THE SPRINKLER VALVE

by Hubb

TABLE OF CONTENTS

INTRODUCTION...................................................................................................................................................................................................1 A Word of Safety...............................................................................................................................................................................................1 What is a Sprinkler Valve? ................................................................................................................................................................................1 Anatomy of a Sprinkler Valve ............................................................................................................................................................................1 Disassembly......................................................................................................................................................................................................2 How the Sprinkler Valve Works .........................................................................................................................................................................3 What a Sprinkler Valve Really Does..................................................................................................................................................................3 ELECTRONIC ACTIVATION ................................................................................................................................................................................4 Advantages.......................................................................................................................................................................................................4 Disadvantages ..................................................................................................................................................................................................4 Direct Current versus Alternating Current ..........................................................................................................................................................4 Wiring the Solenoid ...........................................................................................................................................................................................4 Modifications .....................................................................................................................................................................................................5 BASIC MODIFICATION........................................................................................................................................................................................6 Advantages.......................................................................................................................................................................................................6 Disadvantages ..................................................................................................................................................................................................6 Choosing a Valve for Modification .....................................................................................................................................................................6 The Modification Process ..................................................................................................................................................................................6 Additional Modifications.....................................................................................................................................................................................7 Adding a Safety.................................................................................................................................................................................................7 ADVANCED MODIFICATION: BASIC REQUIREMENTS....................................................................................................................................8 Replacing the Seal ............................................................................................................................................................................................8 Necessary Parts................................................................................................................................................................................................8 Beginning Advanced Modification......................................................................................................................................................................8 ADVANCED MODIFICATION: UPGRADED DIAPHRAGM .................................................................................................................................9 Specific Parts ....................................................................................................................................................................................................9 Beginning Construction .....................................................................................................................................................................................9 Installing the Diaphragm....................................................................................................................................................................................9 Filling the Launcher......................................................................................................................................................................................... 10 ADVANCED MODIFICATION: PISTON VALVE ................................................................................................................................................ 11 Specific Parts .................................................................................................................................................................................................. 11 Building the Piston .......................................................................................................................................................................................... 11 Selecting the O-ring ........................................................................................................................................................................................ 12 Installing the Piston ......................................................................................................................................................................................... 12 Filling the Valve............................................................................................................................................................................................... 12 Final Notes...................................................................................................................................................................................................... 12 ANTI-SIPHON SPRINKLER VALVES ................................................................................................................................................................ 13 Comparison to a Globe Valve.......................................................................................................................................................................... 13 Modifications ................................................................................................................................................................................................... 13 TRIGGERING THE VALVE................................................................................................................................................................................. 15 Ball Valve........................................................................................................................................................................................................ 15 Blowgun Valve ................................................................................................................................................................................................ 15 Other Valve Types .......................................................................................................................................................................................... 15 THE BLOWGUN PILOT VALVE......................................................................................................................................................................... 16 The Nozzle...................................................................................................................................................................................................... 16 Piston Housing................................................................................................................................................................................................ 16 Piston.............................................................................................................................................................................................................. 16 Modifying the Body.......................................................................................................................................................................................... 17 Lever Spacer................................................................................................................................................................................................... 17 Reassembly .................................................................................................................................................................................................... 17 TROUBLESHOOTING GUIDE............................................................................................................................................................................ 18 SOURCES .......................................................................................................................................................................................................... 19

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INTRODUCTION

The Sprinkler Valve is a book dedicated to one of the most widely used valves in pneumatic launcher applications. It is the most comprehensive book ever composed on the subject. Anyone who reads this, whether familiar with a sprinkler valve or not, should find this book helpful. The author assumes that the reader is already familiar with the fundamentals of pneumatic launcher applications; therefore, this book will not cover launcher uses or configurations. What it will do, however, is cover nearly every aspect of using a sprinkler valve for a launcher. ---A Word of Safety ------------------------------------------------------------------------------------------------------------------------------ As with any launcher part, a sprinkler valve will have a rated pressure. It should be noted, however, that this pressure rating is for water pressure and not gaseous pressures. That being said, using a sprinkler valve other than its intended purpose will make its pressure rating moot. When the water pressure exceeds the rated value of the valve, the valve may hold and it may not. Usually, though, if the valve fails while using water pressure, it will generally result in the diaphragm tearing, or the valve cracking. This is because water is an incompressible fluid, and will not expand any further beyond its current volume. Gaseous pressures, on the other hand, are compressible. As the gas is compressed, it will generate higher pressure. If the valve fails while under gaseous pressures, the gas will continue to expand until its pressure is equal to that of atmospheric pressure. And this results in the gases expanded greatly and very fast. This means that it will generally result in an explosion. While using a sprinkler valve for purposes of pneumatic launcher applications, never take the pressure past the pressure rating indicated on the valve. It may hold up and it may not. But it is a chance that no one should take. If the valve fails under gaseous pressures, (1) you will know it and (2) it is not my fault. ---What is a Sprinkler Valve?------------------------------------------------------------------------------------------------------------------ A sprinkler valve is a diaphragm type valve that is built for automatically controlling irrigation systems. It possesses an input and output. It will also possess a solenoid of some sort that controls the valve opening and closing. Currently, there are two types of sprinkler valves being produced. A globe type sprinkler valve is either an inline version or an angled version is the most commonly used types of valves for launcher applications. Their operation is quite simple, they are easy to install, and they are easy to work with. Anti-siphon sprinkler valves are a bit fancier. They are U-shaped and have a device installed to prevent the backflow of water through a system. Both types of valves are covered in more detail further on in the book. ---Anatomy of a Sprinkler Valve -------------------------------------------------------------------------------------------------------------- The most essential part of a sprinkler valve is the diaphragm. This is the heart and soul of the valve and allows the valve to function. The diaphragm rests against an opening and this determines the configuration type of the valve. The first type of configuration is what I call a "barrel sealing" valve. These valves, like piston valves, will seal the output portion (or barrel). They will generally contain minimal parts and are much easier to work with. The next type is a "chamber sealing" valve. As one could guess, the diaphragm in this valve will seal the input portion (or chamber). It will generally possess a guide rod that is connected to the lid and will also generally contain a plastic ring that helps seal the lid to the main body of the valve.

