4 ms·

I'd be more interested as an alternative to chain or belt drives but I'm not sure how you incorporate gearing without power electronics. Chains can be up to 98%

I'd be more interested as an alternative to chain or belt drives but I'm not sure how you incorporate gearing without power electronics. Chains can be up to 98% efficient and I'd prefer not to throw away 10% just to eliminate gears.

svnpenn 4y ago
With these, you could store energy by pedaling, even when going downhill. If you pedal downhill with a chain, that's just wasted energy.
- samstave 4y ago
  Unless you downshift and peddle hard to gain a lot of speed :-)
  - a4isms 4y ago
    You're joking, but to answer the question seriously, the problem with slamming it into your biggest gear and pedalling downhill is that wind resistance increases with the square of your velocity. When going downhill, you are going faster thanks to gravity. A small increase in speed requires a disproportionally large increase in effort. Hand-waving over the inefficiencies involved in an electric power train, you are far better off pedalling and storing the energy on the downhill, then "spending" that stored energy on the flats or even saving it for the next uphill. With respect to going downhill faster with this system, I doubt it can do anything useful in a straight line descent, but in a long, switchback descent of the type seen in the big Grand Tour races on mountain stages, cyclists need to brake into the switchbacks and accelerate out of them. Regenerative braking followed by assisted pedalling out of the corners would be a huge win.
    - a4isms 4y ago
      > Regenerative braking followed by assisted pedalling out of the corners would be a huge win. ...Until the next ascent, where you have to haul the weight of the battery and what amounts to two electric motors uphill... Although it seems sacrilegious to imagine energy-recovery units in UCI bicycle racing, innovation is strongly influenced by the big manufacturers who are trying to sell bikes. It's unlikely there will be a UCI-sanctioned ERU any time soon, but if there was, the key to adoption would probably be the UCI minimum weight regulations. We are now at the point where high-end bikes often need weights added to meet the minimum, and if the rest of the bike ever gets light enough, it could be possible to add an ERU without compromising the total weight for climbing. But that would require breakthroughs in the culture of bicycle racing and multiple technologies.
    - samstave 4y ago
      >"...The problem with slamming it into your biggest gear and pedalling downhill is that wind resistance increases with the square of your velocity." -- Are you much of a biker? (I put on around ~1,000 miles a month on a 29" mtn bike. Knobby tires and all. At no point ever have I worried about wind resistance - and im not a "shave my legs tour de france" (my brother is, but hes an ultra athelete-type-A Doctor) type that worries about my grams per component, corporate spandex or $12,000 week-end ride. So, while you may be "technically correct" you're commenting as "functionally illiterate"
      - Steltek 4y ago
        Mountain bike descents and road bike descents are dramatically different things.
        samstave 4y ago
        Find me a road bike with an electric motor.
        a4isms 4y ago
        They exist, and that's why UCI scan bikes at the race start line for electric motors, it's a serious enough problem that it has a name, "Motor doping." Famously, Femke van den Driessche received a six-year ban after being caught motor-doping in cyclocross. https://www.bbc.com/sport/cycling/36142963 https://www.bbc.com/sport/cycling/36142963 If you don't want to cheat with a motor, bicycle stores sell all kinds of road bikes with pedal assist for non-competitive riding. Trek, for example, make several e-assist versions of their Domane road bikes: https://www.trekbikes.com/us/en_US/ebike_collection/ https://www.trekbikes.com/us/en_US/ebike_collection/
        samstave 4y ago
        Where newsletter and how subscibe
      - a4isms 4y ago
markvdb 4y ago
This system enables regenerative braking on bicycles. That means you also gain a lot... What I would love to see though would be this, applied to a recumbent or a velomobile. Those often have atypically long chains.
- mikepurvis 4y ago
  Would be a game-changer for urban riding, being able to quickly reclaim energy after a stop.
- dreamcompiler 4y ago
  Regenerative braking makes a lot of sense on cars because cars are not very weight-sensitive and more weight works in your favor for regen braking. Regen braking makes much less sense on bikes because bikes are weight-sensitive. https://gocarlite.com/electric-bicycle-regenerative-braking/ https://gocarlite.com/electric-bicycle-regenerative-braking/
  - dahfizz 4y ago
    That blog post is pretty misguided, IMO. I'll assume the math is right, and the potential gain from regen braking is small. But it's free! > The way regenerative braking is implemented is to have the motor continuously engaged. This is wrong. Regen braking only requires the motor be engaged _when braking_. There's no reason you can't coast when you want to coast.
    - Tostino 4y ago
      You are absolutely right about it being small, but free. Do keep in mind, a direct drive is always "engaged" to some extent by the cogging force. An advanced controller can make a direct drives "freewheel", but it actually takes power to do that. Totally worth budgeting for a slightly larger battery to allow a simpler overall design. Now if you say, had a mid-drive bike, or an internally geared hub, there are some complicated mechanical systems you can put in place to lock the freewheeling mechanisms in the gearing when you want to apply the brakes, but I haven't seen anyone design that yet.
sorenjan 4y ago
It's worth noting the "up to" part. Well maintained and cleaned chains are effective, but I would guess that a lot of commuter bikes have dirty, rusty, and worn chains that lose with a lot of efficiency. Couple that with poorly maintained and adjusted gears and alternatives might not be far off in efficiency if they're a closed system with less maintenance requirements.
- alex_duf 4y ago
  You also have to take into account the extra weight of having a dynamo + a motor, I doubt it's more advantageous than a chain on a classic bicycle. For an electric bicycle though, I see it as a really good contender
  - test6554 4y ago
    I'm not sure how this system works, but it seems like adding in battery power might be useful.
    - alex_duf 4y ago
      I'm assuming it was suggested to replace a chain by what is essentially a dynamo + motor. You pedal to generate energy, and move that energy to the wheel through wire and another motor. (I'm not saying this is a good idea, just describing what I understood). I'm curious what sort of efficiency you can expect on a ridiculous system like that.
  - sorenjan 4y ago
    Yes, this particular system is probably far from efficient enough for regular bikes, this is more for larger transportation bikes and similar (like this example [0]). Having a chain on those limits their construction options, and they're already electric anyway. I was referring to different types of gears and power transfer like driveshafts or hydraulics [1], if you can make it perform at a consistent 90% efficiency it might beat chain drive in practice even though it shouldn't in theory. [0] https://youtu.be/N02KMeOkevI?t=81 https://youtu.be/N02KMeOkevI?t=81 [1] https://www.youtube.com/watch?v=NTB7XOQA-XQ https://www.youtube.com/watch?v=NTB7XOQA-XQ

