Introduction

Selecting pneumatic parts is a significant hurdle in air blaster design, particularly for new designers. Pneumatic component manufacturers tend to assume a certain level of technical knowledge and jargon fluency in their product literature, and the sheer variety of part configurations they offer can quickly become overwhelming. Often, there are dozens of different parts that could perform in a given application, and further refinement within that selection comes down to factors other than flow rate or pressure rating. An example product code for just one of the 21 different solenoid valve lines in the SMC catalog is shown below. It looks like a lot, but I'll show you how to quickly identify parts that are useful for our purposes. 

Source: SMC Pneumatics

An Overview of My Preferred Hardware

(A shopping list for people who want the "short" explanation)

As a quick note, I will avoid including specific AliExpress/Amazon links here, except as needed to credit images. Specific listings are removed or become unavailable so frequently that a list of links will not remain relevant for very long.

Tubing and Fittings

I recommend 4mm x 2mm polyurethane air line tubing for all applications involving the Cosmic Nomad. Larger diameter tubing is perfectly fine, but offers no benefit whatsoever, at the expense of increased minimum bend radius, decreased flexibility, and larger fittings. Additionally, 4mm tubing and fittings are directly interchangeable with 5/32" tubing and fittings, which can serve to expand the available range of fittings, valves, and air cylinders you can choose from without resorting to expensive inch-metric conversion fittings. I usually buy mine from McMaster, but any brand or vendor is fine.

The Nomad is configured for gasketed, straight-thread M5 fittings. This means that the fittings do not need additional sealant and have minimal torque requirements. My favorite fittings are barbed with threaded compression collars, as shown below. 

Source: Aliexpress

If you look closely, however, you may notice some subtle differences between the two fittings above. Aside from the fact that one is a straight fitting and the other is an elbow, the gaskets are distinctly different on each. The straight fitting (left) seals with an o-ring that's captured in a shallow face groove at the base of the fitting. This configuration defines a set amount of seal compression and also prevents seal extrusion failure thanks to the outer wall of the groove. Fittings like these are the best options.

The elbow fitting to the right uses a flat gasket. These tend to be less reliable, as there is no sideways constraint for the gasket that prevents blowouts. They require somewhat more torque to seal properly, but lack any sort of compression-limiting feature to protect the gasket and fitting. Avoid these when possible. Both gasket styles are available on both fitting types, and some listings may display multiple gasket styles. Note that some flat gaskets are not just a thin sheet of rubber. These are "metal-bonded sealing washers," and are significantly better than a plain rubber flat gasket. Unfortunately, there's often no way to tell what you're receiving until you have the product in hand, so if you're buying unbranded fittings, it's best to stick with o-ring seals when possible. 

These fittings are commonly labeled "PCx-Mx" or "PLx-Mx" where the first x is the tube diameter in millimeters and the second is the thread size. C is used to denote a straight fitting, where L denotes an elbow. Unfortunately, this nomenclature is shared with push-connect fittings, and there is not a consistent naming scheme for these much more compact barbed fittings. That said, there's nothing inherently wrong with push connects, and they are certainly convenient! Just be aware that plastic-bodied push connect elbows are held on by nothing more than a snap fit at their bases, and can easily get blown off in high pressure applications. It's best to keep plastic bodied elbows under 150 psi.

The AliExpress listing I pulled that image from calls them "Mini Pneumatic Pipe Connector Male Thread M3 M4 M5 M6 1/8 Air Tube 3mm 4mm 6mm OD Screw Through Quick Fitting Fast Joint." You can search for something along those lines or search with the image above to find the right products. The same fittings are also available on Amazon at a higher markup.

If you're following my recommendations so far, you want PC4-M5 and PL4-M5 fittings. If you are not using the auxiliary port on the nomad, you need a M5x4mm setscrew and teflon tape or a M5 pipe plug with a sealing head to block it off. 

Pilot Valves

"Pilot" valves are directional control valves that are necessary to operate a Cosmic Nomad. They connect to the pilot port on the tank and control the air that enters and exits the poppet chamber inside. Pilot valves can be manual or solenoid operated.

Manual Pilot Valves

If you're building a blaster that is either manually loaded or uses a single acting air cylinder to actuate the breech (I'll cover that later), you are almost always going to want a Clippard M-MAVO-3. The regular MAVO-3 is also a valid option, and is frequently easier to source and less expensive, particularly in the US. The downside of the MAVO-3 is that it has #10-32 ports rather than M5. This means you'll likely need #10-32 fittings for 5/32" tubing, as mentioned above, which can connect to 4mm tube just fine. Just make sure to carefully keep track of your fittings if you're mixing inch and metric! I find that #10-32 tube fittings are more commonly offered as push connects rather than the preferred barb style above.

The MJVO-3 that has long been the default manual valve option in the hobby is wholly unnecessary for the Cosmic Nomad. The pilot flow requirements are so minimal that virtually anything can successfully and consistently pilot it, and the nomad does not suffer from inconsistent opening times with a manual valve. The MJVO-3 has a much larger footprint and uses much larger fittings as well.

These valves are both normally-open 3-way valves. That means they control one output, which normally has air supplied to it. When you press the button, air is diverted from that output port to the exhaust, while shutting off the input line. So far, I have not seen a blaster use a manual 4-way valve. Clippard has options for those as well, though they are beyond the scope of this overview. So far, every public Nomad build with a manual pilot valve uses a 3-way valve, and an overwhelming majority use the MAVO-3.

