Ion Design & theory > Tech index > SP Ion > Parts of an Ion > Design & theory
This page is for the more advanced technical specifications on the operation of an Ion.

Design Definitions:
Put simply, this is how the marker operates. When the bolt moves forward, air passages within it become open (the grooves around the middle section of the bolt), which allows air to expand down the barrel and fire the ball. When the bolt is retracted backward, said air passages become closed again, and the marker waits until the next firing. The bolt is driven forward by the same air pressure that fires the ball, whereas the bolt is moved open by the solenoid.
This type of design is generally referred to as a spool valve firing mechanism. This describes a one-piece moving part (the bolt) which also functions as the valve for the marker, movement of which is balanced back and forth (or slightly unbalanced, as in this case). This is significantly less complicated than the traditional stacked-tube design that many previous markers utilize. These involve a hammer, percussive valve, bolt, and a number of connections and housings between them. The stacked hammer design was invented in the late 80's / early 90's and spool-based markers are the next step in development.
The advantages to this type of design generally include decreased recoil, higher air efficiency, decreased energy used per shot, and decreased volume for the shots (meaning they're more quiet than other markers). Similar designs can be found in several other forms, including the Shocker, Matrix and DM series markers, FEP Quest, and some others. In the future we may come to see additional designs like this, since it is a very simplistic method of firing a marker with many possibilities for modification.

Firing Assembly Synopsis: Tech
Now for some technical information and further explanation of the firing cycle. You may wish to use the below animation(s) for reference. The design of the Ion is similar to that of a Matrix, except with rearranged components and an altered function. For reference, the function of an Ion's valve is a blowforward, which is a type of valve whereby the bolt is blown into the forward firing position by the firing air pressure itself, instead of using a solenoid to push it forward. The Ion bolt is shaped similar to that of a Matrix, with a defined "tip" section and a "tail" to guide it, inside a dump chamber to fire the ball. The Ion's boltstop defines the front of the dump chamber and the rear of the predump chamber, which is the passage between the dump chamber and the bolt face. The boltstop also acts as the firing seal to release air when the marker fires. The bolt is held open from constant pressure from the solenoid, similar to a Freestyle bolt, except shaped differently. The Ion bolt uses an expanse of grooves (once referred to as exchange grooves) which release the air in the dump chamber to the predump chamber, then down the barrel through the bolt porting. The reason the grooves are used is to help keep the inner boltstop o-ring from popping out (since it rides on the "ridges" between the bolts grooves).

However, unlike a Matrix, the bolt pushes itself forward and doesn't use a two-way moving solenoid. Pressure from the solenoid is cut off to start the firing process, then re-established once firing is complete, to recock the bolt. Examples of similar markers would include the Freestyle, which is also an electropneumatic blowforward, however has a very different design. An example of a mechanical blowforward would be an Automag, which more resembles a Freestyle than Ion, however is similar to an Ion even though they have many differences.

While the marker rests idle, the front portion of the bolt tip is pressurized from the solenoid, which holds the bolt in the rear/open position. The fire chamber is filled with pressurized air, ready to be released. When the solenoid energizes, its internal valve (armature) opens up the air outlet, which allows the air holding the bolt open to vent back down through the solenoid and out into the open air. As this air is vented, the pressure stored within the fire chamber will push the bolt forward. Once it reaches the end of its forward stroke, the ring of grooves around the middle of the bolt cross under the boltstop o-ring and all the air pressure within the fire chamber will be released down through the bolt to fire the ball.

The marker's bolt will be actuated on the venting caused by the solenoid. The most important factor here is the use of the dwell time, which is the time the solenoid remains energized, which translates to how long the bolt stays forward. The dwell setting must be set to allow the bolt to cycle forward and dump the air to fire the ball. This is my definition of dwell and what it is used for.

Pressure Physics and Bolt Movement: Tech
How exactly does the bolt move forward, and why does the solenoid prevent it from closing when idle? In order to learn the answers to these questions, you'll have to have a basic understanding of what air pressure is, and how it works. This is a simple mechanical concept that many markers use to operate, and is taken into consideration when designing any paintball device such as this.

With regards to the Ion's bolt and the fire chamber/boltstop, the internal diameters themselves are what allow the bolt to move in either direction. Air pressure is applied evenly to all surfaces of its containter, but since pressure is defined as pounds per SQUARE inch, it means the more surface area you have, the more force you end up with. In this case, air pressure contained in the fire chamber pushes on all parts of the bolt at once, and since the diameter of the bolt middle section is larger than the diameter of the tail section (size 14 o-ring on the middle section, compared to size 10 o-ring on the bolt tail), the pressurized air in the fire chamber pushes it in the direction of the greater surface area. This is what pushes the bolt forward during firing.
Forward-acting surface area
Specifically, in the above diagram, the diameter of the bolt pushing forward is larger than the rearward diameter. The exact force can be formulated by calculating the surface area of the two diameters and comparing it to the operating pressure, but I won't go into that here. Just know that, because the front of the bolt is wider than the rear, it is thusly driven in that direction when the marker fires. Once it reaches the front position, the air volume in the fire chamber is vented through the bolt grooves and down out the bolt face (this fires the paintball).

