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Thread: Contraption Vibration

  1. #1

    Contraption Vibration

    Hi Bill

    "CYA friends, after all these years since 1992, and what happened the other day with that RFBR gun, there's a little more light being shed on the subject of how a rimfire contraption vibrates, when fired, and how that vibration relates to rimfire accuracy."


    This is something I looked into a while back and believe there is much more to learn.
    Here is some results from some tests I did that may add to the knowledge pool to help with improving rimfire accuracy in the future.

    This was measuring the vertical movement / vibration at the end of the barrel.

    This was done by shinning an accurate laser measuring instrument at the barrel to measure distance.
    This way there was no inertia or momentum with the measuring device.
    The speed it measured was it took 40 readings from the time of ignition to the time the bullet left the barrel

    From previous tests I had measured that at about 2.5 ms (milli seconds) which is 2500 us ( micro seconds ) depending on velocity


    I need to explain what you are looking at.
    This is a screen shot of an oscilloscope, the graduations down the left side is calibrated in MM so the smallest graduation is .01mm or .00039"

    Along the bottom is the time and in this case it is in ms (milli seconds ) or 1/1000 th of a second
    The ignition is at "0" and by the first graduation of "100" the bullet has well and truly left and gone as it left the barrel at 2.5 ms.

    This is the overall big picture

    Big picture.jpg

    Don't worry about the trace starting just under 0.06 mm on the left as this was the starting position of the instrument for this run.

    This is another test with a zoomed in view, the scale on the left is still the same but the time is now in us ( micro seconds )
    So the bullet left at about 2500 us or 2.5 milli seconds

    Zoomed in.jpg

    Remember there are about 40 reading taken between "0" and "2500" when the bullet left.

    Next thing is how accurate is the laser sensor ?

    This screen shot is of the laser measuring a still barrel with nothing happening
    This shows what we call noise or you could say the randomness of the measuring and it is a 1/3 of a division of .01mm so it is .003mm or .0001" (1/10 thou)
    The specifications for the Laser measurement unit is within 1.5 metric microns or .0015mm or .000059" but I saw double that

    Sensor noise.jpg

    The thing to note here is from ignition that the barrel starts to move down then back to the start height and then down again and back to the start height and stays there relatively flat for the critical time that the bullet leaves then starts to climb up which is the first upward swing on the "big picture" shot.

    When I look back and forwards between several shots at the same settings you can easily see what is noise and what is a real movement.

    Regards
    Graham

  2. #2

    Friend Deveng

    Quote Originally Posted by Deveng View Post
    Hi Bill

    "CYA friends, after all these years since 1992, and what happened the other day with that RFBR gun, there's a little more light being shed on the subject of how a rimfire contraption vibrates, when fired, and how that vibration relates to rimfire accuracy."


    This is something I looked into a while back and believe there is much more to learn.
    Here is some results from some tests I did that may add to the knowledge pool to help with improving rimfire accuracy in the future.

    This was measuring the vertical movement / vibration at the end of the barrel.

    This was done by shinning an accurate laser measuring instrument at the barrel to measure distance.
    This way there was no inertia or momentum with the measuring device.

    The speed it measured was it took 40 readings from the time of ignition to the time the bullet left the barrel

    From previous tests I had measured that at about 2.5 ms (milli seconds) which is 2500 us ( micro seconds ) depending on velocity


    I need to explain what you are looking at.
    This is a screen shot of an oscilloscope, the graduations down the left side is calibrated in MM so the smallest graduation is .01mm or .00039"

    Along the bottom is the time and in this case it is in ms (milli seconds ) or 1/1000 th of a second
    The ignition is at "0" and by the first graduation of "100" the bullet has well and truly left and gone as it left the barrel at 2.5 ms.

    This is the overall big picture

    Big picture.jpg

    Don't worry about the trace starting just under 0.06 mm on the left as this was the starting position of the instrument for this run.

    This is another test with a zoomed in view, the scale on the left is still the same but the time is now in us ( micro seconds )
    So the bullet left at about 2500 us or 2.5 milli seconds

    Zoomed in.jpg

    Remember there are about 40 reading taken between "0" and "2500" when the bullet left.