Solenoid Pilot Valves

This is where it gets messy. I am limiting this section to M3 and M5 body-ported solenoid valves that are commonly available on the used market. I prefer SMC valves because they are generally affordable, well-documented, and in widespread use across industry. I also find their part numbering scheme easiest to understand out of the major brands. Most products they offer follow either formal industry standards or generally accepted norms, and they have a larger range of small form factor solenoid valves with straight-threaded ports than most other pneumatic brands. If you're interested in exploring the full range of SMC's product line, their PDF catalog can be found here.

One of my preferred 4-way solenoid valves

I buy most of my solenoid valves on the used market, typically on eBay. It can be difficult to sift through the range of listings that are sometimes even titled incorrectly. Make sure you check the listing photos to verify that the valve is what it claims to be. These valves can generally be found for $20-30 each if you are patient, and sometimes, you can find multi-valve manifold assemblies that can be separated into individual body-ported valves without any extra parts for about the same price as a single valve on its own.

If you're building a blaster with a solenoid pilot valve, it's much more likely that you'll be interested in using a double acting cylinder, which generally (though not always) requires a 4-way valve. Such valves have two outputs rather than just one, and behave like two 3-way valves stacked next to each other. 

Common 4-way solenoid valve part numbers

M3 Threads

• SYJ3120-XXX-M3
• NVJ3120-XXX-M3
• NVJ3123-XXX-M3
  

M5 Threads

• SYJ5120-XXX-M5
• NVJ5120-XXX-M5
• NVJ5123-XXX-M5
• NVZ3120-XXX-M5

You may notice some common features of the part numbers above. Many, but not all of SMC's smaller valves will have a part number starting with 3. The second digit in the part number indicates the number of solenoid coils and valve positions, and in this case, we want just one solenoid and one position. In fact, the part numbering scheme shown in the first image in this article applies to quite a few SMC valves, and you can often find very similar valves with different family codes (letters at the start) just by recognizing patterns in the numbers. If you find a valve from a different family that looks similar to any of the above, its datasheet will be available for free from SMC, and you can use that information to cross reference its description against the above part numbers. You will find that many valves on the surplus market come from product lines that are deprecated, but documentation is still available.

Common 3-way solenoid valve part numbers

M3 Threads

• SYJ322-XXX-M3
• NVJ322-XXX-M3
  

M5 Threads

• SYJ522-XXX-M5

Note: 4-way valves can be used as 3-way valves by plugging one output port

When searching for these valves, I often omit everything after the first dash in the part number. This yields the greatest number of results but takes longer to sift through. The second cluster of characters, shown above as XXX, refers to the voltage and connection type, explained in great detail in the catalog. The most important character in that code is the first one, which should be 5 or 6, for 24V or 12V, respectively. 24V solenoid valves are much more common, as 24V is frequently used for low-power I/O in industrial equipment. 24V valves frequently do not reliably cycle on a 3S LiPo battery. 12V valves do, so prioritize valves with a 6 in that position. 24V valves can be operated off a 3S LiPo with a small boost converter, available from Amazon, Aliexpress, and many other vendors for a few dollars. Solenoid valves are low-power devices, and rarely consume more than a few watts, so don't worry too much about current here. 1A is enough to drive multiple small solenoid valves at once.

Pneumatic Cylinders

Once again, I like SMC for these. if you're driving a bolt of some kind on a normal 13mm caliber blaster, feeding half length darts, you typically want a 10mm bore cylinder with 60-80mm of stroke length, depending on the specific design requirements. Cylinders are available in either single-acting or double-acting configurations. Single-acting cylinders have a single port for air. When air is supplied, the rod extends (or in some cases, retracts), and when it's exhausted, a spring returns it to its resting position. Single acting cylinders are slower to retract than double-acting cylinders, and you should not rely on the spring return to actuate significant loads. Double-acting cylinders have two ports: one extends the rod, and the other retracts it. A 4 way valve alternates the ports between supply air and exhaust. Double-acting cylinders are very fast and can actively drive loads in both directions.

SMC is the only brand I've found with a part family that covers this application range and offers M5 ports by default. As a result, this is the exact same line cloned by manufacturers in China. If you are buying from Aliexpress, look for a CDJ2B10-[stroke length in mm]. CDJ2B is the cylinder family and 10 is the bore in mm. The D refers to a variant with a magnetic piston head that can be used in combination with sensors on the cylinder body to detect when it reaches certain positions, and for some reason, that's the default and least expensive option from Chinese vendors. If you're looking on eBay, CJ2B10-[stroke length] can sometimes return more results, as it doesn't have the magnetic plunger. These are double-acting cylinders. Interestingly, the Chinese clones of these air cylinders have noticeably larger port sizes inside the end blocks than the genuine SMC versions, which makes them cycle dramatically faster than the SMC cylinders.

Aside from that, the Cosmic Nomad can be used with any sort of pneumatic cylinder attached to the auxiliary port on the back of the tank. Larger cylinders will cycle much slower, but can move significantly greater loads. I will cover more advanced configurations of pneumatic cylinders in a future article. 

Conclusion

I hope this helped to explain some of the basics of pneumatic component sourcing and selection for HPA blasters! Please feel welcome to join the discussion in #pneumatics on the Discord server, linked in the navigation bar at the top of the page. I hope to continue this series with technical deep dives into specific component types and more complex pneumatic systems in the future!