Engineering Malpractice: Ryobi Power Scrubber

P4500 Power Scrubber

I bought one of these on eBay a few weeks ago, to use to clean my aluminum siding in preparation for painting. I paid $60. I got a chance to try it out a few days ago to clean a friend’s deck. It worked quite well for that, for maybe ten minutes. Then it slowed down and stopped, acting like it had run out of battery. I put in a fresh battery, but then when I pressed the switch it just twitched. A second battery did the same.

When I got home I contacted the eBay seller. I asked for a 50% refund and to keep the tool, hoping I could take it apart and fix it. The seller agreed, and sent me $35. I started taking it apart.

Disassembly

Taking the power head apart was fairly straightforward, once you realize that the screw holding the triangular drive has a left-hand thread. Once the cover is off, you end up with a motor with a gearbox/output shaft assembly attached. It separates by turning a lever.

Once you get the gearbox assembly out, you need to remove two layers of planetary gears (keep them organized so you can put them back in the right place). What’s left is the output shaft and bearing in a plastic housing.

Here I got stuck. I couldn’t pound the shaft out, so I put it in a press. That broke the housing, changing the project from an attempted repair to an autopsy. It turns out that there is a snap ring holding it together, hidden behind a rubber seal. To take it apart, use a small hook to pull the seal out, then remove the snap ring. Here is the assembly:

Output shaft assembly
Diagnosis

It became pretty clear that it was a bearing failure. There is a one-piece steel sleeve bearing running on a steel shaft with no lubrication. It is guaranteed to seize up within minutes. It is hard to believe that this design passed quality control and was released to manufacturing. Anyone with any experience working with machines would know that it would fail immediately.

If you look at the Home Depot site, you’ll see that about half the reviews describe a failure like this one. My guess is that the other half is people who haven’t used it enough to have it fail. By the way, Home Depot seems to now be blocking negative reviews for this product.

To verify that the steel sleeve bearing was what it appeared to be, I cut it in half with an angle grinder. Sure enough, it is one piece of steel. It is badly galled, with grooves worn in it:

Steel sleeve bearing

And here is the shaft which also has galling:

Output shaft

The shaft is 10mm in diameter, the bearing is 24mm in diameter (I couldn’t be sure about this because I measured it after cutting it — it might be 25mm). The bearing is 13.25mm thick.

Repair

I looked quickly for a sleeve or ball bearing that would exactly fit and didn’t find anything. There may be something out there, or a combination of a brass sleeve bearing and a steel sleeve that would work. You could also drill out the existing bearing to accommodate an available sleeve bearing.

If you can return it to Home Depot you should do that instead of fussing with it.

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