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Electronically switchable chainless drivetrain developed for Alpha Bike concept


May 2, 2011

The Alpha bike prototype features a fully internal chainless drivetrain with electronic switching

The Alpha bike prototype features a fully internal chainless drivetrain with electronic switching

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The Alpha Bike is an interesting prototype out of the University of Pennsylvania featuring a fully internal chainless drive that can be switched between fixed gear drive and freewheel electronically. Fabricated entirely in-house, the bike's drivetrain, brake systems and onboard electronics are all concealed inside the custom-machined frame and an LCD display on the handlebars updates the rider on important journey information. Oh, and it looks pretty good too...

The bottom bracket of the Alpha Bike is home to the Switchable Integrated Free-Fixed Transmission (SWIFT) Drive system designed by University of Pennsylvania Mechanical Engineering seniors Geoff Johnson, Lucas Hartman, Katie Savarise, Evan Dvorak, Katie Rohacz, with Dr. Jonathan Fiene as advisor. SWIFT uses an electronically-controlled clutch for switching between fixed-gear and freewheeling modes and incorporates a central shaft made from AMS-6514 Maraging steel, a Titanium 6Al4V clutch plate and belt pulleys made from stainless steel.

A front hub houses a drum brake and dynamo which provides power for the electronics, charging two super capacitors which in turn power a suite of sensors and a microcontroller. At the rear there's a compact three-speed planetary gear set actuated by a standard push-pull cable.

The LCD display on the 16 ounce (458 g) 3D-printed handlebars offers the rider useful information such as time, distance, cadence, wheel speed and chosen gears. Bike dynamics information is stored to SD card, which can be examined after completion of a ride.

Sadly, there is no information available on how the performance of the prototype drivetrain compares to more familiar designs. Nor is there any indication that the development might result in a production model.

The purpose of the design project was to "create a bicycle push the boundaries of integrated systems." In that regard, the Alpha team was recently rewarded for its efforts, receiving the Gemmil Award in the University's 2011 Senior Design Competition.

Source: Engadget

About the Author
Paul Ridden While Paul is loath to reveal his age, he will admit to cutting his IT teeth on a TRS-80 (although he won't say which version). An obsessive fascination with computer technology blossomed from hobby into career before the desire for sunnier climes saw him wave a fond farewell to his native Blighty in favor of Bordeaux, France. He's now a dedicated newshound pursuing the latest bleeding edge tech for Gizmag. All articles by Paul Ridden

The display in the handlebar is welcome as are the hidden brakes. Reliable bicycle systems, more than bolted-together components amid constraints for light weight, should lead designers for other vehicles as well.


As a boy I used to ride a neighbour\'s chainless cycle that was then [early 1950s], said to be 40 years old. It used tapered rollers and drove through the backstay tube.


All that technology yet they designed it for the hunched over, uncomfortable backbreaking position.

Gregg Eshelman

Looks damn fine to me, sleek and sporty and if it works, all the better. the design is not uncomfotable, it\'s efficient!


The seat/saddle position only makes sense for a racing bike, and no-one is going to race a belt drive three-speed bike with a dynamo. But it\'s a technology demonstration, not a practical product, and a more sensible design might not have been pictured here.

Alan Braggins

Spiffy. So if you get a flat, how do you change the rear tire?

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