    Next thing is how accurate is the laser sensor ?

    This screen shot is of the laser measuring a still barrel with nothing happening
    This shows what we call noise or you could say the randomness of the measuring and it is a 1/3 of a division of .01mm so it is .003mm or .0001" (1/10 thou)
    The specifications for the Laser measurement unit is within 1.5 metric microns or .0015mm or .000059" but I saw double that

    Sensor noise.jpg

    The thing to note here is from ignition that the barrel starts to move down then back to the start height and then down again and back to the start height and stays there relatively flat for the critical time that the bullet leaves then starts to climb up which is the first upward swing on the "big picture" shot.

    When I look back and forwards between several shots at the same settings you can easily see what is noise and what is a real movement.

    Regards
    Graham

    __________________________________________________ _______


    Friend Deveng:


    Thank you...


    I highlighted a couple of your sentences....


    _______________________________



    If one had a barreled action clamped in a fixture, so the contraption had no recoil movement......barrel naked, no MD...


    If one then aimed a device at the muzzle, capable of seeing the actual barrel vibrations, when fired, as you state your laser is capable of, it would show the muzzle oscillating........


    If one then aimed the measuring device just back of the muzzle, this distance being determined by the stiffness of the barrel, that portion of the barrel would be stationary.


    __________________________



    If one then attached a muzzle device, that had been properly adjusted for this barrel, then aimed the measuring device at the end of it, the end of the muzzle device would be oscillating.


    If one then aimed the measuring device at the exit of the crown, it would be stationary.............I term this the "stopped muzzle" condition.

    ( Discounting what you term "noise", which is present, throughout the universe, whether the muzzle is stopped or oscillating)



    ________________________



    Friend Deveng, it's very simple to visually demonstrate this stopped muzzle condition.......


    Every person I've demonstrated if to in my shop is amazed.......




    This HMC thing, that's come to light in the past few days, is fascinating.........



    I know there's no way to actually prove it, but, when I ground the action face on Selby Wright's Winchester 52 C Model, I now believe I corrected a situation which allowed his action/barrel to obtain "harmonious metallurgical continuity".


    Which is starting to add to the knowledge as to why the TCA actioned RFBR guns have dominated the Big Nationals ever since Flash Ebert brought out his MD-PAS ignition Turbo 20 years ago.



    Thanks again for your work..


    Your friend, BC
    Last edited by Bill Calfee; 06-10-2018 at 02:20 PM.

  3. #3

    Sorry I forgot something

    Hi Bill

    I forgot to say

    The Barrel and action was mounted in a stock

    This stock was then mounted to a linear rail, the same that is used on a CNC machine with the seals removed to reduce friction

    The whole contraption was allowed to free recoil.


    I know when you mount the action / Barrel solidly so it can't move it then is a totally different kettle of fish.

    Regards
    Graham

  4. #4

    Friend Deveng

    Quote Originally Posted by Deveng View Post
    Hi Bill

    I forgot to say

    The Barrel and action was mounted in a stock

    This stock was then mounted to a linear rail, the same that is used on a CNC machine with the seals removed to reduce friction

    The whole contraption was allowed to free recoil.


    I know when you mount the action / Barrel solidly so it can't move it then is a totally different kettle of fish.


    Regards
    Graham
    __________________________________________________ ______



    Friend Deveng:


    I doubt for what we're after in studying contraption vibrations, that it really matters........






    I liked the way you had the laser independent from the barrel........


    I just assumed you had the contraption stationary, along with the laser.


    If the laser can record oscillations at a single spot on the barrel, with the laser stationary and the barrel in recoil, then it matters not whether the contraption is mounted solid, or allowed to recoil.


    Thank you again for your work....


    ________________________________________



    By the way, since you're very willing to participate, in a serious way here on CYA, would you care to guess why me grinding the face of Selby's Winchester 52 C Model allowed, in my opinion, the action/barrel to obtain a state of "harmonious metallurgical continuity"?


    This is probably an unfair question, for you and others, unless you know the physical characteristics of the construction of a Winchester 52 C Model, or the D and E Models also.......


