Testing new discovery

[Taso1000]

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

Not trying to take ANYTHING away from Knife's discovery, but I DID notice an improvement in my groups when I simply added a DIY  PVC slip on LDC to my Nova Freedom.

The ping from  the hammer hitting the valve was reduced considerably and the groups were noticeably tightened.

Just my anecdotal opinion, like the rest of them here.

Correct!  Any weight you add to the barrel or gun, for that matter, changes the harmonics of the barrel and the way it shoots.  The weight can make groups better or worse. 

Just an addition to my previous reply.  The sand/shot filled devices also change the barrel harmonics because they add mass.

We have a grasp on what adding weight or stiffening the barrel does.  We do not understand the effects of the reactive mass (sand/lead shot).

Thanks,

Taso

[rsterne]

I see a little confusion between absorbing the harmonics and countering them.

I don't see a LITTLE confusion over that, I see a HUGE amount of confusion over that.... Harmonic TUNERS are a weight that can be adjusted to cancel out the barrel vibration, or better yet, have the barrel vibrate primarily vertically so that the muzzle is pointing slightly higher when a slightly slower velocity pellet arrives at it (being launched on a higher angle) and slightly lower when the fastest pellet gets there (the lower angle helping to cancel the flatter trajectory)…. This is the principle used by benchrest rimfire competitors.... The tuner is adjusted so that the barrel is travelling upwards, but near the top of it's swing, as the bullet exits.... This requires an extremely fine adjustment, and works best with one particular pellet, at one particular velocity, and even at one specific range.... It is explained in detail on Varmint Al's website.... https://www.varmintal.com/a22lr.htm

What we are talking about in this thread (or at least the way it started), is a Harmonic DAMPER (initially using a dense "slush" of lead shot in oil), the purpose of which is to reduce or at least spread out the barrel vibration, so that more of the pellets (ideally all of them) leave the muzzle when it is pointed in the same direction.... Mike's device is intended to absorb some of the vibration, in effect exactly opposite to using a pendulum, which by definition is a resonance device.... The Damper is a "resonance cancelling device".... compare to a Tuner which is a "resonance adjusting device".... Both devices, by adding mass to the muzzle, bend the barrel downwards slightly, which if you noted in my quote from Varmint Al above increases the tendency of the barrel to vibrate vertically, which is more desirable than a sideways, or random motion.... Imagine if you will a 10 lb. weight hanging on the end of the barrel, it would not be likely to vibrate in any plane but vertical to any significant degree....

If you are using a concentric device containing a fluid (dense or not), that is not 100% full (in which case you may as well use a solid weight), then the mass will not be centered on the bore, gravity will insure it will be below it.... You can rotate an outside mounted (non concentric) device on your barrel anywhere within 360 deg. (assuming there is nothing in the way), and I'm betting that just the change in the initial bend of the barrel due to gravity (when mounted to either side) will make it work differently, depending on orientation, let alone its dynamic effect.... In the same way, moving it fore and aft, relative to the muzzle, will likewise change its effectiveness.... The same thing would apply to a solid weight that is not concentric with the barrel, of course....

This is a very complex subject, well beyond predicting by theory what will happen, IMO.... It is difficult enough to calculate the effect of a solid TUNER on a barrel (see Varmint Al's extensive website)…. Add in the effect of a moving fuild, with infinite possibilities for the mass, viscosity, and degree of movement possible.... and unless you have a Supercomputer for a brain, I wish you luck.... In simple terms, build it, and if it works, then try and figure out why.... With hundreds of pieces of data, we may eventually have some glimpse of understanding of the variables and how they interact....

mr007s, I love the idea of a Flip-Flop being slid along the barrel to tune it.... Probably as effective as any other method suggested.... 

As Taso1000 said....

We have a grasp on what adding weight or stiffening the barrel does.  We do not understand the effects of the reactive mass (sand/lead shot).

I agree 100%....

Bob

[avator]

Here ya'll go, chew on this awhile...
https://www.gatewaytoairguns.org/GTA/index.php?topic=137566.msg1387963#msg1387963

[grand-galop]

I would REITERATE  if anyone has CONCRETE PROOF of the barrel ONLY MOVING VERTICALLY???
 I have seen slow motion clips of the effect of cutting JUST one I inch on a barrel make it move side to side..

[rsterne]

Nope, in fact barrels DO move in many directions.... If you INDEX the barrel, you can reduce the side to side movement, because you are putting the primary vibration plane of the barrel from 6 to 12 o-clock.... Benchrest shooters do that as a matter of course, as it makes using a harmonic tuner more beneficial.... Adding weight to the muzzle also reduces the side to side movement.... and the amplitude of the vertical vibration.... This results in a decrease in basic group size.... That can further be adjusted by changing the weight or its position....

