Neato brush ball bearing hair fix

[Peter101]

My fix for hair seizing the brush ball bearing.

The original ball bearing is replaced with two smaller ball bearings which are located out of harms way inside the brush tube. The shaft/axle which sticks out the brush end does not rotate. This creates space for the hair to wrap around the non rotating axel and not press directly against the sealed ball bearing, provided you clean and remove the hair every now and then. Moving the ball bearing creates the opportunity for the entire brush to get closer to the wall side bumper and rely less on the side brush. I was tempted but opted for more space for hair. The copper washer is because the flare diameter was slightly small.

The bearing spacers are made from of ¼” copper plumbing tube. The outer tube is 3/8” copper plumbing. A thin steel plate (part of a washer) mounts in the original ball bearing position and centers the axel. The axel is a ground 5mm x 100mm high speed steel shaft (overkill, it can break but it will never bend) cut in half. Two 5mm x 8mm sealed ball bearings slide onto the shaft and are positioned with ¼” copper tubes. The last tube on the shaft is slightly squished to make a snug fit which keeps the assembly together when removed for cleaning the hair away. The 3/8” plumbing tubing that I have has an 8mm inside and 10mm outside diameter. One end of the 3/8 copper tube gets flared to retain the brush beaters and bristles from sliding out of their groove and the other end is cut with a tube cutter which reduces the tube diameter slightly and stops the inner ball bearing from sliding all the way through the 3/8” tube.

The shaft is welded to the center of the 16mm diameter steel plate.

The plastic brush has an inside diameter slightly under 10mm but it also has two projecting key ways which need to be removed. I used lettered drills V, W, and a 25/64” to get a round hole with a snug fit on the 3/8” copper tube. The flaring was done in a vice which increased the copper tube diameter slightly so do the drilling and snug fitting testing last. I also counter sunk the brush end to accommodate the copper tube flare.

An alternative design could use a pair of 5mm x 10mm bearings with no 3/8” copper tube. The bearings just get pressed into the brush end; however, if the bearings ever jam the heat from friction might become a plastic melting issue. I expect the 3/8” copper tube will distribute any bearing heat if the bearings seize. If the welding is not an option you can glue the axle into the small ball bearing and glue that into the original ball bearing. This reduces the space for hair to accumulate so it would be my last choice.

Peter

[glnc222]

Impressive machining. For less equipped owners the Botvac-D new brush can be used in older Botvac's by clipping off a flange in the side of the case. See the Mods & Repairs list main page. Added to the index.

[glnc222]

If I understand this, the axle is fixed and the brush rotates around it, so the axle cannot rotate in the case mounting causing friction heat damage? (Two issues, preventing bearing contamination and separately containing damage.)
Very creative. If the brush could be stopped when the bearing freezes, the software would detect this and stop the motor. When I tried this other ways with a deliberately damaged bearing, the brush kept going. I think the shaft rotated within the plastic brush, it's been a while.

The core diameters of the original and D brush, with Vorwerk mounting, differ, so the D end cap is not usable in the old brush -- entire brushes must be changed when using the D. The old brush will still mount with the case flange clipped. Special custom caps for the old brush will not fit the new D brush.

[Peter101]

Yes the shaft and the inner race of both ball bearings are stationary.

The bearing fit on the shaft is good but it is not an interference friction fit. The copper spacers pinch the inner race and this prevents them from spinning. If the bearing ever seized I am sure they would spin on the shaft and behave as a poor bushing so I don’t think a seized bearing would ever trip the over current sensor.

I was not aware that the ID of the brush changed when Neato revised the bearing design. I think the bearing redesign doesn’t address the root cause of the problem, which is no space for hair to accumulate, which always happens. It does however limit the heat damage to a replaceable part so power to them.

I have 4 botvacs and 2 roombas in my extended family so eliminating an ongoing problem pays me dividends; I wish Neato also saw it my way. Despite their faults I like the botvacs best but when asked for a recommendation I answer that vacuum robots are like cars in the 60s, if you can’t fix them yourself they are expensive to own.

Peter

[Peter101]

A small revision to the ball bearing assembly is the addition of a labyrinth hair seal and also the elimination of the copper washer. The seal results in a substantial reduction in hair maintenance.

I added a short length of ½” copper pipe to the existing flare by soldering. The outside diameter of 5/8” copper pipe is 15.88 mm which is slightly under the original Botvac ball bearing diameter and it fits inside the original ball bearing plastic mount without touching the mount. If the 1/2" pipe it is not centered after soldering you can always sand, file, or grind it smaller so that it fits correctly. With the new seal it is more difficult for hair to reach the non rotating axle shaft and tangle around it. I will keep a weekly eye on it for a while but I am expecting a much longer maintenance time span something like once or twice a year.

Peter

[glnc222]

In case never noticed, the method here resembles the Roomba 800 series brush advances using a hollow cavity in the end to trap hair once mentioned by third_deg.

[Peter101]

third_deg created a good extractor design concept and it is why I bought my 880. I can also verify that his design picks up nuts and bolts. The extractor bearing design minimizes hair problems, fingers crossed that this fix works as well

I was starting down the rabbit hole before this fix. How far? Bleed exhaust air pressurizing the brush and other places you want to keep hair and dust free.

FWIW The only roomba artifact that I dislike is that they all sound like clanging toys rather than precision equipment YMMV.

[Peter101]

Neglecting the hair for 4 months:

I finally had to clean the hair cylinder from both ends of the brush. The hair became a dense tangled lump which created friction that slowed brush rotation, you could hear the brush motor was turning slowly (lets say half the normal RPM).

No heat damage was done to any plastic part or the motor. I was waiting for the Botvac software to object to the extra motor load current but I finally relented before the software (assuming the software would object) and removed the hair.

The small bearings I used have a rubber seal and when cleaning the hair it dislodged the rubber seal from the ball bearing. It was easy to push it back into the bearing but was still annoying, I am sure if repeated many times the bearing seal will get damaged.

In rev2 I would add a shield to keep the dense hair ball from pressing against the rubber seal and I would also use a larger diameter ball bearing.

[laser21]

Great design, any chance you could create these and sell them?