Feedback From The Tunnel

Been thinking the last couple days

and have a few questions.

Have always believed that you need to look at the bbl-tuner as a "system". The rest of the rifle is of course part of the system too but wanted to put that aside for a minute.

If you leave the bbl-tuner combo the same and input more energy into the system does the frequency and amplitude both increase or is the frequency a product of length?

Also what does a dampened tuner accomplish? What is actually being dampened?
How do you model in the added weight of the dampening material. Is it just that, added weight?

Has anyone actually measured the F and A on a test bbl?

Richard
 
Richard said:
and have a few questions.

Have always believed that you need to look at the bbl-tuner as a "system". The rest of the rifle is of course part of the system too but wanted to put that aside for a minute.

If you leave the bbl-tuner combo the same and input more energy into the system does the frequency and amplitude both increase or is the frequency a product of length?

Also what does a dampened tuner accomplish? What is actually being dampened?
How do you model in the added weight of the dampening material. Is it just that, added weight?

Has anyone actually measured the F and A on a test bbl?

Richard
Click to expand...

Yes Richard, I've done vibration analysis using a laser accelerometer. The barrel has its own natural frequency that it will vibrate at, at a given temperature and amplitude does not change frequency.

There is a measure able difference in different dampening mediums over and above weight alone. I use tungsten powder for its density, which is about 1.6x more than lead, and it's available sizes and flowability. It's very expensive, so if testing had concluded that a lighter and or cheaper medium worked better, I'd like to, but my own testing and studies done at Texas A&M led me from other mediums, to tungsten powder.

Weight alone has benefits, as does the dampening tungsten, too. Of course, we are limited by rules and gun hadling, as to weight.

Respectfully, I do not wish to share specific numbers that I've spend a ton of time and money learning about tuner design. But it's not floor sweep inside of my tuners. In small quantities, tungsten powder is about $100/lb. I wouldn't be using it if something else tested better.

I understand that some want to know the details of what makes a tuner work, but the thing that is important in this thread is that they do work and how to properly make one work for you. Fortunately, that's the easy part.
 
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Mike

thanks for your reply. I'm still trying to understand what does the dampening system actually damper?
What are you seeing with the testing equipment that changes? Is it freq and amp or both?
Dampening would imply that energy is being absorbed or transferred. How is that possible in a contained system?

I'm not looking for secrets, just trying to understand the basic principle of what is happening.
I have worked with dampening systems in the oil and gas industry but is a whole different setup.

Richard
 
Richard said:
thanks for your reply. I'm still trying to understand what does the dampening system actually damper?
What are you seeing with the testing equipment that changes? Is it freq and amp or both?
Dampening would imply that energy is being absorbed or transferred. How is that possible in a contained system?

I'm not looking for secrets, just trying to understand the basic principle of what is happening.
I have worked with dampening systems in the oil and gas industry but is a whole different setup.

Richard
Click to expand...

It's both frequency and amplitude, at about a 3.5 to 1 ratio on the barrels tested.
 
FBecigneul said:
Boyd; I didn't see a weight for that Cortina tuner.I should re-word that: I didn't see the weight of that tuner.
Click to expand...
The weight is the same contour as the barrel behind it. If you look, there is a parting line and in front of that the outer part is threaded onto threads cut some distance back from the muzzle. There is a smaller "tuner tenon at the muzzle end of the barrel. The point is that just moving that amount of weight works for the barrel lengths and contours that he puts them on.
 
Richard said:
The rest of the rifle is of course part of the system too but wanted to put that aside for a minute.

If you leave the bbl-tuner combo the same and input more energy into the system does the frequency and amplitude both increase or is the frequency a product of length?

Richard
Click to expand...

Richard,
You are on the right track thinking about the whole system.

Natural frequencies are proportional to (E*D^4/L^3)^(1/2), where E is Young's modulus, D is barrel diameter and L is length. As temperature increases during the day, E decreases and D and L increase. Note that if Young's modulus did not change, the barrel would get stiffer because the power of D is larger than the power of L. But the decrease in E is stronger, resulting in a decrease in stiffness and in frequency.

Natural frequencies do not depend on the input. To test for natural frequencies, the object (barrel) is tapped with a hammer and the resulting motion analyzed. Within reason, it doesn't matter how hard the hammer hit is.

Keith
 
Mike, another

question. Are you saying the tune window is better by a factor of 3.5? Or is the actual group dispersion better with the tuner left in the same position. Damped vs Undamped
Richard
 
Richard said:
question. Are you saying the tune window is better by a factor of 3.5? Or is the actual group dispersion better with the tuner left in the same position. Damped vs Undamped
Richard
Click to expand...

No, I'm saying that frequency was changed 3.5 times as much as amplitude but that both did change.
 
FBecigneul said:
Thank you.
I don't think the weight of the tuner, nor the weight of the barrel, matters all that much. It's all in knowing how far and when to turn the tuner.
Click to expand...

