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Kinetic Assist Bike

By Shamus
on Wednesday Oct 3, 2007
Filed under:


Take a couple of sine waves of differing wavelength and amplitude. Now combine them. The resulting waveform is going to be a lot like your average road in western Pennsylvania, which is any shape but flat. The only time you’re not ascending or descending is when you’re at a standstill. This is where I learned to ride a bike.

Anyone traveling under their own locomotive power in this sort of setting will quickly come to appreciate just how much energy is wasted getting around like this. When I would hit a gentle downhill I’d think how nice it would be if my efforts could be somehow stored for later (for the inevitable upcoming hill) instead of increasing my speed now. When I’d hit a steep downhill I’d have to do the most painful thing of all, which is throw away some of my hard-earned potential energy by using the brake. When I hit an uphill I’d think about all the effort I just threw away, and wish I could recover it somehow.

I had this in mind when I wrote this chapter of my book, where the protagonist rides around in a futuristic “kinetic bike” that is able to capture some of the energy normally lost when using the brake or when over-pedaling, and release it later when the landscape turns against the rider.

The other day a reader sent me a link to this. A bit pricey, but facinating. They claim it can go 62 miles on a single charge without the rider pedaling, but I’m sure those are flatland numbers. I’ll bet you’d be lucky to get 20 miles out of it here in sine wave country. Still, you can supplement that with your own contribution, and it looks like it still works as a fully functional bike even when the batteries are depleted.

Just outstanding.

Still no flying cars, though.

Comments (43)

  1. Matt` says:

    That’s pretty cool, but very pricey – could just get a regular motorbike and never have to pedal again

  2. Phlux says:

    I’m sure everyone knows this, but hybrid and electric cars do this also. When you break, the electric motor reverses and basically acts like a generator, putting electricity back into battery with the excess spinning of the tires.

    The tires themselves still have brake-pads I believe, so this is nowhere near 100% efficient, but brake-charging is where hybrids get a lot of their extra gas mileage. You’ll get better performance if you make full and complete stops at lights and stop signs…the exact opposite of gas engines which reward you for maintaining momentum and making fewer stops.

  3. Heather says:

    I have been wondering since I first read your description when someone would catch on and make something like that. Around here it is almost a necessity–bike riding is fun but those hills are killer. I like the idea of a bike which can do both–exercise is a good thing, up to a point.

  4. JB says:

    I thought about something related on my way to work this morning.

    One of the laws in physics says work applied is equal to force times distance.

    Now that means standing still in midair should require no work at all.

    And gliding in the air should require less work than rolling on the ground.

    So how come it doesn’t work like that in real life?

  5. theckhd says:

    I grew up in the eastern half of the state, where we have what you would probably describe as “quaint little hills” by comparison. After living in the central/western part of the state for a few years, I was amazed that anyone tries to travel by bicycle at all. You “westerners” are either gluttons for punishment, or much hardier than us soft “easterners.”

  6. ScottMGS says:

    Several years ago (decades?) I saw a bit on TV about a British inventory who had modified a bicycle so that the rider’s weight bouncing on the seat helped pedal the bike. I gave a few unsuccessful minutes to find a reference online.

  7. theckhd says:

    JB: Standing still in mid-air is not a zero-force situation. The force of gravity is acting on you, and to remain in mid-air you need an equal and opposite force to counteract it.

    The gliding vs. rolling issue is more complicated, but mostly comes down to friction and inertia (wind resistance and drag is different from kinetic friction, and still different yet from rolling friction, not to mention the effects of angular momentum).

  8. Adam says:

    Nothing like a livly physic discussion to get the blood flowing in the morning.

  9. -Chipper says:

    I grew up in the same general area (though I was just south of Pittsburgh). I remember visiting cousins in Chicago & being amazed at the biking opportunities – no hills! I could go for miles with ease!

