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In this document we identify the huge brush-drive motor, then open its speed-reduction gear-box, to give you a peek inside. After such inspection, it is reasonable to claim that every item in this assembly is "special", i.e., designed and manufactured only for Scooba, with only two exceptions: chip-form components used in the EMI-filter network, and machine-screws which hold the motor in place. Information is provided which should tend to suppress any hope of being able to obtain any of the drive's special parts, if attempting a future repair, except to obtain like parts from like assemblies out of another Scooba.
The Cleaning Brush may be called the 'work-horse' in Scooba, since it, along with some cleaning agent, is what really gets new and old dirt scrubbed loose from your flooring. The first figure shows Scooba's opened Cleaning Head, with rotatable brush removed. That brush is driven at fairly high rotary speed by the Brush Drive System's dc-motor and integral reduction gearing.
Figure 1. Brush-Drive System Functions to Spin This Brush
At the brush's extreme left (ours and Scooba's) end, is its drive-coupling to the gear-motor's output shaft. The coupling design could be called a "three-vane-spline" type; in which the brush-coupling is the female socket, and the output-shaft is the male member -- which will soon be seen in the open gear-case figure. Edges of vanes accomplish a self-centering function for the coupling, while the sides of the output-shaft's vanes rotate into contact with the coupling's vanes to spin the brush.
Figure 2 provides an oblique view of the brush-motor and its gear-housing -- the white-casting, at right, in the photo. The view is rearward. Roger had dismounted the Blower Assembly, to obtain this full view of the motor. With no scaling features in that photo, it is not possible to tell that the motor is about 1.5X larger than the motor Roomba's use to run their main-brushes!
Figure 2. Brush-Drive Power Plant
It is possible to view through those oval holes in the motor's housing and see the magnet-wire used to wind the armature. Roughly speaking, the wire-size is several times larger than the wire used in Roomba's brush-motor. That translates into greatly improved reliability, since larger wires are less likely to break at their electrical-connection points.
As one might expect, this is a Mabuchi motor, and with marking RS-545SH-2680. Its housing is 50 mm long, and almost 36 mm diameter. While one may visit Mabuchi Motor Co. , in an attempt to learn more about this motor, none will be found listed with the "-2680" suffix. Various bits of general information, e.g., mechanical details, may be learned, but almost all performance characteristics will remain unknown.
The motor bolts directly to the gear-housing via two-each, ISO M3.0x0.5x6mmLG, #2-Phillips, button-head screws. Vibration-suppression is accomplished by mounting the entire motor/gear-head assembly on special 'rubber' grommets, with shouldered bolts (actually they are shouldered thread-forming screws) that screw into the lower chassis. Two of the screw-heads and grommets can be seen in Figure 2, on top of the gear-housing.
Regarding those vibration-isolators, Roger found that the grommets had been "twisted " out of true, as fitted. He then lubricated each grommet with grease, and "did up the screws to a lesser amount...", and claims, "Scooba is substantially quieter now. It is quieter than Disco for sure".
As can be seen in Figure 3, removal of four TFS3.0x1.4x8mmLG, #2-Phillips, button-heads allowed the gear-case cover to be pulled away, exposing the gear-set. Two additional bolts were removed from the motor's end-bell, so the motor could be dismounted. Compared to the wheel-gearing, this set is fairly simple; there is only one stage of speed reduction. From the motor-pinion to the cluster-gear the step-down is roughly 1/3, then the cluster-pinion drives an idler-gear, which drives the output shaft. Since the gear on the output shaft appears to have the same number of teeth as the cluster-pinion, there is no further speed reduction, so the brush runs at about 1/3rd the motor speed (which we don't know).
Figure 3. Speed-Reduction Gearing Exposed
Notice these gears are lubricated, very sparsely with the same colorless, light-weight grease found used in the wheel gearing. Nothing else is known about this lubricant, or how important its choice pertains to gear-tooth longevity.
Looking to the future now, far into the future, hopefully, there may come a time when an owner suffers a non-warranty gear failure, and decides to attempt the repair job. If that happens, the most reasonable source of custom-parts, like these gears, is from a duff Scooba. However, that is not always possible, especially when the product is newly released, so there may be owners who begin thinking about having a damaged gear custom manufactured for them -- as has happened for Roomba-gears. A hint of what is involved in that process may be found in the Gear-Replacement Considerations section; a process intended only for well-equipped owners!
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