SpudFiles

Taking the grinder to this build as we speak...cut off the grip and bottle-connector...

The plan is to rebuild the grip around the mag and forward the trigger.
The bottle will be replaced by a 12-gram adapter wich doubles as the front grip.This will give me more pressure in a smaller package.
The entire thing will be compacted , same barrel length, same full and semi capability and more powerful..

Still crude, need to build the forward trigger and grip housing etc...but I'm getting there...

You're a great loss to the Syrian revolution

How many shots do you reckon that little 12 gram will give you though?

If it'll last one mag ( 9 shots) I'm fine with it. Haven't put that much rounds through it...probably won't anyway so why not?
I'm all for compactness.

To bad a short barrel would harm performance BAD...I'd love to cut it down to a pistol.The hammer, springs, the action etc could all be housed around the barrel, so everything behind the ( new) grip could go...

Brian the brain wrote:If it'll last one mag ( 9 shots) I'm fine with it. Haven't put that much rounds through it...probably won't anyway so why not?
I'm all for compactness.

Not that far off with your guesstimate mate, should be able to get around 11 - 12 rounds off depending on how much you're charging the build with.
This project is unbelievably nice dude, such a great example of spudding ingenuity.

Not that far off with your guesstimate mate, should be able to get around 11 - 12 rounds off depending on how much you're charging the build with.
This project is unbelievably nice dude, such a great example of spudding ingenuity

Thanks for the compliment ..but why do you assume to know the number of shots I'll get out of it?

Brian the brain wrote:

Not that far off with your guesstimate mate, should be able to get around 11 - 12 rounds off depending on how much you're charging the build with.
This project is unbelievably nice dude, such a great example of spudding ingenuity

Thanks for the compliment ..but why do you assume to know the number of shots I'll get out of it?

No worries mate. It really was just a guesstimate from personal experience using those 12g cartridges. Although I didn't really take into account the pressure that you'd be filling up to so just scratch my comment and give it a test... lol

LOL...not worried at all mate.

Any experience you might have is irrelevant I'm afraid.

The thing is....the valve I am using is quite unique. Pressure is just full-on unregulated CO2...around 1000 psi, while the flow of the valve is enourmous compared to a commercial airgunvalve.
I've counterbalanced it.It has a 10mm port but can be tapped open under full pressure by hand.

What a beaut! When will we see a video of it firing?

On page 3 you'll find this one...
[youtube][/youtube]

Brian i've looked at the build over and over and while im pretty sure its a hammer valve of some sort could you explain / describe its internals please? Possibly even a diagram?

Absolutely in love with the thing so far especially now it runs on 12g disposables.

Regards,
Soul

Haven't worked on in in a while, so it's not yet running on 12 grams.
It's a partially balanced hammervalve.
It only needs a gentle tap to open while the valveport is huge and so is the pressure.

The hammer is in fact a piston.When it hits the valve, pressure flows through the small gap between the valve body and the valvestem and this drives the hammer back.
The bolt is fixed to the hammer and moves along with it
The combined weight allows for the ammo to leave the barrel before the hammer is slammed back.

The hammer contains a poppet valve in its centre.When the hammer hits the valve this pushes the poppet closed.When the hammer is driven back fully the poppetvalve hits a bolt in the back of the gun opening the centre of the piston.
This makes sure the hammer is fully airtight while its being recocked, yet it vents in the rear position and is ready to strike again without having to compress the volume in front of it,

This way it recocks with plenty of force with a minimum of gasconsumption.

This is simply amazing. But judging by your videos you lack a consistent rate of fire? Maybe you need a spring plate to stop the bolt from travelling too far and make it hit the plate each time for better spring consistency.

I'd like to see a cut-away diagram. I never understood how caselman got this configuration to work so well! It fires from a closed bolt?

Hurricane Air Arms wrote:I'd like to see a cut-away diagram. I never understood how caselman got this configuration to work so well! It fires from a closed bolt?

It's a hammer valve straight blowback.

Hammer opens valve, air enters breech that simultaneously fires the projectile and blows back the bolt, which recocks the hammer.

It's exactly the same way a basic semi-auto paintball marker works:

jackssmirkingrevenge wrote:

Hurricane Air Arms wrote:I'd like to see a cut-away diagram. I never understood how caselman got this configuration to work so well! It fires from a closed bolt?

It's a hammer valve straight blowback.

Hammer opens valve, air enters breech that simultaneously fires the projectile and blows back the bolt, which recocks the hammer.

It's exactly the same way a basic semi-auto paintball marker works:

Thank you. So it fires from an open bolt and uses air from the hammer valve to both fire and actuate the gun. I can see how this applies to his gun now. Love it. Prefer blow forward myself though because no air is wasted

I'm assuming you are referring to the ROF dropping slowly in full-auto mode?

about wasting air:
While it pancakes 10mm leadballs like other powerful airguns the semi/full auto action uses only a fraction of air to recock.
It's designed that way.


My design uses a balanced valve with very high flow ( the barrel is smaller) yet it requires little to knock it open at high pressures.
Therefore the springs can be weak and blowback can occur with a minimum amount of gas.
The only air that reaches the piston is what passes between the valve housing and the valvestem...basically fitting together but lacking an O-ring seal.

The piston-hammer-bolt assembly itself is designed to operate with a minimum input of force.Large diameter face to generate the most blowback force..

On the return stroke the blowback-piston is airtight.
When the piston reaches the back a poppet in the centre is opened so the piston( hammer) can be pushed forward immediately without having to compress any volume in front of it.
When the piston hits the valvestem it hits it with the head of the poppet wich is automatically closed, sealing the piston again.

This feature also means the travel of the piston/hammer/bolt assembly is restricted...or better yet tuned.
I can't see how a BFV would be significantly more efficient...BFV's mean dead space and restrictions between the valve and the projectile.


Any inconsistency in ROF is due to the pressuredrop from the tank.In a couple of vids it was already half empty.
With a full tank it's not noticable in operation because the mag only holds 9 rounds.
When I hooked it up to a larger tank it (blank) fired consistently for an extended time.

In the vid where it's spraypainted silver...the tank was near empty so it wouldn't recock in full auto.
But that vid was only to demonstrate the difference between full and semi setting...