How many times can an autococker cycle per second?

[magattack]

Cocker

The main thing about a cocker is trying to overcome the inertis of the back block moving. this creates a problem since the forward motion is because of air pressure. then when to bolt moves back it will compress the air even more causeing a little lag there.

[pbjosh]

Okay,

I have seen the Back block take any where between 16 and 45 ms to open. This is timed on a Racegun Frame. And to close normally is 5-10 ms less.

It was due to the Pressure input, ram, the linkage arrangment, bolt friction, spring weight, and also interia. Change any of these you can change the open/close time.

Air trapped between the BackBlock has so little to do with it, it is funny. With the cocking rod out and decent components the back block goes back in about 15ms or less. Without the bolt it takes even less time.

Josh

[Skittle]

well, if u have to account for all that to get a cocker to shoot really fast what about the sandridge force 5 cocker, it was an electro cocker and they were saying how they could shoot so very fast. So does that mean when u have an electro frame or whatever it affects the moving parts of the gun? How can they make the cocker like that if they cant get it to shoot faster than one that isint electro?

[nerobro]

Originally posted by Skittle
well, if u have to account for all that to get a cocker to shoot really fast what about the sandridge force 5 cocker, it was an electro cocker and they were saying how they could shoot so very fast.

It IS an electrococker, and it does shoot fairly fast. It's a gun that's depenant on it's eye, and without it being set right, you often slow the gun down signifigantly.

So does that mean when u have an electro frame or whatever it affects the moving parts of the gun? How can they make the cocker like that if they cant get it to shoot faster than one that isint electro?

"electro" Doesn't really effect the operation of the gun. Just the trigger feel. the "electro" parts are just how soem people here are choosing to measure their guns.

right now we know that a cocker can fire more than 20 times a seccond with palladins testing. So I suppose we are just down to the ponit of gettign a reg that can recharge that fast (the stabilizer can do 20... )

I'm wondering waht fatter hoses will do for how fast the gun can be made to cycle. Currently I just crank up the pressure on my rock to keep the gun cycling as crisply as I like. (I use that term becasue that's the way the gun feels when a LPR is adjusted "right" Just like the blazer) Hmm... still need to build a test rig...

[ER FFballa 8]

actualy

Actualy some guy on PBC set his race frame to do 294.5 BPs and it cycled that fast.. if we are talking cycling as in the bolt cocking then firing then that is what i've heard.. ok now back to reality the feeding rate and trigger pull effect how many times a second.. i have gotten my cocker to 10 BPS and others with electro frames have gotten better just depends on the person....

[AGD]

ER and the rest of the new guys,

You have posted in Deep Blue where we limit the discussions to factual and theoretical applications of physics to paintball. If you post something you MUST be ready to defend it with facts or a well thought out line of reasoning why it is true. If you post something you just HEARD was true, expect to get shredded here in this forum.

ER, you claim that someone on PBNation had his cocker to 300 cycles per second. I counter with this line of .
calcualtions.

In order to have the bolt travel 1" forward and then 1" back 300 times as second it has to move at least 55 FPS with no accell, decell. Considering the regular cocker bolt speed is about 4 fps this means you need 10 times the bolt speed right off the bat.

1" of forward travel at 55 FPS happens in about 1.65 milliseconds. This requires an accleration rate of about 16,000 feet per second, per second.

To accelerate a 3 oz. bolt at this accel. rate you need 90 lbs of force.

Cockers have a 1/4" piston for the bolt ram. To get 90 lbs of force out of it you would have to put 1900 psi air into the ram.

Unless the ram was hooked directly into the main compressed air tank there is no way the gun could EVER cycle 300 times a second.

So I claim the guy that posted that was either lying to get you to believe him or too stupid to figure it out for himself and is just passing down the myth.

Please hang around and help us dispell the myths that permiate paintball.

AGD

[einhander619]

Physics is phun(nice job by the way, TK!), but I have a much simpler explanation - misplaced decimal.
294.5 = 29.45?
Perhaps it takes someone who is as bad at typing as me to think like this. I hope against hope that noone is ignorant enough to claim 300 cycles per second on a cocker.

[MrMag]

it is SO hard to get a cocker over 9pbs. now i admit that i dont own one. but i have tried my friends old one, and the trigger and bolt just wont allow u to fire anything close to what er has stated. i am not a math/physics wizz like tk, but i can say this with complete assurance. this could be different w/ a racegun however.

