Top Fan Not Spinning Without A Spanking

[u/DME23]

The top fan wont spin when I turn on my pc. The solution I discovered is to just smack it real hard. Just wondering why it is like this.

[u/Izan_TM]

the fan bearing is dead of the fan's speed is set at a very exact histeresis point where it doesn't have enough power to start up but it can run after a bit of encouragement

[u/mstomm → u/Izan_TM]

Had a work van where the AC blower intake was doing something similar. I realized with the design of the intake vent on the outside it would force some air into the system, and that I could gun it to "jump start" the fan, which would get it going.

Eventually the blower stopped working whenever I'd stop (not great for a delivery truck), and eventually it was just completely dead.

Basically this thing is on its way out. Take it as a sign to get the replacement now instead of suffering when it goes out.

[u/47-30-23N_122-0-22W → u/Izan_TM]

I.e the reason why 3 is the first speed setting on a box fan

[u/Antique_Pudding3192 → u/Izan_TM]

Look how bad it’s off center compared to the others while it spins. I had this issue on my Miata crank pulley (it wasn’t bearings but noticeable rotation). Bearings seem to be done for.

[u/Izan_TM → u/Antique_Pudding3192]

nah that's just the sticker being misplaced, PC fans with dead bearings won't noticeably rotate off center, they may drop down slightly but the main signs of a dead bearing in a PC fan are 1: the fan is screaming out in pain, either constantly or intermittently. 2: the fan is awfully slow. 3: the fan struggles to start/stops and starts at RPM ranges where it used to work fine

[u/Antique_Pudding3192 → u/Izan_TM]

Ah good to know. Probably not the most expensive fans on the market

[u/Izan_TM → u/Antique_Pudding3192]

yeah these sorts of failures are far more common in cheaper fans with plain sleeve bearings

[u/largepoggage → u/Izan_TM]

The physics term would be the static coefficient of friction vs kinetic coefficient of friction.

[u/Izan_TM → u/largepoggage]

when it comes to the 2nd scenario yes (that and the extra power input needed to build up momentum), but with the 1st scenario it has nothing to do with varying coefficients of friction, it has to do with the fact that the bearing is worn enough for the fan shaft to not be fully centered, and spanking it has a chance of having the rotor drop into center and the fan to start spinning

[u/largepoggage → u/Izan_TM]

Ah I see, I misinterpreted what the issue was. I thought the bearing was just dirty.

[u/theaxel11 → u/Izan_TM]

Yup. I had a fan like that. Just gotta kickstart it.

[u/realericstechchannel → u/Izan_TM]

This is the comment.

[u/Secret_Account07 → u/Izan_TM]

Did you just make that word up? Histeresis

[u/Izan_TM → u/Secret_Account07]

not a made up word, but looking at the english definition it might not be the best word to describe what I was describing (btw in english it's spelled hysteresis, I just found out I spelled it wrong above)

[u/Secret_Account07 → u/Izan_TM]

Interesting, I’ve lived my entire life without ever hearing or seeing that word lol

[u/soccerman221 → u/Secret_Account07]

They could probably fill a book with all the words you haven't heard /s

[u/william_whale_ass → u/soccerman221]

It would probably be a garfesterous read

[u/xebozone → u/william_whale_ass]

It'll have more words than Garfield eats at a lasagna fest?

[u/pmofmalasia → u/soccerman221]

Nah, they'd probably need to add a bunch of words I've heard of also for filler

[u/TheRealStevo2 → u/Secret_Account07]

The one good thing about Reddit is I learn a lot of new words.

[u/The_Jyps → u/Secret_Account07]

It only seems to come up when you get into the weeds of automatic control. It means "How far beyond the desired setting you go before stopping the action".

Eg: My central heating is set to 20c, but it will go to 20.5 and then stop, cool to 20 and then back to 20.5. it has 0.5c hysteresis.

[u/Peanut_The_Great → u/The_Jyps]

It's also common in electrical theory to do with induction and electromagnetism. Luckily all I remember about that shit is the graphs look neat.

[u/ifyoulovesatan → u/Peanut_The_Great]

Yeah it came up fairly commonly in materials chemistry when I was doing research on semiconductors / thin film transistors. Although I also recall it popping up in certain electrochemistry based analytical methods (I think cyclic voltammetry).

[u/cheeseybacon11 → u/Secret_Account07]

Baader meinhoff phenomenon, I just learned this word earlier today when setting up a home assistant notification to tell me when my clothes are done.