If you want to argue with Varmint Al, then more power to you.... he knows a lot more about this than I ever will.... Your idea of mounting a harmonic tuner in rubber is unique, I have never seen it used by the .22 rimfire benchrest crowd.... If it can be proven to work, they will jump on it immediately, as they have a pretty good handle on what works and what doesn't.... Like everyone is suggesting, build it and see.... Try it with and without the rubber, to determine which is best....

Bob

[grand-galop]

If you want to argue with Varmint Al, then more power to you.... he knows a lot more about this than I ever will.... Your idea of mounting a harmonic tuner in rubber is unique, I have never seen it used by the .22 rimfire benchrest crowd.... If it can be proven to work, they will jump on it immediately, as they have a pretty good handle on what works and what doesn't.... Like everyone is suggesting, build it and see.... Try it with and without the rubber, to determine which is best....

Bob

OK I think you get my point now..

I don't see EITHER bench rest shooter HANGING A WEIGHT UNDER THEIR BARREL.

I wish someone with a bow damper on their rifle to SHIFT IT 90*  if the accuracy is still there..

My point is/ most of the air rifle barrel are PREDRILLED. for the transfer port and no way to predict witch way the harmonic will be .. If it vibrate side to side, the hanging weight will act as a pendulum.

Enough said for me.... It is very hard to explain something nobody want to hear.

[rsterne]

I haven't been arguing that placing the damper concentric is a bad idea, Alain.... In fact, if you look back, I submitted SEVERAL designs where it is concentric with the bore.... Did you miss those?....

I disagree that the lead "slush" will act as a pendulum when hung below the bore.... Pendulums, by definition, are a resonant device.... In fact, it should act as an "anti-pendulum" due to the damping effect, should it not?.... I also agree, and stated above, that if you move the damper to the side (or some other orientation) you are likely to get different results.... I even pointed out that a concentric fluid damper will not act perfectly in line with the bore, because unless it is full (and therefore acting as a solid, not a fluid), gravity will cause the center of the shot weight to be below the bore centerline....

I built my two dampers to mount below the bore for two reasons.... 1. because it was faithful to the original design I was trying to test.... 2. because it was easy to make and fasten to the barrel.... If this damper was a "miracle cure" that worked on all rifles, when simply made and applied, then my groups would have consistently shrunk, and they did not.... Does this prove the idea is without merit, not at all.... All it proves is that this dummy could not make my simple version work.... Did I test the mounted on the side of the barrel, no!.... Why, because that is even uglier than what I used already!.... I also didn't test it on top of the barrel, because although that might be a better position (the lead shot is closer to the barrel centerline than in any other orientation) I didn't want it to obstruct the view in my scope.... Did I try different viscosities of oil, no!.... Did I try different weights, YES!....

Sometimes we learn more from our failures than from our successes.... As we learn more about how these "dense fluid" dampers work, I may try building more, but you can bet they will be concentric with the bore, for appearance, and because logically that is the best position, if for no other reasons.... For me, the "simple" versions didn't work consistently enough to conclude it was better.... Perhaps a better made, concentric version, may be the cat's meow.... Until then, my cat will unfortunately remain silent on the matter of what is the best design.... 

Bob

[grand-galop]

If it can help anyone building this type of device, even the concentric one, don't let any air go in the device before sealing it because the slightest movement will make the fluid take over the airspace.. This is a law of physic..

[Mole2017]

Here ya'll go, chew on this awhile...
https://www.gatewaytoairguns.org/GTA/index.php?topic=137566.msg1387963#msg1387963

Wow, that was some heavy duty work by those two! Very impressive. That pistol all instrumented was something:


As for motion of the barrel, George was getting some complicated acceleration patterns from two accelerometers mount top and side of the muzzle--it wasn't simple.

[Nvreloader]

Mole 2017
Very impressive photo,

A question if I can ask,

Would the bbl band/front sight, change any of the acceleration patterns from two accelerometers,
that were mounted on the top and side of the muzzle and or length of the bbl involved?

I have started reading that post, but most of it is over my pay grade. 

Tia,
Don   

[rsterne]

I intentionally have some airspace in my damper.... because that is what Mike said his had.... As per my post on their construction, 3/4 full of shot, and half the remaining space (plus all the space between the shot) filled with oil.... so the airspace is 1/8 the inside volume.... With the glued on caps, you WILL end up with some air, even if you fill the tube with shot.... and if you try and do that, the air pressure when you push on the cap will be so high you will have difficulty pressing the cap down while the glue sets.... Even the way I did mine there was significant force involved to hold the cap down while the glue set.... The shot sits on the bottom, with oil on top of it, and the air space at the top.... always.... regardless of orientation.... because of the density of the materials....

