Barrel Vibration testing

J

JohnsonGunsmith

Guest
Who is doing or ha done vibration testing with accelerometers or other methods on barrels etc? I have read Harold Vaughns book many times but I want to do some of my own testing and not waste $$$ in the process. I need to know if anyone else is doing or has done this type of testing so I can be as efficient as I can be without negative effects to the results. I am doing all I can to make my bench guns shoot better and would appreciate any help as to who to contact so I can do my own testing while not making any large mistakes in setup or equipment purchase. Also if anyone else is intrested in this type of testing and work I would appreciate your input/help. I am attempting to make a name in the business and the results will be used to benifit all shooters. I appreciate all the help and knowlege I have recieved from this website and would love to be able to give back something and hlp move Gunsmithing and the sport of Benchrest shooting forward.
Thanks in advance
Brandon J.
 
Varmint Al

I have been to His website and I find it very useful. It is mosty full of raw data for tests he has done and not as much on the equipment he uses etc. I could be very wrong and will go back and look at his site because I might have just missed that part somewhere. I also will try to contact him and see what I can use from his extensive testing to help me with my future testing. Thank you Lawrence and I will try to get in touch with the persons you mentioned and see what they have to say. I appreciate your help.
Brandon J.
 
Johnson, please do not think I am being trite, but have you thought about installing a tuner and simply skipping all of the conjecture.
.......jackie
 
In the past, I have emailed Varmint Al, and he responded. If you look on his web site, I think that there are directions on how to email him. I believe that he uses a title line phrase as a spam filter.
 
I have always wanted to use a high speed video camera to see exactly what the barrel does when fired and the position of the barrel at different nodes and between nodes......These are still pretty expensive though
 
I've done a bunch of testing but not on rifle barrels. Couple of things to keep in mind when considering methods:

Any mass you add to the barrel anyplace, in the form of accelerometers for instance, will influence the results, how much will depend on location. Unfortunately, the locations with the most movement which give the best data, are also the locations which will have the most influence on the response of the system being measured.

Duplication of initial conditions is absolutely essential to transient measurement of any dynamic system. If the initial conditions aren't the same from test to test, the system response won't be repeatable. The implications of this will have profound impact on the design of the experiment - both for getting data and for the data having meaning when applied to a particular shooting situation.

Fitch
 
Thanks Fitch I have considered this and how I think about it is we have changing conditions and I need to know what happens in each of the conditions so all the results would be valid and repeatability should be important only if the conditions are exactly the same and all the variables are the same etc. This not being 100% possible it is a try to see the big picture kind of process. Nothing in life is 100% anyway except for death so I am just thinking of running with it. I hope this does not sound like I am ignoring your advice because what you said is valuable to me and I appreciate your help. I understand that you have experience with this type of work and I do not. That being said I place a high value on your suggestions because you know more about this type of work than I do and I do not pretend to know better how to go about this testing.
My focus is on the Vibrations and dampening them. I am focused on consistency and vibrations can hurt you since there are always variables to consider. A gun that vibrates less should be effected less from the slight inconsistencies that we all impart on the gun because we are not machines. This will allow the gun to fire more consistently because the vibrations are less severe so any effect we have on the gun in the shooting process will not be magnified by the vibrations thereby increasing the consistent nature of the gun. I hope that makes sense and describes my intent more fully. I would like to hear more from you guys and all your advice so far has been great.
Thank you all very much,
Brandon J.
 
JohnsonGunsmith said:
Who is doing or ha done vibration testing with accelerometers or other methods on barrels etc?
Brandon J.
Click to expand...

You might pose the question to Dr Geoffe Kolbe of Border Barrels as he has done (and is in the process of doing more) extensive work in this area.
 
JohnsonGunsmith said:
My focus is on the Vibrations and dampening them.
Click to expand...

What you are concerned with is the motion that preceeds the bullet leaving the barrel - nothing after that, other than the rifle system resetting to the same initial conditions before the next shot, matters. The best program for dealing with it is to design the rifle system so it's unconstrained behavior results in an acceptable motion. This can be done in part by the design of the rifle (free floating the barrel to make the response the same simple harmonic function each time, and stress free bedding to give equivelant initial conditions prior to each shot, etc.) and fine tuning by choosing a load that gives the most consistant performance (smallest group).

