Print PDF
Favorite
Email
Step 6Coilgun Research and General Information
Shoot cans, tins, or whatever your heart desires.(With the exception of others, unless they deserve it, not really). I am not responsible for you being stupid with this, If made right you could seriously injure or Kill someone with this.
Experiment with a different amount of capacitors to maximize the Muzzle Energy.
Equations:
-Potential Energy=(1/2)(capacitance in uF/1,000,000)(voltage in V)2
-Kinetic Energy= (1/2)(mass in g/1,000)(velocity in m/s)2
Equations for Capacitors in Parallel
-Capacitance(C) total=(C of 1st capacitor)+(C of 2nd Capacitor)+...
-Voltage(V)max= Lowest rated Voltage
Equations for Capacitors in Series
-1/(Capacitance(C) total)=1/(C of 1st capacitor)+1/(C of 2nd Capacitor)+...
-Voltage(V) max=(V of 1st capacitor)+(V of 2nd Capacitor)+...
-Power=(V)(I)
I-Current
V-Voltage
C-Capacitance
IDEAS POSTED HERE MAY BE OUT OF DATE(4/28/08)
Key Things to Know:
I would recommend reading "all" of the following as a good understanding of system maximization is key to build a worthy gun. Some Very general characteristics to help you create and maximize one are as follows.
A Few Variables
(These statements assume all other variables are unchanged and are as simply put as possible)
(Maximization is reached at the greatest efficiency)
(These are SUPER Generalized statements and are Approximate (in reality there are many, many more factors). But these statements do provide a simpler understanding of the system.)
-The coil:
-The larger the wire diameter and the fewer layers it has the more Capacitance is needed to maximize it.
-The smaller the wire diameter and the more layers it has the less Capacitacne is needed to maximize it.
-The shorter a coil is, a shorter pulse time is needed for maximization, Therefore more layers for shorter coils is required for maximization resulting in a lower maximizing capacitance and a faster pulse time.
-The longer a coil is, a longer pulse time is needed for maximization, Therefore fewer layers for longer coils is required for maximization resulting in a higher maximizing capacitance and a slower pulse time.
-18-22 guage magnetic wire and 30mm Length seems to be a common place in most guns.
Capacitance:
(Discharge time constant(discharge to 37%) is determined by the product of capacitance and resistance) t=RC(for a simple RC circuit)
-A larger Capacitance has a longer pulse time and therefore affects the projectile a longer amount of time and so longer or heavier projectiles are needed for maximization.
-A smaller Capacitance has a shorter pulse time and therefore affects the projectile a shorter amount of time and so shorter or lighter projectiles are needed for maximization.
-The pulse time also relates to the length of the coil, a longer pulse time will be nessesary for a longer coil and a shorter pulse time will be necessary for a shorter coil.
...Take a Breath...
Voltage:
-There is a point where Higher voltage will taper off the output energy of the gun through power dissipated through heat. Power loss=I2*R (where I is current and R is system resistance)
-As far as I know an Increase in Voltage provides an increase in the output of the coil gun, to a point. That point is reached when the dV/dT (Change in voltage over change in Time) is significant enough to produce a large amount of eddy currents.
-Through research and experimentation it seems the best voltage range lies in the range of 200V to 800V, reason being 200V is a low enough voltage to where the wire needed to discharge the same amount of energy is significantly larger, which reduces the current density and increases the coil cost and size. The Upper limit of 800V is due to the higher dV/dT which results in large eddy current losses, experiments with 900V capacitor banks show significant (ie the firing of non-metallic projectiles via eddy currents) eddy current losses.
-In general I recommend using 50J per stage for 200V banks and 200J per stage for 900V.
(These are vague at best, but the limits produce better results)
Projectile:
-Ferromagnetic (objects which can be attracted by a magnet but not perminantly magnetized) material is what your projectile should be made of. I use large galvinized steel nails cut to size. Usually the nails will flip through the air, but if you attach a straw on the back the projectile will be stabilized (The longer the projectile the longer the stabilizing straw must be)
-Greatest effeciency according to projectile length can be reach with experimentation, but in general a projectile the length of the coil and as snug fitting as possible will yield close to maximized projectile deminsions.
