Tuners Spinning Out Of Control
- Thread starter GordonE
- Start date
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martin hammond
Guest
Gordon, I would appreciate any comments and thoughts you have on tuning. thanks martin
Gordon,
Are folks slugging barrels? That's plural....folks. They know the internal construction and dimensions. But they've kept quiet about the whole realm because they didn't want to speak as fact for something that might not be so. External dimensions are important! So is a straight bore with a dimensionally true tapered lap along with the fact that you ordered the barrel to certain specs and the manufacturer either did their job to your specs or they did not. How many gunsmiths send barrels back because they aren't right?
John M. Carper
Are folks slugging barrels? That's plural....folks. They know the internal construction and dimensions. But they've kept quiet about the whole realm because they didn't want to speak as fact for something that might not be so. External dimensions are important! So is a straight bore with a dimensionally true tapered lap along with the fact that you ordered the barrel to certain specs and the manufacturer either did their job to your specs or they did not. How many gunsmiths send barrels back because they aren't right?
John M. Carper
>>How many gunsmiths send barrels back because they aren't right?<<
Well, I know for sure the one who started this thread does that. He received a bunch of barrels last year and I wanted him to fit one on my 10.5 rifle. I went to his shop to drop my rifle off and he was slugging those barrels. He rejected every one of them. He then searched for and found a barrel mfg that would listen to him and produce barrels to his specs and had the QC to get it right. I know of no gunsmith that thinks more about rimfire accuracy then Gordon. Oh, he may not post a lot about his thoughts, but when he does, it is the wise shooter who listens.
Well, I know for sure the one who started this thread does that. He received a bunch of barrels last year and I wanted him to fit one on my 10.5 rifle. I went to his shop to drop my rifle off and he was slugging those barrels. He rejected every one of them. He then searched for and found a barrel mfg that would listen to him and produce barrels to his specs and had the QC to get it right. I know of no gunsmith that thinks more about rimfire accuracy then Gordon. Oh, he may not post a lot about his thoughts, but when he does, it is the wise shooter who listens.
It would seem to me that every aspect of barrel making would effect the tuning right down to the crystalline structure of the metal. Certainly one would seek to understand all the variables in order to more accurately tune but the obvious ones are easiest to ascertain. It must be possible to tune a rifle reasonably well without knowing why or how because I have been able to acheive positive results without knowing anything at all. These tuning threads have helped me immensely. Thanks to all contributors over the years. Guy
Vibe
22 Epperson Cricket
I'm thinking that a tuner will never make a bad barrel shoot great - better maybe but not great. I'm also thinking that there's more than just the dimensions involved. One example I think is relevant (for the more daring in math and physics) is the difference that would be seen in a "race" between 3 wheels made of different materials each of the same outside diameter, thickness, and weight, but different densities (so different ID to make the uniform weight). Say Aluminum, Steel and Tungsten. Which one will reach the bottom of a given ramp first? And why? The why applies here.
Thanks for directing the discussion towards science, Vibe. This is straightforward "Pinewood Derby" physics. Calculate the rotational moment of inertia for each wheel configuration. Assuming a smooth rolling surface which won't affect the downhill performance of the wheels, the one with the lowest rotational moment of inertia wins, because it will accelerate most quickly.
Vibe
22 Epperson Cricket
So the tuner with the highest rotational moment will have the most effect on the barrel motion - and it's not based upon the weight of the tuner.
Jim Pollard
New member
Having gone to school to be a "shop teacher" I love it when some "engineer" type people form a circle and see who can get the others boots the wettest. When are you folks going to get into the effect of the barrel maker having to anneal the barrel because of work harding and the effect of the heat treating and grain structure of the barrel at different diameters in relationship to the barrel node.
don't take me serious--just jerking the chain in fun
Jim
don't take me serious--just jerking the chain in fun
Jim
Don't take this too seriously either, coming from a metallurgist. Selective heat treatment may truly have some benefit, Jim. All kinds of parts have specific areas selectively heat treated for different reasons (gears, shafts, tubes, sawblades, etc....). As higher levels of performance are achieved, small improvements can have a more pronounced effect.