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All sprinkler valves will have arrows somewhere on the body. These arrows will indicate the flow of the fluid and should be paid attention to. If a valve is connected backwards, the valve will not properly function. It should not damage the valve or the launcher, but it will make it unusable until this is corrected.

Sprinkler valves generally possess some form of bleeding device, that is, a device used to manually "bleed" the valve in a controlled manner in irrigation systems. It is either a small plastic screw located on the lid of the valve, or a small flip tab located near the solenoid.

bleed screw bleed tab An equalization orifice is used to fill the pilot volume with the same pressure as the input. It can be found in barrel sealing sprinkler valves in the form of a small plastic piece in the diaphragm. The plastic piece may contain a small filter on the underside. On chamber sealing valves, an equalization hole will not be present, as the gap between the diaphragm and the guide rod is built to equalize the pilot volume.

Some sprinkler valves will have a flow control knob located on the lid. This is a device used to control the output flow pressure of the water supply to lawns. By tightening it, the flow is reduced and by loosening it, the flow is increased.

Other parts may or may not be present on the valve, and these extra parts are usually specific to the valve. The above listed parts are for reference and are common in most sprinkler valves. Take note that, for pneumatic launcher applications, several of the parts are not used in the valve and some parts may affect the performance of the valve. If the valve has a bleed screw, this is usually removed and the hole filled in with epoxy. If the diaphragm has a filter, that filter should be carefully removed in a way as to not tear the diaphragm. If the valve has a flow control, then it should be adjusted so that the maximum flow is allowed through the valve. ---Disassembly------------------------------------------------------------------------------------------------------------------------------------ Taking the sprinkler valve apart is quite simple and usually self-explanatory. To remove the lid, either remove the screws or twist off the plastic lip. The spring can be pulled out and the diaphragm can be carefully pulled off of the lip. If the valve has a plastic ring, it can be slid out of place. The solenoid is simply screwed into place, as is the

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bleed screw. The bleed tab is generally connected to the lid and can't be removed without cutting it off. Anti-siphon valves have much of the same parts, but have an added part known as the back flow preventer.

inline globe valve anti-siphon valve

---How the Sprinkler Valve Works------------------------------------------------------------------------------------------------------------ The sprinkler valve is quite simple in operation. Pressure is applied to the input side of the valve. As this pressurized fluid reaches the diaphragm, the spring holds the diaphragm against the output. The fluid begins to flow either through the equalization hole in the diaphragm or between the gap that is present between the diaphragm and the guide rod. This allows pressure to increase in the pilot area of the valve. Eventually, the equalization hole allows the pressure to become equal on both sides of the diaphragm. Once the pressures are equal, the pressurized fluid holds the diaphragm in place. This is possible due to the fact that the pilot side of the diaphragm is approximately 2.5 times bigger than the non-pressurized output side. Since the pressure is trying to equalize, the pressurized fluid is constantly pushing down on the diaphragm to provide the seal. To operate the valve, the pilot side should be exhausted. The pilot area has a small port that travels to the solenoid. From the solenoid, another port leads to the output side of the valve or leads to the outside of the valve. Once the solenoid is opened, it opens the port and allows the fluid to flow from the pilot area to the output or atmosphere. This creates uneven pressure on the diaphragm. Once the pressures are uneven enough, the pressurized fluid on the input side of the diaphragm will overcome the non-pressurized side and force open the diaphragm. Once the diaphragm is opened, the fluid now flows from the input to the output. The fluid will continue to flow, due to uneven pressures, until the solenoid is closed, which allows the pilot area to re-pressurize, and allows the process to start over. ---What a Sprinkler Valve Really Does ----------------------------------------------------------------------------------------------------- Of course, sprinkler valves are used for automatic irrigation of lawns. But the real reason to have one is for construction of a pneumatic launcher. And they have several features that warrant this. Sprinkler valves are easy to work with, easy to obtain, and usually fit standard pipe fittings. Sprinkler valves seem to lack when compared to well built piston or diaphragm valves, but for the price and ease of use, the make for an ideal valve in many different launchers. It will also provide knowledge and experience on the more advanced valves that one will not be able to get just be reading about them.

