Results

Effects of capacitor bank size

As you can see in this graph, capacitor bank size has a dramatic effect on the raw speed of the projectile. There is a huge improvement in final velocity from using two capacitors and four capacitors in parallel. Using six capacitors in parallel appears to have diminishing returns, but still offers significantly higher projectile velocity.	Plotting the kinetic energy of the projectile, it is apparent that the voltage and projectile energy have an almost linear relationship with the two upper configurations. We can see from this chart that, had we used higher voltage capacitors, the returns we would expect from the coilgun would be much greater. Unfortunately, 450 volt capacitors are the most common, and therefore the cheapest high end capacitors available.	Last but not least, we plot the efficiency of the coilgun with these three different configurations.Surprisingly, the configuration with four capacitors in parallel appears to be the most effecient at high voltages. Because of the drop of efficienty with six capacitors in parallel, I decided it would be better to add a second stage to the coilgun rather than have the capacitor bank have eight capacitors.

Effect of projectile mass

As you can see, the hevier projectile (in pink) exits the coilgun with a lower velocity. This is absolutely no surprise at all.	This is the graph that is more important. As you can see, the hevier projectile has substantially more kinetic energy than the lighter projectile. The reason for this is because the projectile is heavier and thus moving slower, more of the energy is able to pull the projectile forward instead of sucking it backwards.	This graphs confirms our suspicions that the heavier projectile is more efficient than the lighter projectile. As you can see, the heavier projectile is substantially more efficient. I would have loved to get an even heavier projectile, but I was unable to do so.

Effect of coil layers

At lower voltages, it appears that the coil with five layers performs much better than the coil with three layers. However, at higher voltages, the three layer coil performs better.	Here is a plot of the projectile energy. As you probably already know, the coil with three layers performs better at high voltages	Here is an interesting graph. At lower voltages, the coil with five layers was much more efficient than the coil with three layers. In fact, this was the most efficient configuration I have experimented with to date. So if you want to build a highly efficient coilgun, you may want to consider using coils with several layers, a heavy projectile, and lower voltages.

Effect of coil design

As you can clearly see in this graph, poor coil design has a direct and significant impact on the performance of the coilgun. The 12 gauge coil was probably too long, and the wire was probably too thick to allow a reaonable number of windings.	Again, we see in this graph that the poorly designed coil has just over half the performance of the other coil. For a coilgun project, it is necessary to experiment with different types of coils in order to choose the best one for your particular design.	Here, we see the efficiencies of the coils. As you can see, the poorly designed coil has an efficiency of .1 percent, which is terrible. Coilguns are notorious for having very bad efficiencies, but .1 percent is still exceptionally bad.

Conclusion