KHB - Project eTurd - 2000W - LiFePO4 48V 24Ah

[kreal]

New knobby tires, and shorten the frame a bit.

 

[kreal]

Really happy with the result so far, just waiting for 3000w motor.

 

[kreal]

Added a little plastic leftover from my Yamaha nouvo elegance 135 lc conversion. Recycle to the max.

Also added some stickers, because why not.


Use an old mudflap I had from a scooter.

 

[kreal]

Motor and controller mounted.






However this motor has no torque whatsoever, even with a very big 46T sprocket on the back, and 14T in front using 520 chain. I kinda knew that.

Although it has plenty of rpm. But how do I fix more torque, some sort of gearbox ?

14T to 50T to 14T to 47T ?



[youtube]nU3EJ0R2ZIk[/youtube]

 

[ShadowNightmares]

However this motor has no torque whatsoever, even with a very big 47T sprocket on the back, and 14T in front using 520 chain. I kinda knew that.

Although it has plenty of rpm. But how do I fix more torque, some sort of gearbox ?

Yep, you will need a jackshaft
Your desired 14T>50T/14T>47T will have final ratio of 11.99:1
So with 4k RPM in the motor, the wheel RPM will be 333RPM, with 24inch tires (on 18inch wheels) will have 23,8MPH

 

[kreal]

However this motor has no torque whatsoever, even with a very big 47T sprocket on the back, and 14T in front using 520 chain. I kinda knew that.

Although it has plenty of rpm. But how do I fix more torque, some sort of gearbox ?

Yep, you will need a jackshaft
Your desired 14T>50T/14T>47T will have final ratio of 11.99:1
So with 4k RPM in the motor, the wheel RPM will be 333RPM, with 24inch wheels will have 23,8MPH

thanks, didn't know what it was called, I'll search for jackshaft, see if I can make one.

wheels are 17 inch 80/100.

23,8MPH is fine, as long as I can claim a few hills

 

[kreal]

I do have another 14T and 45T sprocket, I could make jackshaft from.

Motor - input jackshaft - output jackshaft - wheel
14T -> 46T -> 14T -> 45T

Would give 20.66MPH with 17Inch tires, and a gear ratio of 10.56:1 as the motor has a rated RPM of 4300

However I have no idea if this would provide enough torque ?

 

[ShadowNightmares]

I do have another 14T and 45T sprocket, I could make jackshaft from.

Motor - input jackshaft - output jackshaft - wheel
14T -> 46T -> 14T -> 45T

Would give 20.66MPH with 17Inch tires, and a gear ratio of 10.56:1 as the motor has a rated RPM of 4300

However I have no idea if this would provide enough torque ?

You need to calculate the speed using the diameter from the tire, not the wheel

About the torque, 14T>46T is 1:3,28, so the jackshaft will give you ~3x more torque than you have at the moment

 

[kreal]

I do have another 14T and 45T sprocket, I could make jackshaft from.

Motor - input jackshaft - output jackshaft - wheel
14T -> 46T -> 14T -> 45T

Would give 20.66MPH with 17Inch tires, and a gear ratio of 10.56:1 as the motor has a rated RPM of 4300

However I have no idea if this would provide enough torque ?

You need to calculate the speed using the diameter from the tire, not the wheel

About the torque, 14T>46T is 1:3,28, so the jackshaft will give you ~3x more torque than you have at the moment

Sounds really good. Made the jackshaft already. 46T -> 14T

 

[rynhardt]

If you use a chain with a smaller pitch, you can get larger ratios. Have a look at the OSET bikes for example.

I'm using #219 (gokart) chain, with a 10T front and 121T rear.

 

[kreal]

If you use a chain with a smaller pitch, you can get larger ratios. Have a look at the OSET bikes for example.

I'm using #219 (gokart) chain, with a 10T front and 121T rear.

Thanks! just can't seem to find sprockets this size around here. Was looking at aliexpress.com, but couldn't find.

I do have a 11T - 420 chain for motor. But still need to find a giant back sprocket then.

The best I can find is 74T for T8F chain.

https://www.aliexpress.com/item/4000780830741.html?spm=a2g0o.productlist.0.0.7b021bd8PckQfg&algo_pvid=794a17a4-faa7-4fe7-87a9-d091e26f81f1&algo_expid=794a17a4-faa7-4fe7-87a9-d091e26f81f1-4&btsid=0b0a556c16229077195432726e1466&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

Oh and my jackshaft failed miserably.

 

[kreal]

So this is what I came up with. Should work ok.

Drilled a hole in the swing arm, and added two barrings to support the jackshaft.




Should give me 9:1 in which if I understand correctly is plenty of torque.



Sadly cannot finish today, it's to late and I cannot make noise cutting the chain to length.

The quality of the bike is very questionable, but hey it's project eTurd. And just me trying out stuff on the bike in preparation for next proper project.

 

[stan.distortion]

Looks like the pigeons are getting out of hand in your shed! Ingenious... terrifying but ingenious. Will your shock still clear when it compresses? And in that speed/ratio calc, doesn't have to be the total height of the tire? I'm guessing 17 is just the rim size but can't make out the tire markings.

 

[kreal]

Looks like the pigeons are getting out of hand in your shed! Ingenious... terrifying but ingenious. Will your shock still clear when it compresses? And in that speed/ratio calc, doesn't have to be the total height of the tire? I'm guessing 17 is just the rim size but can't make out the tire markings.

heh, Still trying to find a donor motocross bike around here. But almost impossible. So had to make my own out of steel.

Unknown if the shock will clear if I bottom out. But me jumping up and down hard on it seems alright.
The motor is still quite a bit under the back tire. So should be alright.

True, I don't know quite how to calculate it, wheels are 17 inch 80/100. Then it should be 23.3 inches ?

 

[kreal]

So final result.



Don't look at the welding on the motor. The sprocket kept falling off, and I got tired of it.



It works pretty good with a gear ratio of 14T -> 42T 420 chain -> 14T -> 46T 520 chain.

9.86:1

Top Speed: 29.94

 

[stan.distortion]

Result!