Team 665 Fan/s and More

[Greg Peshek]

Originally Posted by martin417

I have a suggestion for measuring prop speed. The device you are using in the video looks for changes in light intensity. The room you are in has florescent lights. Florescent lights flicker 120 times per second. This flickering is picked up by the photo-tach and you will not get a good reading, if you get one at all. (try aiming the tach at the overhead lights, you should get a reading of around 3,600 RPM if you are set for a 2-bladed prop). You should make your readings outside, or turn off the overheads and use an incandescent light source like a flashlight, aimed from the far side of the prop (so the beam passes through the prop) at the tach.

Good luck at your regional!

The device in the video is actually a wind speed meter. It has a little (muffin-like) fan in the center that spins and then it turns that into a wind speed. So we're not actually clocking the RPMs coming out of it, just the physical speed of the wind Thanks for the advice in the rest of the post, we'll make sure to look into it.