Additional mechanism can be added in the form of a barrel tuner (adjustable weight) but if this added complication (which is "not" damping) can be avoided, especially on a hunting rifle, it is better.

Trying to modify system behavior by "damping" vibration requires using some mechanism to absorb energy from the system in such a way that it causes the systems vibrations to decay faster than would happen if the energy wasn't removed. Damping (think something like the shock absorbers in a car) can cause a whole new set of problems since it has to be done in such a way that the consistancy of system response and initial conditions aren't disturbed.

The KISS principle applies.

The other issue is to design the testing so that it applies to more than just the system used in the experiment. What you are looking for is proof of general principles that can be applied to more than one particular test article. Testing every possible system, or even one system in all it's possible conditions of use, is a practical impossibility.

At this point in the development of bolt action rifles, I suspect the incremental rate of return measured as group size reduction per dollar spent on testing would be a rather demoralizing number.

The best way to see the big picture is to do the analysis like Varmint Al did (he's an expert at analysis), then do some measurements to confirm what the analysis is telling you.

Fitch
 
Last edited by a moderator:
thanks guys

Fitch you are correct about the $$ to benifit ratio on this deal. I appreciate your information and agree completely with all of what you say. I just talked to someone about building the systems to do this with and he guessed over $10,000 to buy equipment. That has me rethinking everything because my initial reseach showed 3-5K and that was acceptable if I could learn something but over double the price has me thinking it is not worth the investment. I am still working on some new ideas but they are more playing and not really on the level of serious accuracy inhancements. So back to the drawing boards I guess. I might try to rent some of the equipment in the future since I have found a place that does this. That would be much more cost effective. thanks for the websites david I will read them today. and Vibe tanks for the extra contact I will try to get in touch with him in the future.
 
JohnsonGunsmith said:
I just talked to someone about building the systems to do this with and he guessed over $10,000 to buy equipment. That has me rethinking everything because my initial reseach showed 3-5K and that was acceptable if I could learn something but over double the price has me thinking it is not worth the investment.
Click to expand...
Thats insane. You've not said what equipment you have, but you should easily be able to get the tools you need (used) for <10% that. If I was starting with no equipment at all I bet I could be in under a grand. And, it's not like you finish up with the barrel crap and the stuff is useless. It is re-sellable or multi-use for other kewl stuff.

If you're at all experienced with embedded systems, you can buy a dsPic that'll do 9 simultaneous A-D's at 4Mhz 12bit res, for $5. There is a minimum order tho, you need to buy at least 2.

As it's a ds chip, and has many ds functions, it's fast as hell, programmable in C or assembly (all tools free except the programmer), and you won't feel so bad when you let the smoke out of one. Using a circular buffer you could set up your own post trigger for when the bullet leaves, you'd be set. It's got plenty of ram for what you want and you can add more for a buck or two. I've had these running at 160Mhz on a breadboard, stable, and with <.001vdc float on the adc channels, all channels measured simultaneously.

Do you have a scope? Is it a storage Scope? Even if you go brand new from Tektronix you can be into 4 channels for about $2200 and that's with a lifetime warranty. Way fast enough for what you want too, and again, can be resold for damn near new price.

I wouldn't chicken out just cause someone says it's expensive. I'd just shop smarter.
 
4mesh

That sounds more like it. I do not have any of the equipment yet. I do not know why it would cost so much either but I was really discouraged after talking with him. I do not know what I am doing at all and am learning what I need as I go. Some of the things you said to me in the last post was over my head but I do understand the don't chicken out part and If I can do it for under $3000 I would be very intrested. Can you send me info. to get to the correct websites and places to get what I need? I am intrested and want to do some testing. I will be posting results on here after testing if it gets off the ground.
Thanks for the positive feedback and I feel like it is a possibility again.
Brandon J.
 
This is a complicated issue, and I'll probably make a hash of trying to explain where I'm coming from. But that never stopped me before . . .

People like Varmint Al are trying to model a system, so that what is learned can be applied to more than one rifle. But the number of variable are just too large. Any number of physicists have said "oh, it's easy, I'll have a product out real soon now." And of course, nothing emerges.

