Okay, TUNERS AGAIN. Bukys/Schmidt style versus Beggs???????????????

[tim in tx]

Tim Calfee has tried the weight behind the muzzle as is popular in centerfire were weight is a major issue.He went with lighter barrels and the tuner out in front for a very specific reason.

The reason is simply so the barrel will flex and bend more .In a physical sense the barrel can only flex more when weight is added from the forces created on it which ultimately is creating more vertical angular dispersion at the muzzle and less linier dispersion Keith spoke of by making the weak spot just behind the crown about 1 inch back.This is what I am doing and is the only way to correct large velocities and now every thing in between as well,and out in front gives a given weight more leverage to do that and the correct weight in the correct distance from the muzzle will do that .It will point the muzzle up when the area just behind the muzzle is forced down effectivly causing lagging behind or a tip up ,every barrel has this tip up weighted or not and behind the muzzle or in front ,but by adding weight in front we are just making it bigger and timing the exit properly out in front just plain and simply makes it flex enough for the distances we are shooting. For example: In a few weeks we will be trying some large velocity corrections at 1 mile and possibly longer and in front is the only way to get enough correction or bending to go the mile. I know this is possible because I can get a bullet 120fps slower to hit a good 1 moa higher then the faster of the 2 at 1000yds and repeatedly .The fact that I can overcorrect in the adjustment at 1000yds shows there is still plenty of correction left in the bending and that I could converge them out to longer distances with at least 60 fps ,this is a heavy straight taper,brake/ adjustable tuner with plenty of recoil force to make this work . But less recoil force as in rimfires takes more extremes to flex or bend the barrel and center of gravity at only 1 inch below the centerline does not help any either .That is why Bill must hang over the end on rimfires.On genes behind the muzzle the bending or width of tune is narrower then a forward weighted which is iirelivant since you can adjust and keep a precise tune through out the day. but if he were to be shooting 1000yds he would have to make the barrel bend more for more correction either by going to a skinny barrel or adding weight in front of the crown to have enough correction for 1000yds . So my point is it depends on how much do you need the barrel to bend.

Tim in Tx

 

[mks]

Keith, what's your best guess as to frequency of the wave utilized for 'tuning.'

al

Al,
Frequency implies that the wave is periodic, i.e., that it recurs repeatedly for many cycles. Because muzzle motion is transient, there really isn't a "frequency" that can be identified in the same way that we can for steady-state harmonic motion. Below is a plot of the angular motion of a 105mm tank gun muzzle measured by Blakney in 1978. It is for a millisecond of time centered around projectile exit. The time interval begins at upper left. The nose of the shell leaves at "X" and the tail leaves at "O." The shell exits during a part of the curve that is changing horizontally, but has very little vertical change. Not so good for tuning. If it came out earlier or later, the muzzle angle would be swinging downward. Even worse for tuning. The only good part of this curve is the last part where the muzzle angle is swinging up and left. The swinging up motion is good for tuning, but the leftward motion creates horizontal dispersion.

I haven't found any 2D measurements of small arms muzzle angle like these. But one might expect that they behave similarly, with curves that wiggle all over the place with little repeatable motion. The problem of tuning a rifle is one of keeping bullet exits on a good part of the curve (a "window"). The curve may have several good parts, some better than others.

Cheers,
Keith

 

[Vibe]

Al,
Frequency implies that the wave is periodic, i.e., that it recurs repeatedly for many cycles.

Technically that's not true.
A wave form can have period and frequency even if only part of a cycle is completed, or is of any interest. Just as a nodal point can form in the first formation of that wave form - particularly in cantilever vibrations of the lower modes. The most common demonstration of this is flipping a fishing pole one time up and down. The node point will form less than 1/2way through the first 1/2 flip.

 

[mks]

Technically that's not true.
A wave form can have period and frequency even if only part of a cycle is completed, or is of any interest.

If you use frequency to describe a partial waveform, you are presuming that you know what the rest of the waveform would look like, had you waited long enough for it to occur. It is therefore the periodic form that you are referring to. With due deference to Rod's cartoon, Wikipedia says "Frequency is the number of occurrences of a repeating event per unit time."

Let's take an example of a curve that looks like a half sinusoid that occurs in half a second. If you said that its frequency is one cycle per second, you could easily be wrong, because there are an infinite number of other possibilities for the rest of the wave that would cause it to not have that frequency.

Some of the higher modes of barrel vibration do have a chance to become established before the bullet exits (like Chris Long's radial mode), but I think the transient motion is more important. The Lissajous plots of muzzle angle that I have seen do not have features that are repeatable enough to allow classical harmonic motion to describe it.

 

[alinwa]

So really, ya's don't have a CLUE whether or not the angular displacement is greater at the muzzle while using one tuner design over the other.

tim in tx is the only one who's really shown anything, by artificially weakening the area behind the muzzle and forcing the angle. That's real stuff right there!

al

 

[mks]

So really, ya's don't have a CLUE whether or not the angular displacement is greater at the muzzle while using one tuner design over the other.

tim in tx is the only one who's really shown anything, by artificially weakening the area behind the muzzle and forcing the angle. That's real stuff right there!

al

Tim is DA MAN!

