Modular encoder

A printer for forming an image on media, said printer comprising:

• a frame;
• a print drum secured to the frame for rotation about a longitudinal axis of the print drum;
• a print head for ejecting ink onto the print drum to form an image on the print drum;
• a transfer roller for moving into and out of engagement with the print drum to form a nip between the transfer roller and the print drum to transfer an image on the print drum to media fed into the nip formed between the transfer roller and the print drum;
• a feeder for advancing media into the nip;
• a controller for synchronizing the movement of the transfer roller with the print drum, the ejection of ink by the print head onto the print drum, and the feeding of media into the nip formed between the transfer roller and the print drum;
• and
• a rotary encoder for generating an electrical signal corresponding to angular position and speed of the print drum, the encoder comprising:
• a base having a floor with an annular opening, the base including a mounting ring surrounding the annular opening and being vertically displaced from the floor;
• and
• a hub having an external wall that tapers from a top to a bottom and a substantially straight internal wall surrounding a central bore, the tapered external wall of the hub being configured to fit within the annular opening of the floor and being circumscribed with a groove that receives the mounting ring to secure the hub to the base and enable rotation of the hub within the annular opening of the base as the mounting ring slides within the groove.