Thomas wrote on May 18^th, 2008 at 9:59am:


Thanks for letting me know. I'm glad that my suggestion was of use. Your result seems very consistent with expectation. The 400 fps is undoubtedly a slightly optimistic muzzle velocity and .177 cal air rifle pellets lose velocity extremely quickly. Additionally penetrating the first sheet of paper would have also wiped off a few fps. Would it be possible to get a truer reading by bringing the target closer and using the report of the pistol as the timing start?

Aussie

Aussie

I used the two page method because that will be my slinging setup outdoors in the park after the target frames are ready. The sound record also includes the discharge sound. The sounds from a slinging setup should be virtually identical and the tiny sound from the sling itself will be useless unless I find some of those pull string firecrackers. 

tom 
 

Thomas wrote on May 18^th, 2008 at 7:58pm:


Maybe your sling is quieter than mine but I had no trouble hearing or recording the swish, even outdoors. Try it as you may save yourself a good deal of work. The beauty of this method is that it eliminates the need for accuracy in your slinging. I was just banging away at my "couldn't possibly miss it at that range" garage wall at a distance of 8.1 metres.

Even if it really doesn't work you may try adding a small whip cracking tail to your sling which should make a louder swish and have no effect on velocity. Should be easier than the double screen method.

Aussie.

PS. I used the comparatively small distance of 8 metres because the projectile's speed loss should be minimal and the time interval is large enough to be measured with a high degree of accuracy. This gave me a very close approximation of release velocity. The two screen method would be very useful for determining how much velocity drops off at any given distance from the slinger. Provided you can record the sound of the release you would be able to calculate both the average velocity for the entire cast and the final velocity between the screens, all from the one sound recording. INTERESTING! Please write up your results if you go down this path. If you want to be super pedantic you could assume the speed of sound at 300 m/s and make corrections to the time intervals according to their individual distances from the recording device.