Just how fast could a paintgun shoot paint?

Just how fast can a paintball gun cycle? We're about to find out. Just as an exercise in math and theory, a couple of noted Tinker's Guild regulars once sat down and worked out the following, over a day or two, and posted it to the Guild. I've made no changes other than formatting it to HTML, and correcting a few minor typos. The "mechanism" referred to, is a unique powered-loader design that is in development and at this writing, quickly approaching production. Get your calculator out, 'cause here we go....

Curt, it would be extremely interesting to see what would ultimately be the limiting factor in ROF. And also get some hard data on the time it takes to feed the ball into the breech (currently I just know the maximum as its the time between the cycles.) I can certainly feed that fast no problem.

The thing that I've never ascertained is exactly how long after my system feeds the ball into the breech before the next shot.
Because I was using a mechanical system, I had to ensure the feed was significantly greater than the requirements to ensure no balls are chopped. But with your eye set up that is no longer a problem. If we start shooting at 30bps would the sensing time of the electronics become a factor?

I'm pretty sure we if we hooked up, and could get an electronic gun equipped with an eye to shoot faster, then we could break all records. BTW, that's at just under 30bps... I can feed faster (my new prototype being built at the moment should be 25% better hehehe) In fact I can feed as fast as you want, just gets to the point where the paintballs can't take it anymore :), but hey actually since the gun would be firing the ball as soon as it made it to the breech (unlike the RT where there had to be a delay to prevent chopping) the crush factor that was causing me a problem may no longer be there... hmmm....

As to the board. I don't have an angel, just a BM2K for my electronics tinkering, I don't see why it should be any slower... If you are up for it I am. Where in the States are you? Or should I just send my gun over?

The whole reason I ever made an RT shoot that fast in the first place was just to prove I could. It's certainly not something to ever let loose on a field... unless you are wearing full motorbike leathers and helmets... oops did I tell you we were planning a game like this... at 30bps you would need a generous paint sponsor too!

manike

The sensing time of the electronics/eye are not an issue. I have measured about 50ms between the time the bolt clears the eye and the next ball is presented, with air-assist that's more like 20ms.

The eye rises/falls inside of 2 microseconds. That's roughly 10,000 times faster than it needs to be. And is enough time for the PIC to execute 50,000 instructions. (The entire program consists of... ~600 instructions.)

I figure the rate would not become an issue to the electronics until..*crunch*crunch*crunch*... 5,000 bps. At which time I'd
quintuple the clock to 20MHz and boost it to 25,000 bps.

25,000 bps is roughly 125 cases/sec. That translates to about $10,000 in paint.

Remember this is all over the course of a single second.

Lets say A case of paint weighs roughly 16 lbs. I don't actually know, but that seems a reasonable guess. Such a gun would be firing a TON of paint per second. Lets tare off the cardboard and let it cycle for a few more seconds and say that you would be firing a Buick's worth of paint while bunkering someone. Ouch.

In order to deliver this many paintballs, assuming each is .68" in diameter, they would need to enter the breech at approximately 965 miles per hour. That's well in excess of Mach I (at sea level) and quite above 300fps. Actually this would be quite a challenge to design a paintball gun that would slow down the ball sufficiently from a supersonic loader to be safe.

I'd do the air requirements, but inital pass at the math shows that you might be able to light off a stick of dynamite and soak off the resulting pressure before it did any damage. And would require a very fast trigger finger.

-Curt

It all depends on the locations of the sensor you are using in relation to the breech and the bolt. I'm guessing that the eye detects a ball when it is pretty much fully into the breech? Or does it detect it at a point where it is just far enough in to prevent a chop? (These are different locations, but a mm or so doesn't make that much difference to the basic calculation.) Anyway assuming the ball is all the way in and that the bolt is halfway retracted when it clears the sensor (if it is further back than this then the ball has chance to drop before the sensor detects the bolt has cleared and it may screw up my calculations a little, but what it detracts in terms of how long the ball takes to drop in, it adds to the cycle time anyway so it may not matter...) from my quick mechanical calculations...

The acceleration of the ball into the breech is 13.84m/s/s with a 50ms interval and 865m/s/s with a 20ms interval. The first rate makes me think that the sensor is closer to the back of the breech than the centre point looking down the feed stub. If it was exactly centre then we should have got a figure much closer to 9.8m/s/s

This should give rates of fire (assuming cycle time to be 21ms for an RT, what is it that you get for an Angel in terms of how long from when the bolt covers the eye to uncovering the eye when dry firing?) of 14.2bps and 25 respectively.

