The paint ball store wont test homemade guns, the gun ranges will only test explosive powered, lead flinging weapons. I got the same answer every place i tried.
The paintball store, however, sells chronographs, for 120 bucks.
So, seeing as i am a poor student, i built my own, for under 20 bucks.
Here is how i did it:
WHAT YOU WILL NEED:::::::::::
2x infrared phototransistors RADIOSHACK
2x infrared LEDs RADIOSHACK
4x 1/2'' PVC end caps. (to mount the LEDs and transistors in)
1x wooden plank, flat and at least 1.5' long and 3'' wide.
1x AA battery and holder
1x computer
1x 1/8'' x 1/8'' headphone style wire.
A bunch of hook-up wire,
some solder, and a soldering iron.
INSTRUCTIONS:
Drill hole in the caps, for the LEDs and transistors, put transistors and LEDs in caps, glue in place.
Wire the transistors in series, and the LEDs in Parallel, on 2 seperate circuits.
Hook the battery holder to the LEDs, and the headphone cable to the transistors.
Glue the LED circuit to the wood, so that the LEDs are 1 foot apart, and point across the plank.
Glue the transistor circuit so that the transistors point towards the LEDs
put the battery in the battery holder to power the LEDs. Care full, they are infrared, and cant bee seen with the human eye. Take a digital picture of them to see them "On"
Hook the transistor circuit up to the line-in or microphone jack on your computer, open audacity, or some other recording program, start recording sound.
shoot your projectile through both "gates" and then stop recording.
If you look at your recorded sound file, you can see 2 "Peaks" each peak is a photo gate signaling that there is a bullet in the middle of it.
Muzzle velocity can the be calculate with this formula:
Mv= 1/(Time1-Time2)
Mv is the muzzle velocity in FPS
Time1= the time in your sound file when the first gate was broken(Peak1)
Time2= the time in your sound file when the second gate was broken(Peak2)
This equation assumes you have your gates 1 foot apart. if they are 6'' apart, then:
Mv=1x(gate distance in inches / 12'')/(Time1-Time2)
MUCH more detail can be found on this web page.(Not by me)
http://www.inpharmix.com/jps/Jims_chrono.html
PHOTOS:
Edit by MrC:
Dear author,
Do not request topics to be stickied.
EDIT: Yes sir MrC
Here is an example file....Click to make it bigger
