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| POLAND_SPUD |
 Posted: 03/07/2010 0:12 AM Post subject: Directional Control Valves (3way valves and stuff like that) |
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Lieutenant General
Joined: 13 Oct 2007
Posts: 4387
11901.36 Spud Bux
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Directional Control Valves, commonly refereed to as 3,4,5 etc. valves or spool/poppet valves etc., can be very useful for spuders.
They can be used both in pneumatics (to fill/vent QEVs/piston valves) or in combustions (to build automated metering systems).
DCVs are not as complicated as they seem. However in order to use them effectively one has to understand some basic concepts underlying them. Understanding the symbols used to represent how they work is crucial.
I won't write about some basics as there are already some quite good sources of information on them. Though I'll write a bit about their utility from the point of view of a spudder, and which DCVs are the best in general and for particular applications
You'll find the most basic stuff in these links(not all of them are only about DCVs but I suggest reading everything anyway)
Introduction to pneumatics
Pneumatic notes (similar in scope to the first link, though it still might be a good idea to read it)
A book on pneumatics and hydraulics. Again, not everything is 100% relevant for spudders
Here you can find some animations of 2,3 and 4(5) way valves
more symbols
animated intro to DCVs (and pneumatics in general)
Now let's move on from the theory and symbols to how real valves are built. Generally speaking there are two types of valves: Poppet and spool valves
I think that this is best explained...
Here (pay attention to the part discussing valve actuation methods... this notion comes down to 'how do you want to operate the valve? by a push button / lever (with a spring return), a solenoid or maybe you want to pilot it with another valve... etc. )
and here
this site is really great, it has a lot info and links to useful stuff
If you are already familiar with all the info that can be found in links above let's discuss what valve would be the best for what application.
Generally speaking the biggest limitation is the pressure used. Most valves are designed to operate at about 10 - 15 bar pressure max
While this is enough for quite a lot of uses many spudders use higher pressures ( 20 - 50 bar) to get more power
Luckily, some valves can handle high pressures pretty good
Let's compare different valve as far as their ability to handle high pressure is concerned:
POPPET VS SPOOL valves
poppet valves are not balanced so as the pressure increase the fore needed to actuate them increases too.
DIRECT VS INDIRECT acting
indirect acting valves are piloted valves. Piloted valves have small inbuilt valves that pilot the main spool. However since those 'piloting' valves are generally not balanced - as a result they leak when used at higher pressures
To sum it up. The ideal valve for use with higher pressures is a direct acting spool valve
I'll update the rest later... Feel free to PM if you find something that can be posted here
| Description: |
this pic shows how to use a 3 way valve to pilot a QEV. The pink boxes represent the flow through the valve:
the one to the right shows flow in normal position (air flows from the air source (not connected here) to the pilot side of a QEV
the box to the left shows how flow path changes when I 'switch' (by pulling the lever) the valve (air source is blocked off while the pilot side of the QEV is vented) |
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Last edited by POLAND_SPUD on 05/23/2010 17:24 PM; edited 16 times in total |
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| MrCrowley |
| Posted: 03/07/2010 17:00 PM Post subject: |
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Kaleun
Joined: 23 Jun 2006
Posts: 8999
9195.37 Spud Bux
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| It's a shame no one has replied but I found the first link pretty interesting, learned a few things. I'd say it's a must read for anyone wanting to take pneumatics a step further than a basic sprinkler valve cannon.
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| jackssmirkingrevenge |
| Posted: 03/07/2010 17:06 PM Post subject: |
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aspiring machinist
Joined: 15 Mar 2007
Posts: 18061
32519.23 Spud Bux
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Same here, always wondered what those symbols meant  
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| MrCrowley |
| Posted: 03/07/2010 17:13 PM Post subject: |
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Kaleun
Joined: 23 Jun 2006
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| jackssmirkingrevenge |
| Posted: 03/07/2010 17:18 PM Post subject: |
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aspiring machinist
Joined: 15 Mar 2007
Posts: 18061
32519.23 Spud Bux
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| <-------- duly noted
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| Patto |
| Posted: 03/07/2010 18:39 PM Post subject: |
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Sergeant
Joined: 20 Jan 2010
Posts: 96
16.65 Spud Bux
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Very nice  thank you
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| Slauma |
| Posted: 03/07/2010 19:41 PM Post subject: |
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Specialist
Joined: 20 Dec 2009
Posts: 46
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| One reason I think DCVs aren't more widely used is their lack of availability to many. I know McMaster has a selection, ebay has been hit or miss for me, and googling hasn't really yielded any good results. Do you know somewhere where you can order DCVs online?
