Explorations (How can you help!)
Some experiments for you to try: Physics teachers - you can develop a lesson plan around some of these. Kids - lets not forget those science fairs your science teacher is always trying to get you to submit a project for. Professional scientists or engineers - if I can spend some of my personal time on this, so can you. Its your duty to the paintball community and society!

Note since the original of these pages was published, I have it from a good source that at least some of the needed data already exists. Sadly, but understandably, this data will probably never see the light of day for a variety of proprietary reasons.

By now, if you have managed to slog your way through all this, some of the most obvious problems and needs are already evident to you. However, I will compile the ones that stuck out for me, along with some hints at good scientific practice. However, I do not intend to write down all the scientific protocols necessary. Particularly for science projects, I don't want to make the task too easy. I give only a few hints to start you thinking (but see last section here). Moreover, I certainly don't have all the answers.

What is the Trajectory and Range of Paintballs?
Anyone with a lot of open space, a good tape measure, a protractor (or better a transit), at least one chrono, and a maybe a video camera can get into the act here. The question is how well do the simple trajectory calculations match with reality. Are my numbers even close? Before you run out the door to start this project, read this entire manuscript over a couple of times. It will give you insight into all the factors you need to be aware of to provide reliable data. What would I like to see? Well at a minimum, if a video camera would pick it up, the entire trajectory. Also, the point where the ball hits the ground in terms of distance from marker and lateral deflection, and how long the ball took to get there. With a very good extensive set of data, we can work backwards to define better drag and lift coefficients. As a starter read the Lapco Challenge which I discussed in the Relevance Section.

Flatter Trajectories?
I discussed the fact that topspin could produce a flatter trajectory at low spin rates. However, if a marker produced backspin at high spin rate, an even flatter and longer trajectory can be produced. In general, this is what we would like to see all the time. As I already mentioned several manufacturers have come up with bolts that try to produce spin on the ball. These do not seem to be very popular. The unsupported reason given by several people is that they also cause dispersion as well.

The curved barrel by Tippmann Pneumatics is another way of producing spinning paintballs. Admittedly, I have great hopes for this method.

Another way of placing spin on the ball that I have not heard anyone using yet would be to use a slighlty oversized egg shapped barrel with the small end at the bottom so that gas can blow past the ball causing back spin. Remember you saw the concept here first!

Well, here is one anyone can try. Place a very thin film of tape on the top of the muzzle to create drag and hopefully backspin. If the spin is high enough, you will see a small change to a flatter trajectory. Hopefully, the balls won't break and the tape will hold for more than a few shots. Can you think of other ways to do this (without ruining a barrel)? Note: The change may not be much, and as I have already discussed there are a host of other problems to worry about. It could be easy to fool yourself into believing its true. How can you check this?

Find the range of spin velocities
So just what is the spin velocity range of a paintball? I discussed it in some very crude terms, but I would sure like to see real data. Is there a way to do this without a strobe?

Drag and lift coefficients for paintballs
For those with wind tunnels in their basement, just what are the drag and lift coefficients for spherical, ovoid or odd shaped paintballs. How about seams? This one is tough for the average citizen, and I would be surprised if even professionals would can get wind tunnel time for paintball research. But we need those dynamic coefficients!

How do you break a paintball?
Now here is one we all can do with the proper thinking about controls. In paintball, a hit is only counted if the ball breaks and there is at least a dime sized spray of paint on you.(The size varies from field to field.) Therefore, just what are the minimum requirements for a ball to break. I calculated that there is a very rapid falloff of velocity with distance, and discussed several studies related to paintball breakage. The data is in need of controlled scientific experiments. Does "long balling" really do anything, other than scare novice players, and keep you from getting bored on the field? What is the minimum speed to break a paintball when it contacts a surface? Now be careful with this. It is not quite as simple as it sounds. First, you need to know the balls speed accurately at the point of impact. Two chronos would be a real asset. Both hard surfaces, and soft surfaces that mimic the resilience of skin and clothes need to be considered. Then start angling these surfaces relative to the ball direction. Maybe you should also think about shapes like cylinders to represent arms and legs. Oh, and don't forget to measure the temperature, and humidity. For the real daredevils, worry about different manufacturers, shell thickness, elasticity and several other factors I will leave to your creative imagination.

This one is for the very advanced mathematician players: My feeling is that most of the accuracy problems are in the paintballs, not the markers (maybe players too!). Applying group theory, (symmetry groups) and statistical analysis to the problem of paintball deflection would be fun, and might just be useful. Of course, it wouldn't hurt to measure and quantify a variety of imperfections or asymmetries in paintballs to compare with theory. Of course, this project assumes that those with this kind of mathematical knowledge have even heard of paintball.

Temperature changes and markers
Another interesting point is what are the temperature changes over time in the gun. I mentioned that temperature has a big effect on pressure, and pressure is critical to constant velocity. So what are the variations? The temperature will directly impact you accuracy.

The Holy Grail Experiment
The problem of large bore barrels and non matched paintballs is well known. However, as noted in the Lapco Barrel Challenge and suggested in the previous section, there are still some strange things going on. So we have the ULTIMATE EXPERIMENT. An extremely challenging research project that will require real work, real thought and real money to do correctly. Unless you have access to a precision machine shop, and are very clever, it's a tough one to do right. You will also need precision equipment for delivering air and spinning balls. In addition, expensive high speed camera's are a must. Apparently, Air Designs did some work along these lines quite awhile ago, but the results are not completely in the public domain. (AD certainly has the right not to put them there.) I have only heard about some of the results. We need experiments that don't use paintballs, but use precision balls that have different sizes and different imperfections (like a seam!) Plastic balls would be fine if the tolerances can be held and established.

Why not use paintballs? Because paintballs are subject to humidity, preparation conditions, conditioning, pressure variations, temperature, filling factors, chemical aging, probably microbial decay and I am sure a few things I missed. We need to remove the effect of those variables. The relationships between seam orientation, sphericity, velocity, barrel length, pressure, bore size/ball size ratio and a few other variables needs to be locked down and understood. Then you start shooting paint.

Discussing or Arguing Ideas with Me
As far as I know this is the first document of its kind on paintballs. I would seriously like comments and suggestions to improve the scope and impact of this document. (Two, that I already know: its long, and its complex. Hey, you have to start somewhere!)

As far as people contributing to these problems, I would dearly love to have reliable experimental information. However, there are a couple of caveats: First, I do not have the storage space or the time to host and maintain other peoples work. I would gladly include a web reference or published reference, and discuss their results somewhere in these pages. (The one possible exception to this is what I deem critical data by someone without any web page access.)

Second, you should be thick skinned. If you submit your results or a reference to me for comment, I will give them my full attention. I am a professional scientist (a chemist, not a physicist), and will examine your work with the same scrutiny I use in my own work, and those of my colleagues. I don't care if your ideas or results conflict with what I have said here, but I do care about properly documented and well thought out work. You can expect a critical review about a subject that I have become a little familiar with. Remember, however, that I too am out of my natural element with much of this stuff.

If you are trying to come up with experiments to solve a problem, I will offer advice only if you show me you have thought about the problem yourself first. Basically, this is the same rule used in many of the sci.* newsgroups. I don't do homework for students.


Trajectory Equations Section
Results Section
Relevance Section
Discussion Section
Calculations Section


Last Updated: Febuary 5, 2000