Finally building my e-bike

[satanicoo]

Hi guys,

A long time lurker has yet decided on getting his hands dirty!
I have been building and testing my bike. Right now its a friction drive, with a 50mm piece of aluminium diameter that frictions with the tire.

Some data:
-a 6354 RC motor with 230 KV and good for 2800W
-120A HV ESC, the turnigy K-force;
-10S 15AH Lipo set.

And now some math;
3.8V * 10 = 38V battery
38V * 230KV = 8740 RPM
Motors usualy work at best efficiency at 85%/90% RPM, so 7429/7866 RPM, so 7500 RPM at top speed.

I'm pointing for 70km/h.
50mm * pi * 7500 = 1177000mm = 1177 meters per minute = 70 km/h

Right now i have been able to top at 52 km/h, but i only do it for 500 meters top, the motor gets hot (hard to touch) and the friction wheel gets schorching hot (if i touch it, skin off. If i stop for some seconds, smells like burned rubber since its touching the tire)

Am i pushing the motor too hard, or is the transfer method of power a bad one?

I'm considering turning the bike into a single stage system motor directly to the wheel.
Where can i get a big enough sprocket to mount on the rear wheel to get a 10:1 reduction?

Hope you guys can help!

 

[robocam]

Would the 90T work?

http://cyclone-tw.com/order-chainwheel.htm

...Where can i get a big enough sprocket to mount on the rear wheel to get a 10:1 reduction?...

 

[satanicoo]

Hey there,

it would be still kind of small i think, isn't the lowest sprocket for the motor a recomended 13 teeth?
BTW here's the motor: https://pt.aliexpress.com/store/product/RC-Hobby-Brushless-outrunner-Motor-C6364-KV230-1224344/704742_536661094.html?detailNewVersion=&categoryId=200001407

 

[LI-ghtcycle]

Hey there,

it would be still kind of small i think, isn't the lowest sprocket for the motor a recomended 13 teeth?
BTW here's the motor: https://pt.aliexpress.com/store/product/RC-Hobby-Brushless-outrunner-Motor-C6364-KV230-1224344/704742_536661094.html?detailNewVersion=&categoryId=200001407

What kind of roller and tension method are you using?

Here are a few good builds to check out with friction drive:

Kepler Drive:

https://endless-sphere.com/forums/viewtopic.php?f=6&t=74269

Commuter Booster:

https://endless-sphere.com/forums/viewtopic.php?f=28&t=22187

 

[satanicoo]

Hi there,

First of all sorry for the long delay, the job is quite unforgiving and i just feel like sleeping alot.
I have dismantled the motor and support for some photos:

That is an aluminium wheel with the shape of the tire and some cuts for an extra grip.

I dont have a tension there, i basicaly deflate the wheel, mount it close and then flatten it again. Its pretty steep i can't turn it by hand and make it slip.
It still feels hard to make a good efficient friction drive from what i have read, so i will pursue a single stage chain drive method, seems like the most efficient way to transmit power. The noise ain't a problem for me.
How much power and speed can i expect to pull from a motor like this without the risk of a burn up?

 

[satanicoo]

Just added a fan on the motor to try and cool it of a bit.
Also adding some thick sand paper on the traction wheel to prevent it from slipping and overheating (right now covered with duct tape to dry the glue)

Tomorrow will mount it again and test it!

 

[satanicoo]

So i tested the motor again, the sand paper jumped out almost instantly!
Did not use the fan yet.
Made the interface between a hall trottle and the rc controler. Much easier to use than a pot. I was able to hit 48 km/h with 95% trottle using 1800w. However at 100% trottle the motor wines a bit high and power consuption goes to 4000w. Something is wrong. Perhaps the controller isnt compatible with the motor?

Ill add a picture later of the final build!

EDIT: here!

 

[satanicoo]

I'm giving up on the single stage power transfering, i would need to get a very large sprocket.
Stay tuned as i do some math on what to do next!

Any idea on why my motor/controller are behaving like they are on full trottle?