• Link of our Facebook page :   / diy.experiments.youtube  

• Text of the video :

Hi everyone, today we’ll present you our coilgun. A coilgun is a device that uses a strong magnetic field to shoot nails. This experiment is very dangerous because of high voltages so we cannot explain exactly how it works.

Firstly we’ll test our coilgun on different objects then we’ll make some measurements and calculations.

The coilgun’s capacitor bank can accumulate 152 Joules of energy. Capacitors can reach 400V for a total capacity of 2000 microFarads.
This capacitors are charged with a fully automatic system, complex, but with a 72 Watts power.

Have a look at the size of the projectile compared with a standard nail, it’s big and heavy. Let's begin to use the coilgun, we're going to perforate that poor soda can. We press the charge button, then it's fully automated, the capacitors are charged at 400V in 14 seconds. The nail is placed and we push the "FIRE" button! "Perforate" was the right word. Now let's blow this Nutella jar. We wait for the capacitors to charge, we place the aft of the nail in first so then it will hit the glass. Charge finished, ready?
An other.
Two others.
Three others "FIRE”!
The nail managed to pass through the jar without breaking it apart.
Three more "FIRE”!
Common, one last just for fun.
Let's guess what would happen with a jar full of liquid "FIRE”!
Test on a fixed can, test on a 230 Volts turned on light bulb (with a system that prevent a short circuit indeed), we turn it on and "FIRE"!
Unbelievable! The smoke ring was so unexpected and amazing!
Test on an old and already well damaged PSP, test on a piece of tiles, test on a CD.
The nails seems not to have even slow down by breaking the CD, let's try with several CDs at the same time "FIRE"! Triple !
The last but not the least "FIRE" !

Now thanks to a technics we found that does not need any peculiar materials we are going to try to find the nail's speed. From that we will be able to determine its kinetic energy and also the efficiency. The idea is to measure the time that the nail takes to fly one meter in order to find its speed.
The first sensor is the combination of a LED and a solar cell, when the nail passes between them we can observe a difference in the light intensity. The second sensor is a simple switch that send an electric pulse when pressed. With a computer and Audacity software we’ll then find the time that passed between the two signals.
Let's study the sensors reaction, the first creates a little impulsion and the second a large impulsion more visible.
Now we are gonna shoot and analyses those impulsions. We can see first a period where nothing happens, here the nail pass in front of the first sensor, there's another period where nothing happens then the nail hit the last sensor.
We can see that the nail took 0.09 seconds to fly one meter, we can now easily calculate 1/0.09 which makes 11.1 meters per second. By calculating the nail volume and by multiplying it by the iron's density we find a mass of 47 grams. Then with the kinetic energy’s relation 0.5*m*v² we can determine that the nail has an energy of 3 Joules which is tremendous. The coil efficiency is then 2 percent, it's not a big number but it would be difficult to do better.

The smoke ring was so unexpected and amazing that we decided to scarify another lightbulb to see if it's going to happen again, ready "FIRE"! It was a fluke…