60 or 80Nm front hub motor

[rig the jig]

Hi all, may you all have a happy and safe new year. I have a bike conversion with a Yose 36V 20AH battery, a KT LCD5 controller, and a Gen 2 Swytch front wheel hub. I live in a hilly are and find that the motor struggles on the hills, regardless of power setting. Would anybody recommend a stronger motor that would replace the existing Swytch front wheel motor, without any rewiring. Thanks in anticipation.
Rig the Jig.

 

[Peter.Bridge]

How heavy are you ? What is the max current of the KT controller ? Don't know if you could go to an 18 amp max KT controller with the swytch ( akm-100 ) motor : 20% more power. I think just changing the motor but keeping the controller output current the same won't make that much difference

 

[saneagle]

Hi all, may you all have a happy and safe new year. I have a bike conversion with a Yose 36V 20AH battery, a KT LCD5 controller, and a Gen 2 Swytch front wheel hub. I live in a hilly are and find that the motor struggles on the hills, regardless of power setting. Would anybody recommend a stronger motor that would replace the existing Swytch front wheel motor, without any rewiring. Thanks in anticipation.
Rig the Jig.

Another motor will give you exactly the same power if you use the same controller. You need to tell us the current you're running with now.

 

[matthewslack]

There's a limit to how much torque and power can be controllably dispensed through a front wheel. The AKM monster 128 doesn't seem on the basis of a quick search to be available as a front hub. That might be AKM saying they think that is beyond the limit.

As a first relatively low cost intervention I'd agree with @Peter.Bridge and up the current to the max: buy the biggest KT controller you dare, and see what happens. You would probably want to work up gradually from shortish hills, and keep an eye on temperatures.

Other options involve more change: a slower motor but at 48V for example, would make a difference but not with your existing battery.

And of course a mid-drive takes hills in its stride.

 

[Peter.Bridge]

Maybe shunt mod to your existing controller to get a bit more power (search shunt mod on these forums)

 

[rig the jig]

It's a 17 A controller, and I weigh 90KG I'll search shunt mode. Thanks for the info.

 

[Peter.Bridge]

I'm a bit surprised that 17 amp * 36v is not getting you up hills, especially at only 90kg

Could you check the setting of C5

Limiting KT Controller Power(Believe it's clone)

Ok. So I have Carrera Crossfire e bike - it has SR Suntour 250W hub motor, 36V 11.86aH battery, what I believe is KT Clone Controller, Throttle, LCD3 - no PAS sensor(Want it to work on throttle only). The controller is rated for both 36V and 48V. The current battery seems to be too limited and...

www.pedelecs.co.uk

 

[rig the jig]

Hi C5 is set to 10.

 

[Peter.Bridge]

Hi C5 is set to 10.

Ok, that's 100%. I think 17 amps * 36v is approaching the maximum power through a front hub without wheelspin and probably approaching the limit for that motor. You could try a shunt mod but only solder a little bit.

An AKM 128 is a lot more powerful and you could easily go to 20 or 22 amps, but I think is rear hub only and you would need a new controller to give more power

 

[thelarkbox]

Just monitor the motor temperature(touch test should suffice) , struggling up hills and requiring a little more pedal input is what gravity is all about. as long as your climbing and not dropping below 8mph for too long on the steep bits and at the top all should be good...

 

[rig the jig]

Excuse my ignorance is an AKM 128 the swytch hub motor

 

[rig the jig]

If all settings are ok I'll stick with the current set up without the shunt modification. As per usual the support from Pedelecs is first class, thank you for the great info.
Rig the Jig

 

[saneagle]

It's a 17 A controller, and I weigh 90KG I'll search shunt mode. Thanks for the info.

OK, if 17A isn't doing it for you, you probably want a motor that can handle more power. If your KT controller is the smallest size, it won't handle more power than 17A. It comes in two sizes. the bigger one should be OK at 20A. Some KT controllers allow you to turn up the current in the settings, so have a look at that first. Don't go by a downloaded manual. see what happens in your actual settings.

Another thing: I wouldn't want to go much higher than 36v 17A with a front motor unless it's fitted in steel forks, so if you have normal aluminium ones, and you decide to get a new motor, get a rear motor. A Q128H with the easy-peal label is a torque monster. It can handle 25A at 48v. The Swytch motor is similar to a Q100 - much smaller than a Q128.

 

[matthewslack]

Excuse my ignorance is an AKM 128 the swytch hub motor

No, AKM128 is a bigger, more powerful, not legal in the UK motor, mentioned because it is a step up from the Swytch. But does not appear to be available as a front hub.

 

[harrys]

I have the Bafang SWX02 also known as FM G020.250/350 front motor in a front steel fork with a KT20A controller on 48V. Plenty of power for my needs. Probably on a par with the AKM128. Probably expensive though, I got mine used,

 

[Bikes4two]

Excuse my ignorance is an AKM 128 the swytch hub motor

No, the Switch motor if have is the AKM 100SX.

When I was looking for a front hub motor I found the AKM 100SX & Bafang G370 each delivering around 40nm iirc but they were the most powerful I could find so I'd be interested if you find one more powerful than those.

 

[saneagle]

No, the Switch motor if have is the AKM 100SX.

When I was looking for a front hub motor I found the AKM 100SX & Bafang G370 each delivering around 40nm iirc but they were the most powerful I could find so I'd be interested if you find one more powerful than those.

Just to make this clear, the torque of any DC motor is proportional to its current. Torque is not some inherent characteristic of the motor.

When manufacturer's give a data sheet that shows some maximum torque figure at some particular rpm, they also indicate the exact voltage and current. At any other voltage or current, the torque would be different.

 

[Peter.Bridge]

I guess, if your forks are suitable, you could go for a 36v Bafang g020 front hub as per @harrys - there are loads of g020 front hub motors on eBay and Ali. It is a heavier motor, might be slightly more efficient at low speeds, but for more power I think you would need more current from the controller

 

[Ghost1951]

Isn't this the situation where a crank motor excels?

Steep hills, substantial rider, front hub motor not coping?

The crank drive motor doesn't suffer from the lowering of efficiency the hub motor is experiencing as it is slowed beyond its ideal motor speed. With a crank drive motor, you just change down and the motor runs at its ideal speed.

As has been pointed out, there are issues in increasing the power of a front wheel motor beyond a certain amount.

 

[Peter.Bridge]

Isn't this the situation where a crank motor excels?

Steep hills, substantial rider, front hub motor not coping?

The crank drive motor doesn't suffer from the lowering of efficiency the hub motor is experiencing as it is slowed beyond its ideal motor speed. With a crank drive motor, you just change down and the motor runs at its ideal speed.

As has been pointed out, there are issues in increasing the power of a front wheel motor beyond a certain amount.

Yep crank drive motor would work, also rear hub motor would work, just would need enough power. I am 105 kg and use my rear hub up long steep hills,.



I slightly prefer my rear hub to my mid drive on roads / light trails, find it a more relaxing ride.

I think where crank drives come into their own is off road