Barrel Behaviour Theory

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Bigtravoz
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Re: Barrel Behaviour Theory

#16 Postby Bigtravoz » Fri Jun 01, 2018 9:14 pm

Oh and then there’s the metallurgical part of it, heating and cooling cycles effecting molecular structure, tension imparted through various processes including button rifling, fluting etc. natural hard and soft spots from impurities or incomplete homologation of ingredients in the steel manufacturing etc. when mathematical equations can be applied to all of these we can then use theories to equate to the perfect shot every time. But that would make it boring and we would never miss.

John T
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Location: Brisbane

Re: Barrel Behaviour Theory

#17 Postby John T » Sun Jun 03, 2018 10:20 pm

Hello Peter.

Your topic has caught the attention of two of the icons of our discipline, Alan Fraser and Rod Davies; along with those of us who want some empirical knowledge of the building blocks of rifle tuning.

Those who advocate, make, sell and use barrel tuners will be near breathless awaiting your exposition which will augment the gospel according to Esten.

Do not be deterred by "contributions" which attempt to anticipate and then denigrate your theories, before allowing you the courtesy of even your first expression.

Those "contributors" have their own agendas which are tangential to your intention.

Ignore them; just as we who have genuine interest in hearing your theories shall ignore them.

It is timely that you give us your next post.

Regards,
John Tracey.
3.6.18

!Peter!
Posts: 84
Joined: Sun Oct 30, 2016 6:35 am

Re: Barrel Behaviour Theory

#18 Postby !Peter! » Mon Jun 04, 2018 6:25 am

Bigtravoz wrote:So are we inferring that a barrel only waves up and down when a bullet is fired through it? If this is the case you need to re evaluate your thoughts. Calling what a barrel does a wave is incorrect it is closer to a three dimensional oscillation, that also envolves a torsional twist effect.


I'm not inferring that the barrel only waves up and down at all. At present I'm just laying out 101 of waves so idealised 2 dimensional waves are used which is the standard way this material is taught.

Bigtravoz wrote:There are a number of factors and variables envolved and has been proven many times mathematical theory relative to it is just that, theory!


The purpose of this thread is not to be a dissertation on predicting exactly what the barrel will do, but to understand the physics involved so that people may understand what is going on on the target and what changes to try to optimise the rifle system.

Just because you can't calculate the exact barrel behaviour does not mean the laws of physics have been repealed.

!Peter!
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Joined: Sun Oct 30, 2016 6:35 am

Re: Barrel Behaviour Theory

#19 Postby !Peter! » Mon Jun 04, 2018 8:20 am

Continuing on with the theory...

One of the things that's not well illustrated in the physics classroom link I provided is how a travelling wave forms a standing wave. I found the animation below which shows it well. The green wave and red wave are the travelling waves and the blue wave is the resulting standing wave.

Image

This only happens when the travelling waves are the right frequency.

Here is a picture of the result of two wave adding together to show how different the resulting wave can be.

Image

This is a bit I was hesitant to present but I think it is needed... There is a technique to work out what sinusoidal waves make up a wave such as the resulting wave in the image above. The technique is a Fast Fourier Transform. There are other methods but this is the most common and even included in Excel.

If you want to learn more then you can search the web for "Fourier Series" and "Fourier Analysis". BUT BE WARNED this maths is covered about midway though undergraduate engineering degrees. SO I STRESS you don't need to know the maths, for this thread it is sufficient to know that all waves can be represented by a number of sinusoidal waves of various frequencies and amplitudes, and there are mathematical techniques to work out what they are.

The image below is the result of Excel's Fast Fourier Transform on the resulting wave above.
Image

I have attached two versions of the Excel worksheet I used to make these images for people to play with. The file "Wave Interference.xlsx" only has the waves and the file "Wave Interference.xlsm" has the waves and Fast Fourier Transform. The Fast Fourier Transform version uses a macro to automate the update of the calculation and requires the data analysis add-in to be enabled in Excel to work.

The instructions to play with the Excel worksheet are:
- Change the amplitude and frequency of Wave 1 and 2 to see the resulting wave. These cells are highlighted yellow.
- When you want to see the spectrum, press the "Update Spectrum" button next to the cells highlighted yellow and "ok" the message box warns that you are going to override data.

Enjoy!!

!Peter!

EDIT: I found a mistake in the Fast Fourier Transform spreedsheet "Wave Interference.xlsm" and have updated the file and the wave spectrum image.
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Last edited by !Peter! on Wed Jun 06, 2018 2:38 am, edited 2 times in total.

Frank Green
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Re: Barrel Behaviour Theory

#20 Postby Frank Green » Mon Jun 04, 2018 11:14 am

O.K. Bear with me for a minute and if this isn’t the place for this and should be in a different thread then let me know and please forgive me.

