Electric Minibike Gearing

[cmilton45]

I have electrified my minibike. Hawg Ty Minibike almost identical to Baja Warrior. Thick tires; not a small minibike. This bike comes stock with 60 tooth 420 sprocket. I added:
1. 3000 watt brushless Vevor motor
2. 11 tooth 420 sprocket on motor
3. 420 chain
4. 72 volt 20AH battery (not a cheap one)

Bike goes about 40 - 45mph, but just after 10 minutes of use the motor gets very hot. On 2 separate occasions, I burned out 2 motors only after 10-15 minutes of use. No problems with Battery and no problems with controller. Just two separate motors getting burned out.

? Do you think the chain is too heavy for the motor (working too hard ?
? Do you think I need like an 80T or 85T sprocket on the back to increase torque?
? Or is this motor not meant for such a big bike?

Thank you

 

[amberwolf]

Some things to check out:

What RPM does the motor spin at with no load, max throttle? And what speed does it need to be spinning to make the wheel go the speed you are going?


Or, what mph does the wheel spin at with no load (off ground), max throttle?

Under load it will try to spin at around 80% of that, so if the system is loaded down such that it can't go that fast, it will use too much current and the motor will overheat.


Another potential problem is the phase/hall combination: if this is not correct the motor will not behave correctly, and may overheat, spin too fast, or make unusual noises, etc. (color matching of wires is no guarantee of correct wiring). If it has a self-learn function that can be used to fix this, otherwise manual swapping of the wires can be done to find which of the six possible combinations (36 total variations but only 6 actual combinations) is correct and spins the motor at the lowest current in the right direction at full throttle with no load. (there are various posts and threads about finding the right hall/phase wiring combo if you need them).


There are also some other threads about Vevor motors/kits that may be similar to yours, if you want to look for them and see what problems they faced/fixed.

 

[cmilton45]

Amberwolf
I appreciate your input. I will have to research how to measure the RPM. As well, the phase/hall input is very much related to me. I switched those wires around to reverse rotation to work with my current minibike sprocket. Thank you

 

[calab]

Buy this Digital Tachometer Non Contact Laser Photo RPM Tach Meter Motor Speed Gauge

 

[MorbidlyObeseKoala]

some light mods can help the vevor motors handle better at higher current. Drilling out the vent holes or making more of them in the 2 faces of the motor helps airflow and adding a finned heat sink to the exterior of the motor can help a bit.

Amberwolf is right about checking to make sure the phases are properly synced, otherwise the motor fights itself and heats up quickly even without as much of a load as it can normally handle.

 

[cmilton45]

Buy this Digital Tachometer Non Contact Laser Photo RPM Tach Meter Motor Speed Gauge

Thank you Calab

 

[cmilton45]

some light mods can help the vevor motors handle better at higher current. Drilling out the vent holes or making more of them in the 2 faces of the motor helps airflow and adding a finned heat sink to the exterior of the motor can help a bit.

Amberwolf is right about checking to make sure the phases are properly synced, otherwise the motor fights itself and heats up quickly even without as much of a load as it can normally handle.

Thank you
Yes I have seen the venting trick on youtube. Since all these motors look the same, it is hard to know what is good and what inferior. The Vevor I had burned out so I will be looking to purchase any 3000w that works

 

[amberwolf]

From what I've seen in posts, the QSMotors of this type are better built. See their sale thread on here for some discussion and info and to get model numbers you can then look up in threads around the forum for actual builds, etc.

 

[cmilton45]

From what I've seen in posts, the QSMotors of this type are better built. See their sale thread on here for some discussion and info and to get model numbers you can then look up in threads around the forum for actual builds, etc.

Thank you
However, QS Motors only seem to have Hub motors

 

[rafalg]

Just doesn't look like a motor meant for long running time - 3kW of power in closed housing, no cooling, small package... What is the power consumption during a ride?

 

[dominik h]

QsMotor sells also other motors
Qs mid drive motors

 

[A-DamW]

3000 watt brushless Vevor motor

Those motors(commonly known as the "MY1020") are basically bottom of the barrel for quality/design, they can be made to work fine, you just have to do your research to know thier limitations, i.e., making sure the controller is set up correctly, and running the motor in it's optimum efficiency range.

 

[amberwolf]

Thank you
However, QS Motors only seem to have Hub motors

they make several kinds of "middrive' frame mounted motors. see the qsmotors site and their sale therad here on the forum for examples, and there are a lot of discussion threads about them too.