    I would almost bet our friend Hawkeye Wizard knows where I'm going, since I mentioned the particular characteristic that the C Model Winchester has, is also shared by the Remington 03-A3, as Hawkeye is a former US Arsenal engineer.



    Thanks again, your friend, BC

  5. #5

    Friend Deveng

    Friend Deveng


    Friend Deveng:


    I just had a call about something, and based on that call I'd like to ask you a favor.....


    Would you mind posting your pictures on the Rimfire Accuracy site, it's the old Pappas site........that is if you can post there, and want to.


    Guests can read your comments, but can't open your pictures.


    I even logged out and tried it and I couldn't open them either.


    ________________________


    I thought guests were able to open pictures here on CYA, but maybe they can't....


    Wally runs CYA because I wouldn't have any idea how to.....


    Your friend, Bill Calfee

  6. #6

    Answer

    Hi Bill

    "By the way, since you're very willing to participate, in a serious way here on CYA, would you care to guess why me grinding the face of Selby's Winchester 52 C Model allowed, in my opinion, the action/barrel to obtain a state of "harmonious metallurgical continuity"?"

    I have to plead ignorance on a couple of accounts

    1) I don't know the structure of the Winchesters to add an intelligent comment to the conversation.

    2) "harmonious metallurgical continuity" is a totally new term I have not heard of. In this part of the world we use different words and spelling for things but that one is totally new to me so I sorry but I must plead ignorance on that as well.

    As for Posting the images, someone bet me to it.

    Regards
    Graham

  7. #7

    Something to ponder

    Hi Bill

    A Barrel that is drilled straight, is it better than one with the bore that is curved ?


    Between when the bullet starts to move and before it reaches the muzzle

    I am not looking or talking about the end 1/4 of the barrel when the bullet leaves.


    The part of the barrel that the bullet is in has moved from its starting position so the bullet is now not traveling in a straight line, this means it is traveling in a curve relative to a fixed point outside.

    This would mean the bore has to push on one side of the bullet and then even the opposite side.

    Would this not size the soft lead bullet to some degree ?

    Regards
    Graham

  8. #8
    Thank You Deveng sharing this.

    If it is possible to measure vibration what different weight pin gives to barrel,it would be intresting.

    I mean Turbos about 57 g pin comparing 20-30 g pin on different action.Using shooted cases.

    Also it should be intresting to see same way PAS & SAP systems vibration to barrel.

    Also well tuned barrels vibration vs. "untuned" barrels vibration....

    BR, Timo

  9. #9

    Friend Deveng

    Quote Originally Posted by Deveng View Post
    Hi Bill

    A Barrel that is drilled straight, is it better than one with the bore that is curved ?


    Between when the bullet starts to move and before it reaches the muzzle

    I am not looking or talking about the end 1/4 of the barrel when the bullet leaves.


    The part of the barrel that the bullet is in has moved from its starting position so the bullet is now not traveling in a straight line, this means it is traveling in a curve relative to a fixed point outside.

    This would mean the bore has to push on one side of the bullet and then even the opposite side.

    Would this not size the soft lead bullet to some degree ?

    Regards
    Graham

    ____________________________


    Friend Deveng:


    I've seen some very crooked rimfire barrels shoot pretty good...


    If I have my choice I want straight barrels, if for no other reason they're easier to fit and chamber properly....



    Does a rimfire bullet passing through a crooked bore cause more erratic barrel vibrations than one passing through a straight bore?


    I don't know, for sure.


    Your friend, BC


  10. #10
    Hi Graham,

    Thank you for the good effort!

    Can you clarify, what I canīt read in the oscilloscope results,
    maybe it is me who just canīt read.

    On Big picture, the data suggests from 0s to 2500us movement of the barrell only 0,01mm.
    But in Zoomed pic, there is according to my reading skills 0.1mm up and supposedly same amount down.
    So is there some filtering done in the "Big Pic"?

    Can you add a picture zoomed into those 2500us, so just the time from 0 to when bullet leaves the barrell,
    as this is the most interesting data.

    Thank you in advance.

    Tomi

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