SPAL brushless fan

[Bitsyncmaster]

I changed my software to give 5 settings as you adjust the pot.

1) 22.97 %
2) 42.01 %
3) 56.96 %
4) 74.04 %
5) 92.01 %

FYI:
My micro has a 10 bit resolution on setting PWM. So the PWM is divided up into 1024 steps from 0 to 100 %. Not that you need that accuracy in this application. Those values remain at very accurate values since it's all based of the micro clock.

[Bitsyncmaster]

I had to use free air testing RPM of the SPAL fan because the side on intake has a flat surface to put a reflective tape on.

Here are the five speed checks with PWM as last listed.

1317 RPM
2088 RPM
2678 RPM
3385 RPM
4013 RPM

RPM check is only to reference what the fan is doing at those selected PWM control. It means nothing in measuring fan performance comparisons.

By the way, the fan has quite a bit of thrust at high speed. I would guess thrust could be a way to measure performance.

This test was done at 13.0 volts but I don't think voltage affects this fans speed. I will test that.

Tested at 15.0 volts and as expected RPM is pretty much the same. Current drops some at higher voltage, also expected with electronic switching regulator in the fan motor.

[Helirich]

Interesting. I'll think about it while I'm driving. (Got a few hundred miles to go today.)

[Bitsyncmaster]

You could use these fans with stock wiring setup with my controller set to a value that limits the current. Just wire up the fan power and my controller power to the stock fan wires and then it would switch on with the otterstat and AC.

But for that high dollar cost it it going to provide more, less or same amount of cooling?

[Bitsyncmaster]

Now I'm thinking that thrust is a good way to compare fans. Any comments on that thought?

What I was thinking is make a fixture that you bolt the fan and the shroud to that has four arms (levers) that pivot on the bottom. Movement only has to be one inch at the top. Longer arms are best to reduce the affects of friction and weight of the fans. Then a string passing over a pulley with a weight on it is used to measure the thrust which counteracts the thrust.

[Ron]

If you are only looking to compare for performance, why not suspend them from a pivot, mounted back to back, and see which pushes which...?

[Bitsyncmaster]

If you are only looking to compare for performance, why not suspend them from a pivot, mounted back to back, and see which pushes which...?

That would really make it more interesting.

I thought about suspending as an option but you have rotating forces.

[CFI]

This statement is true, but all air speed indicators I know of have static ports. So I'm not sure what your point is. If your saying the placement of the static is important, that's true for a moving vehicle, but for a mounted fan, just place it out of the wind. .

The vast majority of GA aircraft have a static port separate of the pitot tube.

[Bitsyncmaster]

I'm still thinking about this thrust test. I could just hang fan from two wires and setup a pulley weight system but not sure if the weight of the fan would affect the accuracy. I would think the lever arrangement would has less affect with fan weight.

[Bitsyncmaster]

The vast majority of GA aircraft have a static port separate of the pitot tube.

Yes that static port was always plugged from mud dobbers when I was flying. Good thing the preflight had you check it.