    As hard as hill climbing in a bike can be, bike riding is still much more efficient than walking. Bill Gates once mentioned in a speech that scientists compared the efficiency with which various animals move & found the most efficient by far was the condor, which spent very little energy to soar on air currents in order to migrate thousands of miles. Man was very far down the list with his pitiful bipedal locomotion. Then the scientists added man on a bicycle and found that he shot to the top of the list. (Gates used that as an analogy – the computer does the same thing for our brains as the bike does for our locomotion – the real ‘power’ still comes from the same source, the bike & computer just allow that energy to be better channeled & used.)

    Regarding the fancy new vehicle of the article, its styling & price make it obvious they aren’t planning on selling it to the masses. I have to believe you can make something like that & sell it for under $600, though maybe not as stylish & maybe not with the same range.

  10. EnderQON says:

    Schwinn sells a set of electric bikes for a good deal less, and they claim up to 60 miles per charge – http://www.schwinnbike.com/products/bikes_category.php?id=109

  11. Henry says:

    Another solution, perhaps, would be to have some sort of flywheel arrangement. However, this would mean that (a) your downhills were less fun, (b) you’ve got more mass to get up hills (and therefore you end up working harder once the flywheel has spun down), (c) your bike looks bloody daft. Living in Cambridge (England!), I frequently complain about the _lack_ of hills, so maybe a visit to PA would be called for…

  12. theckhd’s comment is true, but does not completely address JB’s question.

    JB, who is not me :), staying stationary in the air is a no-work situation. However, per theckhd’s point, you haven’t got anything to counter the force of gravity. Standing on the ground, you have the normal force from the ground. Since you have a net force, gravity does in fact take over.

    Gravity exerts a force on you across a distance over the gravity field. This is work done on you. This work manifests as kinetic energy in the downward direction; the work gravity does and the kinetic energy would be equal in the absence of drag.

    Staying at one altitude if you have another source of force is indeed a no-work situation, which is why aircraft are able to work as efficiently as they do. (Aircraft are really a neat hack on the “problem” of having an atmosphere that causes drag; convert some of the drag to lift.) Aircraft energy losses come entirely from drag; staying at one altitude at one speed is otherwise a no-energy-change proposition.

  13. (Sorry, kinetic energy doesn’t have a direction. It is more proper to say you have momentum in the downward direction, and that the kinetic energy term and the work gravity does term are equal.)

  14. Avaz says:

    Hah! If you think an electric bike is news-worthy, you obviously haven’t seen the Treadmill Bike. That’s right. And you have to see it to believe it.


    (Personally, I think the energy it takes to run on two legs and to use a treadmill bike are about the same, but what do I know?)

  15. Kevin says:

    “Take a couple of sine waves of differing wavelength and amplitude. Now combine them. The resulting waveform is going to be a lot like your average road in western Pennsylvania”

    Pretty true for South-Central PA as well…

  16. Alan Post says:

    i do a *lot* of bike riding, so am in good condition for doing more of it. with that said, i wonder about the extra weight on these devices. i do fairly well pushing myself up hills, but put me on a heavier frame, make my tires fatter, etc, and i slow right down.

    i suppose i find crawling up the hill a small price to pay for racing down it. ^_^

  17. Craig says:

    electric bikes aren’t very new at all. They’ve been around some time now.

  18. roxysteve says:

    Henry Says:

    October 3rd, 2007 at 9:10 am
    Another solution, perhaps, would be to have some sort of flywheel arrangement. However,

    Not to mention that once the flywheel was spun up to any sort of respectable level, you’d have a problem with precession.

    With the flywheel oriented in any of the three major axes, any attempt to “bank” the cycle into a turn would result in it rearing up on either its front or rear wheel instead. Clearly not optimal for proper control during steering maneuvers. It would also tend to sway alarmingly in any case due to gravity trying to tilt the wheel.

    Lest anyone doubt this thesis, a spot of research will show that banking a bike into a corner has been found to be actually how you get it to turn at cruising speed: the precession effect causes your front wheel to turn as you tilt. The effect of the rear wheel is not significant because it is a very low mass flywheel. You’ll need a much more massive one to store energy in for bike-powering purposes. You could buy off the cost of spinning up such a beast by using gears.

