My neighbor called me and asked me to come check out a problem with her garage door opener. When I went over, the problem was obvious. The drive end of the chain was lying on the floor, and the drive sprocket was still in the chain.
Worse, the drive shaft stub was still in the sprocket. The shaft was cut off clean as if by a lathe cut-off tool. As I checked into the problem, I couldn't find a bearing to support the shaft where it exited the drive module. I looked all around the floor hoping to find it, but had no luck. The shaft was supported only by the edge of the sheet metal frame. The pull of the chain had slowly, over time, completely severed the 1/2-inch shaft.
It was a well-known garage door opener brand. I had one just like it, so I examined my opener. Sure enough, mine also had no bearing. The shaft on my opener was cut about half-way through. It was still intact, but it wouldn’t be for long.
How could any designer or quality inspector accept and improve such a design screw-up? It wasn't that the brass bushing was missing during assembly. It appeared as though it was missing from the design itself.
Since the openers were both out of warranty, my neighbor and I both replaced our openers with other brands.
This entry was submitted by Robert Nepper and edited by Rob Spiegel.
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Garage door openers move the heaviest moving object in your home, so it is surprising that the designers would omit a load bearring from the rotating object. However, it is still common to see metal on metal contact in consumer items. Ususally, the difference between professional and a consumer model from any manufacturer is the quality of the shaft bearrings.
Tim, even though consumer models do not go through the duty cycles of an idustrial product, poor design is not a good thing. As noted in the article, the two homeowners bought other brands.
Good point, Naperlou. This brand lost two customers -- and probably hundreds of others. I would also think there is a liability danger for damage to cars or people.
I wonder if this is an oversight or a deliberate design decision to save money. Either way, it's amazing that the company let the product out the door that way.
The door is supposed to be balanced so that there is very little load on the opener, but still, you'd think that the cycle life would dictate a bearing on the output shaft. I have a friend that owns a garage door business, so I'm going to dig into this one a little bit.
OK, I talked to my garage door guru and here's the story. Without naming names (I have friends that work for the company involved), the shaft routinely breaks on the chain version of the opener. If there's too large a load on the opener, like an improper or broken spring, or if the chain is too tight the shaft will start to wear. My door guru always carries a couple of repair kits for the chain version because the failure is very, very common. The belt version of the opener doesn't have the same problem even though it doesn't use a bearing either. There's enough play in the belt and the rubber motor mount of the belt version to prevent failure.
I think it's pretty clear this wasn't an oversight (since it failed out of warrantee).
Somebody probably got a hefty bonus the year they decided to cut the BOM by a couple $ (look at all the money they've saved over the years). Had the observer not been an Engineer, nothing bad would have happened to the manufacturer's reputation on discovery of this bad design.
Oh, wait. Nothing bad has happened to the manufacture's reputation since we still don't know who it is. But other manufacturer's also read this blog, so now they have an idea for future cost savings ...
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