hardness coefficient and indentation of materials in friction inside geared motors

[chantelauze]

from the basic hypothesis that a life span expectation of an e-bike hub motor is directly correlated with that of its orbital planetary gears ( especially when made of Nylon like the Bafang motors ) or bearings ( Tongxing motors ) i am interested in knowing if there is a way to measure such information : when 2 surfaces ( with ou without teeth ) made of two materials with different hardness coefficient are in friction contact with each one another , which material is going to erode the first : the harder or the softer ? i don't think the answer is that obvious !

is there a universal unit that can be used to measure such erosion factor or hardness coefficient in order to predict the behaviour of one material in friction with another ? ( illustration in underneath photo )
i recently saw a figure that said : " Modulus 1.25 "
what could that "modulus" be , what could be the extreme values of such measurement , on a scale of 1 to 10 or 1 to 2 or ??? is 1.25 a good value ?

( sorry for starting this new thread under that general chapter when it might have been better classified at the Technical chapter , but i don't have enough privilege to do so )

 

[flecc]

I don't know of a universal measuring unit, but the general rule with a pair of friction surfaces is that the harder wears more. A very common example of this is in the cylinder bore of cast iron crankcase piston IC engines with their alloy pistons. The cast iron cylinder bore wears most, becoming oval in the thrust plane due to the softer piston retaining it's circular shape.

Placing the hardest gearteeth on the hub ring of that motor is sensible since it's the largest gear, so will be least affected by the higher wear.

I think most of us just prefer to ride our bikes and not worry about such aspects though.
.

 

[jimmyengland1000]

Having had a motor with all metal cogs, I'd rather have a motor with nylon ones. I found the metal version very noisy and it ruined my rides. Given the availability and relative cheapness of nylon geared hub motors, I wouldn't worry about longevity too much and, as you say Flecc, enjoying the riding is important... I assume that motor manufacturers do, to some degree establish how a motor will wear, which to make the hardest cog etc? Personally, I think the Bafang hub motors look like a really good piece of kit and they appear to be well-engineered.... am I wrong here, Flecc?

"Kindest, most warmest regards", Flecc ...

 

[flecc]

Love the ending Jimmy, wonder how many will correctly interpret the reference?

The Suzhou Bafang motors used in the Quando/Torq 1 are well built, the only criticism I can see is the reliance on magnetic balance in the design. Losing a Hall sensor connection usually causes some noise from hub motors in general, but with these there's mechanical collision between rotor and stator and the racket inside is painful to hear. This design is also the reason why they are markedly more noisy at low revs than their norm, which is very quiet due to the nylon gear train. The noise then isn't collision but vibration around the central bearing of the rotor due to the slower magnetic fluctuations at low revs and lower centrifugal force on the rotor drum.

However, designing that out would probably mean a larger heavier diameter motor. I like it as it is, not much bigger and very little heavier than the Nano, but with a lot more power and reliability.
.

 

[chantelauze]

to confirm Flecc's saying about Hall sensor to be responsible for noisy phenomena, i was told that motor factories are controlling the quality of the Hall position sensor they use , and discard the bad ones that are to be held responsible for excess noise
2 photos fm the Bafang factory to illustrate that point ...would you agree that the 3 pink arrows lead to 3 hidden Hall sensors ( the middle being deffective ) , and that a Hall sensor looks like in attached photo

 

[HarryB]

Love the ending Jimmy, wonder how many will correctly interpret the reference?

This design is also the reason why they are markedly more noisy at low revs than their norm, which is very quiet due to the nylon gear train. The noise then isn't collision but vibration around the central bearing of the rotor due to the slower magnetic fluctuations at low revs and lower centrifugal force on the rotor drum.

However, designing that out would probably mean a larger heavier diameter motor. I like it as it is, not much bigger and very little heavier than the Nano, but with a lot more power and reliability.
.

Yes I find the noise and vibration much worse with the Torq motor compared to the Nano motor. However I do find if I wear a helmet it dampens down the noise and vibration quite sucessfully...

 

[flecc]

Yes, those are the positions chantelauze. The Hall sensor looks like the one, but of course they all look very similar.
.

 

[flecc]

Yes I find the noise and vibration much worse with the Torq motor compared to the Nano motor. However I do find if I wear a helmet it dampens down the noise and vibration quite sucessfully...

Much of the Torq problem comes from the high motor gearing in the 28" wheel Hal, this meaning that much of the time the motor lives at lower revs than it did in the Quando where it came from, that lower geared in it's 20" wheel.

The all round performance in the Quando is markedly quieter as a result. The lower gearing not only means higher motor revs for any given speed, but also means much quicker acceleration than the Torq, so getting into the quiet region much faster.
.

 

[JamesC]

Yes I find the noise and vibration much worse with the Torq motor compared to the Nano motor. However I do find if I wear a helmet it dampens down the noise and vibration quite sucessfully...

The vibration on the Torq is quite a high frequency.

I have been very happy with the improvements made last year with "comfort grips", but still feel some vibration coming through to my shoulders.

Just recently, I fitted a bag on the handlebars with some aluminium brackets that put the bag well forward on the end of these "tuning forks".
If the bag is empty, the normally low level of motor noise is amplified about tenfold !!!

I will be interested to discover whether changes in the wheel build have any impact on vibration.

James

 

[HarryB]

I can put up with the noise but there is something wonderful having a silent electric bike when you serenely pass a panting cyclists. It works best if you try and strike up a conversation. I am hoping that the Kalkhoff will be pretty quiet.

Anyway I was trying to get this thread onto the great helmet debate as that is the way threads seem to end up these day. But none of you lot were going to fall for that were you.

 

[flecc]

I retrued mine completely initially, then months later a second time to give a substantial lateral rim offset when shifting the motor and wheel into the back wheel position, but it made no difference to any motor noise or vibration.

Having the sound behind me helps though, as long as I don't turn my head.

With all this talk of noise in relation to this motor, it shouldn't be forgotten that it's actually a fairly quiet design. The other eZee motor used in the rest of the bikes, Sprint, F series, Cadence etc, is much noisier most of the time, since it's noise increases with speed, the reverse of the Quando/Torq motor. That's because much of it's noise arises from the very different orbital gears, narrow and large diameter:

.

 

[jimmyengland1000]

Love the ending Jimmy, wonder how many will correctly interpret the reference.

At least one other, I see.

Kindest warmest cuddliest regards, Flecc

 

[flecc]

.......... ............

 

[flecc]

--------------------------------------------------------------------- I am hoping that the Kalkhoff will be pretty quiet.

Anyway I was trying to get this thread onto the great helmet debate as that is the way threads seem to end up these day. But none of you lot were going to fall for that were you.

I didn't miss the reference Hal, but didn't rise to the bait.

The Kalkhoff is quiet enough not to be noticed as an electric except on the quietest of country lanes. In most road conditions it's effectively noiseless, quieter than some ordinary bikes with rustling derailleurs or ticking gear hubs.

If you wear a helmet (that thread again ), you won't hear it at all.
.

 

[HarryB]

Ah the Agattu. I am still waiting for the paperwork for the cycle to work scheme and it might be a whole month away apparently.