Posted: 12/16/2007 16:13 PM Post subject: The semi-automatic paintball pistol
Air head
Joined: 12 Mar 2006 Posts: 1392 5185.24 Spud Bux
For a while now (a few months) I have been designing or trying to design a paintball pistol that is magazine fed. I have gone through many different types of valves and ended up on a blow forward type valve, very similar to JSR's full auto breech concept, in fact I credit JSR and clide for bits and pieces of the design.
I have come to understand a lot about three way valves over the last few months, I believed semi-automatic operation could be achieved using a three way valve so I based a lot of design around that.
What I have now ended up with is a system that operates very much like Jack's full auto breech except it is controlled, I added a simple sear to the front of the bolt that would retain it when gas pressurized the system but that alone would not make it semi-automatic unless I made it like that of a mechanical paintball guns sear, too complicated for my design, keep it simple. So what I did was use a 3 way valve as the actuator of the system, when it was at rest the chamber behind the bolt would pressurize and when it was pulled flow from the source to the chamber would be cut off and a pneumatic ram would actuate the sear.
I really believe it will work. Now for the pic, keep in mind this is a concept drawing, not blue-prints so it might be a little inaccurate and a little problematic but it should work for a low pressure prototype.
not bad for free hand eh?
Out of all the projects I have right now this is the main one I am working towards, all the others are side projects, eg. Project R-77.
(if I am not making sense it is because I am real tired)
With resevoir filled, trigger is pulled to switch air supply to pneumatic ram that flips sear to allow bolt to move forward, close ammo port and dump the resevoir behind the paintball.
Yep, looks workable
Needs something to vent the pneumatic ram so it retracts afterwards unless you're relying on a leak (intentional or otherwise ) to vent the air so the spring can pull back the rod.
I like the idea to use a 3-way valve - no air is wasted.... however it seems quite complicated.... I think this design involves machining small parts becase of the stress put on the sear etc...
this might be simpler (it's just a suggestion, i've never tested it but it would surely work.... --->
(BTB you could use a 5/2 way valve insted of a 3/2 valve... it would vent that small piston when the valve is in is in 'rest'/off position)
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I will stick to my idea thanks. Obviously a lot of thought has gone into it and I try to keep machining to a minimum-for the prototype anyway- so my idea of the 3 way was a bolt, washers, nuts and o-rings and then I just have to drill and tap holes for the nipples.
That would work fine, I am sure that could be easily done. Remember, you don't want a valve like that to be bias so you need a washer on the end to seal it (achieving equilibrium), or else it would be difficult to push.
Interesting but perhaps overly complex - given the limited flow actually going into the barrel, you could probably simplify it to just having a blowgun feeding into the breech and get the same results.
Just thinking ahead here, this was drawn as a concept keeping in mind that a high pressure machined version will be built, using an actual 3 way valve meant for fancy pneumatic paintball guns like autocockers or PPS markers.
I want to opt for the 3 way to keep things very small and compact, the magazine will be in the handle so the trigger needs to be small, actual 3 way valves are tiny and high pressure so it should be no problem fitting it in. Not to mention it is an off the shelf part. For the 3 way I will be getting one of these type valve: http://www.zdspb.com/media/tech/animations/threeway1.gif For the chamber port I will need a small check valve.
One thing I am not to sure of though is with a higher pressure version, I think the back of the bolt (chamber side) will be too large, offering too much surface area for the gas pressure to act upon it, so the sear might fail due to excessive pressure. Do you think this will happen?
I thought I could simply decrease the size of the back of the bolt so it has less surface area. I will draw up a concept today.
like I said before i like the idea of using a 3/2 or 4/2 or 5/2 valve... however I agree with JSR it's too complex and there is a lot of stress put on small parts + the limited flow....
upon closer examination I see that this idea is (in some way) a combination of blow forward bolt, my aircylinder/spring design that I presented here, a sear and a 3way valve... don't get me wrong it's you design but it seems to me that it combines all the disadvantages of the beforementioned designs + it's complex....I should have asked this first --> could you enumerate what are the advantages of this design ? I mean why have you decided to do it in this way?
Semi-auto with a simple blowgun - granted, you're using a larger calibre, but the way you've drawn it the flow seems to be the same and if you're using higher pressure it will compensate for this. Also, the spring load on the bolt gives time for pressure to bvuild up behind it before it actually fires.
like I said before i like the idea of using a 3/2 or 4/2 or 5/2 valve... however I agree with JSR it's too complex and there is a lot of stress put on small parts + the limited flow....
upon closer examination I see that this idea is (in some way) a combination of blow forward bolt, my aircylinder/spring design that I presented here, a sear and a 3way valve... don't get me wrong it's you design but it seems to me that it combines all the disadvantages of the beforementioned designs + it's complex....I should have asked this first --> could you enumerate what are the advantages of this design ? I mean why have you decided to do it in this way?
What do you mean by 3/2 4/2 and 5/5 valve? I don't understand what that is. The flow is a lot better than you think it is and will not be a problem at all, 3 way valves work perfectly on other paintball guns and its purpose is not much different.
I chose this design because it is very small and compact, perfect for a pistol, as far as paintball markers are concerned this is very simple. It also seals off the pressure perfectly, only allowing it to escape out the barrel. I see it being efficient.
Do you mind discussing the disadvantages of said designs?
Jack, I did try some designs around something similar to your blowforward design, I kept on ending up with a much too big or long design than I would like and it was getting too complex as a semi automatic design.
It seems the highest pressure I can use in these designs is around 300psi because that is the rating of the 3 way valves. I am not sure which 3 way valve I need because there are a few on the market. I will think about the design some more, see if I can simplify it even more.
Jack, I did try some designs around something similar to your blowforward design, I kept on ending up with a much too big or long design than I would like and it was getting too complex as a semi automatic design.
I don't see how it could be more complex and less compact than this:
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) to vent the air so the spring can pull back the rod.
