Stiction friction snapping

Stiction friction: That is the word I have been trying to remember: "stiction." In physics I learned that friction, the drag that happens when two surfaces slide along each other, has a higher starting value than the value when subsequently sliding along. It is a bit harder to get two surfaces sliding, than it is to keep them sliding along afterwards.

The reason that this has come to mind, is because of a very irritating phenomena has been happening at my house for, maybe, the past two or three years. It is a loud "snap!" sound that happens at the start of certain motions of certain objects in my house.

It first came to mind while using an exercise machine called a "gazelle glider" (which was something like a ski-machine I had used years earlier, except not prone to produce finely pulverized aluminum particles in my breathing space that were produced by the resistance drag in the ski-machine exerciser. The gazelle glider did not have that problem as it was just a free-swinging foot pedal thing, back and forth in the air.) It had bearing surfaces supporting front and back of each foot pedal, rotational surfaces. It worked fine for a long time - months - until one day it started producing a loud "snap!" sound as it began a particular resumption of motion each swing "Snap! Snap!" it went, and the sound seemed to go direct to the joints in my leg, as if battering them a bit, each movement.

Oiling the bearings with 3-in-1 oil, did not stop the phenomenon. Finally I took the exerciser out into the garage; it seemed more harmful than helpful.

Eventually I bought a low cost elliptical exercise machine. It worked fine for a couple months, then one day after coming home from shopping, it too started doing the same kind of "snap!" sound in its foot pedal bearing.

It sounded exactly like the Snap! that the gazelle-glider had made.

It was predictably happening at the exact same place of the movement of the feet each time, when the rotational joint shifted from rotating one direction to the other. It still does that, and I avoid using the exercise machine because of it. I can't afford to keep buying exercise machines.

Meantime, a year or so ago, the swivel chair I use at my computer here, started doing something similar. It produces the identical "snap!" sound whenever it starts to swivel, or when the seat back tilts slightly when leaning back or then leaning forward. It is a bit intermittent, not quite always doing it with an identical movement of the chair; but the hard snap-sound and jarring is always the same.

It not only vibrates hard into my hip joints and lower back joints, its sound operates against the hardwood floor as if a sounding board. The resulting snap! sound resembles the hitting of the floor with a hammer.

It is distracting every time it happens, interrupting what I was thinking about.

Yet this chair is my one luxury I treated myself to a few years ago, since I spend most of my time at the computer anymore.

Now, I don't recall ever hearing and feeling this loud hard "snap!" phenomenon before, and I have lived through some seven decades of life experiences at this point. And now it has happened to not one but three things I need to use at home. The two exercise machines and the swivel chair were bought at different stores. They all worked fine without doing the snap sound, for some time after buying them and putting them into use at home. The snap-sound is identical in all three different metal machine's joints. The snap sound does not start out weak in intensity and get worse with wear, it is full volume from the beginning, and stays that way.

So now I have recalled that there is a starting friction when something begins to slide along something else.

Oil or grease is commonly used to make both the stiction and friction be very low so as to reduce wear and energy loss in the machine, such as the pistons in an automobile engine, each time they change direction of motion, they would have the stiction happening; but the oil provides tiny slippery bearings so as to make it almost non-existent stiction. However, oiling the snapping joints on my exercise machines and swivel desk chair, does not prevent the stiction from happening.

And the intensity of the snap is very intense from the very first time it happens.

And as far as I can tell, it never quits; one has to discard the thing. They each did not start doing the snap-thing until I had had them in use for some time, months at least. And, to make it even stranger, like many odd things happening at my house, they were not that way when I left home to go do shopping - mostly at the local Walmart superstore - but were that way when I got back home. No one else is supposed to access my residence when I am gone, note; they do not have my permission, anyone. (I could rant on about that here lots more about specific happenings, but won't; just suffice to say that there may also be a deliberateness to the phenomenon's starting to happen, following my being away from control of access to the items at my home.)

The stiction snap! seems to have two effects on me: one is that it seems bone-jarring and likely to increase wear on my bone joints; and two, it interrupts my train of thought each time, greatly slowing down my mental efficiency. My RAS (Reticular Activating System) kicks in with its instinctual alert of possible danger, each Snap! and it takes a second or two for me to figure out what is going on, then I try to remember what I was trying to do just before then, to get back on track. The interruption is most intense on the computer desk swivel chair, since it uses the hardwood floor like a sounding board, racketing all over the room, like someone hitting the floor hard with a hammer, right under my seat; simultaneous with all the joints in my pelvis complaining about being hit. It is not always predictable; some movements do not make the snap in the chair, or they will move a little distance of rotation before suddenly snapping.

I have spent huge amounts of time and effort trying to cope with this weird stiction-related phenomenon, yet finding lubricant does not fix it - although it may sometimes let some movement start going before the snap is made, am not sure - and imagining some opposite to a lubricant being put on the sliding surface as mischief while I am known to be away from home. What could that substance be, I wonder.

All this was of little note, except I recently read - can't remember where - that some aircraft - I think it was an aircraft - that was having problems with something that reminded me of the stiction phenomenon magnified enormously, like I endure at home. The airplane's problem, however, was lots more dangerous, was my impression, as I try to remember more about that news item read - a month ago? This now also reminds me of an article I read long ago - maybe a decade ago, where there was a worry that saboteurs were possibly using hydrogen embedded in the ink of felt pen markers, to wipe a line across a metal surface, so the hydrogen would penetrate micro-cracks in the metal so as to increase its rate of fatigue and eventual failure. The article said there was the worry that saboteurs could casually get close enough to an airplane to wipe the modified felt pen marker on a critical spot on airplanes, so they would fail in use. Have the same mentality mischief makers come up with something that greatly increases the stiction in back-and-forth rotational bearings?

Stiction friction is not always harmful: for example, the bowing of a violin string depends on stiction to generate sound, and one applies rosin to the bow occasionally to make the stiction friction stronger.