On a short note we are talking harmonics and vibrations in relation to how the barrel shoots. Are we only talking the barrel itself?

So here is my question right now and again it might be way off subject....So where does the action and stock fit into all of this?

A rifle stock and how it is fitted and I will add how it is made and designed can create harmonic/vibration issues and will effect how the rifle shoots as well and I will say it will effect the harmonic and vibrations back to the barrel.

The action and what goes on with it and how the barrel is fitted up is another.

If I’m getting off of the main subject let me know.

Wal86
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Location: Kilmore, VIC

Re: Barrel Behaviour Theory

#21 Postby Wal86 » Mon Jun 04, 2018 12:03 pm

ditto
Last edited by Wal86 on Mon Jun 04, 2018 8:38 pm, edited 1 time in total.

williada
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Re: Barrel Behaviour Theory

#22 Postby williada » Mon Jun 04, 2018 12:27 pm

Pete you are on the right path. The standing wave is what I tried to address in the other thread Pete but what I am over is posting long explanations getting caught up in opinions that are just that, opinions; because generally people are not trained to understand it. That's not their fault and addressing the concepts is the best way to go. Some may grab one part and think its the holy grail and go off half cocked because you have to water it down then you get the judgmental, convergent thinking, pedants who want to knock it off because one tiny aspects is not technically correct because you have watered it down to meet a common man's understanding a tad in the first place. But over time people can be brought up to speed. That's important. That is a trade off just like we have to make with barrel variables. Its a lot of bloody work which some people grab and you never hear from again and often they don't put back into the sport which drives my interest. So I really admire you for having a crack. You have to develop a thick skin and beware of tyre kickers and treading on some tribe members toes.

Some of our best ideas get developed and patented overseas. A public forum may prevent that legalistic commercialization which is not part of the Australian culture but is creeping in with world trade. I am amused when I see tuner specs etc I ran with many years ago used by other commercial ventures o/s but calculus was invented in two places independently by chance at the time or someone quotes a barrel length determined by my testing for the NRAA which was voluntary over several years using much of my equipment. Yet a political decision was made with one team to run with 30 inch barrels because the leaders said we couldn't get people to extend their gun cases despite a couple of years worth of evidence which is now accepted as optimum. Or a decision to run with a profile that was second best in the testing because of procurement issues that I was not party too. In the end you do your own thing and work with like-minded people because there are those that rest on antiquated past laurels. F Class has shaken a lot of those beliefs now.

I have shared vibration analysis for some 20 years with some notable big time winners in TR and F Class and kept out of the limelight because that is not my quest. I developed the system in the 1980's while working with barrel manufacture because it is quicker and more reliable than data analysis approaches. Working with machinery and metallurgy gives greater insight to the importance of vibration even when chambering. Great barrels have limited life and cleaning rods destroy them.

Wal is a smart man. He has picked up on the fact that bullet speed is less important in normal conditions. Yes of course group size is sacrificed to run at higher speed sometimes to drive through turbulent air or to counter the elliptical formation of groups at very long range or to remain above the transonic zone. SD etc is an indicator and has been flogged to death for years as the holy grail. It has its limits.

The williada method uses vibration analysis. I think I am the first to apply this reasoning to barrels in a productive way. I use horizontal charge tests not vertical ones to paint the picture and a few other techniques I have posted in basic form before. There is obviously a lot more to it at an advanced level. I remember Craig M scratching his head with a predicted load before he won with it. But in order to teach why it works which was my goal, it takes a lot of shots as we debunk the myths. But a trained eye can pick up the big picture in a timed round robin charge test which is why I chose to work with an interested development group in recent years when asked by Craig. Poor Tony was the bunny for a few years because I had limited time due to ill health which modern medicine is now keeping me going. But it did mean theories were independently tested by a few others. This is definitely not to say other methods do not work, its the one I use because I know what I am doing and there are justifiably many ways to skin a cat. The secret is to do what you know best. Learning to read conditions of course is the most important aspect of long range target shooting.

Below is a sample I re-post of a very simple mud map of vibrations which won another Queens prize in FS some years ago for another bloke. It was predicted his worst range would be 1000 yards, which it was where he nearly lost the event. It was an area he had worked out but did not know why his load worked before he decided to run with it on confirmation. There are of course better barrels than what was used but this setup given the time frame was sufficient. That aspect brings in more refinement of the basic vibration analysis.

Vibration.jpg


So Pete, the above map while not perfect may assist with the concepts of where you are taking people.
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williada
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Re: Barrel Behaviour Theory

#23 Postby williada » Mon Jun 04, 2018 1:00 pm

I am not going to steal any one else's thunder and will back off now. This is Peter's thread. Its not just the barrel but a whole system from fulcrum points to stock design to barrel profile and smithing that have to be systematically synchronized. The best barrels eliminate some of the variables when determining cause and effect.

