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Affect of Slowing Down Fans and their Life
- Thread starter LyL18
- Start date
Sleeve bearings (plain bearings, the same type that supports the crankshaft in a car) wear only during starts and stops. While the fan is spinning, the shaft is supported entirely by a thin film of oil. There is ideally no metal-to-metal contact while the sleeve bearing is running. Ball bearings wear constantly, because there is constant metal-to-metal rolling contact. Properly designed ball bearings last a very long time, though.
If a sleeve bearing is run too slowly to maintain the oil film, the fan shaft will ride directly on the bearing, resulting in quick self-destruction. Just about all brushless DC fans (the kind in your computer) are designed to operate reliably between 5 and 13.8 volts[1]. The fan electronics will start operating around 4 volts, but generally with insufficient torque to start the fan moving.
Keep the fan voltage greater than or equal to 7 volts and you'll be fine.
If the ball bearings are high quality and properly sealed, the limiting factor is grease life, which is primarily affected by bearing temperature. The grease slowly breaks down over the months and years, and eventually it just doesn't lubricate like new.
In all cases, the slower the fan runs, the cooler the bearing, therefore the fan experiences less wear, and enjoys a longer life.
Dust eventually gets into sleeve and unsealed ball bearings, gumming up the oil (for sleeve bearings) or grease (for ball bearings). I have an almost totally seized fan removed from an AT power supply that the owner never cleaned out. The fan is extremely difficult to turn by hand (let alone on the original motor) after eight years of dust buildup, and the power supply overheated and caused the machine to constantly reboot. One new fan and a bit of Pentium 166 overclocking later, and the owner has a working machine again
It is possible to disassemble a sleeve bearing fan to clean and re-oil it; I've personally done it twice. Whether you want to do it or not is a matter of how much your time is worth. Use sewing machine or electric motor oil (3-in-one is ok). If the fan is whining loudly, the bearing has already been damaged, so cleaning won't accomplish anything and you should probably throw the fan out. Replacements are only $5 or so
P.S. NEVER EVER USE WD40 AS A LUBRICANT! WD40 is a very light oil that evaporates (dries out) very quickly, collecting dust and leaving no lubricating qualities whatsoever. It's very good for coating metal to prevent rust, to dissolve certain glues (like the kind left behind when you peel a sticker off something) and as a cutting agent while drilling holes in metal.
Don't believe me? Good! Critical thinking =
Check out the Electronics Cooling Magazine (there are magazines for everything) article on fan life here (check out the other articles in that month here for other neat stuff) and Sam's Repair FAQ entries on fans here.
[1] Hah, my first forum footnote. 13.8 volts is the voltage found on a charged car or other 12 v lead-acid battery. Don't power your fan off the cigarette lighter socket while the engine is running, though! Unfiltered auto power is very dangerous for electronics due to the possibility of huge voltage spikes and the virtually unlimited current capacity of the battery.
If a sleeve bearing is run too slowly to maintain the oil film, the fan shaft will ride directly on the bearing, resulting in quick self-destruction. Just about all brushless DC fans (the kind in your computer) are designed to operate reliably between 5 and 13.8 volts[1]. The fan electronics will start operating around 4 volts, but generally with insufficient torque to start the fan moving.
Keep the fan voltage greater than or equal to 7 volts and you'll be fine.
If the ball bearings are high quality and properly sealed, the limiting factor is grease life, which is primarily affected by bearing temperature. The grease slowly breaks down over the months and years, and eventually it just doesn't lubricate like new.
In all cases, the slower the fan runs, the cooler the bearing, therefore the fan experiences less wear, and enjoys a longer life.
Dust eventually gets into sleeve and unsealed ball bearings, gumming up the oil (for sleeve bearings) or grease (for ball bearings). I have an almost totally seized fan removed from an AT power supply that the owner never cleaned out. The fan is extremely difficult to turn by hand (let alone on the original motor) after eight years of dust buildup, and the power supply overheated and caused the machine to constantly reboot. One new fan and a bit of Pentium 166 overclocking later, and the owner has a working machine again
It is possible to disassemble a sleeve bearing fan to clean and re-oil it; I've personally done it twice. Whether you want to do it or not is a matter of how much your time is worth. Use sewing machine or electric motor oil (3-in-one is ok). If the fan is whining loudly, the bearing has already been damaged, so cleaning won't accomplish anything and you should probably throw the fan out. Replacements are only $5 or so
P.S. NEVER EVER USE WD40 AS A LUBRICANT! WD40 is a very light oil that evaporates (dries out) very quickly, collecting dust and leaving no lubricating qualities whatsoever. It's very good for coating metal to prevent rust, to dissolve certain glues (like the kind left behind when you peel a sticker off something) and as a cutting agent while drilling holes in metal.
Don't believe me? Good! Critical thinking =
Check out the Electronics Cooling Magazine (there are magazines for everything) article on fan life here (check out the other articles in that month here for other neat stuff) and Sam's Repair FAQ entries on fans here.
[1] Hah, my first forum footnote. 13.8 volts is the voltage found on a charged car or other 12 v lead-acid battery. Don't power your fan off the cigarette lighter socket while the engine is running, though! Unfiltered auto power is very dangerous for electronics due to the possibility of huge voltage spikes and the virtually unlimited current capacity of the battery.
You make sense! Another thing is don't run your fans warped. I mean make sure they are 'square'. I work in the surveillence industry in a casino and we use Pelco PTZ's (pan, tilt, zoom cameras). Those things are cooled by 60mm Sunon fans held down by 2 nuts, one on each opposite corner. If you tighten them down too far thus warping the fan on 2 corners even slightly will kill the fan live enormously. A fan that lasts years will last a month. Trust me I know that much.
miazmaticdotcom
Gawd
- Joined
- May 3, 2003
- Messages
- 545
I am running a computer case fan off car DC power:
http://www.hardforum.com/showthread.php?s=&threadid=730038
So far, it's been working fine.
http://www.hardforum.com/showthread.php?s=&threadid=730038
So far, it's been working fine.
The normal voltage range available from your car's electrical system (and therefore being sent to your fan) is between 9 and 15 volts while the engine and alternator are running. Lower voltages will occur while the engine is idling or when a low battery is charging. Typical car voltage with a charged battery running at speed is around 14-15 volts.
Due to the way inverters function, the lower the input voltage, the harder the power supply has to work to maintain the desired outputs. However, the lower the input voltage, the slower your fan will spin. This shouldn't be too much of a problem as long as your battery, alternator, and belts are in good shape. Loose connections elsewhere can result in other problems, but unless you're driving a 23 year old Citation around, those shouldn't be too much of a problem
Make sure all your connections are well insulated, because that lighter socket can supply literally 20 amps or more. Melting wires and exploding transistors belong in the lab, not inside your inverter
miazmaticdotcom
Gawd
- Joined
- May 3, 2003
- Messages
- 545
Well, they're all done up with electrical tape and stuff. But you're right, exploding shat does not belong in the back of my mom's car