Post by pkvmax on Jul 26, 2010 12:30:19 GMT 8
I'd like to share here how to use pc for measuring pellet velocity. And of course if you know pellet weight, you can easily find also it's energy. All you need is pc or laptop equipped with sound card and microphone (but not built in mic), you will need also software for sound recording. I recommend freeware Audacity: audacity.sourceforge.net/
You can do this at home or outside. In both, make sure there will be no ambient sounds like barking dogs, noisy motorbikes etc. And because you will have to shoot using pellet, also make sure no one will be hurt during tests (if you are not on the shooting range).
Ok, measure the distance from end of the barrel to the target in meters. Do this as accurate as possible, this is very important for results. I would suggest to use distance 10m, of course you can have shorter or longer, that's your choice (I shoot inside the house and had only 2.81m). Longer distance is better for reading the recorded sound in Audacity. Because you can hear two sounds: sound of the shot and sound when pellet hit the target, it's easier after to find proper pitch in Audacity. Because springers are a bit noisy I also recommend to use a metal can or something like that for a target. It will make different sound than sound of the shot so this also will help to find proper pitch (in CO2 and PCP there is no problem with that I guess). In the middle of the distance to the target place microphone. Start Audacity go to the bottom, mark Length, click small arrow and pop up menu will appear, choose miliseconds. On the top, set the microphone input level like on picture (to reduce ambient sounds recording, I recommend to off the aircon during tests, cooling fans etc- if inside the house). Prepare your airgun, use only one type of pellets for 5 shots, after you can check it with other pellet. Make sure the end of the barrel will be at the same distance to the target. Press recording button and make a shot, after stop recording. You should have something like on picture:
To make it more clear drag the bottom of the picture and pull it down:
Also use zoom tool and click few times on the picture to get something like this:
Next use selection tool:
and select the proper area:
You can see that the first pitch is the beginning of the shot sound, another high pitch after that is the beginning of the target hit sound. Rest is echo from the walls (I shoot inside the closed room). You may have problems with finding the second pitch. That's why I said before to make a target from metal can or something similar. And finding this pitch is very important to this test. Because small difference in Audacity means big difference in velocity.
Ok, after selecting an area I would suggest to use zoom tool again to make it more bigger, so you can see where the blue line crosses black line. That's the shot sound beginning:
and beginning of the target sound:
You can read now at the bottom, the sound length. But this value is rounded by the software. To know more accurate results do the following.
Now, read the time where these lines are crossed (at the beginning and ending of your area). If the grey arrow covers the numbers, just use mouse to move it and see numbers clearly. As you can see I had these numbers: 8.39097 and ending point at 8.40509.
I used Microsoft Excel for doing calculations, but it can be easily done on simple calculator. Anyway, first value minus second will give you the time which pellet flew from the barrel to the target. Now you need to divide the distance by this value and that will be your pellet velocity in m/s. Take a look on my example:
8.39097 - 8.40509 = 0.01412 s
I had 2.81m distance, so:
2.81 / 0.01412 = 199 m/s
If you want to know pellet velocity in FPS just divide your result in m/s by 0.305:
199 / 0.305 = 652.89 FPS
Here you can see my results for 5 shots in excel:
This method is accurate as long as you will find proper pitch and the distance will be all time the same. But because of some mistakes which you can do during testing, best is to confirm your results with digital chrono;)
Anyway I hope this guide will be helpful for some shooters.
All is available also here: www.pinoyguns.com/modules.php?name=Forums&file=viewtopic&p=349171#349171
Enjoy.
You can do this at home or outside. In both, make sure there will be no ambient sounds like barking dogs, noisy motorbikes etc. And because you will have to shoot using pellet, also make sure no one will be hurt during tests (if you are not on the shooting range).
Ok, measure the distance from end of the barrel to the target in meters. Do this as accurate as possible, this is very important for results. I would suggest to use distance 10m, of course you can have shorter or longer, that's your choice (I shoot inside the house and had only 2.81m). Longer distance is better for reading the recorded sound in Audacity. Because you can hear two sounds: sound of the shot and sound when pellet hit the target, it's easier after to find proper pitch in Audacity. Because springers are a bit noisy I also recommend to use a metal can or something like that for a target. It will make different sound than sound of the shot so this also will help to find proper pitch (in CO2 and PCP there is no problem with that I guess). In the middle of the distance to the target place microphone. Start Audacity go to the bottom, mark Length, click small arrow and pop up menu will appear, choose miliseconds. On the top, set the microphone input level like on picture (to reduce ambient sounds recording, I recommend to off the aircon during tests, cooling fans etc- if inside the house). Prepare your airgun, use only one type of pellets for 5 shots, after you can check it with other pellet. Make sure the end of the barrel will be at the same distance to the target. Press recording button and make a shot, after stop recording. You should have something like on picture:
To make it more clear drag the bottom of the picture and pull it down:
Also use zoom tool and click few times on the picture to get something like this:
Next use selection tool:
and select the proper area:
You can see that the first pitch is the beginning of the shot sound, another high pitch after that is the beginning of the target hit sound. Rest is echo from the walls (I shoot inside the closed room). You may have problems with finding the second pitch. That's why I said before to make a target from metal can or something similar. And finding this pitch is very important to this test. Because small difference in Audacity means big difference in velocity.
Ok, after selecting an area I would suggest to use zoom tool again to make it more bigger, so you can see where the blue line crosses black line. That's the shot sound beginning:
and beginning of the target sound:
You can read now at the bottom, the sound length. But this value is rounded by the software. To know more accurate results do the following.
Now, read the time where these lines are crossed (at the beginning and ending of your area). If the grey arrow covers the numbers, just use mouse to move it and see numbers clearly. As you can see I had these numbers: 8.39097 and ending point at 8.40509.
I used Microsoft Excel for doing calculations, but it can be easily done on simple calculator. Anyway, first value minus second will give you the time which pellet flew from the barrel to the target. Now you need to divide the distance by this value and that will be your pellet velocity in m/s. Take a look on my example:
8.39097 - 8.40509 = 0.01412 s
I had 2.81m distance, so:
2.81 / 0.01412 = 199 m/s
If you want to know pellet velocity in FPS just divide your result in m/s by 0.305:
199 / 0.305 = 652.89 FPS
Here you can see my results for 5 shots in excel:
This method is accurate as long as you will find proper pitch and the distance will be all time the same. But because of some mistakes which you can do during testing, best is to confirm your results with digital chrono;)
Anyway I hope this guide will be helpful for some shooters.
All is available also here: www.pinoyguns.com/modules.php?name=Forums&file=viewtopic&p=349171#349171
Enjoy.