!Peter!
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Re: Barrel Behaviour Theory

#24 Postby !Peter! » Mon Jun 04, 2018 1:11 pm

I got some time to add some more info.

It’s not apparent in the physics classroom on waves what happens immediately after a travelling wave is started.

With the exception of a signal generator used in a lab, the initial shape of a travelling wave is rarely a perfect sinusoidal shape as shown in the figures in the physics classroom. However, whatever the shape of the travelling wave, it can be represented by a series of sine waves each having a different amplitude and frequency.

Each of these individual sine waves will lose energy and reduce in amplitude at different rates changing the overall shape of the wave seen. The sine waves which are oscillating at a harmonic frequency will lose energy much slower than the other sine waves.

A good example of this in action is a gentleman who built and tuned his own Marimba which is like a large wooden xylophone (sorry to any musician I just insulted, please forgive me! [-o< ). On the web page below he presents the results of hitting a Marimba bar in various locations with various hammers and records the sound waves and does a Fast Fourier Analysis to show the spectrum of these waves.

http://www.lafavre.us/FFT-mallet-position.htm

From his results you can see that where he hit, and the type of hammer used causes different initial waves which changed over time as the components of the initial wave which are not oscillating at a harmonic frequency quickly lost energy.

Applying this to what the barrel is doing before the bullet exits, we have to look at the relative times of everything. If the bullet is gone before non-harmonic frequencies lose much of their energy then the harmonics has little effect and the shape of the initial wave has greater effect. If the bullet is gone after non-harmonic frequencies have lost much of their energy then harmonics has greater effect and the shape of the initial wave has less effect.

!Peter!
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Joined: Sun Oct 30, 2016 6:35 am

Re: Barrel Behaviour Theory

#25 Postby !Peter! » Mon Jun 04, 2018 1:36 pm

Frank Green wrote:On a short note we are talking harmonics and vibrations in relation to how the barrel shoots. Are we only talking the barrel itself?

So here is my question right now and again it might be way off subject....So where does the action and stock fit into all of this?

At the moment I'm just talking about the physics of waves.

The action and stock have a big influence as well. One aspect is the boundary behaviour discussed in the physics classroom where a pulse goes across a boundary of different densities. Boundary behaviour also comes into play at the other end of the barrel as well.

The other aspect of the action and stock influence I haven't come to yet, but will...

williada wrote:Pete you are on the right path.


That's a relief!! :D

williada wrote:I am not going to steal any one else's thunder and will back off now. This is Peter's thread. Its not just the barrel but a whole system from fulcrum points to stock design to barrel profile and smithing that have to be systematically synchronized. The best barrels eliminate some of the variables when determining cause and effect.

This thread is open to everyone and I welcome all contributions. I'm just giving back to this site as I've learnt a lot from the contributions of everyone here, especially you, williada.

And yes I do have a very thick skin.

Bigtravoz
Posts: 94
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Re: Barrel Behaviour Theory

#26 Postby Bigtravoz » Mon Jun 04, 2018 7:30 pm

[quote="Frank Green"]O.K. Bear with me for a minute and if this isn’t the place for this and should be in a different thread then let me know and please forgive me.

On a short note we are talking harmonics and vibrations in relation to how the barrel shoots. Are we only talking the barrel itself?

So here is my question right now and again it might be way off subject....So where does the action and stock fit into all of this?

A rifle stock and how it is fitted and I will add how it is made and designed can create harmonic/vibration issues and will effect how the rifle shoots as well and I will say it will effect the harmonic and vibrations back to the barrel.

The action and what goes on with it and how the barrel is fitted up is another.

If I’m getting off of the main subject let me know.[/quote]

Actually I see some very relevant points. Different actions attach in very different ways for instance some (such as savages)have a barrel nut which holds the recoil lug and controls headspacing which means that the end of the thread of the action doesn’t butt up into the action where the Remington 700 style actions ( of which there are many different manufacturers) trap the recoil lug between the end of the action and the barrel where other actions (Mauser,and others) actually rely on the barrel bottoming out within the action. Each of these will create different harmonics through the barrel, somewhat like when you ring a bell hanging from a string, unmollested it will ring true For quite a period but touch it with your finger and the vibration is disrupted and the ringing stops. Same would have to occur with different mounting methods both to the action and the stock. It is also why in some rifles having the forestock providing pressure to the barrel helps control group sizes by creating a consistent disruption to the vibration. (Not a method I agree with.)

