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Electric Pedal Assist

Easy attach / detach cables turn any bike into an EV
  (+4, -3)
(+4, -3)
  [vote for,

Electric motor straps to bicycle body under seat or over back wheel. Cables from motor reach out to pedals, and are fastened with an easy clasp device.

Battery in back pack. Pressure from leg pulling one cable, causes other cable to retract powered by motor.

I remember posting a similar idea, but cannot find it anymore.

Pros: No hassle attach to ANY bicycle, including recumbents. Can quickly and easily be transferred from one bike to the next.

Cons: You have to pedal to get the power. (maybe a pro for health)


[edit added: from anno]
The way this is better is in its availability to quickly attach to ANY bike/velomobile of any shape form or size: Kids, adults, tandem, recumbant... Works with rented bikes too, and even with junk cheap cardboard bikes. And unicycles too!

Helps you up the two / three hills for your city ride.

Works with any battery, so real cheap. Its only the motor, one or two cables and one or two pressure detectors (a few cents each, at any electric parts store).

The cable attaches to the pedal bolt, so the pedal is all yours for your feet.

So the whole thing will sell for $80 and be a hit for next xmas, if you buy without batteries.

There's also a more expensive and powerful version for $200.

The extra battery kit comes in various sizes. And costs anywhere between $150-700.

pashute, Dec 09 2012

I paid $1000 for this a few years ago, but they didn't get the idea https://picasaweb.g...5822936024697756994
So this is NOT what I am proposing... [pashute, Dec 17 2012]

Here they got a little closer https://picasaweb.g...5822937217302546098
They couldn't grasp the idea of tight cables only. [pashute, Dec 17 2012]

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       Con- Cables interfere with either leg or chain. Uneven pull increases the risk of knee damage.
MechE, Dec 09 2012

       I suppose it could work. You would need to detect tension and movement. If a cable is moving away from the motor, and is under tension, then retract the other cable.   

       Chains might be better; standard bicycle chains are widely available, of appropriate strength, efficient, etc.
spidermother, Dec 09 2012

       In the chain version, I'm picturing a spool of chain (spring loaded, to maintain tension), from which the chain passes over a power sprocket, then a sensor sprocket, thence to the pedal. The chain is a simple length, of course, not joined into a loop.
spidermother, Dec 09 2012


       I remember posting a similar idea, but cannot find it anymore.
normzone, Dec 10 2012

       Would not work. At all. There is no way intermittent, jerky power being applied to the crank would be better in anyway than a motor applying constant torque. And if you want a bolt to any bike design, google the Zap bicycle motor system. That is truly a universal design. Good concept, but try and build it and fail miserably please
evilpenguin, Dec 10 2012

       The Zap has two very clunky technologies - friction drive, and lead-acid battery. It doesn't seem to be well liked on the forums.   

       I agree about the intermittent power, but this could be fairly efficient, and may work on some dual suspension bikes, without adding unsprung mass - a difficult challenge!   

       The cables might tend to get in the way, though. There's not much room between the foot and the crank.
spidermother, Dec 11 2012

       Idea edited.   

       The way this is better is in its availability to quickly attach to ANY bike/velomobile of any shape or form. Works with rented bikes too, and even with junk cheap cardboard bikes. (And unicycles too!)   

       Helps you up the two / three hills for you city ride.   

       Works with any battery, so real cheap. Its only the motor, one or two cables and one or two pressure detectors (a few cents each, at any electric parts store).   

       The cable attaches to the pedal bolt, so the pedal is all yours for your feet.   

       So the whole thing will sell for $80 and be a hit for next xmas.   

       Please see my edit to the idea - based on this anno.   

       [Meche] - what uneven pull? For the single cable version? Even then its your foot pushing, and in any case that's usually the way we ride, with one stronger foot and on weaker one...   

       In any case your legs are pushing not pulling.
pashute, Dec 11 2012

       //that's usually the way we ride, with one stronger foot and on weaker one...//   

       But it's better if we don't, and we don't want to make it any worse...   

       I misunderstood you; I thought pushing the left pedal would cause the right cable to retract, and pushing the right pedal would cause the left cable to retract. That could be done, but you will need a slightly more sophisticated sensor/control system, as I suggested above. Otherwise, the tension in the powered cable will cause the other cable to retract, resulting in electromechanical epilepsy.   

       I don't like the idea of powering one stroke only. That sounds horribly unbalanced. Even if it's intended only for occasional use, it should be ergonomic.
spidermother, Dec 11 2012

       The uneven pull is the alternating cable pulls. I was trying to, briefly, cover what [evilpenguin] said later. The cable will only be able to pull for about the lower two thirds of the power stroke (by pulling on the off pedal). This is going to tear the heck out of your knees.
MechE, Dec 11 2012

       I repeat, Good concept, but try and build it and fail miserably please
evilpenguin, Dec 11 2012

       [MechE] I disagree. By analogy, two people of very different strengths can ride a tandem bicycle without knee damage to either. The rotational speed of the crank will be constant enough for the rider's legs to accommodate, unless it's seriously overpowered.   

       It might be a little different if the phases didn't match, as would be the case if the cables pulled from in front of or behind the crank, but even that would not be a big problem; although it would reduce the duty cycle.
spidermother, Dec 11 2012

       As somebody who has actually motorized several bicycles both with electricity and gasoline I will say this, keep it simple, stupid. Your idea is flawed in the sense that the electric bicycle community has never done anything like this. If it was a good, achievable idea SOMEBODY would have at least tried it. Nobody has or will. I invite you to try.   