    Or you could invest in a cheap gyroscope, spin it up and have some fun getting to grips with physics in the first person.

    Science should be experienced close up (except perhaps the bits of it that go “bang!”).


  19. Dev Null says:

    Friend of mine works for a mob up in Darwin Australia whos been building these sorts of things for a couple of years now – kinetic assist, charge the batteries with the brakes, etc – so I don’t know where they get off calling themselves a world first. Mind you, the Australian version looked more like a regular bike with a couple of bits attached and less like a spaceship. Didn’t cost 5 grand either, as I recall…

  20. damien walder says:

    As a worker and technican in the cycling industry (who sometimes visits western Pennsylvania as well and non-urbanized NY State areas), I can’t say that any of the hoopla is ringing as terribly significant.

    The bicycle is _already_ the most efficient form of widely distributed transport modes for land. Think about it, you’ll see that these items are dead weight when they are not engaged in motivating the bike forward (reverse is not helpful to most cyclists). Dead weight should always be there for a purpose (eg cargo needed on the ride or at the terminus of ~), including rain gear, which is by and large balanced between weight and function, a gold standard point of reference.
    I have sold upgrade kits to electrify bikes and the best use I’ve seen so far is for the partially disabled who cannot power their riding consistently – for them, it’s a land-based plug for power between rides. The cheap electric “Schwinn” bikes I see pumped out by the local dept. stores are gogin to be a disappointment for any but the most eccentric (who might also praise English sport cars out of a romantic affection) individuals. Between these groups there is not enough to drive the development of best models of this “new” bike type.
    The unspoken problem is an old (entropic) one – the law of dimishing returns, but you can call it many things. Still waiting for the perpetua mobile? Don’t hold your breath…

    If the dynamo/capacitor/battery combo (these are older terms for the hypeinator and hyperbolized junk most industry spins into sexy, new and hot) is all that, why do these prototypes continually fail to outperform a moderately healthy person on a standard (26lb, 700c wheel)commuter bike? For a continent facing peak oil energy crises (Pl), this “assisted bike” is not a great answer. The cities are still not designed for bikes, and there are going to be far too many holding onto their cars for longer than (has been or) is healthy. Big Auto and Big Oil can’t face the tune that carbon shortfalls are playing, and are witholding their own research results (on oil shortfalls) from the general public whoi would be able to do the math if somebody made it clear what the relevant figures were.

    The irony is that in order to drive much of the actual progress in sustainable energy resources, big money is going to have to get out and push. No free rides for any of us.

    And for now, bikes aren’t that good for the planet, either. What’s the paint, tires, and plastic componentry made of? Corn starch? Nope. How much energy to make Aluminum into a frame, how much to make and weld steel?
    Let’s work on that end of manufacturing, too.

    Oh, and recycling the damn tires and tubes would be an improvement.

    Toronto, Ontario, Canada.

  21. Browncoat says:

    I don’t mean to take this off too far of a tangent, but I had a thought:

    As I understand it, when you start your car, your battery drains a certain bit. Any running of electrical systems (lights, radio, horn, AC, turn signals, DVD player, etc) further wears down the battery. But the battery is constantly being recharged (while the car is running) by the alternator.

    What happens when the alternator has done its job and fully charged the battery? Well, the battery is being used a bit to run the electrical systems, but the point is, the alternator has more recharging capabilities which are going to waste.

    What if we install more “batteries” (let's say in the trunk to start–we'll hard wire them into the system in future models) for the alternator to charge. We get home, and plug the fully charged batteries (except the main battery that the car runs on) into a converter which takes that DC current and turns it into AC current the house can run on.

    This is taking wasted energy from the alternator and using it to offset the energy used by the home.