Bigtravoz
Posts: 94
Joined: Sat Apr 22, 2017 7:43 pm

Re: Barrel Behaviour Theory

#27 Postby Bigtravoz » Mon Jun 04, 2018 8:14 pm

In your moving graphic Peter you showed the blue line with peaks much higher than the main waves, this is in theory what using a tuner should be aiming to control, reducing the radical peaks, and potentially increasing or decreasing the frequency of the other waves thus reducing and or stabilising how large each oscillation is to make the outcome easier to read. Somewhat like the ferrite cored lump on various cables cables does to stabilise the frequency through it and stopping radical off frequency waves interfering with other equipment ( there’s a correct name for it that’s right on the tip of my tongue, wish my brain still worked like it did ten years ago, I swear I am getting early onset Alzheimer’s some days!)

I wouldn’t be surprised if tight rubber o’rings and or a strategically placed magnet on a barrel would have similar effect, however the constant vibrations would also potentially weaken the magnet.

It is a topic that I find very interesting and plan to research in earnest over the next few years as I have the funds to be able to. Hopefully the Alzheimer’s holds off long enough for me to be able to lol.

John T
Posts: 146
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Location: Brisbane

Re: Barrel Behaviour Theory

#28 Postby John T » Mon Jun 04, 2018 10:09 pm

Hello Peter.

At the risk of being charged with hypocrisy, I have to say that you need to move on, rapidly, to RIFLE Behaviour Theory, or risk losing your audience.

Why do you persist with standing wave theory when there is no standing wave in a free-end medium?

Regards,
John Tracey.
4.6.18

williada
Posts: 706
Joined: Wed Jul 22, 2009 12:37 am

Re: Barrel Behaviour Theory

#29 Postby williada » Mon Jun 04, 2018 11:35 pm

Well going by the number of hits John there is quite a lot of interest. Bet a few sharp guys from the United Kingdom, NZ and USA are not missing a beat. The ones we have to get into the sport are a new better educated breed because most kids these days finish year 12 maths who will lap this up but sit in the shadows because they have not got the confidence to express themselves or ask questions as do some older guys. Our time has passed. No such thing as a dumb question. I see Travis wants to know more and has an inquiring mind and a practical background. Hard to know where too pitch it at times but a step by step approach will give the best value for those really interested in the long run. After all what boring buggers go to the nth degree to sort components. They can handle step by step. There is always choice for others to read threads with regard to where their own interest lies and they rightly do. Peter has already stated he will move onto other parts of the total system. I got the feeling Peter will win a few but there is great merit in presenting new ideas to interested people even if they can't get their head around some of it. Nuggets can be found that connect the dots for some. =D>

!Peter!
Posts: 84
Joined: Sun Oct 30, 2016 6:35 am

Re: Barrel Behaviour Theory

#30 Postby !Peter! » Tue Jun 05, 2018 9:02 am

Bigtravoz wrote:In your moving graphic Peter you showed the blue line with peaks much higher than the main waves, this is in theory what using a tuner should be aiming to control, reducing the radical peaks, and potentially increasing or decreasing the frequency of the other waves thus reducing and or stabilising how large each oscillation is to make the outcome easier to read.

I think a better way of thinking about a tuner is that it can change the shape and timing of waves.
Bigtravoz wrote: Somewhat like the ferrite cored lump on various cables cables does to stabilise the frequency through it and stopping radical off frequency waves interfering with other equipment ( there’s a correct name for it that’s right on the tip of my tongue, wish my brain still worked like it did ten years ago, I swear I am getting early onset Alzheimer’s some days!)

Sort of. The ferrite lump put on cables is to remove the high frequency/ high voltage spikes that occur when switching DC like what happens in a switch mode power supply and variable speed drives.
Bigtravoz wrote:I wouldn’t be surprised if tight rubber o’rings and or a strategically placed magnet on a barrel would have similar effect

Calling GSells, Care to comment about your strategically placed tight o’ring? :lol: :lol:

Bigtravoz wrote: It is a topic that I find very interesting and plan to research in earnest over the next few years as I have the funds to be able to.

Likewise, I’ve got ideas for experiment setups to investigate this, but I just don’t have time.
John T wrote:Hello Peter.

At the risk of being charged with hypocrisy, I have to say that you need to move on, rapidly, to RIFLE Behaviour Theory, or risk losing your audience.

Why do you persist with standing wave theory when there is no standing wave in a free-end medium?

Regards,
John Tracey.
4.6.18

John,
I’m allowing time for people to digest this material and for me to write it.

If you don’t think a standing wave can occur in a free-end medium then you should re-look at the physics classroom.

These is already enough in this tread to start applying to a rifle system but there are few more key snippets of theory to know to get deep enough understanding.

!Peter!


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