My furnace has recently been failing to heat the house, and after a bit of investigation I discovered that the fault was in the inducer motor. (The inducer motor powers the fan which induces, i.e. sucks, the air through the combustion chamber.) I did some lubrication and manipulation of it, which managed to coax it into working for another day or two until a new motor arrived.
Replacing it turned out to be about maximally difficult; the inducer fan had rust-welded onto the shaft and even copious amounts of WD-40 specialist rust remover did nothing to loosen it. I eventually had to drill out not only the screw which held the fan onto the motor shaft but the motor shaft itself, then I had to resort to using a claw hammer to pry the thing off. Once that was done taking the old motor off and putting the new motor (and new fan which I had fortunately thought to also purchase, just in case) was the work of a few minutes.
Once my furnace was back to heating the house I turned my attention to the motor, because I was very curious what was wrong with it. From the occasional screeching sound, the help of lubrication, and the fact that once in a while turning it backwards allowed it to start spinning freely in the correct direction, I had thought that a piece of metal debris had gotten lodged in the motor.
It turned out to be wrong.
It was actually that one of the two bearings on which the motor shaft rested had rusted out and disintegrated to the point of no longer working.
If you’re not familiar with how a bearing is constructed, there is an inner sleeve and an outer sleeve. These sleeves are held apart by a number of balls. The outer sleeve rotates against the inner sleeve by rotating these bearings; they reduce the friction of rotation because—being spheres—a tiny fraction of them is actually in contact with either the inner sleeve or the outer sleeve. Moreover, they allow the two sleeves to rotate relative to each other by rolling along both, rather than by the sleeves rubbing against each other. They’re ingenious inventions.
There is, however, the problem of keeping the balls between the sleeves. This is done with some walls and also with what one might call a retaining bracket. If you look, you can see that the retaining bracket on the ball bearing of my motor had rusted into nothing in parts (specifically, the lower right part). Actually, that’s probably not quite true; I suspect it had mostly rusted by some small parts hadn’t rusted but instead got caught into the balls, preventing them from rotating smoothly. That would explain why counter-rotating it might occasionally allow the shaft to spin freely—it would have dislodged the tiny bits of metal and moved them to somewhere harmless. Until they fell back in the way, again. Which in practice seemed to be every few hours.
This is the problem with metal—it is very hard, but it is dead. It cannot repair itself from the wear-and-tear of life, so it eventually fails. In theory one could have taken the motor apart and thoroughly cleaned it, periodically, to prevent the build-up of the sort of grime which causes rust, but this is still a living thing fixing a dead thing.
This is the curious thing about life. All things are dying, and can only survive by being continually renewed. Avid fans of Chesterton will note this as Chesterton’s Post:
We have remarked that one reason offered for being a progressive is that things naturally tend to grow better. But the only real reason for being a progressive is that things naturally tend to grow worse. The corruption in things is not only the best argument for being progressive; it is also the only argument against being conservative. The conservative theory would really be quite sweeping and unanswerable if it were not for this one fact. But all conservatism is based upon the idea that if you leave things alone you leave them as they are. But you do not. If you leave a thing alone you leave it to a torrent of change. If you leave a white post alone it will soon be a black post. If you particularly want it to be white you must be always painting it again; that is, you must be always having a revolution. Briefly, if you want the old white post you must have a new white post.
He went on to note, by the way, that these is as true of human institutions as it is of material objects; this is a curious property of our universe—truths always have echoes. You can find this idea in C.S. Lewis’s essay Myth Became Fact, but you can also find it in real life. I once had a pumpkin which grew large and looked beautiful but when I went to harvest it it had turned out that mice had eaten almost the entire thing from the back and inside. It’s a wonderful metaphor for all sorts of things—modern universities, for example—but it also was a very disappointing event in my garden, years ago.
Our universe is full of echoes.
Edit: as Mary in the comments pointed out, the story I quoted is Chesterton’s Post, not Chesterton’s Fence. (Thanks, Mary!)