[ER FFballa 8]

hey

all i was saying was some guy set his to that on the race.. he said it didnt look like it was moving so it probably wasnt.. but there are also guys that set their cockers to 90 on FA and the back block was a blur according to them.. now am i saying this is a fact no.. just what i have heard. i cant say the facts because for me the fastest i have gotten my cocker with sliding slotted trigger was 10 bps...

[einhander619]

90 bps sounds a little more plausible, still nuts, though! I think I'm going to forward this thread to my physics prof, he'll probably make a test question out of it. Even if a cocker did 90 bps, it probably couldn't sustain it for more than a few seconds before it would simply fly apart! Now, Tom, I didn't do the math, but following your example, 90 cycles a second would take something on the order of around 600 psi input pressure to the ram, correct? So much for low pressure...

[ER FFballa 8]

mike

ok i worked out your calculations and my ff with an input of under 300 which cycles at 30 psi is able to cycle at 47.5 bps so why would it be that impossible?? also at 90 it wouldnt fly apart.. cockers are built sturdy they arent the beasts many of you think they are...

[bjjb99]

Using Tom's explanation as a basis, I've come up with the following set of calculations. I included acceleration of the bolt since it wasn't too difficult to calculate. I will use the example provided by ER FFballa 8 to illustrate:

Take your cycling pressure (30 psi) and convert it to atmospheres by dividing by 14.7 psi/atm.

30 / 14.7 = 2.04 atmospheres.

Take this value and convert it to Pascals (a.k.a. N/m^2) by multiplying it by 101325 Pascals/atm

2.04 * 101325 = 2.07x10^5 N/m^2

We will assume that this pressure is constant against the cocker's ram piston. According to Tom's post, the piston is 0.25 inches in diameter (6.35x10^-3 meters). Calculate the area occupied by the piston.

(3.1415 / 4) * (6.35x10^-3)^2 = 3.167x10^-5 m^2

Calculate the force on this piston as a result of the gas pressure.

2.07x10^5 N/m^2 * 3.167x10^-5 m^2 = 6.56 N

F = m * a, a = F/m, calculate the acceleration of the bolt, assuming a weight of 3 ounces (mass of 0.0850 kg)

6.56 N / 0.0850 kg = 77.2 m/sec^2

Find how long it takes for the bolt to move 1 inch (0.0254 meters) with the acceleration calculated above.

x = 1/2 a t^2

t = sqrt(2 x / a)

t = sqrt(2 * 0.0254 / 77.2) = 0.0257 seconds

Multiply this time by 2 to cover an entire bolt open/close cycle.

0.0257 * 2 = 0.0514 seconds

This is the time required for one cycle of the bolt. Take the reciprocal of this number to determine the number of cycles per second, assuming zero delay between changes in bolt direction.

1 / 0.0514 = 19.5 cycles/second

At 30 psi, the max rate I calculate is 19.5 cycles per second. Using the 1900 psi in Tom's post, I get a max rate of 155 cycles per second. The max cyclic rate varies with the square root of the pressure, all other factors (bolt mass, piston diameter, bolt travel) being constant. Quadrupling the pressure increases the max cyclic rate by a factor of two.

BJJB

[nerobro]

Originally posted by MrMag
it is SO hard to get a cocker over 9pbs. *snip* and the trigger and bolt just wont allow u to fire anything close to what er has stated. *snip* this could be different w/ a racegun however.

Your difficulty in getting a cocker over 9 bps is your hand, not the gun.

The trigger is something you can tune to allow yourself to shoot the gun as effectivley as YOU can. the bolt has little to do with the rate of fire of th gun, at the ROF you're mentioning.

Using the racegun frame has almost no effect on maximum rate of fire. All it does is use a solinoid for the sear and one for the 4way. As the parts of the gun see it, the differences are negligable at best. The sear drops faster... and that's about it.

As paladin said earlier, he has had one of his guns up to 20bps... so we know THAT number for sure.

[nerobro]

IIRC the piston in a stock cocker is 3/16" not 1/4" That changes things singifigantly. the only ones with the 1/4" or smaller are the clippard minirams...

[bjjb99]

If I am reading my own calcs correctly, the max cyclic rate varies proportionally with piston diameter. In this case, a 3/16" piston should yield 75% of the cyclic rate obtainable by a 1/4" piston, all else being equal.

BJJB