-Smaller nails, screws, or even sling shot ammo can be used if power tools are unaccessable to you, but you will not get much effeciency with them, expecially spherical projectiles.
System Resistance:
I am still in the process of simplifing this as many factors in coilgun performance relates to resistance.
-Resistance is ultimately the defining aspect of a coilguns maximization. Many think that less resistance is always better, but this is not always the case. The fact that resistance is indirectly related to current (I(current)=V/R) and a greater current produces a greater magnetic field; this points to less resistance and more current for a greater projectile acceleration. Although this is true, resistance also plays a direct role in pulse time, which determines the amount of time the capacitor takes to discharge, and the amount of time the projectile is under acceleration.
-In conclusion one can say the higher the resistance, the longer the pulse time and lower the ampere peak; the lower the resistance the shorter the pulse time and higher the amperage peak.
-Also, with very low resistance ringing occurs in the system due to the coils inductance, resulting in the possible need for a protection diode reverse and parallel to the coil, resulting in a much longer pulse time and current leakage through the diode.(see topic below)
-will be continued...
Protection Diode:
-Many coilguns use a protection diode to prevent back emf(high reverse voltage that results from the coils induction) and to prevent system and capacitor failure. I did research with and without diode protection and the results explain the higher efficiency which my coils have been operating at compared to other much more advanced multistage guns. Experimentation showed an average of around 1/4 velocity loss with a reverse diode compared to no diode protection. As of now no damage has been done to the capacitors or any circuits due to back emf. I will continue to do testing.
I may be wrong on some, or all, of this. : )
USE THE SIMULATOR ON THE FIRST PAGE FOR YOUR APPLICATION
Disclaimer
I take no responsibility for your actions. If you shoot, shock, or otherwise injure yourself or others, Your
On Your Own.
Ideas, Comments, Questions? POST
Experiment with a different amount of capacitors to maximize the Muzzle Energy.
Equations:
-Potential Energy=(1/2)(capacitance in uF/1,000,000)(voltage in V)2
-Kinetic Energy= (1/2)(mass in g/1,000)(velocity in m/s)2
Equations for Capacitors in Parallel
-Capacitance(C) total=(C of 1st capacitor)+(C of 2nd Capacitor)+...
-Voltage(V)max= Lowest rated Voltage
Equations for Capacitors in Series
-1/(Capacitance(C) total)=1/(C of 1st capacitor)+1/(C of 2nd Capacitor)+...
-Voltage(V) max=(V of 1st capacitor)+(V of 2nd Capacitor)+...
-Power=(V)(I)
I-Current
V-Voltage
C-Capacitance
IDEAS POSTED HERE MAY BE OUT OF DATE(4/28/08)
Key Things to Know:
I would recommend reading "all" of the following as a good understanding of system maximization is key to build a worthy gun. Some Very general characteristics to help you create and maximize one are as follows.
A Few Variables
(These statements assume all other variables are unchanged and are as simply put as possible)
(Maximization is reached at the greatest efficiency)
(These are SUPER Generalized statements and are Approximate (in reality there are many, many more factors). But these statements do provide a simpler understanding of the system.)
-The coil:
-The larger the wire diameter and the fewer layers it has the more Capacitance is needed to maximize it.
-The smaller the wire diameter and the more layers it has the less Capacitacne is needed to maximize it.
-The shorter a coil is, a shorter pulse time is needed for maximization, Therefore more layers for shorter coils is required for maximization resulting in a lower maximizing capacitance and a faster pulse time.
-The longer a coil is, a longer pulse time is needed for maximization, Therefore fewer layers for longer coils is required for maximization resulting in a higher maximizing capacitance and a slower pulse time.
-18-22 guage magnetic wire and 30mm Length seems to be a common place in most guns.
Capacitance:
(Discharge time constant(discharge to 37%) is determined by the product of capacitance and resistance) t=RC(for a simple RC circuit)
-A larger Capacitance has a longer pulse time and therefore affects the projectile a longer amount of time and so longer or heavier projectiles are needed for maximization.
