Relationship between wheel speed and e-bike speed

[tonylai]

Hello everyone, I am a student from Taiwan and I am wondering:
1.How to convert the wheel speed(rad/s or RPM) to the e-bike(two wheel drive) speed(m/s or km/hr)?
2.Is there any formula or equation that can represent the relationship between wheel speed(rad/s or RPM) and e-bike(two wheel drive) speed(m/s or km/hr)?
3.I had saw a formula : v=(n*60*L)/1000 where v is e-bike speed, n is wheel's rpm and L is the perimeter of the wheel. Can this formula used for two wheel drive e-bike?

PS:Assume that two wheel's speed are synchronous.
thanks for your answer!!

 

[vfr400]

There's the mathematicians way and the engineers way. I'm an engineer, so I do it like this:
25km/h is approximately 201 rpm for a 26" wheel
so a 202 wheel would be 25 x 200/26 = 19 km/h
300 rpm with a 29" wheel would be 25 x 300/201 x 29/26 = 41.6 km/h
if you were doing 32km/h with a 28" wheel, the wheel would be spinning at 201 x 32/25 x 26/28 = 239 rpm

If you're question is in relation to hub-motor design, to run at 25km/h modal speed, you need a motor that has a maximum rpm of 30% higher than that, so for a 26" wheel, that would be 201 x 1.3 = 260 rpm approx, and if you wanted a modal speed of 32 km/h, it would be 201 x 32/25 x 1.3 = approx 330 rpm

 

[tonylai]

There's the mathematicians way and the engineers way. I'm an engineer, so I do it like this:
25km/h is approximately 201 rpm for a 26" wheel
so a 202 wheel would be 25 x 200/26 = 19 km/h
300 rpm with a 29" wheel would be 25 x 300/201 x 29/26 = 41.6 km/h
if you were doing 32km/h with a 28" wheel, the wheel would be spinning at 201 x 32/25 x 26/28 = 239 rpm

If you're question is in relation to hub-motor design, to run at 25km/h modal speed, you need a motor that has a maximum rpm of 30% higher than that, so for a 26" wheel, that would be 201 x 1.3 = 260 rpm approx, and if you wanted a modal speed of 32 km/h, it would be 201 x 32/25 x 1.3 = approx 330 rpm

Thank you for your reply!
So can I say :
if I have a 26" wheel and it is speeding at 200 rpm, and the e-bike's speed is unknown. The e-bike's speed can be calculated as 25km/hr? No matter it is one wheel drive or two wheel drive?

How about when the e-bike is turning?
Is there any formula or equation that can represent the turning speed that consider steering angle and camber angle? Does it makes differences if it is one wheel drive or two wheel drive?

 

[vfr400]

Thank you for your reply!
So can I say :
if I have a 26" wheel and it is speeding at 200 rpm, and the e-bike's speed is unknown. The e-bike's speed can be calculated as 25km/hr? No matter it is one wheel drive or two wheel drive?

How about when the e-bike is turning?
Is there any formula or equation that can represent the turning speed that consider steering angle and camber angle? Does it makes differences if it is one wheel drive or two wheel drive?

The speed and rpm are the same, regardless of the number of wheels or motors. When you're turning or the road is cambered, it's still the same, but it depends which direction you want to measure the speed.

Say you were riding along a straight road at 15 km/h. Most people would say that your speed was 15km/h, but if you started riding in a circle within the road and the wheel was still turning at 120 rpm (200 x 15/25), you would say that you were riding at 15 km/h in a circle, but a policeman up the road checking your speed with a speed gun would say that you were doing 15km/h if he measured you when you were facing him, 0km/h when you were at right angles to him, -15km/h when you had your back to him and any speed in between when you were at any other position.