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Bicycles

Flywheel Bicycle: KERS for pedal-pushers

By Ben Coxworth
August 16, 2011
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Maxwell von Stein's Flywheel Bicycle stores the power that would otherwise be wasted in the braking process
Schematic of the rear hub assembly used on Maxwell von Stein's bicycle
Schematic of the flywheel assembly used on Maxwell von Stein's bicycle
Maxwell von Stein's Flywheel Bicycle utilizes a continuously variable transmission
Maxwell von Stein's Flywheel Bicycle stores the power that would otherwise be wasted in the braking process
The flywheel on Maxwell von Stein's bike came from an automobile engine
Maxwell von Stein's Flywheel Bicycle stores the power that would otherwise be wasted in the braking process
View gallery - 6 images

In order to help boost their range, many electric and hybrid cars employ regenerative technology where braking energy is stored in the battery instead of simply being wasted. This idea can also be applied to electric-assist bikes, but what about bicycles of the plain old human-powered variety? Isn't it a shame that after having built up some good momentum, you just have to write it all off once you stop? Maxwell von Stein, a student at New York City's Cooper Union for the Advancement of Science and Art, thought so. As his senior project, he recently rigged up a flywheel to an existing bicycle, in order to harness the energy that's lost during braking. That energy can then be used to boost the bike when needed.

The Flywheel Bicycle has a continuously variable transmission in the rear hub. This is linked to a 6.8 kilogram (15 lb) flywheel from a car engine mounted in the middle of the frame. When the cyclist wishes to slow down, such as when they're going down a hill or coming to a stop, they shift the transmission to maximize the flywheel-speed-to-bike-speed ratio. This "charges" the flywheel with kinetic energy - effectively a mechanical version of what happens in an EV where a battery stores the scavenged energy.

Once they want to accelerate or climb a hill, they do the opposite - they shift the transmission to minimize the ratio. This lets the energy stored in the flywheel drive the transmission, giving the bike and its rider a boost. In a ride where speeds vary between 20 and 24 kph (12.4 to 14.9 mph), the system is claimed to not only increase acceleration, but to also produce 10 percent in energy savings.

Maxwell von Stein's Flywheel Bicycle stores the power that would otherwise be wasted in the braking process

Although the added weight of the flywheel would certainly need to be taken into account, the concept behind the Flywheel Bicycle is still definitely intriguing ... enough so that it won von Stein the Nicholas Stefano Prize, which Cooper Union awards to outstanding mechanical engineering senior projects.

Maxwell explains and demonstrates his invention below:

Source: Scientific American

View gallery - 6 images

Tags

BicyclesBrakingregenerative energy systemsKinetic Energy
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Ben Coxworth
Based out of Edmonton, Canada, Ben Coxworth has been writing for New Atlas since 2009 and is presently Managing Editor for North America. An experienced freelance writer, he previously obtained an English BA from the University of Saskatchewan, then spent over 20 years working in various markets as a television reporter, producer and news videographer. Ben is particularly interested in scientific innovation, human-powered transportation, and the marine environment.
31 comments
Fouture
Nice idea, BUT : not only the added weight is a no-no, but the biker will find out that the flywheel makes the bike simply dangerous when cornering, as the centrifugal forces of the spinning wheel will try to keep it going in the same direction.
As any science student who studied his textbook would have known in advance...
patrick.taylor1
I just love the idea of an extra 15lbs to lug around when I am off the bike. Also the idea of a large spinning chunk of metal near an intimate area makes me nervous if there is an accident.!
cloa513
Can\'t believe that won an award- there have thousands of flywheel projects. Nice idea but nothing amazing.
Edgar Castelo
A good idea, but why not a concentric (to the rear wheel) flywheel? THAT would store some energy...
johnsh54
The article makes no mention of the gyroscopic effects associated with flywheels. This effect generates a force at 90 degrees from the force applied to turn the axis of the flywheel, i.e. when you try to take a turn on the bike, the flywheel will attempt to lay the bike on its side (especially with the flywheel being so high up in relation to the center of gravity). This effect is one of the reasons why the \"inefficient\" chain drive in motorcycles has not been replaced by a drive shaft. BMW has made some drive shaft motorbikes, but it uses two, counter-rotating shafts that nullify the gyro effect.
dgate
As usual a lot of negative comments from armchair critics never mind the lad has a working concept which he obviously hasn\'t crashed yet. The gyro reaction effect takes place at the pivot point of the flywheel and this does not happen with the bike just as it doesn\'t happen with a motorcycles much higher revving engine flywheel mass. To get the gyro effect you would have to lift the bike off the surface and pivot it along the center line of the flywheel where it would try to resist. johnsh54 thinks this is what affects shaft drive motorcycles..NOT TRUE ..a shaft drive motorcycle is affected by torque reaction with the frame mounted engine trying to tilt the bike in the opposite direction of the resistance created from driving the rear wheel. Absolutely nothing to do with gyroscopic effect. If anyone doesn\'t understand this I could go on and on like the Duracell bunny.
Michael Miller
Very cool stuff more power to HPv,s
Muraculous
Its a nice basic idea and the gyroscopic effects of a 15lb fly wheel will not be a big factor until much higher rpm is achieved. What he needs is better control of the CVT to slow and accelerate the bike.
I\'d like to see the losses associated with a l-ion battery pack spinning the flywheel and translating that energy through the CVT to the back wheel. A 10% to 50% energy assist for a 200lb package (rider included) could be meaningful.
DrifterToo
johnsh54, you\'ve got a good start, but you misunderstand a few things. 1. When you initiate a turn on a bike, you lean the bike in the direction of the turn, and the lean produces the rotation about the vertical axis. That lean would cause the flywheel to tend to rotate the bike in the same direction. 2. The height of the flywheel has no effect on precession. 3. The balance shafts on engines have nothing to do with gyroscopic effects; they counter second order engine vibration caused by unbalanced crankshaft and connecting rod masses. 4. A properly adjusted and lubricated chain can be 98% efficient. 5. Chain drives still persist on motorcycles not because of any gyroscopic effects of a shaft drive (which are miniscule), but because they are cheaper to make, and the drive ratio can be easily changed, something which is very important in any kind of racing. In fact, chains have been almost completely replaced on cruiser and touring motorcycles by shafts or belts which require essentially no maintenance.
jsrldesign,llc
Judging from the video, apparently the gyroscopic effect was not a big deal in this application. I am interested in the transmission as I do have an application where both the energy storage and the gyroscopic effect are desirable. If you have info on the transmission please contact me at jsrldesignllc@ntelos.net
John
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