The purpose of the bolt "tail" is to offset the diameter of the bolt and allow athe boltstop o-ring to be larger. The boltstop diameter determines the volume of air that can be vented to fire the ball, so larger is better (in this situation). In order to have an o-ring as large as the one used (size 14), the tail is integrated into the bolt to remove some of the forward force and direct it backwards.

The above paragraphs detail how the marker fires. The method by which it recocks is quite similar. The diameter of the bolt tip is larger still than the diameter of the bolt middle section that is responsible for firing the marker.
Rearward-acting surface area
In much the same way that the bolt is driven forward, the bolt will be pushed and held in the open position by the air in front because it has a larger diameter. Technically, the amount of force that acts on the ball isn't the actual diameter, but rather the directional surface area, which is calculated by using the diameters of the bolt and surrounding parts. I won't go into it.

The exact diameters that were used during the design of the Ion were found by careful calculation and experimentation to find the best method for firing the marker. The difference between the forward and rearward force is what allows other o-rings to be the size that they are today. For instance, the bolt sail o-ring is larger than a conventional o-ring in the similar situation, to allow the bolt to open with a quicker speed (and alternately close with a smaller speed). This is why the bolt uses a metric o-ring to seal, instead of a standard 16/70 like other markers of similar design.

Twiek was good enough to provide this animation, which accurately portrays the firing of the marker:
Ion animation
A similar animation was assembled by Chiumanfu:
Ion animation
Chiumanfu also put together this large, complete Ion firing animation. This shows the regulator, solenoid, and bolt all in action together. It's a reasonably accurate vision of what goes on in the marker. Right click the below thumb and select save as if you're on dial-up, since this is a large file.

An animation of the exact bolt movement can be found below.

QEV Use in Ion:
It's also important to remember that the dwell time isn't the amount of time the bolt remains forward, but it's rather the amount of time the bolt takes to reach the forward position, as well as how long it stays there. As it happens, the soleniod takes more time venting the bolt to allow to close, than it does actually firing the ball. Specifically, in the Ion, the stock bolt and solenoid will take nearly 20 milliseconds to reach the forward position (whereas in some markers, the bolt takes only 5-ms or less to move). The remaining dwell time is the amount of time the dump chamber takes to fire the ball by venting out the fire chamber. This long moving time is a result of how the solenoid vents; air is forced back through the middle LP hose fitting and down through the solenoid, which takes a bit longer than some other alternatives.

A QEV (quick exhaust valve) will greatly aid the firing cycle in the Ion, like it will in many other markers. When a QEV is added, the solenoid's venting air will be vented at the QEV location as well as through the solenoid, which cuts the amount of time the bolt takes to move literally in half. Specifically, dwell will be decreased from around 26-ms without a QEV, to around 12-15 ms with one (depending on how quickly the QEV vents).

When you replace the banjo fitting with a QEV, air pressure will be allowed to vent at the new fitting in addition to being able to vent at the solenoid. The QEV is fitted with a cone-shaped rubber poppet which plugs it off when air pressure pushes against it from one direction, however when air pushes against the other side (as when the solenoid vents) the rubber poppet will open up and allow pressure to vent. This is depicted in the below bolt speed animation.

This rendering crudely illustrates the path of air.

Bolt Speed:
Adding a QEV is the only thing you can do that will change how quickly the bolt moves. When the marker fires, the bolt is pushed forward by the air behind it. The bolt's speed and position is dependant on how much pressure is still in the chamber holding it open. This air pressure vents at a linear rate, and thus the bolt's speed is linear as well; it only accellerates for 1-2 milliseconds at the beginning of its movement, and its speed doesn't change during its forward stroke.

Installing a lighter bolt does not make the bolt move faster. Period. I see people saying this all the time on various forums and it's simply not true. Please stop perpetuating this rumor.

When you install a QEV, your bolt will move much faster. This is because the air holding it open is allowed to vent much more quickly. The advantage to this is a higher cycle time as well as slightly increased efficiency. When the bolt takes longer to move forward, at the instant that the grooves pass under the boltstop some air is released before the full force is available, however the bolt isn't fully forward so it ends up venting out (wasted). When the bolt speed is increased [with a QEV], the ball isn't unseated like it is without one. Because of this, less air is required to fire the ball, and efficiency goes up by a slight amount (in most cases).

I have conducted a series of tests using pressure transducers to check the speed and operating pressure of the firing assembly. Using that data I created this animation below, which shows the exact movement and speed of the bolt with and without a QEV.
Bolt speed animation fast Bolt speed animation slow
The first animation is faster which helps to show the time difference between the two assemblies. The second animation is slower which gives you time to read the text and follow the airflow.

Related Links:
Firing assembly maintenance section
Solenoid and internal hoses