    When I was discussing this idea at work, someone from the next row of cubes told me that this is similar to the technology that led to hybrids. Someone else suggested that when the alternator is charging the battery, the mileage you’re getting is worse. Can anyone educate me on this?

  22. Aaron says:

    I used to live in Butler, PA before I moved for the job. The hills there are KILLERS. I’d have paid damn good money for a bike like this! When I was a kid I used to ride my bike between my grandmothers (Leesburgh), my brothers (Mercer), and my dads (Grove City). Some of those hills will break your stupid legs off I swear it.

    Georgia is an entirely different matter. They don’t know what a hill is here in the southern part of the state. I’d STILL get that bike though, it’s just damn cool!

  23. ninjadwarf says:

    “When I'd hit a steep downhill I'd have to do the most painful thing of all, which is throw away some of my hard-earned potential energy by using the brake”

    You did what? Braked?

    No on downhills you pedal flat out in the highest gear you can get in, then use all that speed to start the next uphill climb, staying in the higer gear as long as possible to get teh maximum effect.

    Braking while cycling, whatever will they think of next :)

  24. roxysteve says:

    Browncoat Says:
    I don't mean to take this off too far of a tangent, but I had a thought:

    As I understand it, when you start your car, your battery drains a certain bit. Any running of electrical systems (lights, radio, horn, AC, turn signals, DVD player, etc) further wears down the battery. But the battery is constantly being recharged (while the car is running) by the alternator.

    Hey Browncoat, long time no read!

    Well, not fer nuthin but the battery takes a hell of a whack when you start your car and you need to run your alternator a lot longer than you might think to recharge it. While that is done the electricity (via the voltage control circuitry) is used to power lights, stereos (add up the total watts – especially all that heat your trunk-mounted subwoofer driver amp puts out – to see if your alternator can handle what you are asking from it without a net drain from the battery though) winshield wipers and so on.

    I once saw a see-through battery used to start a car. The lead plates actually tried to tear themselves out of their mountings (the current drawn when you press the starter is theoretiaclly almost infinitely high until the starter motor turns – check out the cable between your starter and the solenoid sometime. It’s about the thickness of your little finger. I had one melt on me once late at night just before I was supposed to cross Snake Pass. Thanks! You’ve reminded me of another attempt by the universe to kill me that I can put in my blog. Where was I? Oh right).

    Anyone who has a battery charger can attest that during winter most people don’t actually put a net charge on their battery on the average commute-style driving regimen.

    Conventional automotive lead-acid accumulators can certainly be used to power a house via the inverter technology you allude to, but you need a few more than a trunk full. You also need to invest in low-energy versions of most of your household appliances to get this idea to fly, ‘cos even with new technology you can’t get something for nothing and stepping 12 volts DC up to 120 volts means the batteries will work very hard for a living.

    Whether you can get a net savings in money in the lifetime of the project I don’t know. The one person I know who tried it hadn’t by the time I lost touch with him, but that was over ten years ago and technology has improved slightly since then.

    Of course, the net energy-debt/environmental impact involved is difficult to assess but must include some allowance for the toxic byproducts of the chip industry that makes this even possible and that of the the battery industry too.

    As to the mileage thing, theoretically, while you draw current from the alternator the resistance offered by the pulley attached to the armature is more so you do indeed spend more gas to move. Whether it is noticeable or not, you’d have to ask Click and Clack on the NPR Saturday morning show “Car Talk”. Personally, I doubt it. You are drawing so much power for things like the fan (which is electric these days), headlights and gosh-knows whatelse that unless your battery is flatter than a very flat flat thing I doubt it contributes much more load.

    Handy home hint: To tell if indeed your battery is flatter than a very flat flat thing when the engine is running, park next to your garage door or some similar surface, then put your headlights on. Rev the engine. If the headlights get noticeably brighter, you have a flat battery (but your alternator is working fine).

    If putting your headlights on while the radio is on causes the fuel pump to cut out and the engine to stall, you are apparently driving my old TR6. Reconnect the ground cable between the engine block and the firewall that I forgot to put back just before I sold it.


