nodes...

[pacecil]

This has been discussed on several threads and since the last one was deleted I decided to bring it up again.

The attached upper pict shows the accepted shape a barrel assumes when vibrated and in the lower pict the "straight" or "parallel" node shape. These are exaggerated in that typically a rimfire would have a few tenths (.0001) amplitude at mid barrel while the muzzle might move a few thousandths (.001). The force to start these vibrations is the moment at the receiver generated by recoil. To get the barrel to flex into a section that is parallel, or nearly parallel to the axis, at the node would require the application of forces as shown in the second view. These forces would have to reverse direction as indicated by the black arrows against the barrel in the black position, and the white arrows against the barrel in the white position.

Half of such forces could come from a moving bullet but a bullet passing through the curved shape shown would tend to push the barrel into a greater angle with the axis. They could also be applied by clamping a rigid sleeve around the node area. Finally they could result from just adding a larger diameter barrel through this section. A larger barrel would flatten, or make straighter the whole curve.

Bottom line is that the most likely shape for a vibrating barrel is shown in the upper picture. The lower shape, while not impossible would be very difficult to achieve in a conventional barrel.

 

[Madrox]

I don't know, you see that little guy everywhere with that funny hat. I think people just sit him down and take the pictures. I don't think there's a real traveling gnome, do you?

Oh, you said node. Never mind.

 

[dankillough]

pacecil,
I did not read the previous thread, so please bear with me. I thought the goal was to move the node to the end of the barrel.

 

[pacecil]

To dankillough..

If you want to move the node to the muzzle you add weight to the end of the barrel as shown in the lower pict on the attachment. It acts like you had just made the barrel longer. The barrel would be pointed down just like it was in the node in the upper pict. This seems undesirable and may be why a straight or parallel node was conjured up.

 

[dankillough]

I agree with how you move the node.

Do you agree that you can find the position of the node by tapping on the barrel and listening for a "dead" spot?

 

[Lynn]

Pacecil
In your firsrt picture you show a partial wave with external forces acting on it in a fashion not talked about here before.If these forces are not there in your opinion why does the wave stop? and why does the barrel go back to its original shape?

What happens when the wave reaches the end of the muzzle and gets reflected back onto itself? Can it produce the shape Bill Calls his parallel node?

If you were to measure to the left and to the right of your anti-node xx-degrees in each direction and measure the amount of barrel bending that takes place and write it down what would happen to your barrel bending numbers if you then added a 13 ounce tuner to the muzzle? Would this look like you flattened out the barrel? Or would it look like the barrel remains the same?

Now do the same thing at the anti-node and what are the results?

I will look for some real photos.

Physical waves
Any waves traveling along the medium in our case a rifle barrel will reflect back when they reach the end. This effect is most noticeable in musical instruments where, at various multiples of a vibrating string or air column's natural frequency, a standing wave is created, allowing harmonics to be identified. Nodes occur at fixed ends and anti-nodes at open ends. If fixed at only one end, only odd-numbered harmonics are available. At the open end of a pipe the anti-node will not be exactly at the end as it is altered by its contact with the air and so end correction is used to place it exactly. If two waves with the
same frequency are combined there will a be a constant interference pattern caused
by their superposition. Interference can either be constructive, meaning the
strength increases as result, or destructive where the strength is reduced.
The amount of interference depends of the phase difference at a particular point.
It can be shown that constructive interference occurs for phase differences of 0-120 degrees,
and 240-360 degrees. Thus destructive interference occurs from 120-240 degrees. For two identical
waves, no phase shift results in total constructive interference, where the strength
is maximum and 180 degree phase shift will create total destructive interference (no signal
at all
Is it at all possible that a phase shift is causing distructive interference?
Waterboy
Edited because my Degrees symbol was showing up as the number (0) zero

 

[Varmint Al]

This has been discussed on several threads and since the last one was deleted I decided to bring it up again.

Hi pacecil. How are things? I agree with your top picture all the way from the breach to the node. Pass the node to the muzzle the picture is incorrect. The muzzle face does not remain in a vertical plane as you show. The axis of the bore at the muzzle will sweep through an angle. See the attached .gif file that shows the muzzle face sweeping through an angle.

When viewing the animated .gif picture, place the mouse pointer near the node. Move the mouse pointer right and left. When the barrel's vertical motion is such that the mouse pointer stays at the center line of the barrel, that is the node location.

I missed the previous thread that was deleted but saw references to it on a board reader site.

Good Hunting... from Varmint Al

 

[Madrox]

I think that ought to be deleted. It offends me for some reason.

