SpudFiles

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

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.

Same here, always wondered what those symbols meant

Here's a list with even more symbols and a tool to draw valves with the symbols:
http://www.smc.co.nz/pages/pneumatic_design.html

<-------- duly noted

Very nice thank you

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?

@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)

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

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

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.

So basically (man I say that a lot ) a DCV can be used for filling and piloting a qev?

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)

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.

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