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We surmise that iRobot's engineers felt that putting the bulk of Disco's weight on the Bumper would not be safe practice, so they added an "L"- shaped arm to each end of the Handle's hinge-shaft and designed them to pick up the main-bot's weight from two special, forward-projecting Cover-prongs, which were added to the Cover for just that purpose. The ends of those "L" arms always overlap the prongs, but only bear against them when Roomba is lifted by its Handle. That is just one half of the mechanical picture needed to define the cause of disassembly hang-up.
Talking about "picture", this might be a good place for a graphic definition of what we just said. Here is an inside-view of the engagement of the right-side "L"-arm and prong; with parts shown separated in the left image, and then slipped into a nominal engagement, in the right image:
From that illustration, the limited, relative vertical travel between an engaged Bumper and Cover should be obvious. In fact, vertical-travel is limited to about two millimeters! Such limited motion is not great enough to permit other engaged features to clear each other as the Bumper is moved into final release.
The other half of the problem relates to the design of the mechanical interface between the outer-Bumper (to which the Handle is attached) and the inner-Bumper (which also serves as a Cliff-Sensors' support bracket, and connects to the main chassis via hinged linkages). That mechanical interface can be envisioned as an array of four telescoping 'cylindrical-pins' and matching sockets, whose common axis of assembly engagement is perpendicular to the plane of the Cover's prong and fork engagement. If an attempt is made to remove the outer-Bumper without also releasing the Roomba-Cover from the chassis, the "L" arms disallow sufficient travel of the Bumpers 'pins' within their sockets to clear the outer ends of those sockets!
To overcome this mechanical restraint, it is necessary to lift the Cover away from the Chassis a small amount. At a minimum, say if one were only interested in taking the outer-Bumper off, that means no more than the front four Cover retaining screws would need removal, the two skirt-screws (if present) would be loosened four turns, the pair in the 'brushes-well, and the all of the screws aft of those positions would need loosening of only two turns.
OTOH, all of the Cover screws need to be disengaged from the Cover, if the Cover is also to be removed.
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This page is currently maintained by G. Plews