  25. Shamus says:

    Braking while cycling: I can’t tell if you’re kidding or what. Certainly you don’t brake on ALL hills, but some are too steep to navigate safely. The road is often curving, and you want to make sure you have firm control over the bike. These hills are not a joke. You need to watch out for loose gravel, sticks, or other items that will cause you to lose control. For curving turns where you can get creamed by a car. For just generally going faster than is reasonably safe on the given bike.

    Yeah, you can go all-out on every descent if you like, but that can be dangerous.

  26. bbot says:

    As a matter of fact, I just added an ebike motor to my bike. It’s pretty neat, but the hub motor and batteries add about fifty pounds to the bike, which would make climbing hills seriously unpleasant without the power assist.

  27. roxysteve says:

    damien walder Says:
    Bedlybeedlybeedly….any but the most eccentric (who might also praise English sport cars out of a romantic affection)

    And here I was under the impression Canadians were nice people.


  28. IronMike says:

    As far as the flying car goes, check this out:


  29. Aaron says:



    Wow you have me outgeeked sir. /salute!

    It’s actually quite interesting to read. My family is a bunch of backyard wrench benders, so I understand most of it. I’d never really looked into battery technology. I have seen on Discovery a documentary on the electric car and why it died out (damn you corporate america). They went into a little detail as to the battery issue, but I admit to being very curious. Excellent post!


  30. LancewithaBee says:

    Add a speaker and sound effects from a PC motorcycle game. For less than $50 you would add a lot of geek toy appeal.
    / no applause, just throw money
    // or a “sound effect electric” bike

  31. Ian says:

    I used to live in east Ohio (Youngstown area — Struthers specifically) and I used to go to Monaca, PA, to see my friends a lot so I definitely know what you mean about the sine waves. Holy crap.

    While driving to my new home in Maryland (and getting a nice, extended taste of I-76/70) I quickly realized that the hills become nothing short of epic after a while. Woo.

    After the relative flatness (relative being the key word) of Struthers, I couldn’t imagine biking through any part of PA. That’s gotta be some good exercise.

  32. roxysteve says:

    LancewithaBee Says:
    Add a speaker and sound effects from a PC motorcycle game. For less than $50 you would add a lot of geek toy appeal.
    / no applause, just throw money
    // or a “sound effect electric” bike

    When I were a lad we used to use two bubble gum cards held on t’ front forks with a spring clothespin.

    For the authentic “Harley” sound you need a set on each side of the wheel. Those cards depicting space monsters were the best in my opinion, although some swore by the American Civil War commemoratives that came with confederate dollars. These “dollars” were no use whatsoever for motorcycle emulation and were used instead for landmark combustion experiments using a magnifying glass.

    Of course, once in a while the cards would undo the little nuts that tension the spokes in the wheel rim if you weren’t careful. Life would then get “interesting” in terms of erratic steering and braking characteristics.

    Better days.


  33. ArchU says:

    The town I live in is getting trains* that work on the same principle. Energy from downhill coasting is regenerated by the engines and stored or fed back into the power grid.

    *We have the trains but the train line hasn’t been opened until stress testing is complete.

  34. The EPA has developed a hydraulic/gasoline hybrid that does an even better job of storing kinetic energy than the gas/electric hybrids. http://www.iags.org/n033104t3.htm Apparently hydraulics store kinetic energy significantly more efficiently than batteries. A quick google search tells me that Ford is talking about a hydraulic/diesel hybrid F150 that gets 60mpg.

  35. Davesnot says:

    hmm.. a topic I know a bit about.. I’ve written 2 mountain biking guide books.. I’ve found there is never really any free lunch.. the extra weight of the motor usually outweighs the help it provides for being just a bike.. more gears is usually the way.. pound the crap outta the big rings as you roar downhill.. then work up the gears as you keep your momentum as long as possible..

    that treadmill bike.. what is that?!! why not just walk or jog.. sheez! whatta world.. maybe if the engineers spent more time riding and less time trying to find a way to ride without their legs.. well.. they wouldn’t need a way to ride without their legs.