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ELECTRONIC ACTIVATION

Setting up a sprinkler valve in a pneumatic launcher for electronic activation is one of the easiest methods to use the valve. The sprinkler valve already comes equipped with just about everything needed to do so. It offers some advantages over other methods of activations, but also has some drawbacks as well. ---Advantages------------------------------------------------------------------------------------------------------------------------------------- To begin with, electronically activated pneumatic launchers will offer some advantages over other forms of activation. For starters, it offers the user to place an electronic "trigger" switch, usually in the form of a momentary switch, in any position on the launcher. And, since a simple switch is used, the trigger pull is very light. Electronic activation also offers additional safety bonuses over other forms. It allows the user to place electronic safeties on the launcher that, otherwise, would be impossible. Last, the possibilities for activation are endless, usually only limited to the user's imagination. This makes electronic activation ideal for uses outside of launchers, such as mine designs for use in paintball and airsoft. Simple tripwire designs, motion sensor designs, remote activation, etc are all possible with electronic activation. ---Disadvantages--------------------------------------------------------------------------------------------------------------------------------- Of course, electronic activation has some disadvantages over other methods as well. Out of the box, a sprinkler valve is designed so that it will open slow to prevent water hammer, which may damage irrigation pipes. Since electronic activation will use the standard pieces of the sprinkler valve, the same holds true with using a gaseous fluid. This means that the performance, compared to a modified sprinkler valve, is going to be much less. Setting up the sprinkler valve for electronic activation may be more cumbersome and expensive as well, as several pieces will be needed to operate the valve, such as switches, batteries, extra wire, and a control box. The last negative, but one of the most immediately noticeable ones, is the use of batteries. Batteries will eventually die off and will need to be replaced. Oftentimes, however, the battery will begin to deplete but still function, further dampening the performance, and this is usually noticed at a most crucial time. ---Direct Current versus Alternating Current----------------------------------------------------------------------------------------------- Normally, sprinkler valves are set to run at 24 volts, but this voltage is rated for alternating current (AC). But it is impractical to operate a sprinkler valve using alternating current. The problem is that most people try to match the direct current (DC) current with the rated AC current, usually in the form of hooking up three 9-volt batteries. Due to the way DC current functions, it will work on lower voltage on DC than it will on AC. The level of magnetism is related to the current in the coil. Due to inductance and resistance on AC, the current is limited. On DC, only resistance limits the current, which is why the current is higher at 18 volts DC than it is at 24 volts AC. This means that two 9-volt batteries will operate the solenoid on the valve and using 27 volts will have no performance gains. In fact, if the sprinkler valve is run on 24 volts DC or higher, the additional current may overheat the coil and ruin it. For momentary use such as a pushbutton fire control, 24 or even 27 volts DC won't hurt them, but there will be no performance gains from using the higher voltage, therefore, for maximum efficiency, 12 to 18 volts DC is recommended, and any additional batteries supplied to the system is a waste. Now, the solenoid can operate on a lower voltage than that above, but this does not come with drastic drawbacks. Using less voltage will generally result in the solenoid opening much slower, and it may not even fully open. This, of course, damages the performance, and sprinkler valves using a solenoid don't need any additional help with that. ---Wiring the Solenoid--------------------------------------------------------------------------------------------------------------------------- This process is simple and straightforward and will not require an electronics background to complete. It is advisable, however, to get a little familiar with terms used, as they will be used in this book. All that is needed is the appropriate batteries, at least one switch, some extra wire (if the switch is to be located too far away from the solenoid), any pieces needed for the chosen batteries, and a project box to hold it all together. Mounting hardware will also be needed to mount the box. The batteries should be wired in series. This means that the negative terminal of one battery should be connected to the positive terminal of the next. Once complete, hook the open positive or negative terminal to a switch, then to the solenoid. If any additional switches are used, hook it next to the first switch. Finally, the remaining open battery terminal should be hooked to the open wire of the solenoid.

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The diagram to the right displays a simple schematic of wiring three batteries and two switches to a solenoid. The symbols used are basic electrical diagram symbols, and these symbols, if needed, can be located with a simple web search for them. Additional pieces can be added or removed as needed, however, the same basic layout should remain the same.

---Modifications ----------------------------------------------------------------------------------------------------------------------------------- Normally, the sprinkler valve is not modified in any way when wired electronically. The exhaust hole can be expanded, but it cannot be any larger than the solenoid seal. This means that the expansion is only going to be minimal and performance increase will not be noticed. It is also more difficult to enlarge the pilot solenoid hole than any other method of modification. In other words, it is not worth the trouble. Unless one is skilled enough to do so, the solenoid should not be modified in any way. And, again, even if the solenoid is modified, it will not be noticed in the performance of the launcher. In fact, the only form of modification that is normally done to an electronic activated sprinkler valve is mentioned above. This simply involves adjusting the flow control, fixing the bleedout device, etc.

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BASIC MODIFICATION Sprinkler valves are often modified when they are to be used in a pneumatic launcher. Essentially, all this modification does is bypass the solenoid to exhaust the pilot. It is a simple process, however, the performance gains of the launcher will be drastic. Note that this section is for the modification of globe valves. Anti-siphon valves are a bit different and are discussed further in the book. ---Advantages------------------------------------------------------------------------------------------------------------------------------------- The most obvious advantage to modifying a sprinkler valve is the performance increase of the entire launcher. It allows the pilot area to be exhausted much, much faster, due to the larger valve used. This allows the diaphragm to open faster, which means that the chamber will dump much faster than normal. Other benefits are that electronics are not needed; therefore, the negative side effects of using them are eliminated. Probably the most useful, yet overlooked, of these benefits include the knowledge and experience gains. Sprinkler valves are often used by beginners, and modifying the valve will provide a much better understanding on how the valve, as well as advanced valves function. This will lead to a much easier time when the user decides to build an advanced valve in the future. ---Disadvantages--------------------------------------------------------------------------------------------------------------------------------- Compared to an electronically activated sprinkler valve in use with a pneumatic launcher, there really aren't too many negative side effects when modifying the valve. About the only disadvantage is the fact that the valve needs to be disassembled, meaning parts can be lost if one is not careful. ---Choosing a Valve for Modification -------------------------------------------------------------------------------------------------------- Either a chamber sealing or barrel-sealing valve can be modified, however, it is easier to modify a barrel-sealing valve than it is a chamber sealing one. It can be difficult to find one or the other in a store, as the store personnel will not take kindly to them being disassembled prior to being purchased. But it is not impossible to tell which one is which, as long as you are able to visually inspect the actual valve outside of the box. One simple method is to look for the flow arrows on the valve. Whatever way they are pointing, stick a finger into the opposite side and feel the plastic straight in. If this piece curves away from the finger, this valve is a barrel-sealing version. If it curves around the finger, it is a chamber-sealing one.

