Painball and science projects

[hitmanng]

One of the co-op students at work yesterday was looking for a science experiment to do for school. And it got me thinking about what we want to know about paintball and the resources of these type of students. I discussed with her the bounce test as related to humidity and time. And accuracy questions. What would you like to know about a paintball, the marker or how they interact??
Hitmanng

[AGD]

Great! Have them crush paintballs on a scale using a drill press or equivalent to steadily increase the pressure. Record the results and give a statistical analysis.

That would be a good project, thanks

AGD

[bjjb99]

Ooo! Ooo! Ooo!

Measure the average force required to break a paintball when its seam is oriented perpendicular to the direction of the force, when it is oriented parallel to the direction of the force, and at various angles in between. Plot crush force versus seam impact angle to see where paintball bounces are most likely. Make some guesses ahead of time and see how they match the data. :)

BJJB

[CHK6]

I guess it depends on the class it's for. I would like to see a price to efficiency chart of using inert gases. Also including different gas ratio mixtures.

Another would be performing the smoke tests in rapid firing situations.

[Redkey]

Since the breaking of a paintball is a very dynamic event it would be interesting to see what different loading rates do to the breaking force.

An impact at 250 feet per second will have different force requirements than an impact at 5 ft sec (drill press or what ever). Although, if all your tests were done the same way on different paintballs it would give you a good A to B comparison under those test conditions.

It would be interesting to see how temperature, humidity, and ball age change the required forces. I wonder how consistant the paint manufacturers hold their tolerances? If there are major differences between batches of paint you'd have to do lots of testing.

[gotmilk4]

im doing a physics project/extra credit paper about the changing air pressures in the paintball gun. i just need to know the following numbers. if anyone knows these, itd be great, because i cant figure these out by myself. thanks:

-how long is the valve open?
-what is the pressure of the air when the valve opens?
-the pressure of the air behind the ball?
-the time it takes for the paintball to leave the barrel? (assume the barrel is as long as it needs to be for the paintball to accelerate fully, but no longer. sorry)
-distance it takes for paintball to accelerate (need this to find volume of barrel)
-how much air pressure (and percent of the volume) is lost to the powerfeed/centerfeed?
-volume of the air used to propel the paintball (i could figure this out, but it would be easier if someone had a number for me)

thanks in advance. hopefully most of these can be answered.

[J_Hoyt]

-how long is the valve open?

The time that the valve is open (dwell time) depends on the gun. An angel or an impulse come to mind as good guns to have for this because they have adjustable dwell times.


-the pressure of the air behind the ball?

For some unknown reason, I think the pressure behind the ball is usually around 120-150 PSI. Just something rattling around inside my head, don't put too much value on it.


-what is the pressure of the air when the valve opens?

Depends on what the regulator lets in. Anywhere from 100-900 PSI


-the time it takes for the paintball to leave the barrel?

The time from when the paintball begins accelerating to when it reaches the end of the barrel ranges from ~0.006 seconds for a 12" barrel and ~0.009 seconds for a 16" barrel.


-distance it takes for paintball to accelerate (need this to find volume of barrel)

Hmmm...maybe it was something from Glenn Palmer I read.... Here's what I read once: When using CO2, a longer barrel would be better for colder days as the gas will take longer to expand. The lower temps do not 'encourage' expansion. CO2 will expand quickly on a hot day so a shorter barrel is all that is needed to get the ball accelerated.
And the volume of a 12" barrel is 13 cubic inches. I also get 82.5 cubic centimeters if that's the way you do things.


-how much air pressure (and percent of the volume) is lost to the powerfeed/centerfeed?

I dont know, what the frig are you asking me for?


-volume of the air used to propel the paintball (i could figure this out, but it would be easier if someone had a number for me)

Figure it out yourself, I'm going to bed.

Good luck.

Joel Hoyt

[athomas]

How about finding the friction coeficients for a paintball.

Other questions asked here.
-how long is the valve open? A few milliseconds depending on gun( low pressure = longer time )

-what is the pressure of the air when the valve opens? Again, depends on gun. Mag is about 350 - 400 psi. More with the level 10.

-the pressure of the air behind the ball? Behind the ball pressure usually varies 60 - 90psi depending on gun. Mags are at 60psi.

-the time it takes for the paintball to leave the barrel? (assume the barrel is as long as it needs to be for the paintball to accelerate fully, but no longer. sorry) Less than 5 ms. Most of the velocity is achieved in under 3 ms.