 

[Lynn]

Varmint Al
I have a question of the "is it possible" type.

In Bill's article he was using dial indicators which would give him the maximum recorded deflections but without any reference/relation to time.Is it POSSIBLE he was seeing the wave being reflected back onto itself like we would see in an electronic circuit?
Waterboy aka Lynn

Edit
Can the node and anti-node be moved to the muzzle by adding a length of bloop tube?
On your modeling of the 6ppc you used a velocity around 3400 fps.On a rimfire rifle at 1050 fps and the bullet taking 3 times as long to exit the barrel(guess) would your model still be accurate?

 

[Carp]

The barrel can flip and do cartwheels all it wants BEFORE or AFTER the bullet leaves the barrel. The WHOLE idea is to get the bullet to exactly leave the barrel exactly when the barrel is parallel with the line of sight. Is it that hard for smart people to understand the simple? It means that anything other than that is WRONG. It seems that removing vertical in any rifle.....rimfire or centerfire is a tuned rifle. If the bullet leaves the barrel exactly at the time that the barrel is parallel with the line of sight then the barrel SHOULD be in tune. That way the muzzle is pointed in the correct position. Am I wrong? Let's not make this more complicated than it should be.

Carp

p.s. I don't care how the barrel bends or distorts as long as it does the same thing shot after shot after shot after shot after shot............................

 

[gambler]

if barrel is parrellel with the line of sight, won't the bullet hit low....i'm nit pickin

 

[Beau]

Depends on where you're looking doesn't it?

 

[Lynn]

Carp
I kind of understand what your saying but think about it like this if you can.

Right now with the available ammo on hand you are probaly adjusting your tuner so the ammo you have shoots at its best.At the next match you are now adjusting it again or repeating the same set-up and praying it still works the same way.

Now if all a person needed to do was to add some length to his barrel via a tuner or a bloop tube and that affectively moved the node or anti-node nearer the muzzle we probaly wouldn't notice alot of difference.Now we add some weight and this dampens the node or anti-node or broadens its range of effectively tuning our barrel.

If your still with me this means we can now shoot a variety of ammo over a period of time and we never have to adjust the tuner.Kind of like the info-mercial "set it and forget it".Right now most shooters are probaly adjusting for weather and lot #of ammo.

If all it takes is a little input from guys like Varmint Al to get us looking in the right direction that is great.If someone says it can't be done and here is the absolute fact on why it can't work that is fine as well and we can all look for accuracy somewhere else.

Up to this point we have Bill Calfee saying he did it exactly like the rest of us for 20 years.He then goes on to say if we hang the weight out in front of the muzzle a certain distance and the weight is adjusted using a certain method we get a no-tune tuner that shoots very well fully admitting his earlier work was a complete waste of time.He says all of this with 30 years of tuner experience under his belt and many record shooting rifles to back him up.

On the other hand we have several groups of guys.

The first group is interested in seeing if they can do this or if it is even possible and are willing to spend there own money,time and barrels on the project but need a nudge from time to time in the right direction.

The second group thinks Bill isn't interested in accuracy or getting rifles to shoot better he's just making money off of his wild ramblings by selling Spec Rifles to unsuspecting shooters.

The third group is trying to figure out why the engineers and non-engineers are having so much trouble communicating what seems like such a simple thing.

The fourth group claims everybody is nuts and crazy but visits each and every post and feels compelled to yell swear cuss and be downright uncivil to the guys discussing it.

I don't understand why some would yell or get upset at guys like Bill Calfee, Varmint Al or Pacecil.Nobody is forced to participate in these posts so the only thing that comes to mind is some form of down the road vindication when the truth is found out.

All in all nobody here is saying tuners don't work they are just trying to solve the equation of the no-tune tuner riddle if it can be done or is it even a possibility.For those of us shooting longrange benchrest who can't see there bullet holes through there scopes the adjustable tuners we have now require a huge amount of time and notes not seen in rimfire or conventional benchrest.Its a venture worth looking into in my case so I visit this forum were tuners are common place in the hopes of improving my groups.
Waterboy

 

[Carp]

Gambler,
You are 100% correct. The POI will be low.
The POI will be lower for every weight that you add to the tuner. If folks don't understand that then they need to actually shoot and not talk about it. Beau uses a good point on where you are looking at because you or we can move our crosshairs of our scopes to accomidate the lower impact.
Lynn,
I used the same tuner setting on my rifle for some 3 years (without any added weights) with a variety of different ammo. Not saying I shouldn't of moved it but never did. I did however do fairly well in the rimfire world practically. Not theoretically. It was with a variety of ammo. Most listed as near the same velocity. But I may add two things. Listed velocity of rimfire ammos is not very trustworthy, number one. Number two, adding weight to a tuner seems to be detrimental to a lot of barrels. I've seen (my own included) more barrels shoot better without the weights on the tuner than with them. I've seen more 2400's ARA shot this year with tuners without weights than with them. Think of it this way......a fishing pole with a sinker at the end and lift it up and down. You get a lot of whip. A fishing pole with just the hook at the end gets very much less. Which is more predictable? I'll go for less weight everytime. I'm no engineer but it definately makes sense in the practical part.

