those okie cushins look ridged , the newer Hy tecs have a flexiable core with a (powder) weighted end, they attach at one end only, allowing the weighed end to act and react to the initial vibration with a slight delay to counter the first movementmy Hi Tec should be here Friday from flea bay, got to go see my friend who owns his welding shop to source a piece of steel to fab my mounting bracket(clamp)then we are off to the race to calm my P-15 down. it has a 23" LW barrel shooting 25 gr(25 cal) at 970 fps. groups are a little bigger than they should be at 50 ydI believe the end of the barrel is flickering multiple times in a not exactly repeating the same pattern with each shot, more fractal in natureour targets show the non repeating results
ADDING A TUNER.... Adding a tuner to the muzzle of a rifle barrel does the following: 1. The additional mass reduces the amplitude of the vibrations. 2. Decreases the natural frequencies by decreasing the lower Mode's frequencies more than the higher Modes. 3. Increases the barrel's vertical end sag due to the extra weight. This would tend to make the vertical plane the preferred plane of vibration. 4. Moves the Mode 2 node closer to the muzzle.
For those of you who haven't seen this website, I suggest you have a look, it explains a lot about barrel vibration modes, and the frequencies involved.... Mode 1 and Mode 2 are the predominant modes of vibration....http://www.varmintal.com/atune.htmIf the bullet/pellet was arriving at exactly the same time during the vibration mode, then it would shoot to the same POI.... Here is Varmint Al's summary of what the addition of a tuner does....QuoteADDING A TUNER.... Adding a tuner to the muzzle of a rifle barrel does the following: 1. The additional mass reduces the amplitude of the vibrations. 2. Decreases the natural frequencies by decreasing the lower Mode's frequencies more than the higher Modes. 3. Increases the barrel's vertical end sag due to the extra weight. This would tend to make the vertical plane the preferred plane of vibration. 4. Moves the Mode 2 node closer to the muzzle.He then talks about what happens when you move the position of the tuner.... This should apply to any "solid" mass rigidly fixed to the barrel.... How a dense fluid tuner varies is only speculation at this point, IMO....Bob
Perhaps I am misunderstanding what you are trying to build.... but sliding a weight along the barrel is basically trying to change the harmonics so that the pellet arrives at the muzzle when it is pointing in a consistent direction.... In other words, you are tuning the barrel for a specific pellet and velocity, exactly what the rimfire benchrest shooters do.... This harmonic tuner I made does the same thing....The threaded steel sleeve is screwed onto the barrel and tightened in place.... The brass weight moves back and forth to tune the vibration of the barrel to your pellet and velocity.... It is 28 TPI, so it only moves 0.003" for each "hour" (30 deg.) you turn it.... I have not had the opportunity to do much testing, but I understand movements as small as 0.002-0.010" can make a big difference in group size, depending on the weight you are moving back and forth....The difference between moving a solid weight and using a mass of "lead slush" (or mercury) is that I think the latter would have a wider "sweet spot", and be less critical on placement.... The reason I suggest that, is that if with one pellet and velocity the barrel is not moving much, the damper effect would be small.... However, with another pellet and velocity, that is not shooting well because the barrel is whipping around, the damper should have more effect.... That, logically, to me would be why it seems to work better on improving "poor" bullets or pellets.... The moving shot "damps" the vibration, rather than "tuning" it to a given frequency like moving a solid weight does.... JMO....I have been giving more thought to the viscosity of the oil in the damper, and I think the "thinner" it is, the better.... We are dealing with a very short duration event here, the pellet is only in the barrel for about 3 mSec (0.003 sec.)…. At 850 fps, it travels the last 2" of the barrel in just 0.2 mSec.… As viscosity increases, the fluid takes longer to move for a given force applied to it.... Think about dropping a single #8 shot onto grease, heavy gear oil, light hydraulic fluid, or water.... It might take days for it to make a dent in the grease, a minute or more to drop an inch through the heavy gear oil, a second or two through the light hydraulic fluid, and almost no delay through the water, even though the water is more dense (ie oil or grease float on water)…. Mercury is probably the ideal fluid, because it is nearly twice as dense as lead shot (13.6 vs. 7.0), so the same weight takes up half the volume.... In addition, it's viscosity is only 1.5 (water being 1.0), whereas a light hydraulic oil (like the power steering fluid I used) is about 80, and 30W motor oil is about 350.... Simply put, for a given force applied, the lighter the oil, the faster the lead shot can respond to the barrel vibration.... and it doesn't have long to respond during the 0.0002 sec. it can affect the flight of the pellet.... Mercury can respond even faster.... Bob
TasoThat is the same thing I found,"A patented POWDER Compound", is several devices I found on line etc.No reference to what type of powder compound, so far. If the patent # is given, and you could find the info in the patent office, it might list what type of powder is used inside etc.Tia,Don
both methods will workBob uses a static weight adjusted to the highest node of the vibratory cycle Grand-galop's pendulum method is reaction, to counter or create an anti force to the vibration, thus neutralize itit is just easier for me to assemble the store bought pendulum
Yes, barrels vibrate in 360 degrees.Since all this is in the educated trial and error part of development I don't think there is a clear winner in which configuration works best. I think we're in the "not know the effect of the dampers" on the barrel harmonic mode. Whether liquid filled or dry even. I could see where the dry dampers will react quicker and thus may be better for higher frequency cancelation. The oil filled dampers may be more suited to lower frequency vibrations. Maybe one of each or two of the same configuration would also work, kinda like anti-squirrel mentioned earlier.I don't know anything. But, if I had a choice of mounted to the side of the barrel versus surrounding the barrel, and if they were both equally effective, I would choose surrounding the barrel for aesthetics. Thanks,Taso
I dont know, but could be everyone is over thinking this. I spent a good amount of time Googling and reading on this subject. I even found post where O-Rings were placed on the barrel and moved to where best groups were produced. Another one had a flip-flop hanging from the barrel, not pretty but effective. Maybe think less is actually more, but like I said, I dont knowI
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