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1) The author’s whole approach is to optimise the current ebike concept/approach for simplicity and cost. With this being the focus, his argument is entirely va

by mft_ 5y ago

1) The author’s whole approach is to optimise the current ebike concept/approach for simplicity and cost. With this being the focus, his argument is entirely valid. In a future world where his ideas resulted in $500 ebike, you’d be free to choose a more expensive option that gave you the intermittent feeling of pedalling you say you require. Others could choose otherwise. 2) Bikes are a very different prospect to small cars and golf carts - size, weight, functionality, cost, legal status, use-cases, etc. There’s a vast difference between an ebike optimised as the author proposes, and a small car - this is a really odd comparison! 3) I’m not aware of Kevlar being used in bike tyres other than a) replacing the steel bead, or b) offering additional puncture resistance underneath the rubber tread. Is there another use that offers the greater wear resistance?

taken_every_ 5y ago
On 3), I've worn my Schwalbe marathons down to the kevlar layer, probably more than 10000km. No issues so far. I recently heard a clicking noise while riding, turns out there was a huge glass shard stuck in it. No problem after pulling it out. Not to sound like an ad, competitors probably have similar performance now
- mkl 5y ago
  OTOH, I got a nail right through one of my Schwalbe Marathons at ~1500km.
  - alexmorley 5y ago
    The marathon plus's are quite a bit more durable IME. And my sister and brother in law literally cycled fron UK -> singapore without a single puncture between them.
    - digisign 5y ago
      Any blog posts from the trip?
    - mkl 5y ago
      My mistake, Marathon Plus is what I have (just looked at my bike). My point is that anecdotes don't prove much, except that these tires are not invulnerable.
johnwalkr 5y ago
1) But you can't just handwave away some inconsequential components in terms of cost (brakes and a chain drive), describe a bunch of extra complexities by not having those components and then say it will be cheaper. Everything described in the article looks like an extra complexity and cost to me, compared to the way most e-bikes are built now. A few red flags stand out to me: A) Brakes. Mechanical bicycle brakes can provide kW of power dissipation for short time periods. e-bike motors are rated for ~250W and even if one were rated for 1000W, they are not going to be able to dump that power into a battery. So if you want regenerative braking, it's either going to need mechanical or resistive braking as well. There's a reason virtually every e-bike design from low-end to high-end does not even have regenerative braking and only has mechanical brakes. Because physics dictates you need mechanical brakes, and regenerative braking barely helps you on a bike anyway. If you're going to go against this trade of of every e-bike that came before, you had better show some numbers or reasoning. This is a physics problem so it's really not something where you can say "in the future when technology is better" especially in the context of claiming that cost will be lower. I'm not aware of any vehicles (bikes or other) that use only dynamic braking. Even streetcars, which historically use resistive braking (with very large components to do it by the way), always have emergency mechanical brakes. B) Mass. If you're going to claim removing the chain and brakes saves significant mass, you better show some numbers. A hub motor is like 2-3kg and I guess a matching generator should be a similar mass. C) FreeDrive system linked by the author. The claim is 5% less efficient than a chain, but this is really hard to believe given that power must be converted from mechanical to electrical and back again. The image of FreeDrive looks like a premium product, not cheap and is controlled by a CAN interface and a human-machine-interface, according to its press release. This is not a component that's going to make your bike cheaper. And if it wasn't heavy, the mass would be in the press release. It's heavy, I'd guess also about 3kg from images. OK, you can think of something lighter but nothing will be able to approach a chain drive. After all, you have to support the same input and output loads in addition to extra components. D) Software handwaves. Why would a bluetooth connection to your phone be preferable or cheaper than a wired display? Sure, you've eliminated 2 or 3 wires, but now you need an adjustable mount and ongoing software maintenance for Android and iOS? What does "<motors that> will hand more control off to software, allowing physical simplification" mean? BLDC motors are dead simple mechanically but basically cannot function without software. Fortunately such software is heavily optimized and available for practically nothing inside commodity motor controllers. Now, all of the above is fine as speculation anyway, except for the fact that the premise of the article is making a cheap Corolla-like e-bike. It gets so close by saying "maybe one will come out of Asia." I would counter this whole article by saying "why aren't the base models of Panasonic and Bridgestone e-bikes sold worldwide?" They start at just over $1000, but are definitely the Corollas of the e-bike world. If they sold 10x as many they probably could be $500. I'm not sure why North America seems to have cheap junky bikes and high-end bikes in stores, with barely any decent commuter bikes (e or non-e) on the market.
KennyBlanken 5y ago
It's an approach situated on numerous presumptions about bicycles and a lot of ignorance about them and basic mechanical/electrical engineering principles. They are proposing a complex electromechanical system with an entire second motor and geartrain to replace a chain and two cogs because they see that setup as "heavy". They're completely unaware that generators (and especially accompanying gearset, and its power rectification/control circuitry) have substantial losses. Two cogs and a chain are over 95% efficient. A generator/motor hybrid bicycle would be heavier, have less range, and both mechanically and electrically much more complex. It could not possibly be cheaper. The blog post is what happens when someone who considers themselves very smart looks at something they know nothing about and says "I know how to fix this."

