Inside the Scooba 5900 vacuum/blower

[vic7767]

Well I finally got around to opening up a Scooba fan. I must say the sealing process seems to be a bit of an overkill but it is very well sealed.

On another note, the visible portion of the fan blade that we all want to clean is just the tip of the iceberg, there is a much larger fan assembly mounted beyond the small impeller. This means that unless you want to take the fan blower assembly apart you may be wasteting your time cleaning the little fan.

I personally would not recommend that a Scooba owner perform the dissection of the fan because you will never be able to seal it as well as the factory assembly.

[Fraggboy]

Vic, thanks for the picture. Are the blades that we can't see pretty bad? When you put it back together, is the vacuum still good?

[vic7767]

Fraggboy, on the one I just took apart the secondary blades are just like you see in the picture. They don't look very bad at all. I just got this one on ebay from a seller that couldn't get it to prime. I don't believe this Scooba has seen any real cleaning action. I did prime it using my aquarium pump, stuck one of my LI-ion packs in it and sent it on a mission. It did quite well. It is now undergoing the brass insert, hex head stainless steel screw mod.

[Fraggboy]

. . .It is now undergoing the brass insert, hex head stainless steel screw mod.

Good for you! I'm sure you got a good deal for it also. Hmm.. **Thinks** You could make a good business by. . .

Anyways, can you elaborate on the brass insert, and hex head stainless steel screw mod?

[vic7767]

I posted a "how too" in the hacker forum on the hex head conversion but now I can't find it to link to. Anyway you can do an ebay or Internet search for 4-40 brass inserts and go to http\\microfasteners.com for the stainless screws.

[Gordon]

I posted a "how too" in the hacker forum on the hex head conversion but now I can't find it to link to. ...

Just a search for "#4-40", and out pops THE LINK!

BTW, if you look inside that Scooba-impeller, I think you will find the blades at its entrance are the same blades seen around the rim, at its exit.

Thanks for ripping into that blower assembly!

Were you able to detect how the impeller is retained on the motor-shaft?

If anyone wants to re-lubricate motor-shaft bearings, that impeller has to be taken off the shaft.

Even accessing the other shaft-bearing may require impeller removal, since (if I remember correctly) the opposite end of the motor is capped, {Edit: I remembered correctly, but the wrong scenarios was embedded! Correction follows:} What appeared to be a "cap" is an open 'rubber' sleeve. Once you dismount the Blower Asm, and up-turn its forward end, the EMI-PWB will be obvious, and the motor's shaft and bearing will be visible through a large hole in the PCB, hence the front-bearing can easily be given a tiny droplet of light-oil (mineral, sewing-machine, Three-In-One, types).

Unfortunately, it is more likely that the hidden shaft-bearing is the one that needs re-lubrication more badly!

[vic7767]

Gordon, thanks for the search key, I tried "brass", "allen head", "stainless steel", etc and got nothing.

I do plan on delving deeper into how the impeller is mounted. I suspect it is just pressed on but a 1 inch wide stiff blade tool should be able to pry it off.

Looking at the back of the motor does not reveal any motor mounts. I thought it might be glued in place but as you suggested there may be mounts beneath the impeller.

Update- looks like a small diameter punch will be needed to drive the motor shaft off of the impeller, now I'm looking for my Colt SAA tool kit for some punches.

[eqwalker]

Goodness, looks like taking apart your Scooba for cleaning the impeller is not the way to go for the average user. With that being said, what would be the best way to clean the impeller? Maybe some spray cleaning solution or something? I have had my 5900 for about a year now and it is working great (knock on wood) but I did take a flashlight and look into the fan and I do see where the impeller is dirty. I do, occasionally, have to prime my 5900 before I start a cleaning mission (especially if I let it sit for some time), but I always get it going. I do store the tank separately and also suspend the 5900 so the wheels are elevated. I just want to try to keep my 5900 going strong. Also, has anyone tried to sleeve the front wheel bearing so it doesn't wear out so quickly?

[vic7767]

eqwalker, yes it is a little bit beyond the daily maintenance routine and normally I would post this in the hacker forum but I think some Scooba owners don't venture there. The main purpose was to expose the internal impeller mechanics to the Roomba Review Forum

I clean the impeller using Q-tips that have been soaked in Orange glo degreaser.

I do remember long ago that someone with a machine shop posted some pictures of some brass bearings that were mounted into the sides of the plastic holder. Thus avoiding the wearing out of the plastic wheel.

[bob_ninja]

If I were to clean the fan blade without taking anything apart, what sort of tool could reach down to it? Qtips are too short. Any tips?

I am looking for a simple/quick/easy way to clean the fan, if possible.

[Fraggboy]

bob_ninja, I have seen some long Q-Tips before, but I don't know where one would get them. Maybe at Wally World? But, one thing tho, you would want to stop the fan blade from spinning while you use pressure to clean the blades. And, with the information Vic has uncovered, this cleaning is only getting a fraction of what we should be getting.

[vic7767]

Based on a statement by Gordon in this thread, further inspection of the impeller indicates that the internal fins of the impeller force the debris to move from the innermost blade fins to the external fan that is visible while the Scooba is not dismantled. The centrifugal force of the impeller makes this happen. Therefore my statement about just cleaning the visible fan blades may not be effective is hereby retracted. If you diligently clean the blower/vacuum fan blades, it may help your Scooba perform more efficiently.

[bob_ninja]

bob_ninja, I have seen some long Q-Tips before, but I don't know where one would get them. Maybe at Wally World? But, one thing tho, you would want to stop the fan blade from spinning while you use pressure to clean the blades. And, with the information Vic has uncovered, this cleaning is only getting a fraction of what we should be getting.

Hmm, well I'll try to find them and attempt some sort of cleaning, see if I can do anything. Thanks.

