Contraption Vibration

Deveng

Member
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

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

View attachment 1414

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

View attachment 1415

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

View attachment 1416

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:
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
 
Friend Deveng

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
 
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
 
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
 
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
 
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
 
Friend Deveng

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

 
Hi Graham,

Thank you for the good effort!

Can you clarify, what I can´t read in the oscilloscope results,
maybe it is me who just can´t 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
 
Reply Timo

Hi Timo

I have not tried different weight pins

But I am trying to isolate the different sources of vibrations as they all add to each other.
That is why I asked Bill about Mike Mullins electric ignition, which by the way works.

The reason for this was that the pin was making vibrations and I wanted to remove them.

To measure PAS v SAP I don't know if you could see that as any difference would most probably be buried in the noise.

But there was a difference between 6:00 and 12:00 pin positions from memory
I even tried 3:00 pin position as well


Regards
Graham
 
Reply Taavetti

Hi Taavetti

On the "Big Pic" the filter is on, you can see a tick box on the far right.

It shows a dip of about .0075mm or 3/4 of a division being .01mm then it starts to move up

The time scale for this is at the bottom of the graph "Time , ms" and the first number is 100ms so 2.5ms is really too small to judge at the scale.
So it is basically showing the ringing of the barrel after the bullet has left.


What it does show that is a little revealing is the first 3 positive peeks and the valleys in between.

This is there are several vibration waves and they are interacting with each other and what you see is the sum result of the different waves.

So this proves the vibration situation is not a simple system.

The Zoomed in one shows where the action is from 0 to 2500us

This you have to ignore the little giggly bits so to speak, look at the Sensor noise to get an idea of what you have to ignore,
The Sensor noise should be a dead straight line.

Regards
Graham
 
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