Botvac Brush Bearing Mod for durability

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Botvac Brush Bearing Mod for durability

Postby glnc222 » April 22nd, 2015, 7:45 pm

Separated from existing thread for topic identification.

This mod has not been built and is still only a suggested possibility.

for older Botvac; the Botvac-D introduced May 2015 has a new brush mount
see new model thread http://www.robotreviews.com/chat/viewtopic.php?f=20&t=18580&p=131041#p131027
[edit] This new brush can be used in the original Botvac by easily removing the small extra shroud on the side of the original case. See further posts below or German http://www.roboter-forum.com/showthread.php?11222-Neuer-BotVac-2015-!/page6

The problem reported with the Botvac brush bearing is wearing out the bearing with fiber debris, especially in a pet environment. Moreover, when the bearing seizes up it will spin inside the plastic housing heating up and warping the plastic -- not fail safe.
Botvac's were originally supplied with a "shielded" bearing more susceptible to contamination than a "sealed" bearing later provided (and seems to be in the separately sold brushes). Yet even these sealed bearings are subject to wear, just maybe longer lasting.

Since there seems to be less of a bearing failure problem in the XV models (correct me if wrong), there may be value in converting the Botvac brush mounting to the type of mounting in the XV.
[edit] Incidentally there is no issue of lower friction from ball bearings compared to a bushing in this assembly as the friction of the brush on the floor is the dominating factor. The Botac brush is nothing more than a little longer XV brush.

The Botvac brush end is made to eliminate a metal shaft at the end, using a wide bearing over flanges in a plastic end plug. The plug is hollow and can hold a metal shaft. The flanges for the wide bearing would have to be cut off. Then a bushing could be used on the shaft similar to the XV models, and the wide bearing could also be used over the bushing instead of the rubber grommet holder in XV models. The rubber holder can be made from a slice off a bottle stopper in hardware stores (see photos). The solid bushing may be less susceptible to seizing up from debris without the tiny parts inside ball bearings. This is the unknown factor which would have to be tested.

Assorted photos illustrate the construction involved.
P1010009.JPG

Image

To avoid cutting up the plastic plug at the end of the brush a replacement for that plug would need to be constructed. A 3D printer would seem to be needed though there may be some alternatives.
A copper tube might be inserted into the brush end with ends of tube bent out in flanges. A wide flange washer might be retained by the tube flanges to replace the disk end of the plastic plug. The plug retains the brush vanes. Maybe they do not need a retainer, who knows?
A replacement plug might be carved out of wood or plastic. Experiments would be needed. None of these possibilities has been tried. It may be cheaper just to buy another Botvac brush.

To mount the installed metal shaft -- just a quarter inch or so protruding from the brush end -- a bushing can be used similar to the XV models, sized for the Botvac housing.
A 3mm ID bushing just the depth of the ball bearing is available such as this one at Ebay:
http://www.ebay.com/itm/10-Pcs-Plain-Oilless-Bearing-Sleeves-Composite-Bushing-3mm-x-5mm-x-5mm/321323663292?_trksid=p2045573.c100033.m2042&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20131017132637%26meid%3D4d7f473ce3b541128f44d7bfad04135f%26pid%3D100033%26rk%3D2%26rkt%3D4%26sd%3D171739006154
The bearing ID is a little wider so this would need some tape around it.
Slicing up a rubber grommet of suitable size, for the inner core, can also provide a thick layer.
There may be other bushings available as well. The original XV bushings are brass or bronze. They were changed from a rounded type to a straight form in newer models.
P1010011.JPG


Example of bushing or bearing mount on XV model with rubber grommet:
Image
Image

P10100012.jpg
Last edited by glnc222 on July 12th, 2015, 8:23 pm, edited 1 time in total.
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Re: Botvac Brush Bearing Mod for durability

Postby glnc222 » June 9th, 2015, 9:40 pm

Possible method for practical construction, not tested yet.
bushing.jpg
possible method not tested


(thickness of a dowel plug can be adjusted with layers of masking tape for a tight press-fit)

[edit] The dowel plug dimension would be close to 3/8" or 10mm, adjusted by wrapping with tape or sanding thinner as needed.
If the dowel is run the entire width of the brush there would be no issue of it sliding back and forth.
Last edited by glnc222 on June 20th, 2015, 11:54 pm, edited 1 time in total.
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Re: Botvac Brush Bearing Mod for durability

Postby third_deg » June 11th, 2015, 5:05 pm

I'm looking forward to seeing you test it....