 

[Boyd Allen]

Al,
If you go back and look at pictures of one of Calfee's rimfire pistols that were published in PS, you will see that he thinned down the center of the barrel. Also, Merill Martin did an experiment on a .22 match rifle, decades back, thinning the center of the barrel to double deflection with a given load, and adding weight at the muzzle with a couple of split collars. He was able to tune out the difference in vertical between high velocity and target velocity ammo at 50 yards. This was pre BOSS, and well before I had read of Calfee. One thing that is interesting to look at is the formula used to calculate the deflection of a cantilevered beam. Playing with different barrel lengths and contours with Lilja's program can also be instructive. I have had tapered barrels stepped when mounting tuners, initially to remove weight economically, but upon consideration, this may have mad them more responsive to a given weight of tuner. Of course this is just a guess.
Boyd

 

[tim in tx]

Tim is DA MAN!

Thanks Al and keith But no I am nowhere near what you guys can do.It is nice to see the scientific brains hard at work,you guys give mechanical engIneers[shooters] a good solid foundation to start with.I am sure as gene said can happen if we all pool together on this.The collective knowledge that is on the brc forums is unreal .I am just a shooter and like you guys and am looking for that majical tune or the truth which ever comes first[lol]...Luckly I can make anything I need to test any theory or claim and I am glad to share.Good luck to you all. Tim in Tx

 

[CYanchycki]

Well fellas this is when things are getting above my head.......................

Pretty much anything after Rodney posted is getting to technical for me. It is to bad Shelley is gone. He had thoughts and ideas and that is what I hope the rest of you fellas who have the knowledge can try to figure out. Then HOPEFULLY share it so a match will be decided by who can read the wind and not get burned by it and not all the other BS that goes into trying to make a rifle shoot.

I guess that would make the sport boring but there are a lot of us who UNFORTUNATELY do not have the knowledge or ability to experiment. We want to compete non the less.

Thanks for all you have given and are giving to the sport.

Calvin

 

[Lynn]

Tuning pianos for over 3 decades now I have traversed from the old fashioned method of doing it by ear to using modern Electronic Tuning Devices (ETD) and then like many others, I presently use a combination of the two called hybrid tuning. The ETD's are extremely accurate but cannot fully address issues that we remedy by using a trained ear.

Vibration segments on a string are supposed to be perfect divisions related to fractions. The null points appear at 1/2, 1/3, 1/4, 1/5 ect... of the length of the string in theory. Because the string is fixed at both ends, it is stiffer there, and upsets the whole perfect symetry that is supposed to occur. The result is increased inharmonicity as you move higher up the ladder of smaller string segments (partials or overtones). This is why pipe organs and pianos cannot be tuned to each other; piano tuners equally split up the errors that occur from inharmonicity.

I assume that a rifle barrel is effected in the same way but maybe to a lesser degree because only one end is fixed in the action. The fundamental frequency or its first partial overtone are what I see depicted in theories of rifle barrel harmonics. Naturally, these two have the highest amplitude or actual movement. Certainly attaching anything like part of a scope on even the rearward section of a barrel will effect whats happening at the end of it. Its position and mass will effect the vibration by either dampening or even sympathetically vibrating with it, possibly even increasing sustain of the vibration. It will also effect where the segmentation occurs.

I have moved the strike point of piano hammers on strings quite a bit from where it should theoretically be (1/7th of the speaking string length) and notice that the 7th harmonic does not increase in amplitude like it should as I move away from its null point. This flattening/widening of the null point is a result of string stiffness as you near its hitched end. Although rifle barrels are excited in a different way from shooting as opposed to piano strings being hit by hammers, the barrels are much thicker and stiffer than strings and also firmly attached and partially dampened at one end...I cannot imagine that these would not widen out a null point to an area rather than a perfect intersection....as theory would say.

Either way, we deal with the anomolies of piano string inharmonicity by fudging a perfect theoretical tuning; we divide the errors up in an ordered progressive way. If there is (rarely)an issue with an unwanted overtone and I adjust the strikepoint of the hammer, I do so with experimentation. There is no way I could work out the theory, measure the string and aim for a sweet spot and find it...at least not yet. I guess this is no different than what the folks do with the barrel tuners.

I'm sure there are a few scientists grinning and thinking that excited strings, organ pipes, and rifle barrels follow the same principles of physics. I agree in part, but disagree also, because real life applications don't show such a perfect match. We have all this technology now to test things yet the irony is in the fact that Pythagorus had much of this figured out 2500 years ago.

His "FEA" analysis of the time was composed of a long rope hitched between two posts with reflective mirrors attached on it at different lengths. Parts of the heavy rope were carved away to compensate for the slight mass of the mirrors in order to keep the rope mass constant. The rope was strummed and the light off the mirrors were reflected on to the side of a cliff. A crude but effective ocsiloscope. Because of the long rope length, the vibrations were slow enough to watch and actually count in relation to time. He figured out that there is an inharmonicity occuring that does not follow the perfect mathamatical theory of segmentation...in the context of musical notes of the scale, this error is called the "Pythagorean comma". Because of this error, the vibration segments do not have perfect null intersections, nor do they have precise location points as theory would imply. The null may not be as flat or long as I've seen in some of B.C.'s sketches, but it certainly is not as perfect of a point as many of his detractors claim either.

