Syntegra is a bogie developed by Siemens incorporating an axle mounted gearless electric drive in an inside wheel bearing bogie.
The design was unveiled at Innotrans in 2006, and began service trials in 2008 on the Munich U-Bahn.[1][2]
The motor design is a hermetically sealed simple co-axial gearless synchronous motor (a permanent magnet, three phase drive, passively cooled design); the motors can also be used for electrical dynamic braking, and also as an active electric brake.[1][3] The wheelset bearings are mounted on the inside of the wheels and support both motor, axles and wheel. A traction link from motor to the vehicle frame frame transmits tractive forces.[3]
The bogie frame has a single central cross member which supports via pivots two longitudinal beams (in a 'weighing scale' arrangement) connected to the wheelset via the primary suspension.[3] The cross member supports the vehicle body via the secondary suspension of two outside air springs.[1]
The prototype bogie weight is 5.6t, with a 1.6m wheelbase and a maximum axleload of 14t.[1] The prototype motors are rated 110kW, with 96% efficiency.[4]