The gray CHM and 880 deck represent iRobot's discoveries on the topic. Many many failed attempts (Including one of my own that looks similar to this) ultimately lead to what they sold and patented of course.

My personal take is this basic design flaw is something that will continue to haunt Neato offerings.
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Re: Botvac Brush Bearing Mod for durability

Postby glnc222 » June 11th, 2015, 5:45 pm

I don't have a fiber problem here and do not know when I might try it. If you look here https://www.youtube.com/watch?v=F9U2mypXvmw at the VR200 looks like a major make-over, treating both ends for the new Botvac-D.

An M.E. acquaintance says the wood screw shank is maybe not a well machined shaft. A machine screw with flat section might be better, and it might just be wrapped in tape instead of needing a separate plug. Actual shafts are available from ServoCity.com for one. There is also some plastic tubing that might serve as a plug.
There might be need for a small washer between the flange washer and the bushing.
These things never turn out as simple as they first appear.
3D printer owners might have an easier time, reproducing the original end cap.
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Re: Botvac Brush Bearing Mod for durability

Postby mfortuna » June 12th, 2015, 7:28 am

One of my antique RC cars had two piece bushings similar to this:

http://www.astbearings.com/spherical-pl ... rings.html

I did post a picture many years ago but I can't find the same RC bushing online. But the above is similar.
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Re: Botvac Brush Bearing Mod for durability

Postby glnc222 » June 12th, 2015, 12:53 pm

A spherical bushing was originally used in the XV model (though in a rubber grommet) and later replaced by a straight bushing. I think the original was to make it easier to work the exposed drive belt, inelastic, onto the geared end of the brush when installing. Easy removal for cleaning was the objective. However the flexibility produced excess flexing of the end sometimes causing wear on the rubber parts in contact with the brush, affected by some small manufacture deviations in brush length (some users needed adjusting washers). Just a theory. The Botvac replaced the exposed belt entirely, so straight bushings should suffice. The problem is to get a very short one for the need to get the brush end as close to the wall as possible. Old bushings from XV's would suffice if available.
The rubber mounting of the bushing provides the needed flexibility.
Some bushings available listed top of this thread.
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Re: Botvac Brush Bearing Mod for durability

Postby mfortuna » June 13th, 2015, 8:27 am

Here is a picture of the two piece bushings. The smaller ring fits inside the outer bushing. They work very well.
Attachments
bushing.jpg
bushing.jpg (42.6 KiB) Viewed 9486 times
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Re: Botvac Brush Bearing Mod for durability

Postby glnc222 » June 15th, 2015, 5:49 pm

French forum member built one version with concentric fitting. http://www.kelrobot.fr/forum/attention-botvac-defaut-conception-t2826-80.html#p15893
Image

Possible problem with shaft too long rubbing the housing:
Image

There is no bushing between the shaft and the bearing. This design would be for locking the outer side of the bearing into the case, so that when the bearing seizes up the shaft is stopped causing a motor error message and stoppage, preventing damage. Yet I do not see any tape to secure the bearing. The regular plastic shaft into the bearing will just spin within the bearing damaging that part.
Like they say, lots of moving parts...

[edit] this is just a preliminary version which will undergo further work in France, with bearings on order etc.

[edit] Maybe should use a thinner regular hex nut on the end instead of lock nut. Thread locking glue.
-- better a hex head bolt. Or a round head cap screw.
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Re: Botvac Brush Bearing Mod for durability

Postby fanofrobots » June 16th, 2015, 7:40 pm

Thanks for sharing, I can't wait someone will find real solution to the bearing problem, i'm considering to sell my botvac 70e because of it.
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Re: Botvac Brush Bearing Mod for durability

Postby glnc222 » June 16th, 2015, 11:18 pm

Measurements of interest:
brushbearing.jpg
as measured with ruler

correction: inside diameter 8mm per better measurement with caliper

As previously shown the hollow center of the end cap is 4mm.
capscrewspec.jpg


It would appear the M4 cap screw head fits the inside of the ball bearing and has the needed thickness.

