A printer having an imaging drum rotatable around its longitudinal axis, receives a pattern of ink corresponding to an image to be printed. A transfix roller rotates around its longitudinal axis, and is selectively held against the imaging drum by a transfix force, the interface of the imaging drum and the transfix roll forms a transfix nip. An image is formed on the substrate passed through the transfix nip by the marking ink on the imaging drum. A motor drives the imaging drum through a power train with a speed and direction controlled by a motor drive unit. A substrate sensor detects the substrate at the transfix nip, and outputs a signal to the motor drive. The motor drive varies the torque applied to the imaging drum in response to the signal, to maintain a constant rotational speed of the imaging drum.