Syntegra is a bogie

Bogie

A bogie is a wheeled wagon or trolley. In mechanics terms, a bogie is a chassis or framework carrying wheels, attached to a vehicle. It can be fixed in place, as on a cargo truck, mounted on a swivel, as on a railway carriage/car or locomotive, or sprung as in the suspension of a caterpillar...

 developed by Siemens

Siemens

Siemens may refer toSiemens, a German family name carried by generations of telecommunications industrialists, including:* Werner von Siemens , inventor, founder of Siemens AG...

 incorporating an axle mounted gearless electric drive in an inside wheel bearing bogie.

The design was unveiled at Innotrans

InnoTrans

InnoTrans is the world's largest trade fair focused on the rail transport industry. It is held every two years at the Messe Berlin exhibition centre, which has outdoor standard gauge railway sidings which can be used to exhibit railway vehicles...

 in 2006, and began service trials in 2008 on the Munich U-Bahn

Munich U-Bahn

The Munich U-Bahn system is an electric rail rapid transit network in Munich, Germany. "U-Bahn" is the German contraction for Untergrundbahn or "subway." It is operated by the municipally owned Münchner Verkehrsgesellschaft...

.

Design

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. 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.

The bogie frame has a single central cross member which supports via pivots two longitudinal beams (in a 'weighing scale

Weighing scale

A weighing scale is a measuring instrument for determining the weight or mass of an object. A spring scale measures weight by the distance a spring deflects under its load...

' arrangement) connected to the wheelset via the primary suspension. The cross member supports the vehicle body via the secondary suspension of two outside air springs.

The prototype bogie weight is 5.6t, with a 1.6m wheelbase and a maximum axleload of 14t. The prototype motors are rated 110kW, with 96% efficiency.