It may be possible to feel the diaphragm, pressing up on it to feel for a guide rod, but this can be misleading in some situations, and may not indicate the correct assumption. ---The Modification Process ------------------------------------------------------------------------------------------------------------------- To begin modifying the valve, it should be disassembled. This is a pretty simple task, and is described above. It helps to place each part onto a clean towel or similar so that the pieces can be kept up with. Some valves will be different, and the tools needed for disassembly will be dependant on the valve. Next, a hole needs to be placed in the lid of the valve. The position of the hole will be dependant on the type of valve, and the way the hole is drilled is going to be dependant on the tools one has at hand. The first thing to do is to decide where the hole is to be placed in the lid. For sprinkler valves that do not have a guide rod, the hole can simply be placed in the center. For those with a guide rod, however, the hole should be placed to the side of the rod. It may be easier to drill the initial hole through the bottom of the lid, rather than the top, in this situation.

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Next is to decide how the threads are going to be placed into the lid. The threads will be needed in order to secure a fitting to the lid. For basic (3/4" and 1" valves), a 1/4" NPT fitting is standard. With a pipe tap: Drill a hole in the lid using a 7/16" drill bit. Follow this by appropriately working a 1/4" NPT tap into the hole. Without a pipe tap: Drill a hole in the lid using a 1/2" drill bit. Follow this using a metal fitting to cut the threads.

without a guide rod with a guide rod Now, a fitting needs to be placed into the hole. Wrap teflon tape around the fitting and just screw it into place. To properly use the teflon tape, hold the fitting so that the threads to be wrapped are away. Begin wrapping the tape in a counter-clockwise motion, placing enough layers so that the threads begin to disappear through the tape. Make sure the tape is clean before wrapping, then thread the fitting into the hole. Try to make the hole as straight as possible, as a crooked hole may cause it to leak even with the tape. If this is a problem, the tape can be skipped and epoxy used instead. Place a decent amount of epoxy around the threads completely and then thread it into place. Make sure not to get any epoxy on any areas that don't need it, such as the diaphragm or the guide rod. Now go around the inside and outside of the cap using the epoxy to seal it up. Be sure to allow the epoxy to thoroughly dry before proceeding any further. The type of fitting used is going to be user dependant. Common fittings are close pipe nipples and hose barbs. A pipe nipple will allow the trigger (pilot) valve to be placed directly next to the cap. Barb fittings allow the user to place a hose on the valve so that the pilot valve can be relocated to any position of the launcher. Once the fitting is in place and any epoxy is dry, reassemble the valve in the same manner in which it was disassembled. Note that all the pieces should be washed with water and allowed to dry to ensure that no filings or other debris is present, which will cause problems later. ---Additional Modifications --------------------------------------------------------------------------------------------------------------------- Remaining modifications include fixing the flow control and the bleed device. Normally, the solenoid is removed and its hole is filled with epoxy. If the sprinkler valve has a bleed tab, filling the solenoid hole with epoxy will fix its position. If desired, the solenoid can be left in place and the sprinkler valve wired for electronic activation as well. ---Adding a Safety-------------------------------------------------------------------------------------------------------------------------------- A safety is not normally added, but is always a good idea and, therefore, recommended. Adding a safety valve usually comes in the form of a ball valve placed between the sprinkler valve and the pilot valve. Take note, however, that the safety valve should be placed directly next to the pilot valve. If it is placed near the sprinkler valve, and the trigger is relocated with a hose, opening the safety valve may trigger the pilot area, causing the launcher to fire prematurely.

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ADVANCED MODIFICATION BASIC REQUIREMENTS

A sprinkler valve can be upgraded even further than standard modification. This will enhance the performance of a valve even further. It is advised, however, that one should become familiar with the standard modification process before attempting advanced modifications. When a valve is to be modified in this manner, it is best to choose a barrel sealing sprinkler valve. These type valves are much more basic and a lot easier to work with. A chamber sealing valve could be used, however, there are several additional features of the valve that make these modifications much more difficult and these features will not be covered in this book. ---Replacing the Seal---------------------------------------------------------------------------------------------------------------------------- Advanced modifications will replace the diaphragm. The diaphragm seals the valve body and that top to prevent leaks. Since the diaphragm will be replaced, another method will be needed to seal the valve. The first, most obvious choice is an o-ring. Take the valve body to a parts store to ensure that the correct size is obtained. Find an o-ring that will fit snugly into the groove when slightly stretched. It should be somewhat exposed when placed into the groove. Another choice is to obtain a rubber gasket. This works well, but is a bit more complicated. The gasket will need to be trimmed and may need holes placed through it for the screws. Just place the gasket onto the valve body. Most hardware stores will have a teflon cord. This cord will work well for sealing the groove and should be packed into the groove appropriately. The cheapest method for sealing the valve body, however, is to use the diaphragm. A ridge will be located on the diaphragm and should be trimmed from it. This, of course, will be the correct size, and will not require a trip to the store. It will, however, destroy the diaphragm, making this modification irreversible.