Bob

[avator]

Here ya'll go, chew on this awhile...
https://www.gatewaytoairguns.org/GTA/index.php?topic=137566.msg1387963#msg1387963

Wow, that was some heavy duty work by those two! Very impressive. That pistol all instrumented was something:


As for motion of the barrel, George was getting some complicated acceleration patterns from two accelerometers mount top and side of the muzzle--it wasn't simple.

George blew me away with his tenacity and knowledge. His collection of toys and the fact that he pretty much mastered them all is mind boggling. I mean, the guy literally went into his attic and pulled out stuff most of us don't even know exists.

[avator]

.... the dude made a device to keep a C02 cart warm.... in the gun.

[Nvreloader]

Taso

Thank you for the info,
What I found for the material used inside that recoil damper is,
Clean Sterilized Sand, size of 15-20 mills, and the inside tube is filled between 75 to 90% of volume.

The inventor is: Robert S. Mizek,  Current Assignee New Archery Products Corp

Quite interesting reading all the designs of these devices etc.

Tia,
Don

Taso

That 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

Don,
I found the patent number on the packaging label: 5016602
Thanks,
Taso

[Mole2017]

Mole 2017
Very impressive photo,

A question if I can ask,

Would the bbl band/front sight, change any of the acceleration patterns from two accelerometers,
that were mounted on the top and side of the muzzle and or length of the bbl involved?

I have started reading that post, but most of it is over my pay grade. 

Tia,
Don

In reply 264 of that thread, he has a picture of both accelerometers on the end of the barrel. The picture I copied has either an accelerometer, miniature microphone, or some optical sensor (I see a faint fiber coming out of it) on top near the band. I'd have to reread parts of that to be sure. My understanding from a relatively fast reading was that he based this motion conclusion on the end of the barrel accelerometers. In the picture I copied, I think that is another miniature microphone or a pressure sensor on the side of the valve body. He was testing for a couple of things at different times in that thread.

My experience with accelerometers is that you can think of the signal from them as like that of a microphone--they don't measure the same thing, but the signals are "loaded" about the same with stuff all across the spectrum of what is happening. I used to tell the students that if you can hear it (e.g. noise and sounds from an apparatus), the accelerometer can see/feel it. If you can get displacement or even velocity instead, things can often be easier to understand. Acceleration can be a tough signal to make sense of in real life.

[grand-galop]

Just an addition to my previous reply.  The sand/shot filled devices also change the barrel harmonics because they add mass.

We have a grasp on what adding weight or stiffening the barrel does.  We do not understand the effects of the reactive mass (sand/lead shot).

Thanks,

Ta so
[/quote]

For those of you that have the desire to look for a method to find the closest frequency to match their rifle, look at the video provided in the link..

The best frequency for canceling the barrel vibration is when the mercury look like a target....That type of frequency is REGROUPING THE FLUIDS TOWARD THE CENTER..

YouTube ( Abstract sound frequencies with liquid mercury in a subwoofer)

[KnifeMaker]

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

Not trying to take ANYTHING away from Knife's discovery, but I DID notice an improvement in my groups when I simply added a DIY  PVC slip on LDC to my Nova Freedom.

The ping from  the hammer hitting the valve was reduced considerably and the groups were noticeably tightened.

Just my anecdotal opinion, like the rest of them here.

Of course you noticed an improvement by adding an ldc. It is the air striper effect and is well known.


Additionally, you added weight to the end of the barrel, helping the needed vertical rather than as much 360 barrel whip.


 Now add this to the LDC and watch what happens. 


Knife

[K.O.]

been wonderin' about a non magnetic mass suspended in ferro fluid... If it would be more effective than just fluid damping..?

something along this direction... could have springs in it also...

https://www.researchgate.net/figure/A-ferrofluid-inertia-damper-based-on-levitation-of-a-nonmagnetic-object_fig4_316217925

[K.O.]

well actually maybe no springs and three magnets or more... stacked  neodymium (stacked round or cylinder)... two glued to the caps arranged to suspend ( N-NS-S) the middle magnet in ferro fluid... magnetic spring..

https://www.kjmagnetics.com/products.asp?cat=1&scri=18&scri=19

[Taso1000]

I did a little research on particle dampers.  From one research paper I found, they said that the particle damper attenuates more frequencies than viscous dampers.

I have not found if the particle damper attenuates frequencies quicker than viscous dampers. 

I did find that by hitting an object, you can pick up the resonance frequency with a microphone.  Does this frequency match the barrel frequency when fired?  My guess is that the resonant frequency would be slightly different as there are different forces involved.

I have not found how to tune particle dampers yet.     I'm sure it's got to be a simple equation as in what mass of particles (sand) is required.

Thanks,

Taso