat-sealing the ends of nylon, polylon, etc, twine, rope, stops unraveling from happening.
Heat injury to these materials, the very same CLASS of plastic (so many kinds there are, too!), thermosetting,
if they be precision molded gears = DEATH, not P.B. & J. sammiches :wink:
Non-contact "IR" thermometers, those point and shoot pistol-looking things, are very useful,
but cannot work reliably if aimed at anything silver in color.
hth, though, I talk too much. I don't mean to be a blowhard;
I just can't sit on my hands when I see what appears to be the obvious, and no sure answers to questions asked.
You understand why now, they, the makers, nearly all use thermosetting plastics? Because they are ready to roll, right from the mold.
This lessens cost of manufacture greatly.
A great company like HONDA, can and does engineer/choose thermoset plastic of such a grade of heat tolerance and fatigue resistance,
that, as said: you will get thousands and thousands of service hours from your whisper-quite, petrol-sniffing, Honda 2000EU.
Of course, I have one for years now. It starts right up every time. I use it several times per year. It will outlive me by decades.
Quality is all in the maker's name, goodwill, know-how and PRACTICAL RESULTS. Honda is not a boiler-room workshop operation.
So take a clue? Demand quality and thou shalst receive quality.
Five years from now, there will be NO "peanut buttered plastic gears in ebikes, ever again.
Quality does count, DUH, says this Curly! That's why, poor as I am, I bought, through Justin, HIS OWN SPECIFIED eZee motor kit,
made by the best-reputationed maker of ebike parts in China.
It is not perfect. It is amazingly good. I have yet to hear of an eZee motor's catastrophic failure, whilst running within or near its published design limits (450W continuous).
