Fri 12 Mar, 2010
I spent more time with the Audacity software this afternoon and have uncovered an interesting interpretation of the acoustic data re: that 401.8 foot per second shot I was warbling on about the other day. You will recall that the problem was, I had a hard time believing that the particular shot in question (as represented by this video, 20100307132756(2)), had ever actually made it up to the 401.8 fps claimed by the chronograph. Before chucking in the towel on this “record breaking” shot, I had attempted to analyze the sound of the shot by looking at a graph generated by the aforementioned software. As it turned out, I needed to boost the bass and change the tempo with out changing the pitch. That done, the following graph emerged. It helps to magnify this photo to see what I’m going on about.
If we look at the area shaded in the darker blue, it seems this represents the time the bolt was actually in flight. For all intents and purposes the bolt leaves the machine at the first initiation of the sound pulse. The thump from the catapult going off, and the string vibration, and the whirring from the bolt, all smooge together and show up as the area of decreased frequency between the .015 mark and the .041 mark. It all culminates with the heavier bass tones of impact, witnessed by the denser lines visible on the graph from the .041 mark onwards to the end. I believe that the bolt from the video was in flight from the .006 mark to the .041 mark. In other words it took .35 seconds to zip downrange and punch a hole in the archery backstop.
The other piece of information we need to confirm the velocity of this shot, is the range to the target. I had previously misreported that as being 50 yards. More careful measurements with a tape measure now show it to actually be 47 yards from the face of the target to the tip of the bolt as it rested on the machine in the cocked position.
Armed with this new information, 47 yards in .35 seconds works out to be 402.8 feet per second. This is very close to the 401.8 feet per second reported by the chronograph.
It appears that I may have psyched myself out and allowed morbid incredulity to defeat what my eyes were seeing on the chronograph. At least for now, that’s my story and I’m sticking to it.
For one brief shining moment, it looks like Firefly jacked a 7,000 grain bolt up to 401.8 feet per second, and generated 2507 foot pounds of energy. Who knows?, maybe that was what caused that strand to break. In any event, the above video and its sound signature, along with the positively measured 47 yard range, is evidence anyone else can analyze if they want. I present it in this posting to hold witness to my belief that this level of performance was momentarily achieved by Firefly.
Good on you old girl. Now we have to fix you up so you can do it again.





