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| POLAND_SPUD |
| Posted: 03/07/2010 20:16 PM Post subject: |
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Lieutenant General
Joined: 13 Oct 2007
Posts: 4387
11901.36 Spud Bux
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@Slauma
I'll write more about that later (I'll edit the first post). I realize that CDV are not something you can buy at Lowes or Homedepot. They are normally used in pnumatics, stuff that is used in automated plants and things like that
You can order DCV from many places:
1. directly from manufacturers (Clippard, Festo, Humprey, Bosch Rexroth, SMC to name just a few) or their distributors (in most cases you can order them online from their sites) or online shops selling pneumatic equipment
2. ebay (links directly to 'pneumatic valves' category)
option no 1 can be quite expensive so I guess that ebay is the best source of valves...
the only problem is that you have to visit it from time to time to find the best bargains and stuff you want, and that you have to understand some basic notions about DCVs (so that you can buy exactly the best valve for your particular application... so for example if all you need is a DCV for filling&venting a QEV gun you might be better off with a manually actuated valve than a solenoid valve... similarly one with a spring return would be better than a toggle valve)
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| iknowmy3tables |
| Posted: 03/12/2010 16:30 PM Post subject: |
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poopie joke comedian
Joined: 15 Dec 2006
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I think you should post this kind of info on the wiki or on the how to.
One thing I've wanted to do is organize this kind of info so newbies could quickly pick up on how to build semi automatic and fully automatic pneumatics, then maybe just maybe the nerf community would build some decent nerf guns
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| POLAND_SPUD |
| Posted: 03/12/2010 23:04 PM Post subject: |
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Lieutenant General
Joined: 13 Oct 2007
Posts: 4387
11901.36 Spud Bux
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yeah i know I am still adding new stuff to this... I add a short how to on buying them too or maybe add some videos...
once that's done it can be sticked I guess
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| bobgengeskahn |
| Posted: 03/13/2010 17:39 PM Post subject: |
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Corporal
Joined: 23 Jul 2009
Posts: 73
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| yeah, I'd like to 2nd the stickie idea. I've had to read and dig for months to figure out a fraction of what is in this thread.
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| Gun Freak |
| Posted: 03/13/2010 20:02 PM Post subject: |
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The Anti Hybrid
Joined: 25 Jan 2010
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| So basically (man I say that a lot ) a DCV can be used for filling and piloting a qev?
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| POLAND_SPUD |
| Posted: 03/13/2010 20:31 PM Post subject: |
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Lieutenant General
Joined: 13 Oct 2007
Posts: 4387
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yes, among other things...
if you wanted to do this with ball valves you'd need two valves - one for piloting and one for filling. You would have to open the first one to fill the gun, then close it and then open the other one to pilot the gun. With a dcv valve you can pilot and fill the gun with just one valve and it can be attached directly to the main valve, which lowers mass and pilot volume when compared with a setup with two separate valves)
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| ramses |
| Posted: 03/15/2010 15:16 PM Post subject: |
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Major General
Joined: 29 May 2008
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| POLAND_SPUD wrote: | yes, among other things...
if you wanted to do this with ball valves you'd need two valves - one for piloting and one for filling. You would have to open the first one to fill the gun, then close it and then open the other one to pilot the gun. With a dcv valve you can pilot and fill the gun with just one valve and it can be attached directly to the main valve, which lowers mass and pilot volume when compared with a setup with two separate valves) |
or a 3 way ball valve... but that might actually be considered a type of DCV.
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| POLAND_SPUD |
| Posted: 03/15/2010 15:28 PM Post subject: |
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Lieutenant General
Joined: 13 Oct 2007
Posts: 4387
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well yes...
though ball valves are not ideal... to open a simple BV you need to turn the handle 90 deg. With a 3 way BV you need 180 deg turn...that's a lot IMO opinion..
now if you compare that with a push button valve with a spring return... well it feels much better and more like a trigger on real guns
ohh btw I updated the first post...
and I think I might have found a way that would allow to use some indirect acting valves at higher pressures.. but I've got to test it first
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