> you really start to feel the air resistance and it becomes exponentially harder to go beyond 45kph
Nitpick: it becomes cubically harder. ;)
Re:Show HN: Long Range E-Bike
by antisthenes on Saturday November 13, 2021 @12:08AM
(#29207566)
Nitpick to nitpick: cubically is a subset of exponentially.
Re:Show HN: Long Range E-Bike
by newaccount74 on Saturday November 13, 2021 @12:48AM
(#29207748)
You are both wrong. Air resistance increases quadratically with speed, not cubically. And you mixed up polynomial with exponential.
Quadratic: x^2
Cubic: x^3
Polynomial (eg. 3rd degree): a + b x + c x^2 + d x^3
Exponential: e^x
Drag force rises quadratically with speed. Power is force dot velocity; in this case force and velocity are in the same direction, so dot product becomes simple mulitiplication making drag power (exertion, formally: work per unit time) cubic with speed.
Re:Show HN: Long Range E-Bike
by newaccount74 on Saturday November 13, 2021 @04:41AM
(#29208648)
Oh, you are right! Sorry.
Those speeds sound like bogus. I can maintain about 40kph on my ebike on a flat surface, but that requires pedaling in addition to the motor and is a fairly energetic exercise.
Also, pushing beyond 45kph, you really start to feel the air resistance and it becomes exponentially harder to go beyond 45kph for any long period of time, unless going downhill.
Most ebikes don't really come with the chainring size to go up to high speeds, unless modified with a giant 50+ size, which is more apt for racing road bikes (non-electric)