Roomba upgraded CHM support bearing (and carpet upgrade)

thingiverse

The Roomba (500 series) is a capable robot and a valuable roommate but suffers from an underpowered transmission. Dirt, fur, PLA strands, and other debris often enters the gearbox, causing resistance to build up in many Roombas. This repair/upgrade targets one of the primary failure modes of the CHM/cleaning head/gearbox. The main issue is that due to debris entering the gearbox, this resistance grows progressively worse until the heat eventually causes the plastic housing to deform and fail, resulting in either a brush box error or a failure to rotate the main cleaning brushes. This problem typically occurs primarily at the two output wheels (where debris enters) and the first driven gear, where rotational speed is highest. A bearing shim is used to fit into the CHM deck, preventing the metal gear axle from moving into empty space beyond the CHM chassis. This part fits precisely into the space behind the CHM and aligns with the edge of the chassis. It has a radial cutout that allows sufficient range of motion for the gearbox/brush motor to effectively adjust its height while preventing the motor tab from touching the support lug at the bottom of the CHM, ensuring proper fitment and reducing wear on the height adjustment wheel and bushing. This part was designed based on the green CHM module but may also fit other CHM modules (black and red). If your CHM has not yet failed, this part will prevent it from failing. Since iRobot has replaced older CHM modules, the only other repair strategy is to replace the CHM with a new grey CHM (~$50).