As discovered when adding ball bearings to an XV brush, very small size variations can prevent fit of metal parts, and some polishing or grinding can be needed even when the nominal specification is for the same size. Polishing can be performed by spinning the shaft in an electric drill.

Also: the shaft size on XV model brushes is also 4mm. The straight bushings used with this shaft along with the orange rubber grommet is a separate part listed on Aliexpress around $4 a pair.
The problem with using a bushing is securing the shaft inside the end cap hollow tube very tightly so the cap will not spin around the shaft when it is locked in place by clogging the bushing.

[edit] The table above must be for a particular brand. An M4 screw in the hardware store had a much smaller head. However, an english 10-32 cap screw fit just slightly loose in the bearing. The hex nut will not fit into the brush core, but the threads are of a size to cut into the plastic cap. Just a tad over the 4mm shaft size. The direction of brush rotation would be tightening the screw.

The XV model bushings and holders are over 10mm long twice as long as needed for Botvac. The holder diameter is about right, 17mm, and compresses.
Last edited by glnc222 on June 18th, 2015, 7:14 pm, edited 1 time in total.
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Re: Botvac Brush Bearing Mod for durability

Postby shirgal » June 18th, 2015, 6:55 pm

Neato Botvac Bearing size in mm is :16 X 8 X 5.
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Re: Botvac Brush Bearing Mod for durability

Postby vic7767 » June 18th, 2015, 7:46 pm

Here's another way to search for the replacement style bearing for your Botvac brushes.

688-2RSEMQ Miniature Ball Bearing ID 8 x OD 16 x W 5mm Sealed UBC/USBC
Roomba and Neato Mods, come visit: http://www.vic7767.com/

http://www.Robot-Doc.com/
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Re: Botvac Brush Bearing Mod for durability

Postby glnc222 » June 19th, 2015, 12:24 am

Here is a bushing like the XV model but sized for the Botvac, 4x7x4 mm. http://www.amazon.com/Genuine-Oilite%C2%AE-Sintered-Bronze-Bearing/dp/B006AWJREC
Most of the 4mm I.D. ones seem to be too long 6mm, while these 4mm long ones allow a gap between the bushing and the end of the brush. These bushings can be imbedded in a slice of rubber stopper about 5/32" thick.
Wrapping with some tape could make this bushing fit inside the existing ball bearing, but rubber stoppers are inexpensive. Besides, you might use this only when the bearing has already failed.
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Re: Botvac Brush Bearing Mod for durability

Postby glnc222 » June 22nd, 2015, 5:02 pm

I am collecting parts to see if a bushing can be used. It may take a month for the bushings to be delivered from China. Only larger sizes are available locally.

In the meantime a 3/8 in. dowel fits the 10mm hollow core of the brush. The cavity narrows towards the middle so that a couple inch piece fits in tightly. An M4 machine screw was in hardware with a flat shank section near the head, which will be cut off for a shaft. The 4mm shaft fits into a 5/32 in. hole and threads into a 9/64 in. hole. Rubber bottle stoppers to slice are in the hardware store.

The plug retaining the brush blades cannot be replaced by a simple fender washer. The blade ends protrude over the bearing to compact space. There is no room for an in-line fender washer. It appears possible to make a holder from a 7/8 in. bottle cap, found on smaller containers. Slots can be cut similar to the Neato plug. Another method might be hooking wire over the blade ends and held by the dowel pressed into the core.
Results await delivery of bushings. They could be used either with the Neato plug or a replacement.
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Re: Botvac Brush Bearing Mod for durability

Postby fanofrobots » June 22nd, 2015, 5:32 pm

thanks for the update
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Re: Botvac Brush Bearing Mod for durability

Postby glnc222 » July 11th, 2015, 1:37 pm

Original Brush Cap Needed

Experiments reproducing the convoluted brush cap are not promising. A shaft and bushing can easily be made, but common materials such as bottle caps are very hard to work and a 3D printer would be needed. Bottle caps have stuff inside and are soft plastic which does not cut properly.
brushparts.JPG


The bushings are called "sleeve bushings", among many types. A flanged version would be preferred but was not readily available in the small size.

