Weird grinding noise from motor, with little drive

[Northern Irelander]

The other morning I was doing a fast down hill descent, pedals had spun out due to max speed

After this downhill, was an uphill bend, all was well until I had to give some heavy pedalling to get up the hill.

The motor appeared to stop instantly with a horrid loud grinding noise, I was able to pedal but only about 5mph.
The rear wheel free-wheeled OK, it only made the noise when the motor kicked in. (Powacycle motor, same as Quando/Torq motors qbikecreation2)

Fearing the worst of shredded nylon gears and reluctor ring I limped home.
I stripped the hub and motor down, but nothing seemed to be wrong, a little grease had travelled on to the red collar but that was it.

Upon reassembly the motor apeared to be quiet and smooth again.

Any explanations peeps??

by chance does any supplier stock nylon gears (just in case )

 

[flecc]

No, it's not the mechanical aspect of the motor, it's caused by the temporary loss of a Hall sensor connection to the motor. The motor has three power current wires and five Hall wires in it's cable to the controller, and the Hall sensors in the motor tell the controller exactly when to fire off the power pulses to the phase windings at the correct moments. If a connection is lost and the small signal from a sensor is missed the result is haywire firing and the motor can sound as though it's tearing itself to bits.

In doing what you did the connection was re-made accidentally and the problem corrected, not uncommon. The loss of a connection can occur at a time of sudden high loading, I've experienced this myself on one occasion very similar to yours. I think the drop in voltage due to the sudden load causes the "iffy" connection to lose it's very small signal current transfer.

The usual cure is unplugging and replugging the connectors to the controller, though on rare occasions a Hall sensor can fail or a controller can fail, needing replacements. There's no half way stage in this though, so nothing for you to worry about.
.

 

[Northern Irelander]

ahh many thanks, great explanation Flecc, thats exactly how it was.

It gave no prior warning, I changed a tyre over a week ago, when the connectors were disconnected (only by the 5 pin mutli-plug, as I have bullet connectors on each individual wire for threading through the sprocket cassette tool) bike had been running well for over a hundred miles before the gremlin kicked in.

Will keep an eye on the connectors and any breaks in the rubber flex.

Thanks again

 

[eddieo]

I had a similar experience in the summer with my wisper, awful grinding noise then failure, wheel and motor where swapped under warrenty......

 

[Northern Irelander]

I had a similar experience in the summer with my wisper, awful grinding noise then failure, wheel and motor where swapped under warrenty......

Thanks, my warranty is long gone, we're on our own kiddo!