The Alpha Bike

The Alpha Bike was created by 5 grad students studying Mechanical Engineering at the University of Pennsylvania.



Bike Hugger
posted the above photo on their flickr of how the drive system of the Alpha Bike connects, claiming it to be the worlds least efficient drive train. I looked into the Alpha bike a little more and realized they used some amazing processes to create this machine. It goes from fixed to free with an internal belt drive. With the help of rapid prototyping and 3D printing (more on that later) they were able to manufacture the whole bike in-house.

Lets get nerdy…

Alpha’s bottom bracket houses the bike’s SWIFT Drive Technology. The Switchable Integrated Free-Fixed Transmission uses an electromechanical actuated clutch to switch the bike’s configuration between fixed-gear and free-wheeling modes. Metallurgical considerations played a major role in selecting materials for all of the transmission components. The strength and weight of Titanium 6Al4V made it the material of choice for the clutch plate, while AMS-6514 Maraging steel was used for the central shaft due to its extreme harden-ability (56 HRC). Bronze was used for its self-lubricating proper- ties at the core of the clutch, while 6061-T6 Aluminum was used for lower-stress components. The geometrically complex belt pulleys were made from Stainless Steel using Direct Metal Laser Sintering, a process which allowed us to create otherwise un-machinable parts. The rear hub incorporates a compact three-speed planetary gear set actuated by a standard push-pull cable. Finally, as shown in the picture on the right, the belt is easily accessible by removing the bottom bracket plate, making maintenance of the belt simple.

The bottom bracket went from a 30 pound solid block of metal to a 2.3 lb part.

If you are still reading this, you might be interested in checking out the Reprap 3D printer which can take manufacturing out of overseas factories and into your home. If you get a reprap it can actually replicate its own part to make one for a friend. This kind of home printing might just be the next big technological breakthrough.

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  1. Gunnar

    What you mean “least efficient”? Wouldnt it be the most efficient?

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  3. Zach Bossington

    It seems pretty efficient to me but Bike Hugger claims it isn’t.

  4. Simon Warner

    It looks awful – A vee belt with a tensioner? Please!

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