Pressure induced ball breaks

[Poe]

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Peak pressures above 150 psi tends to break balls down the barrel due to really high acceleration and G forces.
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The above was pulled from the "Barrel Efficiency, Tech Tip #1" thread.

Judging from your earlier threads I'm assuming you came to this conclusion through testing? I only ask because the Goblin markers accelerate paintballs to 300fps in less than an inch. Do you think the increased breaks you noticed in your tests could have been caused by the barrel length or some other factor?

[Smoothice]

Good luck getting 300 fps on those bad boys.

Out of the many many shots mine have seen getting over 250fps is a challenge...

[Ando]

I can't even get mine to register off a chrono.

Geoff Manning, I'm guessing he's a tech for the Goblin said I needed to use a optical gate chrono due to the lack of barrel.

Doesn't sound right to me but what the hell do I know. Mine is good up to 25ft, 30ft it sometimes bounces. Anything over that...bounce...bounce...bounce...

[Poe]

Good luck getting 300 fps on those bad boys.

Out of the many many shots mine have seen getting over 250fps is a challenge...

Although 250fps in 0.7" still requires significantly more than 150psi, you might want to try the following to simulate the 300fps results obtained by others.
- Use HPA instead of CO2
- If using CO2, keep the shell warm prior to firing (DO NOT EXCEED 80F)
- Pull the trigger quickly. It's not a hammer/sear just a trigger on a pivot.
- If filling with CO2, turn the tank upside down so liquid CO2 is entering the shell not gas. This is only good for a couple fps when it's cold, much more when warm.
- Disassemble and lube the cartridge before using as Goblin recommends in their videos .
- Use the brass spacers and large paint for a tight fit.

[Ando]

[Poe]

I've been able to get several Goblins to exceed 300fps using the methods described above.

The topic is pressure breaking paint though. Please go here if you have difficulties or would like assistance with your Goblin.

[Ando]

I've been able to get several Goblins to exceed 300fps using the methods described above.

The topic is pressure breaking paint though. Please go here if you have difficulties or would like assistance with your Goblin.

What are you using as a chrono and what are you putting inside the shells to reach 300?

[Poe]

Not much activity in this part of the forum eh?

Since it's not pressure alone, does anyone have any ideas what would cause higher (than 150psi) pressure to break more balls? I wonder if this only applies to Automags.

[Ando]

Still didn't answer my Q

What does your setup look like. I'd like to know what your using to get a tight fit on the balls.

[athomas]

Not much activity in this part of the forum eh?

Since it's not pressure alone, does anyone have any ideas what would cause higher (than 150psi) pressure to break more balls? I wonder if this only applies to Automags.

Higher than 150 psi could cause the ball to deform and possibly split at the seam, depending on the quality of the ball. Automags and most other paintball guns don't have to worry about this. Their peak pressure behind the ball never goes above 60psi. That is the pressure at which the ball moves away from the breach. The only way to get a higher pressure impulse, is to have a nonrestrictive method of delivering air. Basically, the air supply in the chamber has to be instantly available behind the ball. That is really hard to do because there is a definate amount of time required to open any valve or port to allow the air to flow. If the port is not fully opened the air flow is restricted and the pressure doesn't reach full value and the ball moves away using a lower pressure. The higher pressure is never realized as the starting pressure is reduced by the ever expanding volume.

[Poe]

Higher than 150 psi could cause the ball to deform and possibly split at the seam, depending on the quality of the ball. Automags and most other paintball guns don't have to worry about this. Their peak pressure behind the ball never goes above 60psi. That is the pressure at which the ball moves away from the breach. The only way to get a higher pressure impulse, is to have a nonrestrictive method of delivering air. Basically, the air supply in the chamber has to be instantly available behind the ball. That is really hard to do because there is a definate amount of time required to open any valve or port to allow the air to flow. If the port is not fully opened the air flow is restricted and the pressure doesn't reach full value and the ball moves away using a lower pressure. The higher pressure is never realized as the starting pressure is reduced by the ever expanding volume.

Like I said in my original post, the Goblin markers accelerate paint to 300fps in less than 0.7". The average pressure required to do this is significantly higher than 150psi yet the paint survives. I completely understand why other markers can't do this, but I'm more interested why Tom's data is telling him 150psi breaks balls.

[Poe]

Any thoughts athomas?

Maybe newer paint is better?

[Smoothice]

Any thoughts athomas?

Maybe newer paint is better?

Maybe the goblin is just that awesome?

[athomas]

Maybe the lack of a barrel allows the ball to deform without fracturing. I've seen guys shoot automags with 2" barrels before. They worked fine. Actually, a very short barrel is quite accurate. There is less induced spin on the ball to produce curving. They are very inefficient though.

If I can find my spreadsheet that I did a few years ago, it had all the calculations for accelerating a ball based on an automag chamber size. I would like to run the numbers on a short barrel to see where it falls. I haven't been able to find it. I know its here somewhere though.

[Poe]

Just throwing this out there to see if my math is correct...

Assuming an average pressure behind the ball of 150psi and a barrel length of 0.7", the maximum velocity would be 175fps? A 2" barrel would be 300fps?

Accuracy vs barrel length is interesting. Maybe I'll bring that up on the Punkwork forum. Speaking of which, if you haven't yet visited it's worth a trip.