Painting Fan Blade Tips

[Bob Bidonde]

Do you paint the tips of your fan blades a bright color? The optical illusions of watching an engine running with painted fan blade tips are interesting. I notice intermittent stops, and what appears to be reversal in the direction of rotation. Could this be useful in determining a running fault at idle? Perhaps misfiring?

[mass A man]

Very interesting. Some record turntables have "lines" on T.T. perimeter for matching the record speed to the proper rpm with a speed adjustment. The "lines" will travel either backward or forward to show person that the turntable is either slow or fast. "Lines" will appear stationary when correct speed is attained (78, 45, 33-1/3 rpms). a slight change in engine speed will do the same thing I presume on your car.

[1955cj5]

Maybe like a timing light....

[nkaminar]

Bob, good idea. I think that is a good safety feature. Bright white or florescent pink or green.

Modern florescent or LED lights flicker at 60 Hz. Our eyes cannot perceive the flickering but the lights have a strobe effect on the fan blades. The illusion of the fan stopping or changing direction at idle is because of a change in rpm. A strobe can be used to measure the rpm but it can be a multiple of the rpm.

[Bob Bidonde]

Does anyone have a video of an "A" or "B" engine running with painted fan tips?

[nkaminar]

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Bob, you may not be able to pick up the strobe effect from the overhead garage lights with a video. The frame rate for the video may be quite different than the 60 Hz of the lights. Worth a try though. You could try with an incandescent bulb or sunlight so that the frame rate of the video would have its own strobe effect.

I thought about how to paint the tips. I thought about holding brush against the fan while it was rotating, but then thought about all the paint splattered about the garage when the "paint hit the fan." I thought about spray paint on the rotating fan but that did not seem like a good idea either.

[Bruce of MN]

Originally Posted by nkaminar

I thought about how to paint the tips. I thought about holding brush against the fan while it was rotating, but then thought about all the paint splattered about the garage when the "paint hit the fan." I thought about spray paint on the rotating fan but that did not seem like a good idea either.

You'd need a real slow idle to mask the hub properly.

[fourfords]

My aluminum two blade has yellow tips. A nod to WW2 aircraft for the same reason: safety.

[Big hammer]

When I started working on light aircraft one thing I was taught, paint the prop tips and paint the backside flat black. This was a visual to the owner that you did some work on the aircraft not just looked at it . Watching from the front you can see the rotation cw and ccw at different speeds, I don’t think you would see an engine missing, so if you paint the tips for safety OK but to see an engine miss probably a waste of time