I agree with Vibe on the physics of tuner design, proposing that a larger diameter, lighter weight, stiffer tube (commercially available carbon fiber or metal matrix/ceramic composite tubes come to mind) with a relatively lighter weight applied to the tube can be just as effective at tuning barrel vibrations, and can certainly be of more benefit when "making weight" becomes an issue.
The concept of tuner "downforce" as shown elsewhere is so misguided that anyone with a basic understanding of physics should be able to see why it is not valid.
I agree with Vibe on the physics of tuner design, proposing that a larger diameter, lighter weight, stiffer tube (commercially available carbon fiber or metal matrix/ceramic composite tubes come to mind) with a relatively lighter weight applied to the tube can be just as effective at tuning barrel vibrations, and can certainly be of more benefit when "making weight" becomes an issue.
The concept of tuner "downforce" as shown elsewhere is so misguided that anyone with a basic understanding of physics should be able to see why it is not valid.
Absolutely Not!
The internal dimensions and consruction determine the accuracy of a barrel - has nothing to do with tuning.
The internal dimensions and consruction determine the accuracy of a barrel - has nothing to do with tuning.
How do you know if Wilbur can remember back to 1972?
mistermike
Michael Gallant
With all sincerity in asking, could you explain this statement further? Why is tuner "downforce" not valid?
Thanks,
Michael
mistermike
Michael Gallant
Gordon,
If a sporter barrel can be "tuned" by its profile, couldn't the same concept be applied to a 10.5 or 13.5 rifle?
(Nice to see you on the board)
Best,
Michael
If a sporter barrel can be "tuned" by its profile, couldn't the same concept be applied to a 10.5 or 13.5 rifle?
(Nice to see you on the board)
Best,
Michael
So the tuner with the highest rotational moment will have the most effect on the barrel motion - and it's not based upon the weight of the tuner.
Vibe,
I'm not so sure this is true. One important effect that constitutes tuning is control of the range of muzzle angles over a range of times of bullet exit, which in most cases means increasing the range of angles, rather than decreasing it. An infinite rotational moment of inertia (about the muzzle), after all, would decrease the fluctuation in the angle to zero, and would not be conducive to tuning. I haven't spent a lot of time analyzing this, but I think maybe what we want is a high tuner mass while minimizing the increase in muzzle rotational moment of inertia.
The other part of tuning is controlling the phase of muzzle angle to be rising during bullet exit, which can also be accomplished with muzzle mass alone.
Comments?
Cheers,
Keith
Vibe
22 Epperson Cricket
Because a "downforce" is simply a weight -> Force =Mass x Acceleration. Weight = Mass x Acceleration due to Gravity, and the dirction of Gravity is down. So "Downforce" is by definition simply weight. What is being (incorrectly) called "downforce" in this discussion is some mass mounted some distance in front of the muzzle - this is not the same as "downforce" as this describes a torque in the simplest of terms, and is closer to an attempt to describe a specific change in the Moment of Inertia about the muzzle.
Vibe
22 Epperson Cricket
I wish I could find an online copy of a test report I read about (long ago). Really it was more of a gun rag gimmic, but there was a bit of good science behind it. The gist of it was that someone built a high rpm gyro and mounted it to the muzzle of a rifle producing a VERY high, dynamically induced moment of inertia, and of course, since this gizzmo was not light, a pretty fair mass at the muzzle as well. While I got the impression that it was simply a gag to attract readers, the 10/22 it was mounted on produced some fairly respectable increases in offhand accuracy.
But in benchrest, you are correct, we do not want an infinite increase in moment about the muzzle, what we want (and I can't calculate the value yet), is enough mass at he muzzle to cause the First order oscillation to be near motionless at the top of it's swing at bullet exit, while at the same time causing the 2nd order vibration (the one with a node at the muzzle) to track the range of vertical that points the slow shots high and the fast shots lower in such a way that they hit the same point at the target. Varmint Als FEA shows some of this as it happens.
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martin hammond
Guest
vibe, let me help you out with this one. 4.5oz to 4.7oz and a roll of aluminum tape. martin
Vibe
22 Epperson Cricket
Let me help you out Martin.
http://en.wikipedia.org/wiki/Moment_of_inertia
By the way the axis about which we are interested is the one perpendicular to the bore, parallel to the horizon, and passing thru the center of the muzzle.