---Necessary Parts------------------------------------------------------------------------------------------------------------------------------- Whether a piston or diaphragm is chosen, hardware will be needed. First, a bolt will be needed. Choose a short bolt that is completely threaded. An appropriate sized nut and lock washer will also be needed. The purpose of these advanced modifications is to allow the sprinkler valve to perform better. Ideally, one should use pieces that are as lightweight as possible. Nylon hardware can be used in place of the steel hardware, and will drastically cut the weight. Be sure to trim off any excess parts of the hardware as well. Trim the nut and the head of the bolt to about half its thickness and be sure to remove any exposed threads on the bolt. A spring rest may also be needed. It is generally a flat washer that fits into the spring to keep it from slipping. Whether this is needed or not will depend on how the valve will be filled. It will add weight and slow the opening time, but will allow the launcher to be filled from the pilot side. By moving the fill valve to the pilot area, the spring can be eliminated. --Beginning Advance Modification ----------------------------------------------------------------------------------------------------------- As mentioned above, advanced modification processes of a sprinkler valve is to enhance the performance beyond the basic modification. But it does require that the user be familiar enough with the basic modification first. These modifications are easy to mess up, and this error rate is only enhanced when the user is not familiar enough with the sprinkler valve to begin with. So, start by modifying a few sprinkler valves beforehand. The modifications are designed so that any modified sprinkler valve can be upgraded, so this is not a total loss. To begin these advanced modifications, follow the basic modification process to prepare the valve lid and body. This should include tapping the lid and filling in any unnecessary holes.

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ADVANCED MODIFICATION UPGRADED DIAPHRAGM

A homemade diaphragm valve functions by having a disk seal against the exhaust (barrel). When the pilot is emptied, the high pressure in the chamber forces the disk away from the exhaust, breaking the seal. If one has modified a sprinkler valve, then this should be familiar, as this is what a sprinkler valve is.

Some diaphragm valves, such as sprinkler valves, will contain a spring. The spring forces the diaphragm to make a seal against the exhaust port (barrel) of the valve, in turn, allowing the launcher to be filled through the main chamber instead of the pilot chamber. A sprinkler valve is already a type of diaphragm valve. This means that the user should already be familiar with how they function. This modification will replace the current diaphragm with one that is more suited for pneumatic uses. It will, in turn, allow the valve to open faster and further, which will increase the performance. ---Specific Parts ---------------------------------------------------------------------------------------------------------------------------------- Along with the basic parts mentioned above, this will require some special parts. The first part needed is a neoprene washer. Choose one that, when laid flat, will cover the valve body to the point that it touches the sealing groove. The washer should be approximately 1/8" thick. If necessary, multiple washers can be used and stacked, but this will make the process just a little more difficult. A disk will also be needed. This disk should just be slightly larger than the output lip inside the valve body. Metal fender washers are ideal as they are strong enough to support the valve, but thin enough not to add too much weight. ---Beginning Construction---------------------------------------------------------------------------------------------------------------------- The first thing to do is to decide if the spring is going to be used. The spring will make the build easier and more user friendly, but it may not allow this particular modification have a noticeable performance increase compared to the basic modification. Start by placing a hole through the exact center of the neoprene disk. If it is a washer, the hole will already be present. Also, a small flat washer may be needed between the bolt head and the neoprene washer, and this will be dependant on the individual pieces used. Insert the bolt through the washer and place the finder washer on. Tighten down the nut. If the neoprene washer begins to curl, the nut is too tight. Ideally, the neoprene washer should remain as straight as possible. If a spring is going to be used, the spring rest should be placed between the fender washer and nut. If a spring is not used, then an equalization hole will be needed in the diaphragm. This is where the difficulty comes in when using multiple layers of neoprene washer. Simply use a sewing needle and poke it through the neoprene washer. Work the needle through the neoprene washer back and forth several times. Doing so will ensure that the equalization hole will not close up later. ---Installing the Diaphragm -------------------------------------------------------------------------------------------------------------------- Now that the diaphragm is built, it needs to be installed in the valve body. Set the diaphragm onto the valve body so that it rests flat. The fender washer should be on top. Slowly press the diaphragm into the valve body. The diaphragm will begin to form a bowl shape around the fender washer. Check to ensure that it is even all the way around and, if it is not, remove it and try again.

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---Filling the Launcher--------------------------------------------------------------------------------------------------------------------------- If the spring is to be used, the launcher will be able to be filled from the chamber, as it is with the basic modification. But to reap the true benefits of this modification, it is advised to not use the spring. In this case, however, the launcher will now need to be filled from the pilot side of the sprinkler valve. Normally, this would not be a problem but it should be noted that additional fittings or modifications would be needed. Probably the easiest way to install a fill valve is to simply tap another hole into the lid and thread the valve into place as was done for the exhaust. Alternatively, a close nipple can be used and a tee placed on it. One end of the tee will lead to the fill valve while the other end will lead to the pilot valve.

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ADVANCED MODIFICATION PISTON VALVE

In order to complete this modification, it becomes imperative to understand how piston valves work. They are not that difficult from a diaphragm valve in the way they function, but they are constructed completely different. A piston valve works in a similar manner as a diaphragm valve. It possesses the same parts (main chamber, pilot chamber, a seal, the fill valve, and the exhaust valve). Instead of a flexible piece of rubber, however, a piston valve uses a solid piece with a seal. When piloted, the whole unit, called the piston, moves away from the exhaust port (the barrel), allowing the main chamber to dump into the exhaust. In general, a piston valve will perform better than a diaphragm valve. It does so by allowing much more flow through the valve.

