Is the SWX02 quiet?

[topographer]

How quiet/noisy is the above motor?

(It's not just a question of volume is it? Electric motors can have an irritating tone even when the volume is not high. I caught a bit of formula e on telly a while back and the multiplication of lots of high pitched motor whines was repellent to my ears even though the volume was less than you'd get from formula one.)

I know one SWX02 is not gonna sound remotely like that but how does it compare to other motors for loudness and tone?

 

[anotherkiwi]

It will be quiet if you use a sine wave controller. My mate has a front bafang motor with a square wave controller and it is very noisy. Marc over on electric trike has an oil cooled SWX02 with steel planetary gears because 60+ volts (...!) and he says it sounds like a coffee grinder at full power

 

[topographer]

Fascinating. I didn't know controllers affected motor noise.

 

[Deleted member 4366]

Most of the OEMs seem to use Lishui controllers. I'm not sure whether they're sine-wave or not, but I'd say probably not - based on the sound. The motor noise isn't bad, especially if you have a rear motor, where the noise gets lost behind you. Kunteng sine-wave controllers make motors almost silent.

You have to understand that a square wave controller is firing pulses of energy at the motor, which more or less knock it round. At low speed, the frequency is low enough to hear, like a grinding sound, which smooths out as you go faster. I don't know whether it's just the wave-form or whether there are other factors in the controller that give better timing of the pulses, but you can easily tell the difference in the noise between different types of controllers with the same motor.

I love my Q128C-Kunteng setup. It just gives pure smooth torque. I can't hear any motor noise at all at any speed when I'm on the bike.

 

[Woosh]

I'm not sure whether they're sine-wave or not, but I'd say probably not - based on the sound.

They are for the 6-FET series, not for the 9-FET series.
Their algorithm for Hall-less motors is not perfect, the result is that there is a difference in noise level between the 'with hall' and 'hall-less' versions of the same SWX02, albeit quite small, still perceptible with the 6-FET sine wave Lishui controllers.
I use both, so I have good experience.
In use, you soon don't notice the motor noise anymore. BTW, the reason so many suppliers specify their bikes with Lishui controllers is down to reliability. Lishui controllers are simply the best.
http://www.lsdzs.com/en.php

 

[Deleted member 4366]

Lishui controllers are simply the best.

That's your opinion. I think KT controllers are better.

 

[topographer]

Kunteng sine-wave controllers make motors almost silent.

It's great how I can hang around here gradually picking up all these nuggets of information like a bird picking up seeds. Let's just see if I can remember it all.

I love my Q128C-Kunteng setup. It just gives pure smooth torque. I can't hear any motor noise at all at any speed when I'm on the bike.

Dream bike, especially if you have the LCD3 with it. I wish OEMs made bikes like that. The state-of-the-art seems to be in your garage rather than on manufacturers premises. They're even scared to give us a lot of amps. Anyone would think Amps were addictive and prone to being abused...oh wait...

 

[Woosh]

I wish OEMs made bikes like that.

there is always a cost benefit trade-off.
The Q128H (I have it on one of my bikes) has a higher reduction ratio than the SWX02 and is marginally quieter. However, because the rotor spins nearly twice as fast, the wear and tear on the gearbox is also higher. The Q128H is actually cheaper to buy than the SWX02 but because of a number of factors (if anyone is interested, I can go into more details), I prefer the SWX02 to the Q128H.

 

[GLJoe]

You have to understand that a square wave controller is firing pulses of energy at the motor, which more or less knock it round. At low speed, the frequency is low enough to hear, like a grinding sound, which smooths out as you go faster.
...
I love my Q128C-Kunteng setup. It just gives pure smooth torque. I can't hear any motor noise at all at any speed when I'm on the bike.

But why does it make any noise in the first place?
If you put pulses of current through a resistor for example, there is zero noise.
Leaving out the obvious of things like tyre noise, What is it in the drivetrains of these systems that translates electrical power into sound (that can vary with the harmonics of the driving supply current)
?

 

[topographer]

there is always a cost benefit trade-off.
The Q128H (I have it on one of my bikes)

Which bike do you have it on?

 

[Woosh]

sorry TG, I should have said one of my workshop bikes.
I still have it. If I have some free time next week, I'll make a video to show the difference between the SWX02 and Q128H.

 

[topographer]

but because of a number of factors (if anyone is interested, I can go into more details), I prefer the SWX02 to the Q128H.

