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Old Oct 27, 2007, 02:18 AM
I'm Ginger & called Adam
Ginger Adam's Avatar
Hereford, UK
Joined Oct 2002
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Question
Headspeed from video footage?

Can the headspead of a chopper be worked out from video (actually the audio channel) of a flight - either filmed from the ground or onboard footage?

Adam
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Old Oct 27, 2007, 02:56 AM
0 Carbon fp? don't breed!
DarkHorse's Avatar
www.dhrc.rchomepage.com Gloucester/Cheltenham Gloucester, Great Britain (UK)
Joined Oct 2004
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If the motor, gear and paddle noise doesn't cloud the audio too much. Yes if you can filter out the noise to reveal a clear fat low frequency sine wave of the main rotor. Then you can measure the number of samples or time taken for 2 cycles and work out the RPM (using an audio editor program).
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Old Oct 27, 2007, 03:30 AM
I'm Ginger & called Adam
Ginger Adam's Avatar
Hereford, UK
Joined Oct 2002
2,903 Posts
KISS principle - I hadn't thought of that ! I was thinking a bit of software (like that used to measure aircraft speed by doppler) but you're right about simply viewing the wave in an editor.

I'll give it a go and see how clear it looks.

Maths check - 1600 rpm would be about 53Hz (assuming I get a 'beat' from both blades)?

Adam
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Last edited by Ginger Adam; Oct 27, 2007 at 03:48 AM.
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Old Oct 27, 2007, 09:11 AM
Our Daddy and Heli Junkie
Fred Bronk's Avatar
In Heli Wonderland
Joined Aug 1999
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I have been told with video at around 30 fps the rotors will looked "stopped" about every 900 rpm.

This shows in a couple videos I have of a Raven with a 1800 HS, the blades seem stationary much of the time.

FB
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