In this modification, the sprinkler valve's diaphragm is going to be replaced with a homemade piston valve. The piston valve, if built correctly, will open even further than a homemade diaphragm valve, which will yield even better results. If this modification is completed successfully, it will bring out the best of a sprinkler valve. ---Specific Parts ---------------------------------------------------------------------------------------------------------------------------------- Note that pistons can be made of just about anything. This particular piston, however, is one that I have designed and have found to work quite well while still being easy to construct. The main piston body will be constructed of pvc pipe. Sch40 pipe can be used, but it is not necessary. 2" thin walled pvc (200 psi pipe) works great and is lighter than the Sch40. A thin neoprene washer will be needed. 1/16" thick is fine. A flat washer that is smaller than the output of the main body will be needed. Finally, the hardware mentioned above will be needed. Some specific tools will also be needed. The pvc used for the piston body will be turned into pvc sheet. This means that it will need to be split and heated then pressed flat. This can be done by boiling it, but using a heat gun is a bit easier. A bow compass is a good idea, since perfect circles will be cut. A ruler (mm) or set of calibers, a razor, a rotary tool with a grinding wheel, and drill bits (1/32" and 1/4") will also be needed. An o-ring will also be needed, but the size can't be determined at this time. Take note that, although the spring can be used, it is not recommended in this modification. ---Building the Piston ---------------------------------------------------------------------------------------------------------------------------- Start by measuring the diameter of the main body. Set the bow compass to exactly half that and make two circles onto the pvc sheet. Apply pressure to the bow compass so that an indent will be made, which will be in the center of the disks. Use the grinding wheel to slowly and carefully trim the disks from the sheet. Make sure that the two disks are as uniform and even as possible. Close the bow compass by approximately one millimeter and repeat the above process to make a third disk. Use the 1/4" drill bit to drill a hole through the exact center of all three disks. Place the flat washer onto the bolt and follow this with the neoprene washer. Place a larger disk onto the bolt, followed by the smaller disk, followed by the remaining large disk. Install the nut. Use the razor blade to trim the neoprene washer so that it is approximately the same diameter (maybe a little smaller) as the disk it rests against. Fold the neoprene washer away from the plastic disk. While holding it in this position, use the 1/32" drill bit to drill a hole through all three disks. This hole should be placed as close to the edge as possible while being able to be covered up with the neoprene washer when it is released. This will form a check valve in the piston.

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---Selecting the O-ring -------------------------------------------------------------------------------------------------------------------------- Ideally, a floating o-ring will be selected. In order to do this, however, one should understand just what a floating o-ring is. In floating o-ring designs, there is no radial squeeze on the seal’s cross-section. The o-ring’s outside diameter is larger than the cylinder bore diameter, in this case, the inside of the valve body. Peripheral squeeze is applied to the outside diameter as the o-ring is installed into the valve. Incoming air pressure forces the o-ring against the groove wall, and a seal is affected as shown below. Floating designs offer a number of advantages, including greatly reduced breakout friction and longer seal life.

To select an appropriate sized o-ring for this modification, the piston should be built and it and the valve body taken to a hardware store. Find an o-ring, using the above method for it, making sure that it will fit in the groove formed in the piston. ---Installing the Piston--------------------------------------------------------------------------------------------------------------------------- Once the piston is complete, check to ensure that it will fit. It should slide smoothly in the sprinkler valve, and the o-ring should catch the edge of the valve and seal. Use a water based grease to lubricate the o-ring and set it in the valve body, making sure the neoprene side of the piston rests against the output. Now, install a bumper. A piece of pool noodle about the same diameter as the piston is ideal. The piece of foam should be about twice as thick as the piston to ensure that it will provide enough cushioning. Glue the bumper to the lid, making sure that the pilot exhaust fitting is not obstructed. ---Filling the Valve-------------------------------------------------------------------------------------------------------------------------------- Once the bumper is in place, the valve can be reassembled. Because of the design of the piston, the valve must now be filled through the pilot area. This is due to the o-ring and the in the piston. The equalization hole will allow air to flow from the pilot to the chamber, but due to the neoprene washer sealing the hole, it will not allow it to flow in the opposite direction. Now, the o-ring can be left off and this will allow the launcher to be filled from the chamber (if the spring is in place), but this is not advised, as it will not provide much improvement over standard or upgraded diaphragm modifications, which basically defeats the purpose of installing a piston valve. ---Final Notes ------------------------------------------------------------------------------------------------------------------------------------- This modification is not all that complicated to do, and it provides a noticeable increase over basic modification. It will provide much knowledge on all aspects of pneumatic launchers, and this by itself may be worth completing this modification. In short, this particular modification is using a sprinkler valve at its finest.

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ANTI-SIPHON SPRINKLER VALVES Sometimes, an anti-siphon sprinkler valve is used. These types of sprinkler valves are U-shaped and are used to construct an over / under launcher. They have the advantage of making the over / under launcher have a very close configuration as well as eliminate the need for additional pipe fittings.

Anti-siphon sprinkler valves do have disadvantages, however. They have less flow than a globe type sprinkler valve, as seen in the below diagram. They also tend to be more expensive. In some circumstances, they will contain some of the same parts as a globe valve, but some anti-siphon sprinkler valves will have a piston instead of a diaphragm, making the modification process much more difficult.

