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All in one valve

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: bobgengeskahn » Sat Feb 20, 2010 10:24 pm

POLAND_SPUD wrote:lol you've just missed what I've mentioned in two posts.. ports can't be on the same level


Hi there...
I've been lurking for a long time now just reading and reading on a lot of this stuff and I've been thinking about this problem of having ports on the same level as you guys have mentioned... what if instead of having the O-ring on the cylinder... you have it around the port on the inside of the cylinder body? granted then you could probably have spacing issues, but im sure there would be a way to trouble shoot that. but has something like this been tried before?
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Unread postAuthor: POLAND_SPUD » Sat Feb 20, 2010 10:37 pm

the idea is to have a valve that could run on unregged CO2 or HPA at around 850 psi (using a similar setup to the one that JSR uses to fill his projects) but could use cheap and easily available push button valves and to pilot the valve...

In the semiauto MKIII and all it's previous versions as well as in basically all piston/QEV guns out there the pilot valve must handle the same pressure as the main valve... and it's not that there are lots of off the shelf valves that can handle more than just 10 - 15 bar


so instead of machining both the main valve that can handle 800 psi or more and the pilot valve for it I concluded that it could be better to use a regged down circuit to fire the main valve... add to that an inbuilt loading mechanism and you've got something pretty cool...

once you had this thing machined you only have to add a couple of parts to it such as the barrel, magazine, a small push button valve and a simple regulator and you've got a gun

EDIT
IDK really. I've never seen even one DCV valve that would have o-rings there so I guess it doesn't work too good
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Last edited by POLAND_SPUD on Sat Feb 20, 2010 11:58 pm, edited 1 time in total.
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Unread postAuthor: iknowmy3tables » Sat Feb 20, 2010 11:04 pm

POLAND_SPUD wrote:lol you've just missed what I've mentioned in two posts.. ports can't be on the same level

anyway apart from that nice drawings... do you plan to build any of them ?


woops yeah your right sorry,
well it's unlikely I'll build any of them them, I live on campus and this university doesn't have any workshops open to students like me, I hardly have the materials to do it at home, with the number of orings there will be lots of friction which would make a rough trigger pull, over all I just don't like the design enough my self to dedicate time and resources which could be spent other things and ideas

@hi bob, it's a decent idea but it's really hard to do, orings need precision to seal right, it's easier to do this using sleeving pipes and coupler bits, or grooves with mills and lathes, prefabricated tube/pipe or the rotational evenness of lathe cuts make this easy to make this is pretty hard, I however now that you metion it I think I might have an idea of how it could be done
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Unread postAuthor: maverik94 » Sat Feb 20, 2010 11:41 pm

WOW!! That is ingenious John!!! You mentioned this idea to me on chat and now you have revealed it to the world!!!! The concept seems to be perfectly sound. However, the actual implementation may be a little difficult, but not impossible. This design is so simple, yet it is so great! None of the animations on the page are working for me, but that's probobly because of my slow internet connection. Anyway, keep up the good work John and all others working on this concept. I have faith in you!! :P
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Unread postAuthor: iknowmy3tables » Sat Feb 20, 2010 11:42 pm

alright about bob's idea, it's almost impossible to cut a grove with equal depth relative to the surface if the surface is curved using basic tools, but if you use a sleeving pipe and cut the groove out of that and glue it on it could work, however you need a pretty precise o-ring thickness and if your like me I usually use o-rings from a set, I also don't know how to determine the diameter of the o-ring needed if the hole is drilled with a drill bit because a circle projected onto a curved plane becomes an ellipse, I also don't know if the orings will stay in place without a wall on the inside which would be pretty tricky
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Unread postAuthor: bobgengeskahn » Sun Feb 21, 2010 12:07 am

Could something like this work???...
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Granted that the shape of a hole drilled into a curved surface is an ellipse, but an ellipse is still just a circle, so an O-ring in something like this, with a relatively tight fitting cylinder should make the O-ring keep its shape and thus keep a seal after it has rotated...
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Unread postAuthor: iknowmy3tables » Sun Feb 21, 2010 1:27 am