svnpenn 4y ago

With these, you could store energy by pedaling, even when going downhill. If you pedal downhill with a chain, that's just wasted energy.

samstave 4y ago
Unless you downshift and peddle hard to gain a lot of speed :-)
- a4isms 4y ago
  You're joking, but to answer the question seriously, the problem with slamming it into your biggest gear and pedalling downhill is that wind resistance increases with the square of your velocity. When going downhill, you are going faster thanks to gravity. A small increase in speed requires a disproportionally large increase in effort. Hand-waving over the inefficiencies involved in an electric power train, you are far better off pedalling and storing the energy on the downhill, then "spending" that stored energy on the flats or even saving it for the next uphill. With respect to going downhill faster with this system, I doubt it can do anything useful in a straight line descent, but in a long, switchback descent of the type seen in the big Grand Tour races on mountain stages, cyclists need to brake into the switchbacks and accelerate out of them. Regenerative braking followed by assisted pedalling out of the corners would be a huge win.
  - a4isms 4y ago
    > Regenerative braking followed by assisted pedalling out of the corners would be a huge win. ...Until the next ascent, where you have to haul the weight of the battery and what amounts to two electric motors uphill... Although it seems sacrilegious to imagine energy-recovery units in UCI bicycle racing, innovation is strongly influenced by the big manufacturers who are trying to sell bikes. It's unlikely there will be a UCI-sanctioned ERU any time soon, but if there was, the key to adoption would probably be the UCI minimum weight regulations. We are now at the point where high-end bikes often need weights added to meet the minimum, and if the rest of the bike ever gets light enough, it could be possible to add an ERU without compromising the total weight for climbing. But that would require breakthroughs in the culture of bicycle racing and multiple technologies.
  - samstave 4y ago
    >"...The problem with slamming it into your biggest gear and pedalling downhill is that wind resistance increases with the square of your velocity." -- Are you much of a biker? (I put on around ~1,000 miles a month on a 29" mtn bike. Knobby tires and all. At no point ever have I worried about wind resistance - and im not a "shave my legs tour de france" (my brother is, but hes an ultra athelete-type-A Doctor) type that worries about my grams per component, corporate spandex or $12,000 week-end ride. So, while you may be "technically correct" you're commenting as "functionally illiterate"
    - Steltek 4y ago
      Mountain bike descents and road bike descents are dramatically different things.
      - samstave 4y ago
        Find me a road bike with an electric motor.
        a4isms 4y ago
        They exist, and that's why UCI scan bikes at the race start line for electric motors, it's a serious enough problem that it has a name, "Motor doping." Famously, Femke van den Driessche received a six-year ban after being caught motor-doping in cyclocross. https://www.bbc.com/sport/cycling/36142963 https://www.bbc.com/sport/cycling/36142963 If you don't want to cheat with a motor, bicycle stores sell all kinds of road bikes with pedal assist for non-competitive riding. Trek, for example, make several e-assist versions of their Domane road bikes: https://www.trekbikes.com/us/en_US/ebike_collection/ https://www.trekbikes.com/us/en_US/ebike_collection/
        samstave 4y ago
        Where newsletter and how subscibe
    - a4isms 4y ago

