Usually, the traction motor is three-point suspended between the bogie frame and the driven axle; this is referred to as a "nose-suspended traction motor". The problem with such an arrangement is that a portion of the motor's weight is unsprung, increasing unwanted forces on the track. In the case of the famous Pennsylvania Railroad GG1, two bogie-mounted motors drove each axle through a quill drive. The "Bi-Polar" electric locomotives built by General Electric for the Milwaukee Road had direct drive motors. The rotating shaft of the motor was also the axle for the wheels. In the case of French TGV power cars, a motor mounted to the power car's frame drives each axle; a "tripod" drive allows a small amount of flexibility in the drive train allowing the trucks bogies to pivot. By mounting the relatively heavy traction motor directly to the power car's frame, rather than to the bogie, better dynamics are obtained, allowing better high-speed operation.