There's certain things that are a given, such as a shorter/stiffer/thicker barrel will oscillate at a higher frequency Why? Stick a ruler over the end of the desk and smack it. A longer/softer/thinner barrel will oscillate more and likely has a lower resonant frequency.Adding weight to the end changes things, of course, and adding more barrel clamps will "shorten" the end that oscillates. Adding more mass to the end (not an adjustable weight) will likely drop the frequency/increase the oscillation if I remember my wave theory, but at this point, I'm perfectly happy to sit back and read.
Quote from: anti-squirrel on June 22, 2019, 11:14:59 PMThere's certain things that are a given, such as a shorter/stiffer/thicker barrel will oscillate at a higher frequency Why? Stick a ruler over the end of the desk and smack it. A longer/softer/thinner barrel will oscillate more and likely has a lower resonant frequency.Adding weight to the end changes things, of course, and adding more barrel clamps will "shorten" the end that oscillates. Adding more mass to the end (not an adjustable weight) will likely drop the frequency/increase the oscillation if I remember my wave theory, but at this point, I'm perfectly happy to sit back and read.Agree. And the frequency is most sensitive to changes in the length.Found these formulas for estimating natural frequency of simple systems on the inter-web:http://www.me.utexas.edu/~dsclab/leks/DSC_Vibration_Modeling.pdfCheck out appendix C, formula (C-33) and appendix D, formula (D-10). First is the barrel only, second approximates the barrel with a weight on the end.Here is a pretty good overview of spring mass damper theory:http://www.me.utexas.edu/~dsclab/leks/DSC_Vibration_Modeling.pdfEqn (21) in this is equivalent to the result in appendix D in the above link.
I drew up another design, this time for a double damper with one chamber each side of the barrel....The holes could be any size you want, also the hole for the barrel.... You could use setscrews to slide it along to adjust the position.... The advantages are that it moves the weight of the shot up close to the barrel C/L, it isn't in the way of the scope, and it would work with a full length reservoir, providing there was about a 1/8" gap between the reservoir and barrel or shroud.... It also eliminates one other concern I have with the concentric designs, where they have limited clearance between the inner and outer tubes for the shot to move around in (the shot has to climb up between the inner and outer tubes)….If you don't have access to a machine shop, you could probably fabricate this by using copper tubing and end caps, soldered to a thin flat plate that goes across the two tubes, leaving enough room for the barrel between them.... A simple clamp, with a couple of screws below the barrel could provide the clamping action, or even cable ties....Bob
The advantage of 3D printing a damper, Matt, is that you could close the ends, leaving one end thick enough, and with a hole, that could be tapped for a removable plug to fill it or change the mass or fluid.... If the hole was 11/32", it could be tapped to 1/8" NPT for a pipe plug.... providing the printed material was strong enough for threading, of course....Bob
I took a hint from George Schmermund. I don't have the high tech equipment, so I downloaded "spectrum analyzer pro " on my smartphone. I use a Samsung S9, it has a sound processor that operates at 48000 hz, so these frequencies can be analyzed by using the built in microphone. His 2240 ( iirc ) had a 133 hz harmonic. By tapping on the barrel of my 2240 with 14 inch barrel I found a harmonic at 193 Hertz. I tapped on the barrel of my new Hatsan Flash QE, it has a harmonic at 366 hertz. I did not hear the 2240 at all because the human ear cannot hear much below 200 hz, but I can definitely hear the Flash. If I can figure out how to duplicate those frequencies then I may be able to try the dampers without wasting ammo.
My device is heavy. Too heavy for hunting. At 14-something oz's.
By tapping on the barrel of my 2240 with 14 inch barrel I found a harmonic at 193 Hertz. I tapped on the barrel of my new Hatsan Flash QE, it has a harmonic at 366 hertz. I did not hear the 2240 at all because the human ear cannot hear much below 200 hz, but I can definitely hear the Flash. If I can figure out how to duplicate those frequencies then I may be able to try the dampers without wasting ammo.
Did you tap on the shroud of the Hatsan, or the unshrouded barrel? Could you attach a damper to the barrel, and the tap it and record the frequency and see if it dies away faster than without the damper?
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