---Comparison to a Globe Valve-------------------------------------------------------------------------------------------------------------- Most anti-siphon sprinkler valves will contain a flow control and a guide rod; however, the guide rod is used for a different purpose than it is in a globe valve. As one can see, this type of valve is a combination of a barrel-sealing and a chamber-sealing valve. Due to the center of the diaphragm (therefore, the position of the guide rod) over the output section, the guide rod will not go completely through the diaphragm as it does in a globe valve. The guide rod, in this circumstance, is used for the flow control of the valve. This means that the anti-siphon valve can still be pneumatically modified in most circumstances. It should be noted, however, that some anti-siphon sprinkler valves will be completely different on the inside. Some of these valves will have a piston rather than a diaphragm. If this is the case, it will be very difficult to pneumatically modify the valve, as it will be very easy to damage crucial internal components to allow the valve to function. ---Modifications ----------------------------------------------------------------------------------------------------------------------------------- Anti-siphon sprinkler valves will have slightly worse performance, even when modified, compared to globe valves. The positive qualities, however, will still warrant the use of them. Note that there are several additional things that can be done to the anti-siphon sprinkler valve to increase its performance, but it will still lack when compared to a globe valve due to the flow restrictions.

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Basic Modification: If possible, the flow control can be removed and the valve lid tapped for a pilot valve. If this is the case, the guide rod should also be removed and there should be no obstruction between the pilot area and pilot valve threads. Follow the procedures for the basic modification of a globe valve to complete this. Valve Body: Due to the turns present on the interior of the valve body, the flow is going to be not up to par. But by eliminating one of the turns, the flow can be slightly increased. Use a drill bit to drill through the output side of the valve body. The drill bit should be large enough to make the hole as big as possible, but not so large as to damage any threads that may be present. The blow diagram will display the proper place for this modification.

Solenoid Port Modification: In situations where the valve cannot normally be modified conventionally, it will still be able to be pneumatically operated. Do this by removing the solenoid first. Drill out the exhaust port as large as possible while not damaging the exterior of the valve. It may be possible to drill the lid from its inside at an angle to make as large a hole as possible, and the remaining unused hole should be filled with epoxy. Once the solenoid is removed, use a metal bushing to screw it into the solenoid port. Work slowly and carefully, as the bushing will need to cut new threads over the existing ones. Once the threads are cut, remove the bushing and saturate its threads with epoxy. Install it into the solenoid port. Backflow Modification: The backflow preventer is what makes the anti-siphon valve function as it is intended to do. For pneumatic launcher applications, however, it is not needed for function, but is needed for seal. Remove this piece and fill it in with epoxy, making sure not to get epoxy on any of the sealing gaskets or o-rings. It should be fixed in the open position. Once the epoxy has cured, place it back onto the valve. Advanced Modifications: Advanced modifications, such as upgrading the diaphragm or building a piston, may be possible in this type of valve, but will be very difficult to do and will not provide a lot of enhancements to the valve. Therefore, advanced modifications are advised against.

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TRIGGERING THE VALVE

In any sort of piston or diaphragm valve, it will need a trigger valve, also know as a pilot valve. These valves are generally smaller valves and easy to operate. They allow the modified valve to purge the pilot area of air, which causes the valve to function as intended. ---Ball Valve --------------------------------------------------------------------------------------------------------------------------------------- Almost any type of valve can be used to pilot the sprinkler valve; there are only a handful of valves that are actually used. One of the most common types of pilot valve is a simple ball valve. A ball valve has some advantages and some disadvantages. One of the primary advantages of the ball valve is its flow rate. It should be noted that these types of valves are nearly completely dependant on the user, and will most often have inconsistencies. In other words, the user may open the valve at a certain speed on one pull, then a different speed on the next. This will, of course, affect the way the pilot is dumped, which will affect the way the diaphragm opens, which will affect the flow rate of the fluid in the launcher. And this will happen on every pull. In fact, the opening times of a ball valve are so bad that it is just about impractical to use without modification. One way of fixing this problem is to add a spring to the valve. In a closed position, the valve will be stationary. The spring should be situation in such a way to allow the valve to remain closed, but a slight jar will activate the spring, causing the spring to open the valve. One of the best methods of fixing the negative aspects of a ball valve is to not use a ball valve to begin with. ---Blowgun Valve--------------------------------------------------------------------------------------------------------------------------------- This is perhaps one of the most commonly used types of valves that is used to pilot a sprinkler valve. It offers several features that warrant this. For starters, this type of valve is simply a push button momentary valve, meaning it is very easy to operate. This means that it can be set up in such a way to allow a natural "trigger" feel to the launcher. These are commonly mounted in some type of handle configuration to make it even more user friendly, such as placing it inside a trimmed out piece of pvc pipe, then mounting the pipe to the launcher.

Although these valves are ideal for use as a pilot valve for sprinkler valves, they do have one major drawback; that is the flow rate is horrible. Out of the package, using a blowgun as a pilot valve may not provide any performance increase much beyond that of using the solenoid. But, this shouldn't discourage one from using this valve as a pilot valve. In fact, the next section in this book will cover the blowgun valve and will demonstrate the process of modifying it to allow it have a flow rate that is almost as good as a ball valve. ---Other Valve Types ---------------------------------------------------------------------------------------------------------------------------- As mentioned above, any number of valves can be used to pilot a sprinkler valve, and this is usually only limited to the fitting that is applied to the lid of the sprinkler valve.

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THE BLOWGUN PILOT VALVE Blowgun valves were introduced in the previous section, but they are so commonly used to pilot a sprinkler valve, that it deserves its own section. One of the questions that arise is on the modification of a blowgun to make it have better performance. This section will demonstrate the different modifications that can be done to the blowgun valve in order to bring it up to par. It should be noted that modifying is slightly more difficult than performing the basic modification to a sprinkler valve. But the modification process is not all that difficult and the payoff will be worth the effort, not to mention the knowledge gained by doing so. Pictured below is a Husky blowgun, assembled and disassembled. These are the most commonly selected types of blowguns and can be obtained at any credible hardware store for cheap.

