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.