Wednesday, April 16, 2008

Adding metal bearings to the Roomba 500/Roomba 570 Gear Box

Before buying my Roomba 570, I was aware that the Roomba 500 series had a design flaw that causes the gear box to fill with dust and hear which would eventually cause it to malfunction. This video on YouTube by another Roomba owner details the problem.

I was hoping that iRobot would have already resolved the issue by the time I got my Roomba. After running my Roomba for a week, I opened the gear box casing to find it full of fluff and cat hair. The dust and hair enters through rather large gaps between the roller/brush driver cogs and the hole in the gear box casing they protude out of.

I found this post by vic7767 from RoombaReview. vic7767 uses ball bearings to allow the driver cogs to protude from the gear box casing whilst keeping the gear box casing sealed (no gaps around the edges).

The sizings of the ball bearings are pretty standard and I found a local supplier of bearings that had all three sizes necessary in stock. The sizes (Dxdxw) are 23x17x4mm, 10x15x4mm and 6x10x3mm.

Here's some pictures of my mods:

Medium sized driver cog with the bearing mounted. The cog had to be filed down a bit to fit the bearing.

The large driver. This had to be filed down several millimetres too.

The large driver cog and the bearing next to it.

The smaller driver cog in place. The hole in the cog assembly had to be widened with a file.

The opening on the left is what things are like without bearings. Even with the driver cog inserted, the opening left plenty of room for dust and hair to get pulled in.

Both driver cogs with bearings fitted.

The cogs fitted in the cog assembly with the bearings. No more gaps for dust to get in. Nice.

The smallest driver cog (mates with the motor shaft) along with its matching bearing.

The smaller cog fitted onto the cog assembly. Slow and careful filing gave the cog a nice tight fit.

The cog assembly from the inside with all cogs fitted.

The fitted cogs and bearings again.

Roomba on his back with the back cover off.

The driver cogs with the brush and beater fitted.


At November 23, 2008 at 9:43 AM , Blogger Unknown said...

Hi there, that is a great looking mod! I just ordered a 570 and was going to do this mod before i even run the bot, unless of course irobot has done something to remedy this problem. I highly doubt that. Anyway i have been looking for those bearings at Mc-Master Carr and they are hard to find. What are the odds of you putting together a mod kit or something to that effect. If you could supply those bearings to me that would be fantastic. I looked at the website for the supplier maybe the three part numbers if you could. Thanks

At November 23, 2008 at 5:11 PM , Blogger PaleBlueDotCitizen said...

Excellent fix! I shall try this as soon as I get a new gearbox that isn't melted where the steel axles fit. Glad my video helped you too!


At November 23, 2008 at 5:14 PM , Blogger PaleBlueDotCitizen said...

Excellent fix! I shall try this as soon as I get a new gearbox that isn't melted where the steel axles fit. Glad my video helped you too!


At December 29, 2009 at 11:12 PM , Blogger Unknown said...

Thanks for this blog, with two cavalier king charles spaniels indoor all the time they make so much hair, I just added the bearings to our 570 Roomba. Only one comment, I had a little trouble with the gears binding not sure if it was from uneven filing or too tight and off axis. It runs ok with wait and see if any gremlins pop up. Cheers Paul

At February 6, 2011 at 2:12 PM , Blogger Unknown said...

Man, your info and what you did makes the 570 last 4-5 longer. Like the other folks, How exactly can i get those bearings?

Please help

At April 11, 2011 at 2:52 PM , Blogger Unknown said...

There is why not to do bearings mod and where to be careful, when you really think that it is good idea:
1)it takes many hours to complete. It is easy to dismount, it is easy to cut holes, but you have to fit inner outer diameter exactly and it takes lot of time.
2)it is mistake to think, that ball bearing is always better than friction bearing. Original friction "bearing" is more resistible to dust than ball bearing (but protects against hair).
My 6703ZZ Japan usd10 bearing still works after 2 month but technically is after death, because you feel lot of resistance if you try to rotate. You can use 6703-2RS, which has rubber shields instead of metal shields in ZZ bearing. It should be much more resistible against dust, but it costs twice more.
If you really want to use bearings than take care for:
Biggest bearing is thin and big. If you press it in a bit elliptic hole (not much strength is necessary, it adapts to ellipse and makes resistance to rotation. This resistance is not significant for Roombas motor but it is disaster for bearing.
Make picture of the place where gearbox string is fixed to motor. It will help you to place the motor back correctly.


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