Carp

 

[mr. nobody]

ok, let me tell you something i saw at the range one day. a guy i know had rebarreled a rifle. he had a harrel tuner on it. i shot it for him. then he put a noodle tuner on the harrel tuner. the next few shots i shot hit way lower than those without the noodle tuner on it. i understand some of what people are talking about. with the added wieght of the noodle tuner the muzzle of the barrel would have been pointed down further than without it. that would mean what? what does the added wieght mean? it shot ok before the noodle tuner, but not good with the noodle tuner. explain to me the difference between the 2 ways.

 

[Carp]

Mr. Nobody,
The addition of the noodle is the same as adding length to the barrel (as Lynn says) or weights to the tuner it makes POI lower. The problem that I see is a longer barrel or heavier at the muzzle is that the muzzle has more travel, making the parallel part harder to achieve.

Carp

 

[Tom C.]

so is the whole barrel moving up and down? looks like the part not moving
much is around the breech. if the whole things whipsawing around is the action
doing it even worse being on the tail end? instead of fighting the vibrations
couldn't some sort of device be used that would minimize or cancel them. a
tuner(?) it looks like, helps to arrest the best place for the exiting of the bullet.
could something be used to truly tune and subdue the vibrations in the whole
barrel or gun? i'm thinking along the lines of a cancellation device, equal and
opposite reaction to the gun being fired type of thing. maybe a parallel barrel
or a sleeve filled with something to soak up or slow down the barrel vibrations that would enclose the barrel. uhoh i'm starting to think too much, my brains gonna explode from the overload. later, keep thinkin' it's the only way we ever accomplished anything, huh.

 

[Lynn]

Tom
In shortrange benchrest some of the railguns used a sleeved barrel filled with epoxy.On the longrange guns the barrels diameter is often times 2 inches in diameter and shooters have put large diameter tubing over there barrels that in essence hold the action and muzzle in a steady state while allowing the center to vibrate up and down.
The smallest 10 shot group at 1,000 yards was done this way by a forum regular.
Waterboy

 

[pacecil]

Lynn - In your firsrt picture you show a partial wave with external forces acting on it in a fashion not talked about here before.If these forces are not there in your opinion why does the wave stop? and why does the barrel go back to its original shape?
The only force shown is the moment applied to the barrel where it joins the receiver. This moment represents the recoil forces. They exist for just an instant and when they stop the barrel is left to vibrate in it's natural mode. While this moment is being applied the barrel is vibrating in what is called the forced mode. While in a forced mode the vibration pattern may not be exactly as shown. All vibration stops when the energy that was put in it at recoil is dissipated in the form of heat.

What happens when the wave reaches the end of the muzzle and gets reflected back onto itself? Can it produce the shape Bill Calls his parallel node?
The wave is not reflected back from the unsupported muzzle.

If you were to measure to the left and to the right of your anti-node xx-degrees in each direction and measure the amount of barrel bending that takes place and write it down what would happen to your barrel bending numbers if you then added a 13 ounce tuner to the muzzle? Would this look like you flattened out the barrel? Or would it look like the barrel remains the same?
This is a good question. I think the barrel would tend to be "flatter" when the weight is added. I think the measurement you are proposing would become less after you added the weight. Look at it this way. If you were to add a lot of weight it would be like you were adding a rigid support at the muzzle and in effect moving the node right up next to the weight where it would be nearly "straight" and "parallel".


Now do the same thing at the anti-node and what are the results?
That's where we added the weight - at the antinode.

Any waves traveling along the medium in our case a rifle barrel will reflect back when they reach the end.
Not so, waves aren't reflected from the unsupported muzzle.
In a vibrating bar supported at one end, vibrating as we all seem to think it does, there are no harmonics, only the fundamental and an overtone.

 

[pacecil]

dankillough asked, Do you agree that you can find the position of the node by tapping on the barrel and listening for a "dead" spot?
Sure, The "dead" spot is the node.