When we were shooting the RT at 26bps we calculated the cost to be 0.05$X26X60=78$ per minute... when we were shooting perfect circle balls (rough cost guess 0.25$) it would be $390 per minute or $6.5 per second. And that we were actually doing. I worked out the paintballs were required to travel at a rate that would have been approx 60bps if they were not feeding into a gun and that means they had to feed within a 16.6ms maximum which works out as an acceleration of 1245.6m/s/s. this means at the point where the hit the bottom face of the breech they are travelling at 21m/s, or approx 70fps. hey I could shoot people with my loader...

Now I could in theory feed 25,000 bps but the mechanism would be 1790 metres wide... just over a mile so I think you'd need a pretty big back pack Curt to make it portable enough for you to carry around...

Oh yeah I love technical, haven't done much maths since my discussions with Miscreant a long time back!

manike

If we are only feeding 5000bps (lol) then the mechanism is 360 metres wide so I guess the limiting factor is how strong you are and if there would be any bunkers big enough to hide behind.

... Hehehe just checking my figures and I made a mistake on mechanism size... for 25,000bps it would be 384 metres wide, and for 5000 it would be 180 metres wide... hey miniaturisation already, anyone wanna try carrying that?

manike

I just got back from McDonalds and was thinking about this the whole way.

A 9V will run the Defiant with my board for.. perhaps 5000 shots. Maybe less. But lets say that's right.

This means that the afore-mentioned mythical paintball gun firing at 25,000 bps would require 5 battery-changes per second.

Even with a lever-changer thats quite a tall order.

Since many of the parts inside the gun would need to cycle at supersonic speeds, the shockwaves produced by the various surfaces would cause a lot of stress on the frame, most of the moving parts would need to be made of a strong, light metal. A good Titanium alloy springs to mind, but Magnesium might work better if you kept it well lubricated.

This gun would be loud, since the loader and moving parts would all be supersonic, it would not be hard to pinpoint the location of the person using it, we could call it the 'Thunderclap 2000' or something.

Now lets talk recoil.

Since all of the moving parts inside the marker are cyclic, and vibration issues aside, a ton of paint per second flying out means you have to exert a ton of recoil, its an integral over the second, with a bunch of impulse forces.. lesse.. if I remember my diff eq's properly you would need to excert a conitnuous force of 785 lbs on the gun. So brace yourself.

It is likely that most of the parts of the gun, including the barrel, would need to be liquid-cooled.

Back to the issue of gas. Lets say this hypothetical paintball gun is very efficient. 800 shots on a 68cc 3000 psi tank.

PV=nRT, holding nRT constant (a bad assumption, T will plummet.)

Taking:
P1 V1 = P2 V2
and
1 atmosphere = 14.7psi

Our 68cui tank pressurized to 3000 therefore represents 13,877 cubic inches of air.

This would suggest that roughly 1/800th of that is required to fire a paintball, so 17cui of air (at normal sea-level pressure) to fire a paintball.

Okay back to our gun then.

At 25,000 bps it would require 250 cubic feet of air, pressurized to, lets say 400psi. Unless you had some industrial compressors ganged together you would experience a bit of shootdown.

But thats okay! Since the Rate of fire dictates a faster muzzle velocity than is allowed (the balls simply cannot exit quickly enough at 300fps) you would have a fountain gushing forth from this gun, thick with literally tons of paint and shell and what have you, making an impenetrable wall in front of you that you could walk behind and not be hit from any enemy paintballs.

-Curt

Using some real rough figures and assumptions cos I hate calculus...

300fps is about 94m/s... and since a ball would have to travel at least it's own diamter before the next ball could be fired... that equates to a rof of 1734 balls per second... and a feed mechanism of 6.2 meters wide... hmm getting towards the constructible.

Now taking that the ball really should be allowed to exit the barrel before the next one is fired, and this will also allow for a amount of time for the bolt to cycle. Using a 12" barrel... a ball travelling at 300fps will take 0.0032 seconds to exit the barrel (yeah I know I'm assuming it is travelling at 300fps for the whole barrel length) so lets round it up to an even 0.005 seconds considering it is accelerating from rest to 300fps. Now while the ball has been travelling down the barrel you have reloaded the next one so it can fire as soon as the first exits. This gives you a rof of 200bps. Doesn't sound that much anymore does it? lol!

Now this would mean my mechanism would have to 1.4 metres wide... hey we could mount that on a 4X4 for big games!

Now the problem is getting a marker that would cycle fast enough... Doc? Hehehe and then an air system to feed it with enough air. We'd want the bolt to cycle as fast as possible to give as long as possible between each shot to feed (has always been a problem for me as feeding rate requirements go up exponetially with ROF due to a fixed cycle time)

manike