markvdb 4y ago

This system enables regenerative braking on bicycles. That means you also gain a lot... What I would love to see though would be this, applied to a recumbent or a velomobile. Those often have atypically long chains.

mikepurvis 4y ago
Would be a game-changer for urban riding, being able to quickly reclaim energy after a stop.
dreamcompiler 4y ago
Regenerative braking makes a lot of sense on cars because cars are not very weight-sensitive and more weight works in your favor for regen braking. Regen braking makes much less sense on bikes because bikes are weight-sensitive. https://gocarlite.com/electric-bicycle-regenerative-braking/ https://gocarlite.com/electric-bicycle-regenerative-braking/
- dahfizz 4y ago
  That blog post is pretty misguided, IMO. I'll assume the math is right, and the potential gain from regen braking is small. But it's free! > The way regenerative braking is implemented is to have the motor continuously engaged. This is wrong. Regen braking only requires the motor be engaged _when braking_. There's no reason you can't coast when you want to coast.
  - Tostino 4y ago
    You are absolutely right about it being small, but free. Do keep in mind, a direct drive is always "engaged" to some extent by the cogging force. An advanced controller can make a direct drives "freewheel", but it actually takes power to do that. Totally worth budgeting for a slightly larger battery to allow a simpler overall design. Now if you say, had a mid-drive bike, or an internally geared hub, there are some complicated mechanical systems you can put in place to lock the freewheeling mechanisms in the gearing when you want to apply the brakes, but I haven't seen anyone design that yet.

sorenjan 4y ago

It's worth noting the "up to" part. Well maintained and cleaned chains are effective, but I would guess that a lot of commuter bikes have dirty, rusty, and worn chains that lose with a lot of efficiency. Couple that with poorly maintained and adjusted gears and alternatives might not be far off in efficiency if they're a closed system with less maintenance requirements.

alex_duf 4y ago
You also have to take into account the extra weight of having a dynamo + a motor, I doubt it's more advantageous than a chain on a classic bicycle. For an electric bicycle though, I see it as a really good contender
- test6554 4y ago
  I'm not sure how this system works, but it seems like adding in battery power might be useful.
  - alex_duf 4y ago
    I'm assuming it was suggested to replace a chain by what is essentially a dynamo + motor. You pedal to generate energy, and move that energy to the wheel through wire and another motor. (I'm not saying this is a good idea, just describing what I understood). I'm curious what sort of efficiency you can expect on a ridiculous system like that.
- sorenjan 4y ago
  Yes, this particular system is probably far from efficient enough for regular bikes, this is more for larger transportation bikes and similar (like this example [0]). Having a chain on those limits their construction options, and they're already electric anyway. I was referring to different types of gears and power transfer like driveshafts or hydraulics [1], if you can make it perform at a consistent 90% efficiency it might beat chain drive in practice even though it shouldn't in theory. [0] https://youtu.be/N02KMeOkevI?t=81 https://youtu.be/N02KMeOkevI?t=81 [1] https://www.youtube.com/watch?v=NTB7XOQA-XQ https://www.youtube.com/watch?v=NTB7XOQA-XQ