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Caselman automatic revisit

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Caselman automatic revisit

Unread postAuthor: Antonio » Thu Jan 17, 2008 3:29 pm

Does anybody know how the caselman airgun recycles?
There is a pdf document on youtube:
http://jrrabrahao.discovirtual.uol.com. ... selman.zip

(password: caselman)
This is one of the videos
[youtube]http://www.youtube.com/watch?v=POCGiy5VpxI[/youtube]

After reading and looking at the diagrams I still dont get why the caselman is an automatic. It works partly like a spyder paintball gun but the gas is not ported out the back of the valve.
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Unread postAuthor: ALIHISGREAT » Thu Jan 17, 2008 4:01 pm

is it a gas-blow-back-bolt? where the High pressure air recocks the mech?
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 17, 2008 4:04 pm

thread about it here

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The hammer (9) strikes the valve stem (2) which allows a burst of air into the barrel between the projectile and the bolt (17) - this fires the projectile and pushes the bolt back, recocking the hammer and allowing the cycle to continue, unless the bolt is caught by the trigger sear.
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Unread postAuthor: Antonio » Thu Jan 17, 2008 5:53 pm

jackssmirkingrevenge wrote:thread about it here


The hammer (9) strikes the valve stem (2) which allows a burst of air into the barrel between the projectile and the bolt (17) - this fires the projectile and pushes the bolt back, recocking the hammer and allowing the cycle to continue, unless the bolt is caught by the trigger sear.


Ah you already posted exactly the same lol. I guess ill take mine off in some time. Thnx for explaining though. As u said in your other post, this mechanism prob only works under high pressure. The projectile needs to have lots of friction with the barrel inorder to recock the hammer. I think it also has to do with mass. As most ppl here are using platic bb pellets, this gun doesnt seem feasable for our level or building''. The lower mass projectile would give little reaction force to the hammer.
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 17, 2008 6:09 pm

In the case of the caselman, the surface of the bolt on which the pressure is acting is identical to that of the projectile - since we're working with lower pressures, we need a larger area to get more force from the pressure, enough to recock the hammer.
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Unread postAuthor: ALIHISGREAT » Thu Jan 17, 2008 6:16 pm

autos or semi autos that have a gas blow back kind of thing waste power because some is used to recock the mech so if i were you i would make a BtB style auto with a qev and 'snap-valve' because this does not waste any air recocking the mech or you could make your own valve that supplys pulses of air to a blow-foreward bolt and you will make JSR very jealous :D
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Unread postAuthor: Antonio » Thu Jan 17, 2008 6:25 pm

jackssmirkingrevenge wrote:In the case of the caselman, the surface of the bolt on which the pressure is acting is identical to that of the projectile - since we're working with lower pressures, we need a larger area to get more force from the pressure, enough to recock the hammer.


Well but we also need less force to open the valve. So all in all its the same. I thought about it before, the physics of automatic fire. When u look at impulse the P*A*t has to be bigger than the m*v of the hammer. (P is operating pressure, A is area of the hammer, t is dwell time, m is mass of the hammer and v the velocity when it hits the valve). Then the hammer also has overcome a certain force to open the valve. This is m*a ( of the hammer) which is m*(v/(m/k)^0.5) which has to be bigger then the the P*A of the valve (k is the spring constant of the spring behind the hammer).

As though I thought about this all and kinda have it on paper I cant really put it to practice as I dont know the spring costant of my hammer spring and friction matters. Also in the formulas above I havent taken into account the spring behind the valve.

Coming back to the caselman. We can take that the area of the hammer is the same as in our guns (bb ball size) only the pressure is higher but to compensate this high pressure you need a high hammer velocity which in turn means there is more energy in play''
As I said before I think it has to also do with the mass of the bullet. By law of conservation and inertia, a heavier projectile will exert more reaction force on the bolt.
But yeah anyways I dont know where I am getting here. Its all really tricky and hard to put to practice :)
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Unread postAuthor: Antonio » Thu Jan 17, 2008 6:29 pm

ALIHISGREAT wrote:autos or semi autos that have a gas blow back kind of thing waste power because some is used to recock the mech so if i were you i would make a BtB style auto with a qev and 'snap-valve' because this does not waste any air recocking the mech or you could make your own valve that supplys pulses of air to a blow-foreward bolt and you will make JSR very jealous :D


Well to be honest I think the caselman design is more efficient than a spyder paintball gun as all the air extracted'' from the valve go out of the barrel. K higher pressure and not always efficient due to highspeed flows, there is a balance some where between high and low flow airguns.
Btw I am not really sure what u mean with this BtB design and the snapvalve thingy?
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 17, 2008 6:32 pm

He's referring to the Deathray, completely different concept from your hammer fired designs.
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Unread postAuthor: ALIHISGREAT » Thu Jan 17, 2008 6:35 pm

Btw I am not really sure what u mean with this BtB design and the snapvalve thingy?


yeah sorry i should have linked :oops:

http://www.spudfiles.com/forums/deathray-marble-machine-gun-t12290.html

He's referring to the Deathray, completely different concept from your hammer fired designs.


but it would be more efficient right?
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 17, 2008 6:42 pm

ALIHISGREAT wrote:but it would be more efficient right?


Yes, in general piston valves offer faster opening times and greater flow than hammer valves. With that in mind, I'm currently reworking this prototype with two main modifications based on all I've gleaned from experimentation and discussion since I first made it - namely a "proper" pop-off valve and a flow to the pilot area that is identical to that on the chamber.
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Unread postAuthor: Antonio » Thu Jan 17, 2008 6:49 pm

jackssmirkingrevenge wrote:
ALIHISGREAT wrote:but it would be more efficient right?


Yes, in general piston valves offer faster opening times and greater flow than hammer valves. With that in mind, I'm currently reworking this prototype with two main modifications based on all I've gleaned from experimentation and discussion since I first made it - namely a "proper" pop-off valve and a flow to the pilot area that is identical to that on the chamber.


I just looked at ur design, have you thought about a breech system or something? Or just a flowforward close breech? Yeah it is true that piston designs have better properties. I thought about going to it as well. But after my experience with the drozd type of valve; I just had to many problems with sealings which restricted fast movement. I am reading u work allot with expoxy, I have no experience with it. Can i c it as two compenent glue (stabiliet)?
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 17, 2008 7:10 pm

As a breech system I would use the blow forward breech, that or using cartridges :D

I am reading u work allot with expoxy, I have no experience with it. Can i c it as two compenent glue (stabiliet)?


That's it, like fibreglass resin ;)
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Unread postAuthor: Antonio » Fri Jan 18, 2008 4:51 am

jackssmirkingrevenge wrote:As a breech system I would use the blow forward breech, that or using cartridges :D

I am reading u work allot with expoxy, I have no experience with it. Can i c it as two compenent glue (stabiliet)?


That's it, like fibreglass resin ;)


Ah I worked with that before yeah. But I dont c the use of it at these small scales and weird shapes as is most of the times used on big planes''.
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Unread postAuthor: PinHead » Sat Apr 18, 2009 10:45 am

That thing has quite a bit of power for an air gun, what kind of pressure/caliber is he using?
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