by mft_ 5y ago

taken_every_ 5y ago

On 3), I've worn my Schwalbe marathons down to the kevlar layer, probably more than 10000km. No issues so far. I recently heard a clicking noise while riding, turns out there was a huge glass shard stuck in it. No problem after pulling it out. Not to sound like an ad, competitors probably have similar performance now

mkl 5y ago
OTOH, I got a nail right through one of my Schwalbe Marathons at ~1500km.
- alexmorley 5y ago
  The marathon plus's are quite a bit more durable IME. And my sister and brother in law literally cycled fron UK -> singapore without a single puncture between them.
  - digisign 5y ago
    Any blog posts from the trip?
  - mkl 5y ago
    My mistake, Marathon Plus is what I have (just looked at my bike). My point is that anecdotes don't prove much, except that these tires are not invulnerable.

johnwalkr 5y ago

1) But you can't just handwave away some inconsequential components in terms of cost (brakes and a chain drive), describe a bunch of extra complexities by not having those components and then say it will be cheaper. Everything described in the article looks like an extra complexity and cost to me, compared to the way most e-bikes are built now. A few red flags stand out to me: A) Brakes. Mechanical bicycle brakes can provide kW of power dissipation for short time periods. e-bike motors are rated for ~250W and even if one were rated for 1000W, they are not going to be able to dump that power into a battery. So if you want regenerative braking, it's either going to need mechanical or resistive braking as well. There's a reason virtually every e-bike design from low-end to high-end does not even have regenerative braking and only has mechanical brakes. Because physics dictates you need mechanical brakes, and regenerative braking barely helps you on a bike anyway. If you're going to go against this trade of of every e-bike that came before, you had better show some numbers or reasoning. This is a physics problem so it's really not something where you can say "in the future when technology is better" especially in the context of claiming that cost will be lower. I'm not aware of any vehicles (bikes or other) that use only dynamic braking. Even streetcars, which historically use resistive braking (with very large components to do it by the way), always have emergency mechanical brakes. B) Mass. If you're going to claim removing the chain and brakes saves significant mass, you better show some numbers. A hub motor is like 2-3kg and I guess a matching generator should be a similar mass. C) FreeDrive system linked by the author. The claim is 5% less efficient than a chain, but this is really hard to believe given that power must be converted from mechanical to electrical and back again. The image of FreeDrive looks like a premium product, not cheap and is controlled by a CAN interface and a human-machine-interface, according to its press release. This is not a component that's going to make your bike cheaper. And if it wasn't heavy, the mass would be in the press release. It's heavy, I'd guess also about 3kg from images. OK, you can think of something lighter but nothing will be able to approach a chain drive. After all, you have to support the same input and output loads in addition to extra components. D) Software handwaves. Why would a bluetooth connection to your phone be preferable or cheaper than a wired display? Sure, you've eliminated 2 or 3 wires, but now you need an adjustable mount and ongoing software maintenance for Android and iOS? What does "<motors that> will hand more control off to software, allowing physical simplification" mean? BLDC motors are dead simple mechanically but basically cannot function without software. Fortunately such software is heavily optimized and available for practically nothing inside commodity motor controllers. Now, all of the above is fine as speculation anyway, except for the fact that the premise of the article is making a cheap Corolla-like e-bike. It gets so close by saying "maybe one will come out of Asia." I would counter this whole article by saying "why aren't the base models of Panasonic and Bridgestone e-bikes sold worldwide?" They start at just over $1000, but are definitely the Corollas of the e-bike world. If they sold 10x as many they probably could be $500. I'm not sure why North America seems to have cheap junky bikes and high-end bikes in stores, with barely any decent commuter bikes (e or non-e) on the market.

KennyBlanken 5y ago

It's an approach situated on numerous presumptions about bicycles and a lot of ignorance about them and basic mechanical/electrical engineering principles. They are proposing a complex electromechanical system with an entire second motor and geartrain to replace a chain and two cogs because they see that setup as "heavy". They're completely unaware that generators (and especially accompanying gearset, and its power rectification/control circuitry) have substantial losses. Two cogs and a chain are over 95% efficient. A generator/motor hybrid bicycle would be heavier, have less range, and both mechanically and electrically much more complex. It could not possibly be cheaper. The blog post is what happens when someone who considers themselves very smart looks at something they know nothing about and says "I know how to fix this."