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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 o

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.
    - HPsquared 4y ago
      Does cogging actually absorb energy though? (When averaged out)
  - KennyBlanken 4y ago
    Regeneration on a bicycle is only possible on hub motors, which usually have a planetary gearset to have acceptable low-end torque, and that gearset has significant drag. Mid-drive bicycles are able to leverage the freewheel, and thus have very high coasting efficiency. You don't really seem to know much about this. It's odd that you seem to have formed strong opinions on said subject. There is fierce competition in the industry for efficiency/range/price...not really sure why you think you can just casually stroll in and go "well DUH, folks, just do..."
  - samatman 4y ago
    It's certainly opinionated, I don't view 50-100 stops in ~30 miles as at all unreasonable. Something which is rarely done but easily could be for a bike is regenerating first into a couple supercapacitors, which are 99% efficient and fill and discharge as fast as you can push current. They don't have the capacity to be as useful in cars, for a bike they can also provide a nice kick to overcome starting torque. The downside is it's another two drink can's worth of volume to add somewhere on the bike.
nradov 4y ago
I doubt it. Due to weight balance, most of the braking force is on the front wheel. This system only drives the rear wheel. Any regeneration gains would be minimal.
- wiredfool 4y ago
  It would be awesome for replacing the drag brake on a tandem for controlling speed on long descents. This is a niche in a niche though.
  - a4isms 4y ago
    I had a drum brake on my tandem for this very purpose. It wasn't even hooked up to a brake lever, it was wired to an old three-speed shift lever so you could set the amount of drag between none, some, and more.
    - wiredfool 4y ago
      My tandem doesn’t have the brake, but it does have the braze ons for it. I haven’t bothered because I’m not doing loaded touring or mountain routes.
- Tostino 4y ago
  Not at all true, I built a dual suspension bike with a direct drive hub in the rear. I have it setup to regen, and I can use that to stop without touching my mechanical brakes for 95% of my riding. You generally only recover 5-10% over the course of a ride, but I am in FL with no hills, your results may vary!
- aidenn0 4y ago
  The controller on my e-bike indicates ~120 watts of regen from the rear-wheel. I'm pretty sure that's limited to increase life of the battery; there's plenty more available under heavy breaking.
- HPsquared 4y ago
  That only comes into play under hard braking. In most cases (gentle deceleration) there isn't much weight transfer: the rear wheel is fine for light deceleration.
jeffbee 4y ago
There already were regenerative electric bikes. The first-generation Specialized Turbo had regeneration linked to the brake levers, and nobody cared. Not worth the complexity. Later Specialized bikes have a regen mode you can engage manually but it's still basically never worth it.
- wolverine876 4y ago
  Why isn't it worth it? It seems like free energy. Or is the weight a problem?
  - jeffbee 4y ago
    Most of the energy is being lost to wind resistance and rolling resistance and parasitic friction. The fraction you can regain by recovering potential energy down hills, multiplied by the round-trip generator-motor efficiency, just isn’t relevant to the overall experience.
    - wolverine876 4y ago
      Thanks. A couple thoughts: I read somewhere that rolling resistance didn't add up to much, but maybe I need to recheck that. Also, I wonder if it's different for city riding, where riders need to stop every block or two and start again.

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.
  - HPsquared 4y ago
    Does cogging actually absorb energy though? (When averaged out)
- KennyBlanken 4y ago
  Regeneration on a bicycle is only possible on hub motors, which usually have a planetary gearset to have acceptable low-end torque, and that gearset has significant drag. Mid-drive bicycles are able to leverage the freewheel, and thus have very high coasting efficiency. You don't really seem to know much about this. It's odd that you seem to have formed strong opinions on said subject. There is fierce competition in the industry for efficiency/range/price...not really sure why you think you can just casually stroll in and go "well DUH, folks, just do..."
- samatman 4y ago
  It's certainly opinionated, I don't view 50-100 stops in ~30 miles as at all unreasonable. Something which is rarely done but easily could be for a bike is regenerating first into a couple supercapacitors, which are 99% efficient and fill and discharge as fast as you can push current. They don't have the capacity to be as useful in cars, for a bike they can also provide a nice kick to overcome starting torque. The downside is it's another two drink can's worth of volume to add somewhere on the bike.

nradov 4y ago

I doubt it. Due to weight balance, most of the braking force is on the front wheel. This system only drives the rear wheel. Any regeneration gains would be minimal.

wiredfool 4y ago
It would be awesome for replacing the drag brake on a tandem for controlling speed on long descents. This is a niche in a niche though.
- a4isms 4y ago
  I had a drum brake on my tandem for this very purpose. It wasn't even hooked up to a brake lever, it was wired to an old three-speed shift lever so you could set the amount of drag between none, some, and more.
  - wiredfool 4y ago
    My tandem doesn’t have the brake, but it does have the braze ons for it. I haven’t bothered because I’m not doing loaded touring or mountain routes.
Tostino 4y ago
Not at all true, I built a dual suspension bike with a direct drive hub in the rear. I have it setup to regen, and I can use that to stop without touching my mechanical brakes for 95% of my riding. You generally only recover 5-10% over the course of a ride, but I am in FL with no hills, your results may vary!
aidenn0 4y ago
The controller on my e-bike indicates ~120 watts of regen from the rear-wheel. I'm pretty sure that's limited to increase life of the battery; there's plenty more available under heavy breaking.
HPsquared 4y ago
That only comes into play under hard braking. In most cases (gentle deceleration) there isn't much weight transfer: the rear wheel is fine for light deceleration.

jeffbee 4y ago

There already were regenerative electric bikes. The first-generation Specialized Turbo had regeneration linked to the brake levers, and nobody cared. Not worth the complexity. Later Specialized bikes have a regen mode you can engage manually but it's still basically never worth it.

wolverine876 4y ago
Why isn't it worth it? It seems like free energy. Or is the weight a problem?
- jeffbee 4y ago
  Most of the energy is being lost to wind resistance and rolling resistance and parasitic friction. The fraction you can regain by recovering potential energy down hills, multiplied by the round-trip generator-motor efficiency, just isn’t relevant to the overall experience.
  - wolverine876 4y ago
    Thanks. A couple thoughts: I read somewhere that rolling resistance didn't add up to much, but maybe I need to recheck that. Also, I wonder if it's different for city riding, where riders need to stop every block or two and start again.