I'm afraid not look at it from a different angle, see how the profile of the oring is flat but the profile of the rod is round, it results in uneven compression and orings don't compress much you need a curved base in the groove to match the curved surface of the rod
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Unread postAuthor: POLAND_SPUD » Sun Feb 21, 2010 2:06 am

you'd have to find a way to make it stay there

also bear in mind that you've got to reach that place somehow to machine an o-ring groove there
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Unread postAuthor: bobgengeskahn » Sun Feb 21, 2010 2:18 am

what if you were to take a metal cylinder body, drill and tap it for a fitting; then take a sleeve for the inside that has already been drilled slightly larger for the O-Ring. You could make the spacer out of a plastic like delrin, that would allow a tight fit for the bolt assembly while being lubricated...

I would do a drawing for it, but im trying to use paint on a track pad and its a little challenging at the moment... ill try to draw a sketch and scan it in when i get a chance.

edit: Also, after my last post before i got distracted... i was trying to find a resource for square O-Rings... if they exist; or trying to find some other kind of sealing method that would work better... i just like this rotating bolt design too much to see it not done lol
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Unread postAuthor: POLAND_SPUD » Sun Feb 21, 2010 2:42 am

@bobgengeskahn
sure it could be done... but it increases complexity of the design

no offence but personally I don't think that rotating valves are better then those which move 'back and forth' so to speak (linear motion)... they seem worse in almost every possible aspect

so in the end after solving a lot of problems you might end up with a valve that is much more complicated than it should be, costs a lot, is difficult to actuate, has poor performance etc.

if you design something and you encounter something that's difficult to solve it's usually better to try something different.. even if a given design seems perfectly ok in theory there is a great chance that you'd encounter some problems that you didn't expect
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Unread postAuthor: iknowmy3tables » Sun Feb 21, 2010 4:26 am

well the thing about rotating valves is that they rotate, so you can attach a motor or servo directly to it,

bob I believe I understand what your saying and it should work if you grind the curve in the end of the pipe right and secure the pipe at perfect depth, also square orings don't exist and wouldn't replace your need for a curved surface it would just mean you'd need a square groove, the only thing that would get rid of the curve is a ball to replace the rod and that would be really hard to align, btw you can use sheet rubber to seal things too
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Unread postAuthor: john bunsenburner » Sun Feb 21, 2010 5:17 am

From what I see here the only real constraint in using this type of valve is the sealing. It would be great if anyone here could supply numbers on how much pressure different types of lubricants can withstand in different gaps. (so weather thick grease can contain 200psi on a 0.05mm gap that is 1cm long and so on). Going from there its fairly simple to tell a feasible design from one that would require machining that is not possible for a hobby machinist. Maybe someone out there has some figures, or at least a theory on the subject

I assume it would be possible to put ports at different levels with holes in the spool to connect them, I don't even think it would make matters a whole lot more complex, depending on how many levels are needed.

On a slightly different note. It was suggested to me to build a valve with ports that close and open as the spool moves about. Perhaps that would be something to try, though it makes matters a whole lot more complex...


As for bob's idea; instead of using a round spool, why not use a Square one? On a lathe square holes CAN be bored(though its not the easiest or cheapest thing to do, it is be possible), though it may turn out to be a whole lot simpler to cast the body for such a valve it sounds doable.
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Unread postAuthor: dewey-1 » Sun Feb 21, 2010 8:05 am

iknowmy3tables wrote:
also square orings don't exist and wouldn't replace your need for a curved surface


O-Rings have different profiles: round, square and quad.

Go to
www.mcmaster.com/#o-rings

So technically, square cross sectional o-rings do exist!
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Unread postAuthor: iknowmy3tables » Sun Feb 21, 2010 11:20 am

well I guess I was wrong about square o-rings, but they still don't help in this case,

hey guys you ever see the inside of a bathroom faucet valve? check it out because the bathroom faucets don't actually use a plunger on a screw like the one you'd use for a garden hose, the rotating piece basically sits on a rubber gasket and this plane on sliding plane is the exact kind of sealing we're looking for in a rotary valve
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Unread postAuthor: john bunsenburner » Sun Feb 21, 2010 3:52 pm

Personally I would prefer to use an up-down valve, like poland_spud.

Anyone have opinions on the grease and tight parts idea?
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