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Until late in 2007, there was not much that could be said about Scooba's Blower Assembly. The original issue of this page could only show its location within the robot, point out mounting features, and discuss the air-flow through the blower and out of the robot. However, in this update, many new details are at hand, and it has become possible to consider the possibility of performing certain maintenance operations on the Blower Asm.. Unfortunately, the prospects for accomplishing such maintenance are slim to none; and reasons are provided.
The Blower Assembly occupies an appreciable volume within the robot. Looking down into the lower-chassis assembly, the Figure 1 scene shows a large, black assembly occupying Scooba's left-front quarter. Ignore the metal-cased motor at field center; that is the brush-motor. The Blower's motor can't be seen, because it is shrouded and hidden from view by parts of the Blower Assembly.
Figure 1. Top-View of Blower-Housing and Outlet Duct
At lower left, is the Blower's volute-housing, and an oblique view of the circular inlet to the impeller. After slight compression, the air moves off to Scooba's left and travels out of the robot along the curved duct-work heading aft. Notice, surrounding the Blower's housing, three Blower-Assembly vibration-isolation mountings are visible.
Figure 2 provides a straight-on view into the Blower's intake port, where a good view of its Impeller is given. Most of the Impeller can't be seen; its outside diameter is almost twice the size of the inlet's diameter!
Figure 2. View of Impeller at Blower's Intake Port
It is that Impeller, spinning at high speed, which has drawn air, dry-debris, wet-debris, and dirty cleaning solution off of the floor, and into the Dirty-Tank. Then the moving air leaves the DT and passes through the removable filter-screen (illustrated in Figure 3), finally reaching the rotating Impeller which has been 'attracting' it! The air briefly swirls around in the Blower's housing, then blasts free of the robot.
Figure 3. Air-Flowing Toward the Blower Intake
Compressed-air leaving the impeller housing is split into two paths. Figure 4 shows a side view (from the robot's left side) of the exhaust ducts.
Figure 4. Blower's-Outlet is Divided by Small and Large Ducts
The small duct branches off to divert a flow of high-velocity air to the "Debris Air Jet" shown in the first figure of the hydro-pneumatic-path section ; while the large duct dumps most of the air-exhaust onto the floor (just forward of the left-wheel) via the "Air Outlet", shown in the second figure on that same page.
When this document was issued ca., Spring 2006, the following paragraph is all that could be stated about the Blower's method of assembly and the materials used. No prediction could be offered regarding disassembly to effect any repair, or even re-lubrication of motor-shaft bearings:
The view of the housing and ducts in Figure 4 also shows the reason it has not been feasible to learn more about the Blower-Assembly; and that is "bonding agents". Three types are shown in that single view. There is an opaque-white adhesive, used to glue two halves of the blower-housing together -- which also seems to capture the motor in a plastic shroud. There is a milky-white bond-line where the housing joins the pair of ducts, and there is a translucent-white adhesive used, apparently, to pre-bond the two ducts together prior to assembling that unit to the housing. Internal Blower-Assembly information will remain deferred, until there is a definite need to break one or more of those bond-lines. |
It is now some year and nine months after writing that paragraph. Inoperative 5900s are being sold for parts. RoombaReview member "glo69" purchased such a Scooba, salvaged the items that interested him, then donated to me many other Scooba subassemblies. A Vac/Blower Assembly was in that group, and it has since yielded a good amount of information, information that was not feasible to obtain early in 2006.
I will now back-track through that paragraph to correct, as necessary, what was written. and to append newly acquired data.
Even though the Blower Assembly is bonded together as a unit, the assembly can be dismounted from the lower-chassis assembly. Dismount entails TFSs' removal from the vibration-isolation mounts, three places, and removal of two TFS from the exhaust-duct's flange (one TFS at that flange can be seen in Figure 1) to chassis interface. With those fasteners removed, the entire Blower Assembly may be lifted off the chassis, to reveal a scene such as shown in Figure-2, here. Note: A two-wire harness will be tethering the Blower to the Control Module. If the assembly is to be dismounted from the robot, to work on it or to replace it, see the Control Module pages for guidance to the blower-motor's enclosed pigtail connector. Once the Control-Module's lid has been dismounted, the sealed harness-via, through which the two-wire harness passes on its way into the Module, will be visible. The sealant looks like a clear, silicone-RTV elastomer, but the applied material is very much weaker than any ordinary (i.e, procurable at your local hardware supply) RTV-silicone. This sealant seems to exhibit greater adhesive strength than tensile strength. This is to say: The material is easily removed from the seal-box and from the wire's insulation. Your problem will be to figure out what may be used as an equivalent sealant when you re-seal the wire-harness!
Let us say you have split apart the Blower's housing parts, and made a saw-cut through its splitter-casting. This is what you will see inside:
Figure 5. Blower's Interior
You now have a fairly complete view of the Impeller, which permits some of its features to be pointed out:
Now that we are inside the Blower, what work may be done? Cleaning is not too reasonable, since that which is feasible may be done without dismantling the Blower. Lubrication of the motor-shaft bearing (the one behind the Impeller) can't be done while the Impeller is in the way. About the only justification for having gained this access, is to attempt correction of noise caused by some Impeller surface rubbing against the adjacent housing. IOW, while Scooba was scrubbing floors, it tended to emit a loud, high-pitched sound. Subsequent performance of Scooba's Self-Tests confirmed the sound to be coming from the Blower.
You then know which sub-assembly is producing the noise, but you may not know if the source is from a dry shaft-bearing, or from parts rubbing together. Once the Blower Assembly has been disconnected from the robot, there are two prudent tests that should be done. One is to use your finger tip to rotate the Impeller, in an attempt to determine if bearing-drag is severe. A second trial would be to power the Blower-motor with Scooba's battery and listen for / to the noise. You would like to know which source it is, before splitting the housing apart. Lubrication of the bearing under the Impeller is not an option; while the forward sleeve-bearing could be re-lubricated without dismounting the Blower Assembly!
With the Impeller now exposed, close inspection of all labyrinth surfaces could reveal a zone with appropriate rubbing marks. If such marks are found, do not think about removing material from the Impeller! Its balance will be perturbed. Instead, you might consider using a Dremel-motor with a small-size rotary-file fitted to it to remove a small amount of material from the rub-spot on the housing. But, bear in mind this over-riding problem: The process of splitting the large housing castings apart will have left a jaggy edged pair of adjoining surfaces, and might have slightly distorted the casting. Quite possibly, if you were to simply re-bond those joints, a revised spatial relationship between Impeller and its adjacent housing would result. Its a gamble! You won't know if operating clearance will result, or if the rubbing will be more severe! Yet, one way to shift the odds in your favor would be to spin the Impeller just after pushing glue-doped housing parts together. You would use a low-voltage, perhaps a six-volt lantern battery, to power the motor. Then, while the glue begins to set / cure you would eliminate any sound of rubbing by shifting one housing-casting relative to the other.
Don't even think about it. I show you why in this page.
In summary, it is a sad situation!
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This page is currently maintained by G. Plews