From another website

 

[Growler]

Calvin
The fun of tinkering and experimenting is an attraction to this sport but IMO The top 20 shooters are the shooters that practice, practice ,practice and learn to read wind flags well. These 20 could probably swap rifles and still be in the top 20. 90% of this is shooting and reading flags, 10% or less is the last few thou in each group that the FINE details of the tune gain you. Too much emphasis is placed on the newest and latest bullets, powder, gain twist barrels, tuners and scopes. This is all important but miss one flag and a screamer goes 1/2 inch. At my level I will concentrate on the flags as I see more gain to be had improving my shooting skill than some of the smaller details. The details will come when I can recognise how goups are forming and why. You will compete and improve your placing faster buy shooting and paying attention to the flags effect on the group rather than the tuners. This is for my level of skill and I am not speaking for anyone else. BUT when its January in Canada its easier to bench race than get out to the track.

Rob

 

[CYanchycki]

You are right Rob. I am far from the point of having TOTAL confidence in my equipment, bench manners, and wind reading. I guess that is why it is nice to have multiple rifles. I plan on setting one up just to play with and HOPEFULLY figure out at the farm. That will be the test as to whether or not the tuner thing makes sense or not. Kind of like my day in the gopher patch. The rifle that appears to be my number 1 will stay simple and basic.

Yes, most definately winter sucks up hear. Granted this has been the MILDEST with the least amount of snow I can EVER remember in my almost 46 years walking the ground of Manitoba.

Calvin

 

[Boyd Allen]

Lynn,
What a learned, well written, informative, and interesting post you have given us. It does a fine job of explaining why theory may only get you part way there, and adds new (to me) information to the discussion of tuners. Thank you.
Boyd

 

[Vibe]

If you use frequency to describe a partial waveform, you are presuming that you know what the rest of the waveform would look like, had you waited long enough for it to occur. It is therefore the periodic form that you are referring to. With due deference to Rod's cartoon, Wikipedia says "Frequency is the number of occurrences of a repeating event per unit time."

Let's take an example of a curve that looks like a half sinusoid that occurs in half a second. If you said that its frequency is one cycle per second, you could easily be wrong, because there are an infinite number of other possibilities for the rest of the wave that would cause it to not have that frequency.

The Thomson sub gun fired at a rate of 500 rounds a minute - and usually only held 30 to 50 rounds - yet the frequency was valid.
On a lighter note this sort of reminds me of a skit of a hippy clocked at better'n 80 miles an hour
"Man that's impossible, I haven't even been out an hour".
http://www.youtube.com/watch?v=MhliLCJKZGA

If we are dealing with part of a cycle that appears to be a particular wave, describing it in those terms is perfectly valid, even if it then does something else after we are no longer concerned, or it no longer affects our outcome.

 

[mks]

The Thomson sub gun fired at a rate of 500 rounds a minute - and usually only held 30 to 50 rounds - yet the frequency was valid.

I think the correct analogy would be trying to define frequency if you only fired one round. Without more information, you have no idea when the next will fire, thus frequency is unknown. If you have fired 30 rounds, then it is definitely a periodic event. We may have to agree to disagree on this one.

 

[Vibe]

I think the correct analogy would be trying to define frequency if you only fired one round. Without more information, you have no idea when the next will fire, thus frequency is unknown. If you have fired 30 rounds, then it is definitely a periodic event. We may have to agree to disagree on this one.

Possibly. Though to continue your analogy of the 1/2 wave form - quite obviously you would need much more than a single data point to have determined even that - and probably enough to make some valid generalizations.

 

[jackie schmidt]

Come on, Francis, NEVER let a good dose of practical application get in the way of a good theory.........jackie

 

[CYanchycki]

Thanks Francis I needed a GOOD chuckle after the day I had today.

I am hoping the tuner works just as you and Paul say and along the lines that Rodney appears to find it working for him. That is all I want and need to know.

Calvin

 

[Vibe]

Stick with me kid; you'll have diamonds as big as your elbows.
I suppose in Canada you remember the old line by Ethel Mermann, "Pure as driven slush".

Coming to Murfreesboro, AR.? I think 42 carats is the largest found - not as large as an elbow, but it could happen.
LOL.

 

[Gene Beggs]

Gene Begg's classes in practical application go deep enough for me.
put da round things on your barrel near the end the bullet comes out.
Shoot da good load.
Twist the round things when told to do so by your DA thing.
Bring the wood home.
Well, I didn't quote Gene exactly but this is how the tuner works. Talk of frequency, wave form, periodic event, Thompson sub-machine gun?, angular displacement confuses Cal Yanchycki and me. We, and Jackie, will watch the windflags and adjust the tuner, though we don't know why.......... Oh, we keep copious note as well. They help.
Thank you, Gene Beggs

Francis, you da' man, I like the way you think! Keep it simple; huh?