[Tricity]

Contrary to common wisdom, it seems possible to put oil on *both* shafts of the impeller motor. First of all, though, thanks to those who posted detailed information on the Scooba disassembly and specifically on the vacuum unit http://mysite.verizon.net/gsplews/18BlowerAsm.htm

Disassemble the Scooba to the point where you can see the impeller as in Figure 2 of the above link. Remove the three screws that hold the impeller in vibration-dampening rubber grommets and carefully pull it toward you until you can see the back of the motor. In this process, you need to twist the air ducts. Now, take a syringe with a small (22ga) needle of 1.5 Inch length. Fill the syringe with oil - about 1 ml of oil will do the job. Carefully guide the needle into the lower vent opening of the motor and lower it (tilting it outwards towards the motor case) until you hit the bottom. Squeeze about 0.5 ml of the oil into the bottom of the motor. Remove the syringe. Hold the vacuum assembly vertical so that the impeller faces downward. Turn the impeller slowly and slightly tilt the motor so the oil can distribute along the bottom. The oil will now flow into the impeller-side shaft. Don't forget to drop a minor amount of oil onto the other shaft end. Turn the impeller unit around and let the excess oil flow out of the back of the motor. Reassemble.

The impeller collects a lot of dirt. Figure 8 at http://mysite.verizon.net/gsplews/impeller_destruction.htm shows that the motor corrodes over time. Otherwise, the bearings (steel in brass) would not need any maintenance. In the process, the motor draws a lot of current due to increased friction. In my case, the impeller was actually failing. I powered the motor with a lab power supply and it drew more than 2A at 14.4V. After cleaning and oiling, this current dropped to 1.5A - which tells me that the motor runs more efficiently now.

[Gordon]

Contrary to common wisdom, it seems possible to put oil on *both* shaft{-end}s of the impeller motor.

Nice work / good thinking, Tricity!

Permit me to add a few tips to your process:

At this point...

...Now, take a syringe with a small (22ga) needle of 1.5 Inch length.

It will be wise to either select a needle which has been blunted (commercially available for epoxy application), or snip off the sharp tip of a theraputic needle, then smooth burred edges using a fine grit knife-sharpening stone (smooth enough that you are willing push the blunted end along your skin). The reason for that is: As the needle tip reaches inside the motor assembly--on its way to the bearing near the impeller--the tip will be gliding along a slot in the armature, a slot that is partially filled with fine copper wire. Digging into that wire bundle (possibly scraping insulating 'varnish' off a couple wires, maybe breaking a wire) is to be avoided.

Fill the syringe with oil - about 1 ml of oil will do the job.

I suggest using sewing-machine oil (3 In One Oil).

When the syringe is ready to be inserted, first shine some light into the entrance slot and try to determine whether an armature-slot is in alignment with the vent hole. You will see either a green 'wall', or two (small) green walls with a dark gap between. If you see the green wall, rotate the impeller through one magnetic detent, and check for the dark-gap (the "slot"). You then have a fairly clear path for the needle to pass along.

Continue with...

Carefully guide the needle into the lower vent opening of the motor and lower it (tilting it outwards towards the motor case) until you hit the bottom. Squeeze about 0.5 ml of the oil into the bottom of the motor. Remove the syringe. Hold the vacuum assembly vertical so that the impeller faces downward. Turn the impeller slowly and slightly tilt the motor so the oil can distribute along the bottom.

...and to permit the oil to wick between the bearing's bore and shaft.

The oil will now flow into the impeller-side shaft. Don't forget to drop a minor amount of oil onto the other shaft end. Turn the impeller unit around and let the excess oil flow out of the back of the motor.

At this point it would be prudent to block up the loose blower assembly so its shaft is held nearly vertical, and leave it that way until the next day--some 20+ hours later.

Very few owners have caught on to the true nature of these motor bearings (and similar bronze bushings used in iRobot's gear-cases and brush-end bearings). They a basically metal sponges. They are manufactured by packing bronze particles in a forming-die to compress the particles to a certain density and bearing shape. They are then sent into a furnace and baked at high temperature to cause neighbor particles to weld (the sintering process) together. When done, a sintered bearing will have a certain porosity, and it is those voids which are then filled with oil.

Oil impregnation is commonly done in vaccuo at slightly elevated temperature. Without a vacuum chamber, and at room temperature, many hours will be required to even come close to re-filling the voids. For sintered-bronze bearings which are more easily accessed, you would not care to take the extra time, just give 'em a drop of oil whenever you think of it. These 'buried' blower-motor-bearings ought to be given a good 'drink'!

Reassemble. ...

[Tricity]

Gordon, many thanks for your additions and thoughts . Too little patience I had, when writing the report

About blunting the needle. Yes, stubs are available. Snipping off the sharp point of a medical needle with a wire cutter is not easy as you squeeze the opening shut. I found it practical to twist the needle inside the jaws of the wire cutter until the needle metal is thoroughly scored. The tip then breaks off easily. As a prudent person, I wrap the tip in adhesive tape before discarding it (anybody wants to trust a Roomba to scoop up the needle tips before somebody steps into them?)

I suggest using sewing-machine oil (3 In One Oil).

- Good idea. I myself like gun oil, but this is just a matter of preference. Not recommended: WD40 or similar (unless you have to break free the shaft). WD40 is not viscous enough and wears off pretty quickly.

Very few owners have caught on to the true nature of these motor bearings [snip] and it is those voids which are then filled with oil.

- Right. This is why I mentioned that the bearings usually don't need maintenance. Usually - that is, in the absence of microscopic dirt particles, of course.

Since yesterday, the Scooba has been on three missions, and it leaves much less water on the floor than before. A good sign. It also tells me that the vacuum blower's efficiency has been slowly degrading - slow enough not to be noticed.