[LarryM]

Good evening,

I am attempting to build an electric motorcycle and I found the QS138 motors which seem fairly popular with lots of builds online using them.
I did however notice there are 3 different versions with different ratings online and I wanted to know if there was anything on the variations that I am not seeing. They appear to just be different wattages with basically the same top speed. The version 3 model also appears to have an integrated gearbox for a little bit of reduction.

Is there some reason that the 3000 watt rated and the 6000 watt rated models both have the same climbing grade (what a dumb stat) and top speed? The version 1 is the higher wattage one so it might make sense that its less efficient but a 100% increase in efficiency is not logical.

Here are the links I am looking at they appear to be a real subsidiary of the manufacturer as far as I can tell so you would expect their information to be accurate. There is a lot more information in graphs and stuff I can't read because of Chinese legends.

v1 - 578.0US $ |QS Motor 138 70H V1 72V 100KPH 6000W Continous 10kw Peak Sprocket Mid Drive Motor Powertrain Motor Kits for Electric Dirt Bike|Motors| - AliExpress
v2 - 578.0US $ |QS Motor 3000W Electric Motor 5000W 138 72V 100KPH New V2 Mid Drive Motor Powertrain Motor Kits for Adult Electric Motorcycle|Motors| - AliExpress
v3 (doesn't have a combo for some reason) - 319.0US $ |New Arrival QS138 70H V3 72V 100kmph Mid Drive Motor with 1:2.35 gearbox for Electric ATV Dirtbike Motorcycle|Motors| - AliExpress


I am very new to motor sizing and banging my head against a very complicated subject of power, efficiency, weight, longevity, and type. Thanks for any help!

LarryM

 

[LarryM]

Does anyone understand the difference in those charts well enough to provide any insight on best choice?

 

[EJFitz]

I also don't know a whole lot about motors, but I've been trying to learn a lot in the past week. You should check out BigGuyLittleBikes video on YouTube (

). It's a video about hub motors specifically, but he includes a spreadsheet that will likely be helpful for choosing any kind of motor. Another good idea would be to go to QS motors website (QSMotors.com) and send them a message saying what you're building and what you hope to get out of it. I've heard from others that they're very helpful and could get you on the right track. Best of luck!

 

[Picassoster]

They are basically the same motor - with same performance. The V1 had some issue with the sproket attaching to the shaft thus they updated to the V2 that has a stonger design. The V2 also comes with different mounting brackets and option for a belt pulley.
The V3 is the same motor with an integrated 2.35:1 gearing reduction so it delivers more torque but lower rpm (same power) - It's used to avoid a dual chain transmission usually needed to reach 7:1 or higher ratio with standard sprokets. The downside is that it's larger so you need more space to fit in to the frame.

 

[Jordan325ic]

The QS 138 is normally listed as a 3kw motor, but it is usually sold with a 10kW capable controller, and I have not heard of any issues running it at that power level (and much higher). So whether it is listed at 3kw or 6kw is arbitrary, the only differences are the V1,2and3 as explained above and maybe 70H or 90H.