Cooper Union student builds flywheel-powered bike

12 comments
By Peter Suciu, from Detroit, MI | Thursday, Oct 20, 2011 6.00pm

The constant quest to ride waves of green lights in New York City, inspired Cooper Union's engineer student, Maxwell von Stein, conceptualize a method to harness a bike's braking energy when stopped at a red light and then return it on command to help give riders a boost when green flashes.

And von Stein wanted to do it without a battery: the solution, integrate a 15-pound steel flywheel from a Porsche into a Continuously Variable Transmission (CVT) drivetrain for a bicycle.

As part of his senior project at New York City's Cooper Union for the Advancement of Science and Art he integrated a mechanical flywheel into a bicycle; one that could be ideal in urban environments. "The bicycle is already the fastest way to get around NYC," von Stein told BikeRadar. "A bicycle with a flywheel could make you even faster! The model I built helps when you need to slow down, but not when you need to come to a full stop. Incorporating a clutch between the flywheel and rear wheel would allow the flywheel to keep spinning when you come to a full stop. When the light turns green, you’d engage the clutch and accelerate."

While this might not sound all that complicated, one aspect raised has been whether this system would add more weight? But von Stein counters that the system only adds 20 pounds to the weight of the bike. "That's a 10 percent increase when you consider the weight of the rider and the bike," says von Stein. "Why do you want a light bike? You want a light bike so it's easier to pedal up to speed. That's where the flywheel comes in. It's another means of propulsion."

He does admit that the benefits depend on how you ride, and notes that a rider who rarely uses the brakes—say on a long training ride— would only be slowed by the flywheel. But he notes that in cities, where brakes are used quite often the weight might be outweighed by the assist in getting back up to speed.

Von Stein maintains that in a ride where speeds vary from 12- to 15mph (20- to 24 kph) the system can actually produce about 10-percent energy savings. That would certainly be helpful for the daily commute. And the concept was intriguing enough that it has attracted a bit of attention; so far von Stein has been awarded the Nicholas Stefano Prize, which Cooper Union presents to outstanding mechanical engineering senior projects. "The Flywheel Bicycle is a hybrid bike that uses a spinning flywheel to store and release energy," said von Stein. "You want high capacity with minimum weight. Instead of a heavy flywheel, it’s best to have one that spins as quickly as possible."

For this reason von Stein used a large chainring on the output of the transmission and a small sprocket at the flywheel. "Ideally an infinitely variable transmission would allow the rider to use the full capacity of the flywheel," he said, adding that flywheels have another advantage over batteries and electronic powered motors. "Flywheels provide greater acceleration because they can be charged and discharged quickly."

No plugs required, just a bit of pedaling.

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User Comments

There are 12 comments on this post

Showing 1 - 12 of 12 comments

  • Wonder how well it corners? Still good work though.

  • "...the system only adds 20 pounds to the weight of the bike. "That's a 10 percent increase when you consider the weight of the rider and the bike," says von Stein. "Why do you want a light bike? You want a light bike so it's easier to pedal up to speed. That's where the flywheel comes in.

    Von Stein maintains that in a ride where speeds vary from 12- to 15mph (20- to 24 kph) the system can actually produce about 10-percent energy savings."

    10 per cent more weight for everyone to save 10 percent more energy for some users, hmm what's the point?

  • Only adds 20lbs?

    I'm going to fit two to my MTB. That'll show you all.

    Somebody please, please, please post this somewhere where the MTB weight-weenie brigade frequent!!

  • @ tarquin_foxglove

    What's the point? The point is 10% more weight doesn't require 10% more energy.

    This cycling fan has shown imagination and determination to realise this idea.

  • This is flywheel driven KERS. It's a neat solution only hampered by the use of low tech materials

    I read about a system in development for use in cars that uses a 4kg carbon flywheel, but it needs to spin in vacuum to avoid coming apart (can't recall RPM but very high) and transfer teh power to and fro via a magnetic gearbox. All very first gen but one could certainly imagine a lighter version on a bike where there's not as much energy to store.

  • Yes, he's actually saying that 10% more weight requires 10% less energy.

    I'd love to try this on some techy, stop start MTB trails....and I bet you'd get some crazy handling effects with that thing spinning away!

  • I can't help thinking that this could be done better with a gearbox, instead of the chain system.

    The mass of the flywheel can be minimised by making a flywheel with a bigger radius, or making it spin faster. It will thereby store much more energy for a given mass of fllywheel. He's taken the chain driven gear ratio as high as he can, and there is not much more room to make the flywheel bigger.

    I would prefer a system with a hub gearbox and coaster clutch style system, with a flywheel inside the spokes of the rear wheel. That would be much neater, and you could probably arrange for a much higher gear ratio, or even variable gear ratios to get the most efficient coupling between the braking action and the flywheel.

  • Ideally it would capture energy from the front wheel, and power the back wheel

  • think you guys with better ideas should make what you're talking about- talking is easy- he's actually gone and made something which is brilliant in my book.

  • random thought , if he had mounted the flywheel horizontally would it act like a gyroscope and keep you upright when stopped (byebye stoppies)??

  • bomberesque, the F1 flywheel that you talk about was mounted in a vacuum to reduce the losses, not to stop it flying apart. It spins up to about 60,000rpm. It was connected to the gearbox using a clutch and a Torotrak CVT. The whole system would be way to complex, large and heavy for a bike.

    The other thing to consider with high weight flywheels is the gyroscopic affect. It can actually be quite bad if mounted in the wrong orientation. Might make cornering difficult.

    We thought about trying to use the effect to help with anti-roll in an F1 car, but the lap time reduction in the 'anti-roll' was outweighed by the lap time increase due to the weight.

    Interesting idea though, could have legs using the right tech.

  • wozzer10; fair enough about the flying apart thing, either the article I read was wrong or I misremebered it. as for it being overcomplex to ever be useful in a bike, the same would be said of the electronics that we now take for granted in our mobile phones. Also, the energy we'd be talking about in a bike is sooo much less than a car that I suppose it could me severely simplified from the system you've experience with. I have faith. faith doesn't always return product though

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