Dumb E-bike Math question

dsimon · #1 03-09-2022, 03:58 PM

So if an average ebike can go 20 mph and I can average 20 mph does that mean I can easily go 40mph?

Sorry I was a window licker-in school

gemship · #2 03-09-2022, 04:02 PM

Quote:

Originally Posted by dsimon

So if an average ebike can go 20 mph and I can average 20 mph does that mean I can easily go 40mph?

Sorry I was a window licker-in school

No because the ebikes are power limited to only go as fast as 20mph. What it does mean is that you will be able to get up to 20mph very easily and sustain this speed for a much longer distance.

Mark McM · #3 03-09-2022, 04:11 PM

Quote:

Originally Posted by dsimon

So if an average ebike can go 20 mph and I can average 20 mph does that mean I can easily go 40mph?

Yes. Provided that you are riding from stern to bow on a ship that is going 20 mph. If you are riding from bow to stern, then the motor assist stops when you reach 0 mph.

dsimon · #4 03-09-2022, 04:14 PM

Quote:

Originally Posted by Mark McM

Yes. Provided that you are riding from stern to bow on a ship that is going 20 mph. If you are riding from bow to stern, then the motor assist stops when you reach 0 mph.

AngryScientist · #5 03-09-2022, 04:15 PM

Good thing there wasnt a pandemic when you were in school. window licking sounds gross.

There are different classes of ebikes.

Quote:

Class 1 ebikes are limited to a top speed of 20 miles per hour, and the electric motor works only when the rider is pedaling. A bike that has an electric motor that assists only during pedaling is called a pedelec.

Class 2 ebikes are also limited to a top speed of 20 miles per hour, but they have throttles that work when you're not pedaling. That doesn't mean the motor won't assist you if you decide to pedal. Most Class 2 ebikes offer electrically assisted pedaling alongside throttles. As with Class 1 ebikes, you can generally ride them the same places as an analog bike.

Here's where it gets confusing. Class 3 ebikes can go up to 28 miles per hour and must have a speedometer, but may or may not have a throttle.

AngryScientist · #6 03-09-2022, 04:16 PM

Quote:

Originally Posted by Mark McM

Yes. Provided that you are riding from stern to bow on a ship that is going 20 mph. If you are riding from bow to stern, then the motor assist stops when you reach 0 mph.

Relatively speaking, of course.

dsimon · #7 03-09-2022, 04:18 PM

OK Angry let's say the Pinarello E-road bike. why would I be governed if I am adding to the electric machine?

Louis · #8 03-09-2022, 04:26 PM

No, you can't just add the speeds. Note the ^2 term on velocity...

Mark McM · #9 03-09-2022, 04:30 PM

Quote:

Originally Posted by AngryScientist

Relatively speaking, of course.

Mark McM · #10 03-09-2022, 04:31 PM

Quote:

Originally Posted by Louis

No, you can't just add the speeds. Note the ^2 term on velocity...

But what if it's on a moving conveyor belt?

prototoast · #11 03-09-2022, 04:32 PM

Abstracting away from the rules governing e-assist bikes, there's also just an underlying physics question.

If you alone can produce W1 watts and do velocity v1, and the e-bike alone can produce W2 watts and do velocity V2, what velocity will you be able to do with power W = W1 + W2.

This is a tricky thing to calculate, as it depends on a multitude of factors, but at a very high level, V(W1 + W2) < V(W1) + V(W2).

http://bikecalculator.com/ provides some estimates of speed at a given power that we can use as an example.

If you can do 250w on your own, with the default settings on bikecalculator, that results in a velocity of 21.5 mph.

If your e-bike can do 300w on its own, that results in a velocity of 23.0 mph.

If you and your e-bike work together to do 550 w, that results in a velocity of 28.6 mph.

To do 44.5 mph (the sum of the two velocities), you would need a power of approximately 1965 w, or almost 4x the sum of the combined power output.

Louis · #12 03-09-2022, 04:33 PM

Quote:

Originally Posted by Mark McM

But what if it's on a moving conveyor belt?

European or African conveyor belt?

dsimon · #13 03-09-2022, 04:37 PM

Ooooh I so hate you people right now

I waz just a strong Soldier not the smart one

Ralph · #14 03-09-2022, 05:03 PM

Quote:

Originally Posted by AngryScientist

Good thing there wasnt a pandemic when you were in school. window licking sounds gross.

There are different classes of ebikes.

Not part of your question.....but I see lots of E bikes all the time around here. I don't think any of them were bought by a younger healthy cyclist just to go faster. They all seem to be bought by someone who needs some "assist" so they CAN go riding. I have seen a couple E Mtn bikes that were bought to make off road easier for a younger rider.

Personally....I don't understand the desire to buy a powerful E bike just to go faster. (Rant over... sorry)

dsimon · #15 03-09-2022, 05:08 PM

Quote:

Originally Posted by Ralph

Not part of your question.....but I see lots of E bikes all the time around here. I don't think any of them were bought by a younger healthy cyclist just to go faster. They all seem to be bought by someone who needs some "assist" so they CAN go riding. I have seen a couple E Mtn bikes that were bought to make off road easier for a younger rider.

Personally....I don't understand the desire to buy a powerful E bike just to go faster. (Rant over... sorry)

great question.. I was thinking about commutability and speed .... Since gas prices Just a thought