Husky blowgun parts ---The Nozzle ------------------------------------------------------------------------------------------------------------------------------------- Whether the entire blowgun is modified or not, the nozzle should be removed. It restricts the flow of the blowgun so much, that it is the majority of the reason why these things don't perform as they should out of the package. The nozzle is simply a small piece that is screwed into place. These threads are generally 1/8" NPT threads, meaning that it can be replaced with another fitting if desired. ---Piston Housing--------------------------------------------------------------------------------------------------------------------------------- Separate the piston housing. If the piston housing has an o-ring, remove it. These can easily be removed using dental picks or similar, however, be careful not to damage it. On the piston housing, there should be two adjacent holes. These holes need to be enlarged. Make them as large as possible, but also make sure the valve pin o-rings are not exposed. A good start would be to use a drill bit that, when centered in the current hole, the edge of the drill bit touches the threads. On the above blowgun, a 1/4" bit was used.

---Piston -------------------------------------------------------------------------------------------------------------------------------------------- Now, we need to modify the piston. There is a narrow portion on the valve pin between two o-ring grooves. Remove the o-rings and clamp the valve pin in a vice. Slowly file out this narrow section (noted in red in the image to the right), making it about half the diameter it once was.

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---Modifying the Body --------------------------------------------------------------------------------------------------------------------------- The last step in modifying a blowgun is to work on the body. Use a drill bit that will drill the input and output portion of the body (usually, these are different sizes), but one that will not damage any threads. Another option would be to cut the tip off, then drill the holes.

---Lever Spacer ----------------------------------------------------------------------------------------------------------------------------------- Some people advise to add a spacer in between the piston and the lever. What this does is push the piston down a bit further. In some circumstances, it may help performance, but in most (including with the Husky blowgun), it will push the piston too far and hurt performance. ---Reassembly ------------------------------------------------------------------------------------------------------------------------------------ Once the pieces have been modified, make sure there are no burrs on any of them. Wash the pieces by running them under water and replace the o-rings. Lubricate the internals with air tool oil and reassemble the blowgun.

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TROUBLESHOOTING GUIDE As with any man-made piece, a sprinkler valve may have issues from time to time. This section hopes to provide a fix for the most common of these problems. The valve is leaking from around the cover Make sure the diaphragm ridge is properly placed into the grooves and not damaged. If the diaphragm has been replaced, make sure the o-ring (or other material) is clean, properly sealed, and not damaged. The valve makes a honking or airhorn noise This "honking" is caused by the diaphragm moving back and forth causing short burst of air to exhaust. It generally indicates that the pilot valve is too small and is a common problem in solenoid activated sprinkler valves. The valve is leaking air out of the barrel The diaphragm is not sealing properly and generally indicates that the diaphragm is either dirty or damaged. The valve will not seal during pressurization This is probably the most common problem and is caused by a number of things: 1) In homemade piston or diaphragms, the equalization hole may be too small. Do not attempt to adjust the equalization hole in the factory diaphragm. 2) A leak is present in the valve top. If the valve is modified, this leak will probably be present where the fitting is placed into the top and can be fixed with some epoxy. 3) The valve may be on backwards. There should be arrows on the valve, indicating the flow. 4) If the solenoid is still in tact, it may be defective. 5) The bleed screw or tab is opened too far. 6) The chamber is filling up too slowly, not allowing the air to equalize quickly enough. This problem is usually caused by using a hand pump. First, try moving the fill valve to the pilot area. A less feasible option is to place a ball valve between the chamber and valve, opening it when the chamber has pressure. Another option is to cover the barrel to hold back the pressure until the diaphragm seats. The best option, however, is to use a compressor or regulated high pressure air source. Air leaks out of the pilot valve when fired and not the barrel The diaphragm may be damaged or the equalization hole is too large. Also, if the diaphragm is homemade, it may not be even along the edges or it may not be the right size. The equalization hole could be partially filled in, but the best bet is to replace the diaphragm. The solenoid will not actuate the valve The solenoid is defective, it is not opening fast enough, or it's not powerful enough to exhaust the pilot. Replace the solenoid, enlarge the pilot exhaust, add another battery, or modify the valve. After firing the launcher, the diaphragm gets stuck in the open position If filling from the chamber, move the fill valve to behind the diaphragm. If that doesn't fix the problem, make sure the diaphragm is clean and not obstructed. Also, make sure the spring is properly aligned. If this does not fix the problem, replace the diaphragm.

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SOURCES

The sources are what made this book possible. Some of the information in this book is gathered from personal experience and knowledge, but a lot of it was gathered and collected from these sources. In fact, the personal experience and knowledge could not have been collected without these sources.

Spudfiles.com - Spudfiles is, by far, the most extensive website and forum on the subject of any type of homemade launcher to date. Without it, none of this would be possible. The Spudgun Technology Center - The Spudgun Technology Center started it all. Spudtech is no longer active, but is currently archived through Spudfiles and is home to a host of knowledge. Orbit Irrigation Products, Inc - Orbit sprinkler valves are probably the most commonly used sprinkler valve for a launcher due to its simplicity and ease of modification. Hall Consulting's Gas Gun Design Tool - This site is the host of the GGDT, or gas gun design tool. It is the standard in designing a pneumatic launcher, being able to predict, with rather close accuracy, the performance one can expect from their design. Husky Tools - Husky is the standard blowgun. There are many other choices, but this particular one is rather easy to work with and modify, which warrants its appearance in this book. RainBird Sprinkler Systems - Rainbird is another company that makes many different types of sprinkler valves. Their primary usage is in anti-siphon sprinkler valves. RL Hudson & Company - These guys know o-rings and their website has vast knowledge on the subject.