I'd like to know. No hurry...when you have time.

I think you said somewhere that you like to take a motor up a hill and see how soon it starts struggling and as a result you have more faith in the Bafangs.

 

[Woosh]

I'd like to know. No hurry...when you have time.

I think you said somewhere that you like to take a motor up a hill and see how soon it starts struggling and as a result you have more faith in the Bafangs.

beside wear and tear, one important consideration is the likelihood of failures.

Motors often fail because:
1. hall sensors die
2. magnets get detached from rotor
3. overheating causing insulation to melt

When you use a high reduction ratio motor, you are likely to need hall sensors. The sensorless These sensors are sentitive to heat. Sensorless motors are not affected by this problem.
Higher rotational speed means higher probability that when you run over a pot hole on the road, your rotor hits the side of the stator and causes a magnet to detach.
The reason to have higher reduction ratio is to produce more power with less copper. Motors are still made of steel and copper. More steel and copper can handle more power and dissipate more heat. The Q128H has less steel and copper in comparison.
The gearbox in the Q128H has two stages, 6 nylon cogs compared to single stage, 3 nylon cogs on the SWX02. I think that the Q128H gearbox wastes more energy.

 

[Deleted member 4366]

I wish OEMs made bikes like that. The state-of-the-art seems to be in your garage rather than on manufacturers premises. They're even scared to give us a lot of amps. Anyone would think Amps were addictive and prone to being abused...oh wait...

The Wisper Torques have what you want.

 

[topographer]

The Wisper Torques have what you want.

I thought the Q128 had more torque and climbed steeper hills than the Wispers.

 

[Deleted member 4366]

Yes, but you were asking about OEM bikes. I don't know of any OEM bikes that use a Q128. The Wisper is the closest.

 

[topographer]

beside wear and tear, one important consideration is the likelihood of failures.

Motors often fail because:
1. hall sensors die
2. magnets get detached from rotor
3. overheating causing insulation to melt

When you use a high reduction ratio motor, you are likely to need hall sensors. The sensorless These sensors are sentitive to heat. Sensorless motors are not affected by this problem.
Higher rotational speed means higher probability that when you run over a pot hole on the road, your rotor hits the side of the stator and causes a magnet to detach.
The reason to have higher reduction ratio is to produce more power with less copper. Motors are still made of steel and copper. More steel and copper can handle more power and dissipate more heat. The Q128H has less steel and copper in comparison.
The gearbox in the Q128H has two stages, 6 nylon cogs compared to single stage, 3 nylon cogs on the SWX02. I think that the Q128H gearbox wastes more energy.

Thanks for writing out your reasons. Err...did you ever test the AKM? I've not heard of Wisper having any problems with it.

 

[Woosh]

Thanks for writing out your reasons. Err...did you ever test the AKM? I've not heard of Wisper having any problems with it.

Motors often fail because:
1. hall sensors die
2. magnets get detached from rotor
3. overheating causing insulation to melt

those reasons are the same with any e-bike motors, including direct drive and crank drive motors.
The difference in probabilities come from the design of the motors. Direct drive motors do not have gearbox, but usually run at higher current and have more magnets and larger rotor diameter so the risk is highest.
Geared hub motors and crank drive rotors spin at higher speed, but have fewer magnets and smaller rotor's diameter, have lowest risk.
That is why geared hub motors are generally very reliable, more so for sensorless geared motors.
(if you count out the probability of failure of the gearbox).
Among geared hub motors, the higher the rotor's RPM, the higher the risk.
That's why higher reduction ratio has a cost.
That is my view on motors, I can't comment on specific brand.

 

[Deleted member 4366]

Among geared hub motors, the higher the rotor's RPM, the higher the risk.
That's why higher reduction ratio has a cost.

Higher RPM of the rotor allows you run the same power with less torque between the rotor and gears, so wear would be less, not more.

 

[Woosh]

Higher RPM of the rotor allows you run the same power with less torque between the rotor and gears, so wear would be less, not more.

higher RPM:

1) less torque: agreed.
But less torque does not reduce the risk of frying the Hall sensors or reduce the copper temperature while the risk of detached magnets (when riding over potholes) increases with RPM.

2) higher RPM increases the risk of failure of the gearbox. If the gearbox has two stages, the lower torque only reduces the risk of failure of the first stage, the second stage cogs incur the same wear and tear compared to single stage gearbox.