Bingo! But, there are advantages to having more weight at the muzzle. As Jerry mentioned earlier, a light tuner can affect tune but is more about tuning for that moment. A heavier tuner makes the node wider and stays in tune better. Moving virtually ANY amount of weight changes tune.

We're getting off subject. There are probably 5 people that care how a tuner does what it does, and 5000 that would like to just know how to make them work. The latter is much easier than the prior, too....and NO ONE knows all there is to know, yet.
 
mks said:
Richard,
You are on the right track thinking about the whole system.

Natural frequencies are proportional to (E*D^4/L^3)^(1/2), where E is Young's modulus, D is barrel diameter and L is length. As temperature increases during the day, E decreases and D and L increase. Note that if Young's modulus did not change, the barrel would get stiffer because the power of D is larger than the power of L. But the decrease in E is stronger, resulting in a decrease in stiffness and in frequency.

Natural frequencies do not depend on the input. To test for natural frequencies, the object (barrel) is tapped with a hammer and the resulting motion analyzed. Within reason, it doesn't matter how hard the hammer hit is.

Keith
Click to expand...


Keith,
I think I just said that. Lol!

That said, is it possible for you to calculate barrel rise from different amounts of barrel deflection on the vertical plane? A less stiff barrel will sag more than a very stiff barrel. How much does elasticity at varying loads matter to the speed? IOW, If I could deflect a barrel downward by .1 vs 1.000, how fast would the rise be, comparatively? Thanks!
 
If you look at Vaughn's work, the position of the center of mass relative to the axis of thrust gets into the muzzle rise amplitude situation pretty strongly, so stock design is another significant variable.
 
Mike, I don't think

it's off the subject at all. In my experience it's always been easier to fix something if you know how it works.
If for some reason the tuner is not doing what you think it ought to be doing, don't you agree it would be easier to "fix" the problem if you understood how the thing worked??

Richard
 
On the subject of tuner weight, a fellow that I know, who shoots short range group reported that while his Beggs tuner worked fine with his LV rifle that it did not seem to get much response on his HV that has a heavier contour, stiffer barrel. To remedy that situation he added a third disk and that solved the problem. It is probably best to test rather than do assumption engineering. Also, I think that tuner adjustment is about muzzle swing and damping is about higher frequency vibrations. When a rifle is fired, both happen.
 
Boyd Allen said:
On the subject of tuner weight, a fellow that I know, who shoots short range group reported that while his Beggs tuner worked fine with his LV rifle that it did not seem to get much response on his HV that has a heavier contour, stiffer barrel. To remedy that situation he added a third disk and that solved the problem. It is probably best to test rather than do assumption engineering. Also, I think that tuner adjustment is about muzzle swing and damping is about higher frequency vibrations. When a rifle is fired, both happen.
Click to expand...

Agreed, but there is a point where there is too much weight and it doesn't work like you'd think. Conversely, a stiffer barrel will be overweighted sooner than a less stiff barrel. I had to work that one out...for a while, myself.
 
Boyd Allen said:
If you look at Vaughn's work, the position of the center of mass relative to the axis of thrust gets into the muzzle rise amplitude situation pretty strongly, so stock design is another significant variable.
Click to expand...

I agree that stock design and positive compensation are not coincidental. Simply using a tuner doesn't require knowing the angle or stiffness of the stock.
 
Richard said:
it's off the subject at all. In my experience it's always been easier to fix something if you know how it works.
If for some reason the tuner is not doing what you think it ought to be doing, don't you agree it would be easier to "fix" the problem if you understood how the thing worked??

Richard
Click to expand...
No. Not if you understand how easy it is to use a tuner in the first place. How they do it, just complicates it greatly to 99.22913% of people reading this. :)

What I'd like to see at this point, is why what I see happen, time, after time, after time, after time, after time...can be happening... Instead of telling me what you think is a reason for why I can't get the results I see, please tell me why I AM. No doubt, No if's and's or but's... I AM getting these results...consistantly and repeatably. I'm all about knowing the why's and the how's......Until someone claims that the results don't add up to them. At that point, I've already concluded what matters to my scores and am only interested in why what I do, does work, not why it doesn't.

We're way beyond theory, even if some theories don't agree with the results.
 
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Well,

I guess we will have to agree to disagree on this part. I understand where your coming from but progress comes from knowledge (understanding) of whatever it is your dealing with.

Richard
 
Excessive Complication

Mike, I agree wholeheartedly with you in that some are still trying to make something hard out of using a tuner and introducing things that are of no concern to most shooters. I agree, we are far beyond theory and into practical, simple, repeatable use of tuners. I think it was you that said, 'Tuners are easy to use if you don't try to worry about how they work.' And how true that is.

I'm sure looking forward to the Cactus match in Phoenix. For me, showing is much easier than telling.

Hang in there, you've made great progress!

Gene Beggs
 
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