-distance it takes for paintball to accelerate (need this to find volume of barrel) Depends on pressure behind ball. Higher pressure means less distance to reach velocity.


-how much air pressure (and percent of the volume) is lost to the powerfeed/centerfeed? Depends on how much longer the ball is in the barrel and how much pressure is remaining after the bolt returns to rest in the breach. While the ball is still in the barrel, air pressure will take the easiest path of escape. This path could be up the feed tube. Once the ball has exited the barrel, then momentum will carry the air out the front as well.

-volume of the air used to propel the paintball (i could figure this out, but it would be easier if someone had a number for me) I think that the average air usage to fire a painball is around 200 ci-lbs(cubic inch - pounds).

[gotmilk4]

yea, friction coefficient of a paintball would be good to have too. i was going to just use the coefficient of a sphere, but then a paintball isnt perfect, it has bulges/seams etc.

just to clarify, i still need an exact number one these questions:
-drag coefficient for paintball (quality paintball, not anything like BE)
-length of time valve is open.
-distance for ball to accelerate (ive heard 8-10 inches, does anyone know the exact distance for a mag, doesnt matter which mag)
-exact number for the amount of air lost to the powerfeed/centerfeed

other than that, you guys have been great. thanks for everything so far.

[aCiD]

I also happen to be in the same situation. I posted the question on another board, so I'll just paste it here again.

I got a physics ISU (Independant Study Unit) that was assigned today and somehow wanted to incorporate paintball into it... We need an experiment based somehow around physics...

Any suggestions as to a possible specific experiment would be greatly appreciated. Of course it has to be something that can be measured using next to no lab equipment... (Devices on hand, laser range finder, Radarchron, cameras.)

Eg. What velocity must a ball be travelling to break on a)Mask b)chest c)leg, things like that. Or course I would love to do this one, but can't because I have to way of measuring the velocity of the ball on impact.

Any suggestion or thought is appreciated!

-Brad

Some suggestions that came from the other msg boards were good as well, they can be seen here: http://www.thetrpc.com/forum/topic.asp?TOPIC_ID=663

[aCiD]

I have decided to do the project on the force required to break the ball, as Tom suggested earlier, but not just the force required, but the force over time. As the pBall doesn't always hit the same surface, it will have different decelleration times depending on the impact surface. Eg. a time of almost 0s when impacting the mask, and a slightly greater time when impacting your chest.

The final results will be measured most likely in G's, against the different impact surfaces. Also some other potential variables to be used are the age of the pBall, shell type, and environmental conditions.

[johnny dee]

OMG..!!! u could have alot of fun doing this project(im a dork). u could use alot of physics equationsto figure out a lot of different things. velocity-v=d/t velocity= distnce divided by time. the rate at which it fall from a building, keeping that the rate of fall for any object is 9.8m/s/s or 9.8m/s squared. m=meters s=seconds. finding the friction in different boer and length barrells...ill have to get back to you with the equation for that...yeah i know im a physics dork but hey i like it. hope this helps

[aCiD]

What I'm doing is a modified version of Tom's. I'm crushing balls, but dependant on the angle of the seam to the right bisector of the force. For various types of paint, and different "ages" of paint.

-Brad

[Redkey]

These tests were performed using a 100 lb load cell with data being collected at 20 points a second. Half the tests were done with the seam vertical the other half with the seam horizontal. The angles were just eye-balled so I would expect up to say... 5 degrees of error.

I cannot remember the loading rate... probably something like 0.5 inches per minute. The system is accurate down to less than 0.1 lbs and 0.001 inches.

I have load - displacement curves for each of the tests around here somewhere. I haven't bothered to put together a summary of the findings yet.

[aCiD]

Would you happen to know off the top of your head approximately how much force it took the rupture the ball? I plan on conducting my experiment tomorrow and just wanted to know before I began.

Thanks

[Redkey]

I believe that all the loads were less than about 50 lbs. Balls tested with the seam vertical were weaker than ones tested with the seam horizontal.

I'm guessing most were between 20-30 lbs. I ran the tests back in sept... and cannot remember the actual numbers.

If I have time I'll try and post a summary.

I might play around with doing the tests at much faster loading rates. I have some ideas for doing this... but, I'm not sure i can get fast enough data sampling rates with the equipment I have access to. hmmm....

I'm interested to see how your tests work out. If you can you should also post a description of how the tests were performed.