    Kinda looks neat in some twisted way, though.

  36. Nefke says:

    Netherlands means low-land for a reason: very good bike riding here!

    But then again we´ve got dikes and bridges to climb ;).

  37. Ben Finkel says:

    I’m not sure I like this new color/format change…


  38. Archgeek says:

    Concurance with Ben Finkel… the previous design was very nice looking, but this one’s verging on angry fruit salad.

  39. Henry says:

    To RoxySteve: You’re entirely right about the gyroscopic precession, of course. I have a good degree in engineering from a good university, during which gyroscopes were covered in some depth, and that particular aspect still didn’t cross my mind! Just goes to show it’s not what you know but how you apply it to the problem ;-)

  40. David A says:

    Buy a car.

    Sorry to necro, but you did throw up a link.

    I remember having so much fun with my bike. And then I bought a car. Now, I couldn’t imagine going back. Cars are so much more fun – true dat that a bicycle offers some exercise…

    …but a bike itself is just an upgrade to it’s predecessor, walking. So you can either walk to the store, or ride a bike, or drive a motorcycle, or drive a car.

    Either way, I’m flabbergasted to see why any adult would still ride a bike. It’s the sort of transitional activity – in between distinct eras of personal transportation (motorized and non-motorized) – that gives pause to evolutionary advocates.

    There is a better way to get from point A to point B. And there are also ways to do so with more exercise involved in the process. Owning a bicycle, much less riding one, is such an antiquated thought, especially given that where you live, there’s snow on the ground what, four months out of the year?

    And granny-killing heat in the other eight? This is why Americans own cars, and will never give up that freedom and thrill for mass transit or anything like it.

    I will give points to my critics that this comment did stray off-topic several times.

    • EmmEnnEff says:

      “This is why Americans own cars, and will never give up that freedom and thrill for mass transit or anything like it.”

      Until the oil runs out…

      The real reason for why Americans are joined at the hip to their cars, is because frankly, mass transit options in most of America are bad. Really, really bad.

      Throw in taxpayer subsidies for building and maintaining roads, and low-to-none gasoline taxes and it’s no surprise that cars are their preferred mode of transport. FREEDOM and DEMOCRACY has little to do with it.

      • David A says:

        Do you remember getting your license? Do you remember your first car?

        The freedom that car represented? You can leave, come and go as you please, travel for miles – drive the whole day and finish in another state.

        A car can do that. On demand. A bus can’t. A bus won’t.

        No mass transit can do that. Light rail, bus, subway, whatever. You’re sharing a dirty public space with complete strangers. If a crazy person decided your seat was his toilet, then you better get out of the way.

        If you needed to go downtown and the only bus has already left, you’re stuck. If you need to go BACK to the Home Depot because the piece you bought was wrong, you’re stuck. If your spouse called and needed you to pick up a few things on the way home, you’re stuck. You can’t carry groceries plus a bag of dog food onto a bus.

        Do you live on mass transit? Then I guess your kids won’t be doing sports, because how are you going to be getting them to practice? Are you going to stick around and watch them for the hour and a half so you can escort them home? I hope the local Amtrak terminal isn’t too far away.

        I’m not just talking about location and convenience. I’m talking about transitioning from Netflix to Blockbuster. Why would you give up the FREEDOM of a car for the rigidity and structure of public transportation?

        In what twisted universe is public transportation a better deal? Freedom and Democracy has everything to do with it.

        Look at Europe, where they have all the public transportation in the world – do they have our freedoms? Do they have the bill of rights? How much of that “service” is about population control?

        Let me ask you this: does any nation in Europe offer constitutional protection to speech, assembly, and the press? Of course not, not even the UK has that. America is #1 in freedom, and that freedom is best symbolized by our cars.

        I drive a Ford. What car do you drive?

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