On the other hand, testing one rifle will let you make improvements, but how to extend them? For example, one of the variables is bolt thrust, and that depends not only on lug fit, but on how you resized the brass, etc.

It is one of my favorite analogies. Imagine doing the testing with a free-recoil muzzleloader, where the variables really are just the barrel (I think). Then repeat with a bolt gun, or some other form of breechloader. That will begin to show how much the action and cartridges affect the system.
 
Question:
I am not sure if this applies to dampening or not BUT if it does....
On a rail gun the barrel is usually held in place with a block of some sort....and the action hangs off of the back end.
This being the case dampening or tuner is it possible to change the position of the barrel in the block to create a dampening or tuner effect?
 
Well, I had about a 20 minute post binned by a power outage and what may have been a tornado. Not that I'm the most experienced person on such things, having only been front and center in two, but it was exciting enough to get me to the basement in a hurry. Wow, that came in faster'n anything I ever saw before. I have to assume it wasn't a tornado since the two I have been in gave all sorts of warning. This, I expected things to be removed from the house before I could make it down 2 flights of stairs... 30 min before was out mowing the grass and it was beautiful. :confused:

Anyhow, Charles, you should probably avoid these thread cause any minute now the post police will be stopping in to give you all sorts of flak for having an opinion, and then sharing it too. omg, How dare you! :p

I'm pretty much supportive of anyone who actually WANTS to find answers, and is willing to not just 'wing it'. Have you ever attempted to test something gun related and failed to achieve the desired result? Did that make the testing any less important, or dissuade you from trying the next thing? nope. I'll allow, this isn't an easy undertaking but mostly, I think I fall into the category of folks who things that the technology is there and that yes, it is easy. However, that is the part that is easy. Building the mechanical device that allows measurement, A-without influencing the result adversely, and B-can eliminate the S/N ratio coming from the Z axis, well, that's not so easy.

Anyhow...

Brandon...

Have you done any programming?
Experience with electronics?
Is this something that interests you enough to make up for the lack of the previous two?
Do you have any idea the learning curve it will take to do this if the first two answers are no?
Do you think I am implying that makes it impossible, or even unlikely?
Are you willing to spend $3-400 just to see if this has the slightest possibility of success?

So, then I'll just ask, what tools are available to you now? Check this list...
Decent quality Digital Multimeter?
Oscilloscope?
Digital Storage Scope?
Signal analyzer?
Breadboard? Solder Iron?
Milling machine?
Lathe?
Drill Press?

Are you at least passingly computer savvy? Meaning, not afraid of anything? I'm flying blind here so any of these answers would be a great help in saying what direction to go. Work can be made up for with $$$. Conversely, $$$ can be saved with lots of work.

Last but not least, Are you interested in seeing what these vibrations do, or are you actually interested in seeing if they exist and if they can be quantified, and their results quantified? I'll assume since you brought up Harold's name that you noticed in the book he used no tarot cards or voodoo dolls to find answers. He also didn't see things and attribute them to what he wanted them to be (as some around here do). He isolated the problems and quantified them, then decided what the big fish were and what the little fish were.

Regardless of what path you decide to take, I think the $$$ figure in question should ride somewhere around a grand, and that spread out over a fairly long time if you are frugal with $ and thrifty with time.
 
Brandon,

While, this is not the ideal processor for what you're looking to do, and is no substitute for the right stuff, it is dirt cheap, and is everything you need to get started the "hard work, low money" way. If you can conquer these two things then this barrel deal will be a breeze. The chips that go on these boards are no where near the speed of a dsPic, but you absolutely could hook this to a gun and do serious testing. And, there's 2 spare boards to mess with later.

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en538340

http://www.microchipdirect.com/ProductSearch.aspx?keywords=DM164130-4
 
Can you dampen vibrations by using a very THICK heavy rubber bushing placed and moved up and down the barrel?
I have wanted to try this in the same manner as a tuner.
I know you can find the sweet/dead spot by tapping on a barrel and listening to it.
 
Vern, they sell gizmos specifically for that. I forget the name of the company, but they make various other gun products as well. Like recoil pads and such. Sorry, the name escapes me...
 
You must log in or register to reply here.
Back
Top