[Fordas]

I've seen it suggested before and dismissed so I decided I'd give it a go and see what kind of power and utility there is to be had. Oh and I apologize for the terrible impression

 

[JoergS]

Cool! But sorry, the power is somewhat disappointing. My rubber operated single shot gun would have sent the arrow all the way through the whole target structure. I suggest you look for a regulator that does 150 bar instead!

 

[Fordas]

Cool! But sorry, the power is somewhat disappointing. My rubber operated single shot gun would have sent the arrow all the way through the whole target structure. I suggest you look for a regulator that does 150 bar instead!

aye, part of the reason i'm sticking to 800psi if possible is the final weapon will be actuated by a push button 3 way 2 position valve and higher pressure would make the valve nigh impossible to actuate. to be honest i was more hoping to get performance comparable to the verminator mk2, do you have any numbers for the arrow velocity of the verminator mk2?

 

[JoergS]

Yes, the Verminator Mk2 does about 90 m/s with the 26 gram arrow.

You will have a hard time finding a QEV or solenoid valve that operates under high pressure AND has a high troughput. The ones that somehow work are usually "needle valves".

That is why I decided that forcefully opened valves are the way to go. Rubber works, but a cool hammer valve is best IF you have the right machinery to make one. I don't. So for me, rubber it is.

 

[Fordas]

Yes, the Verminator Mk2 does about 90 m/s with the 26 gram arrow.

You will have a hard time finding a QEV or solenoid valve that operates under high pressure AND has a high troughput. The ones that somehow work are usually "needle valves".

That is why I decided that forcefully opened valves are the way to go. Rubber works, but a cool hammer valve is best IF you have the right machinery to make one. I don't. So for me, rubber it is.

thanks for the numbers but 90m/s? that's a hair over 105J, i thought it was meant to be 70 something joules? regardless thanks for the target energy

 

[JoergS]

Well, the Verminator is tuneable by tightening the hammer spring. This is at almost full power. You can even get it to 120 Joule. We ship it with around 80 Joule for a good amount of shots at full power (55 shots on a full tank).

It used to be weaker, but then the Swedes decided to use the system box of the 7,62 cal. airgun. That one has a larger air throughput.

The Bobcat arrow has the same system box, but we ship it adjusted to 105 Joule.

 

[Fordas]

Well, the Verminator is tuneable by tightening the hammer spring. This is at almost full power. You can even get it to 120 Joule. We ship it with around 80 Joule for a good amount of shots at full power (55 shots on a full tank).

It used to be weaker, but then the Swedes decided to use the system box of the 7,62 cal. airgun. That one has a larger air throughput.

The Bobcat arrow has the same system box, but we ship it adjusted to 105 Joule.

ah thought as much. fair cop,well fx airgun's site quotes 60J so that gives me a whole range of target energies, from 60J to 120J. thanks for the info my man.

 

[Fordas]

Cool! But sorry, the power is somewhat disappointing. My rubber operated single shot gun would have sent the arrow all the way through the whole target structure. I suggest you look for a regulator that does 150 bar instead!

I have had further thoughts, the pressure only affects the theoretical max achievable velocities. The max for 55bar, with a 0.5m long bolt, with an internal diameter of 7.5mm, with a mass of 28g, is 93.1m/s (305fps). This is the theoretical max as it assumes constant pressure at all times, however, in actuality, the pressure will drop as the arrow accelerates along the launch tube, being that air is first transferred from the initial volume (be it from a hammer valve or from a minor air tank) and then into the bolt as it travels along the launch tube, further increasing the overall volume of the system. This causes the pressure immediately before the bolt escapes to be lower than the initial air volume's pressure. the way to get closer to the maximum velocity of your chosen pressure is to increase the initial air volume, thus reducing the ratio between the initial air volume and the final system volume and therefore reducing the drop in pressure. the way this is achieved with a hammer valve gun is by tightening the spring, this lets through more of the regulated air before the valve closes, thus increasing the initial air volume. similarly on a system utilizing a minor air tank such as mine or Joerg's homemade, the way to increase the initial air volume it to increase the minor air tank's volume. All other parameters withstanding, a higher pressure system will achieve the same final velocity as a lower pressure system with a proportionately larger initial air volume. this means that ANY final velocity (as long as it is below the maximum achievable with the system's pressure) may be attained with the appropriately sized initial air volume. in theory, the maximum velocity for Joerg's 300bar system should be 217.6m/s (712fps, 662.9J) assuming identical launch tube and arrow, and the only way to get closer to these numbers is by increasing the minor air tank's volume.

TLDR: Basically what this means is that performance on par with Joerg's tuned up bobcat arrow is mathematically possible with a system only regulated to 55 bar (800psi)

P.S the amount of physics and maths involved with calculating the various intricacies and nuances of these airbows could easily fill a few engineering dissertations so there is much more depth to be delved into here.