Fans spinning faster after a while

[thewhat]

Just something I noticed with SpeedFan:

As you can see, in 16 minutes "Fan1" speed increased by about 10 RPM, while "Fan2" increased by about 15 RPM.
I should also mention that "Fan1" are actually 2 fans (joined with a simple cable splitter), while "Fan2" are 3 fans.

Now, either SpeedFan is somehow secretly increasing the speed little by little (it shouldn't, below a certain temperature threshold) or something else is causing them to rotate faster over time.

(Again, to avoid confusion: fans are always supposed to be spinning at 18% and 20% speed and they are, according to Speedfan. But the actual RPM is always changing a little bit.)

What's the explanation? Is it because of fans/motherboard/PSU warming up?

 

[lsv]

Could be the fans warming up and being able to spin easier as the lubricant inside warms up slightly from use?

 

[thewhat]

I guess that could be possible.

The fact that the 3 fans ("Fan2") increased slightly more in speed than the 2 fans made me think about some "electrical" explanations.. I'm not sure there's any logic behind it, I'm just observing.

 

[Flat Mop]

Wierd... stupid idea, but maybe it's to do with the fan blades gaining momentum over time.

 

[The Boston Dangler]

you need to post temps and fan speeds from the same time

 

[Flat Mop]

you need to post temps and fan speeds from the same time

that would definitely help.

 

[imabiggles]

Wierd... stupid idea, but maybe it's to do with the fan blades gaining momentum over time.

Nope, else we have a free energy machine. It has to do with the warming of the monitoring circuitry, the fan rotor warming slightly, and mostly pushing warmer (less dense) air - loads the fan less, hence spins faster. Should settle out once the case temp settles.

 

[Flat Mop]

Nope, else we have a free energy machine.

Problem, science?