i need help its all about the gears

[kazimirski]

hi my English not so good so I well do my best I have bike wich gng motor and I want to make it 1 gear like real motor for speed and acc
I was tink to make it gear radio like this its have 3.5 KW and 72-83 V 10 ah
this is my bike I want to make my rear wheel to 24" tell me plz if its good idea I want like 60 kph
http://postimg.org/image/bqis4zr2z/

 

[Chalo]

Your reduction ratio is about 19.6:1. The wheel speed that corresponds with 60 kph is 520 RPM. Your power requirement to maintain 60 kph on level ground is about 2300W at the wheel. So if your motor can produce nearly 2.5 kW at about 10,200 RPM under load, then you are in the right ballpark. I know nothing about the motor you're talking about, so I don't know if that's true. Certainly a 10,000+ RPM chain drive will be very noisy!

 

[kazimirski]

i don't tink its make 10,000 rpm i tink its less like 6000 i don't real know the 24 its where I well pedaling

 

[ferret]

The GNG motor is 67 kv so assuming 80V from the battery, you're looking at 5360 motor RPM.

 

[kazimirski]

so I don't get to 60 kph ? so tel me what I ned to change

 

[r3volved]

My GnG gets me up to 55km/h at 1500w. Stock belt pulleys, stock chainwheel and 16t rear sprocket w/ 26" tires.

72V @ ~30a should get you over the 2000w hump and maintain 60 with decent riding conditions.

 

[dusan]

Why you want use 48t sprocket on rear wheel?
Gng under load has around 50kV.
As Chalo wrote, 60kph = 520 rpm at 24" rear wheel. With 48t chainring and 12t rear sprocket, it's 130rpm at crankset. With stock ratio 20:1, it's about 2600 rpm at motor. I think 18s lipo could do it. You will need around 30-40amps continues current.
And I think, mid drive kit without gears doesn't make sense, then use hub.

 

[kazimirski]

maybe I well change the prockets 11t to 13 and the chainring 48t to 44t I want to have a lot of power to go uphill and stop and I want max speed of 60-70KPH
I want to make it like LMX adam bike

 

[kazimirski]

and if I do its like http://endless-sphere.com/forums/viewtopic.php?f=28&t=48963 its well be 11to 54t to 13 to 39 can I get speed and power?

 

[Chalo]

Your motor has a value called kV, which is RPM per volt. I don't know what that value is. If you know what it is, or what its RPM is at its rated voltage, then you can extrapolate what its RPM will be at your planned voltage.

If it's not limited by the current capacity of the controller, a BLDC motor will usually operate most efficiently at about 80% of its free speed, and make the most power at about 50% of its free speed. That is important because you need the RPM required for 60kph with your gearing to correspond with the power required for 60kph. Just looking at your plan and making guesses about the electrical characteristics of the motor and your vehicle weight and layout, I think you need higher gearing (lower reduction ratio). But that's only a guess.