Thrust bearing features: while the bearing fixes the end of the brush in the plane perpendicular to the robot body, what holds it in place side to side? It appears some of the plastic parts are sliding against each other and the bearing may play a role. If a shaft into a bushing is used, the end will likely be spinning against the side of the housing as a thrust bearing, which may well be practical with the small forces.

Bushings and machine screws are available to use the original end cap modified with the tabs for the bearing cut off, as shown above in the French experiment.

The best approach could be modifying the original Botvac to use the new Botvac-D brush when it becomes available separately. The socket in the side of the case may need to have a flange removed. The flange does not bear any forces and merely serves as a cover. The new brush end incorporates the cover in the brush end instead of being part of the housing.
Image

Maintaining the bearing: to preserve the bearing periodicially pry it off the brush and remove accumulated debris between the bearing and the end of the brush. This debris will rub against the seal.
http://www.robotreviews.com/chat/viewtopic.php?f=20&t=18765&p=132458&hilit=separate+black#p132458

Image

[edit]New Botvac-D brush Fits Original Botvac (slightly modified)
A German user fitted the new brush with more durable bushing mount in the original Botvac easily cutting off the extra flange on the side of the case. The original brushes should also still be usable without that little shroud piece.
Post http://www.roboter-forum.com/showthread.php?11222-Neuer-BotVac-2015-!/page6
As it does not appear the vanes on this brush are removable, it should become available in a few months separately.
Last edited by glnc222 on May 24th, 2017, 3:51 pm, edited 1 time in total.
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Re: Botvac Brush Bearing Mod for durability

Postby glnc222 » August 22nd, 2015, 1:52 pm

The new bearing on the "D" brush is the same as the VR200. The belt side has a different plug than the VR200. The VR200 has a metal shaft. If you can find VR200 brushes, it might be possible to replace the belt side with the plug from an old Botvac. Or move the VR bearing to the old Botvac brush. No one has done this yet.

[edit] Vic7767 mentioned the end cap plug in the "D" brush has double sided tape inside, what makes it hard to remove, for cleaning or even use on an old original brush. Warming the end in the sun, on an incandesent lamp, briefly with a hair dryer etc. may help.
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Re: Botvac Brush Bearing Mod for durability

Postby glnc222 » April 4th, 2016, 3:02 pm

April 2016. The Botvac-D combo brush is now listed at Amazon U.S. though still not in stock at Robotshop.
http://www.amazon.com/Neato-Botvac-D-Brush-Kit/dp/B018JR4T48/ref=sr_1_1?ie=UTF8&qid=1459795756&sr=8-1&keywords=botvac+D+brush
The blade brush was not found.

[edit] Also at SmartAccessoryNation drop shipper Neato direct:
http://www.smartaccessorynation.com/botvac-model-accessories/botvac-d-seriesbrush-kit

[edit] The D blade brush has some listings on ebay.

[edit] April 2016 brush in stock at RobotShop.com.
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Re: Botvac Brush Bearing Mod for durability

Postby Thunderstorm » January 16th, 2017, 5:59 am

The best approach could be modifying the original Botvac to use the new Botvac-D brush when it becomes available separately. The socket in the side of the case may need to have a flange removed

I just performed it. The robot worked for about a minute, then i heard some strange noise, so I stopped it. When i put the brush away, it was very hot near the metal part of the bearing, and he bearing is no longer moves (except for about 1 inch). I assume I accidentally broke the new brush :(

What did i wrong?
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Re: Botvac Brush Bearing Mod for durability

Postby Thunderstorm » January 16th, 2017, 9:24 am

Now I realised what caused the problem. In my case I should cut not only the flange on the gray case but also the flange on the black part that covers the brush. Now it is okay.
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IMG_0065.JPG
the flange on the black part that covers the brush
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