       1st - what kind of motor are you using? AC or DC? what kind of gears will it use? What kind of amps are you thinking of drawing? What kind of range to do expect? How heavy is this motor and how will that affect the center of gravity? (that's not even including the bad idea if putting the batteries in a backpack, which ruins center of gravity)   

       2nd - what kind of batteries are you proposing? Do you have any idea what kind of range the present technologies offer?   

       3rd - how in the hell does it mount to any bike? Universal sounds nice, but sturdy reliable struts are not universal.   

       4th - how do you pedal backwards? If you have ever had to balance a bike while turning (sarcasm) you would realize the crank had to turn backwards occasionally to balance the rider. Your setup didn't seam to address this   

       And //Works with any battery, so real cheap.// is total bull. Very few technologies are practical for the purpose of electric bicycles. There is a vast community of electric bike builders that would lambaste you idea. Post there. Sorry to be so negative but this just so happens to be a realm I'm quite versed in and I am giving my evaluation of your idea. Its not a good idea
evilpenguin, Dec 12 2012

       Your giving your evaluation instead of thinking how small the problems your posing are, and instead of helping me find a simple solution for each case.   

       Because it works on tension only, it is easy to attach under the seat or on the back rack, with a rope fast -connection. There are literally hundreds of sturdy solutions for exactly that.   

       You point out that cyclers pedal backwards. But if you look into it, you'll see that it will work just the same. When you pedal backwards say the left pedal is up, you aren't putting strong pressure on the RIGHT pedal, right? So either your not putting much pressure (pedaling pressure) on the left pedal at all, in which case the motor is not working and the cable flows freely with the pedals, or you put strong pressure on the left pedal (don't see why or how, but say you do) Then the right pedal will be pulled up.   

       Cheap: It could be sold at the price of a hub motor. Except that hub motors are sold mostly as kits or in pre-installed bikes, and this could be bought off the shelf and easily attached by the cyclers. So my claim is valid.   

       [Meche] your worried about the knee strain in case of a single sided version. So drop that version, and concentrate on the two sided one. Then somehow your worried about the motor working when the pedal is at level stroke. That's easy to solve too. Just enable the motor when the cable is not fully extended.   

       Hey people, join the team instead of bashing the idea.
pashute, Dec 16 2012

       Two people of very different strengths can ride a tandem, but not people with two very different cadences. That's the problem here (and it's not two sided vs one sided as [pashute] mentioned). It's that for any practical geometry, the motor will pull halfway through the power stroke. This will result in the resistance disappearing from the pedaler just when they are maximizing their force. The leg/knee is not meant to work this way, and it will result in the pedaler stomping downwards quickly and damage to the knee.   

       And as far as using any battery the problem is weight. Cheap batteries are heavy. A lead acid electric assist bicycle is completely impractical to ride if you're going any farther than the assist can help you with (which is not very far). Light batteries are expensive.
MechE, Dec 17 2012

       I'm not bashing the idea; but it is important to point out potential problems.   

       I don't think it's as bad as that, [MechE]. As I said, the resistance will not disappear unless the motor is severely overpowered (enough to cause wheel spins, or throw you off the back). Otherwise, the cadence-mismatched tandem partner, or this motor, needs to accelerate the entire mass in order to accelerate the crank.   

       Have you ever messed around on a tandem? Suddenly, or erratically, stomping on one set of pedals may be slightly annoying for the other rider, but it never causes the resistance to disappear, or to fluctuate enough to cause knee problems.   

       The human leg can easily adjust to a wide range of speeds - for instance, crank speed fluctuates much more when riding up a steep hill in low gear than when riding on the flat, cadence and effort being equal.
spidermother, Dec 17 2012

       I see this idea as a cartoon drawn by Rube or Suess, not as a practical solution.   

       [pashute], visit china. There are literally hundreds of thousands of pedal assist bicycles used legitimately, in their own lanes on the street. Many of them are homemade. You will never see your setup on any of them.   

       I apologize for my lack of humor when annotating your idea. Speaking from years of experience motorizing bicycles, your idea is just not workable. It does not sound like your proposing a funny, joke of an idea here, so I took it seriously.
evilpenguin, Dec 17 2012

       evil, I responded with a solution to each of your concerns, except for "Not done till now". Are you using a computer mouse? Did you ever fly in a fixed wing plane? Did you ever receive a fax? All ideas that were declined by experts, because they weren't done till now.   

       Spider, you aren't bashing the idea, but evil definitely is.   

       Yes its good to point out the problems, but better if the problem is simple to give advise on possible solutions.   

       In any case, I think I replied with a solution or at least path of solution for each of the challenges posed, so that the benefits are still retained.   

       Except for the batteries. Lead acid batteries can be in a bike trailer, giving extremely long rides.
pashute, Dec 18 2012

       [Spider] Ever had a chain break under load? The resulting stomp can seriously hurt the knee, and this would partially recreate that with every stroke.
MechE, Dec 18 2012

       Continuous power is better than intermittent, for comfort and efficiency; but I still think you're exaggerating the problem. Sure, a broken chain causes the resistance to drop to nearly zero; but adding a kilowatt or so of assistance, even intermittently, does not.   

       Try pulsing the power on an electrically assisted bike while pedalling. It makes no readily detectable difference to the pedalling resistance, because the inertia of the system prevents the very rapid acceleration that would be required for the pedal to get away from you. Your leg easily accommodates the small speed fluctuations, with no special effort. Unless our understandings of this idea are different, I don't see how this will be much worse.
spidermother, Dec 18 2012

       It may depend on the strength of the assist, I'll admit. I still think a continuous drive (which can be added with the addition of only a single sprocket to the off side pedal) is a better design. There is at least one where the drive can be swapped between bikes with that mod in place.
MechE, Dec 18 2012


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