-A smaller Capacitance has a shorter pulse time and therefore affects the projectile a shorter amount of time and so shorter or lighter projectiles are needed for maximization.
-The pulse time also relates to the length of the coil, a longer pulse time will be nessesary for a longer coil and a shorter pulse time will be necessary for a shorter coil.
...Take a Breath...
Voltage:
-There is a point where Higher voltage will taper off the output energy of the gun through power dissipated through heat. Power loss=I2*R (where I is current and R is system resistance)
-As far as I know an Increase in Voltage provides an increase in the output of the coil gun, to a point. That point is reached when the dV/dT (Change in voltage over change in Time) is significant enough to produce a large amount of eddy currents.
-Through research and experimentation it seems the best voltage range lies in the range of 200V to 800V, reason being 200V is a low enough voltage to where the wire needed to discharge the same amount of energy is significantly larger, which reduces the current density and increases the coil cost and size. The Upper limit of 800V is due to the higher dV/dT which results in large eddy current losses, experiments with 900V capacitor banks show significant (ie the firing of non-metallic projectiles via eddy currents) eddy current losses.
-In general I recommend using 50J per stage for 200V banks and 200J per stage for 900V.
(These are vague at best, but the limits produce better results)
Projectile:
-Ferromagnetic (objects which can be attracted by a magnet but not perminantly magnetized) material is what your projectile should be made of. I use large galvinized steel nails cut to size. Usually the nails will flip through the air, but if you attach a straw on the back the projectile will be stabilized (The longer the projectile the longer the stabilizing straw must be)
-Greatest effeciency according to projectile length can be reach with experimentation, but in general a projectile the length of the coil and as snug fitting as possible will yield close to maximized projectile deminsions.
-Smaller nails, screws, or even sling shot ammo can be used if power tools are unaccessable to you, but you will not get much effeciency with them, expecially spherical projectiles.
System Resistance:
I am still in the process of simplifing this as many factors in coilgun performance relates to resistance.
-Resistance is ultimately the defining aspect of a coilguns maximization. Many think that less resistance is always better, but this is not always the case. The fact that resistance is indirectly related to current (I(current)=V/R) and a greater current produces a greater magnetic field; this points to less resistance and more current for a greater projectile acceleration. Although this is true, resistance also plays a direct role in pulse time, which determines the amount of time the capacitor takes to discharge, and the amount of time the projectile is under acceleration.
-In conclusion one can say the higher the resistance, the longer the pulse time and lower the ampere peak; the lower the resistance the shorter the pulse time and higher the amperage peak.
-Also, with very low resistance ringing occurs in the system due to the coils inductance, resulting in the possible need for a protection diode reverse and parallel to the coil, resulting in a much longer pulse time and current leakage through the diode.(see topic below)
-will be continued...
Protection Diode:
-Many coilguns use a protection diode to prevent back emf(high reverse voltage that results from the coils induction) and to prevent system and capacitor failure. I did research with and without diode protection and the results explain the higher efficiency which my coils have been operating at compared to other much more advanced multistage guns. Experimentation showed an average of around 1/4 velocity loss with a reverse diode compared to no diode protection. As of now no damage has been done to the capacitors or any circuits due to back emf. I will continue to do testing.
I may be wrong on some, or all, of this. : )
USE THE SIMULATOR ON THE FIRST PAGE FOR YOUR APPLICATION
Disclaimer
I take no responsibility for your actions. If you shoot, shock, or otherwise injure yourself or others, Your
On Your Own.
Ideas, Comments, Questions? POST
| « Previous Step | Download PDFView All Steps | Next Step » |
im using a 400 volt 330 uf cap. i pulled out of a busted antec power supply with a single charger curcuit running off 1.5v.
Q: does using a brass barrel decrease its power?
If anybody has any sugestions for my simple set up please tell me!
they get crazy voltages (21000v) but i dunno how much current
SO MUCH MATH! anywho, love this ible!
You'd also need to make sure everything was really well insulated. Spark plug wires are mostly rubber for a reason...
Check out this article if you want more information on how plugs work:
http://auto.howstuffworks.com/ignition-system2.htm