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Most of the marker's functions and aesthetic features are contained in its body, which contains the main components of the firing mechanism: the trigger frame, bolt and valve. Most marker bodies are constructed from aluminium to reduce the marker's weight, and feature custom milling and color anodizing.
External design
The largest external and ergonomic difference in marker bodies is in the trigger and barrel position. Designers of expensive models attempt to position the trigger frame forward towards the center, or slightly forward of center of the body on speedball-oriented markers. This allows the HPA tank to be mounted in a position allowing compactness and balance without requiring any additional modifications that allow the tank tank to fall down and forwards. Such aftermarket "drop forwards," may create a larger gun profile, which can result in eliminations due to hopper hits. Users often modify less expensive markers to allow a similar mode of operation, albeit by sacrificing a low profile. Alhough this not important in games where equipment hits are not counted, in most games, including woodsball games, hopper hits are counted as an elimination. Some markers mount the barrel farther back in the gun body to preserve a compact design, sacrificing the positioning of the trigger forward on the marker body.
Trigger frame
Triggers are very important functional features, being the player's primary means of interaction with the marker. The amount of force required to fire the marker, as well as the distance the trigger travels before actuating, called the throw, has a marked effect upon the player's ability to achieve high rates of fire. Expensive markers use electronic trigger frames with a variety of sensing methods, including microswitches, hall effect sensors or break-beam infra-red switches. These triggers have very short throws, allowing a higher rate of fire. Non-electronic markers sometimes use carefully set pneumatics to achieve a light and short trigger pull.
The trigger frame on non-electronic mechanical markers simply use a series of springs and levers to drop a sear, which propels the hammer in the body forward. On electronic markers, the trigger frame houses the electronics that control the solenoid, as well as features such as ball detection systems. Upgraded circuit boards that add improved features are available.
Bolt and valve assembly
The bolt and valve assembly is the mechanism which fires the marker. The valve is a mechanical switch that controls whether or not the marker is firing. The bolt directs the flow of air and controls the entry of paintballs into the chamber. The bolt and valve may be separate components, as in many blowback and poppet-based electropneumatic markers. Alternatively, the valve may be built into the bolt, as in spool-valve electropneumatic markers.
Most modern markers have an open bolt design. When the marker is at rest, the bolt is in the "back" position, and the firing chamber is exposed to the stack of paintballs being fed by the loader. Some markers have closed bolt designs; in the rest position, the bolt, and paintball to be fired, are forward and the feed stack is closed off from the chamber. Closed bolt markers were thought to be more accurate because there is no reciprocating mass when the marker is fired. However, tests have shown that the position of the bolt has little effect on a marker’s accuracy. [2]
Bolt and valve in mechanical markers
The majority of mechanical markers employ a simple blowback design utilizing a poppet valve (also known as a “pin valve”), which is opened when struck by a compression force, provided in the form of a hammer propelled by a spring. These sorts of markers generally use a “stacked tube” design, in which the valve and hammer is contained in the lower tube, while the bolt, which is connected to the hammer, is in the upper tube (Some manufacturers, however, such as Tippmann, have managed to incorporate the valve, hammer, and bolt into a single tube, as exemplified in the Tippmann 98 Custom). The hammer is held in the back position, with the spring compressed, by a sear. When the trigger is pulled, the hammer is propelled forward by the spring, into the valve. The air released by the valve is then simultaneously channeled up to the bolt to fire the paintball, and back to push the hammer back into the cocked position (hence the name “blowback”).
Poppet valves are usually easy to replace and require little, if any, maintenance. The downside to this design, however, is its high operating pressure, which leads to a larger recoil and arguably less accuracy. Some markers, such as the Autococker, have a separate firing and recocking sequence, which decreases the recoil caused by the cycling of the hammer. Any marker with a hammer, however, has a significant firing delay when compared to a full electropneumatic.
Some markers are a hybrid of mechanical and electronic features. In these markers, the hammer and spring continues to activate the valve, but the hammer is released by a solenoid in an electronic trigger frame.
Bolt and valve in electropneumatic markers
Instead of the spring and hammer used to actuate the valve and cycle the bolt assembly in mechanical markers, electropneumatic markers use the rerouting of air to different locations in the marker. This rerouting is controlled by a solenoid that is activated by the trigger. The two types of bolt and valve mechanisms in electropneumatic markers are the poppet-valve and spool-valve.
Poppet-valve-based electropneumatic markers are very similar to mechanical blowback markers. These have a stacked-tube construction, built around a poppet valve, that is opened when struck by a force. Whereas mechanical markers provide that force with a hammer propelled by a spring, the valve in poppet-valve markers are activated by a pneumatic ram. The bolt is connected to the ram. Poppet-valve markers have the same disadvantages as their mechanical counterparts: external moving parts, a reciprocating mass and a louder firing signature. However, they are also more gas efficient than spool-valve models because the poppet valve only releases the precise amount of air needed to fire the marker. Examples of markers that utilize this mechanism are the WDP Angel, Planet Eclipse Ego, Bob Long Intimidator, and Bushmaster.[3]
In Spool-valve-based electropneumatic markers, the bolt also acts as the valve. This eliminates the need for a stacked tube construction; spool valve markers have a more compact profile. Instead of a cycling hammer or ram that strikes a pin valve, the movement of the bolt is controlled by the routing of air into small chambers in front of or behind the bolt. An air reservoir behind the bolt contains the air that is to fire the paintball. When the marker is at rest, air is routed to the front of the bolt to prevent the air in the reservoir from escaping. When the trigger is pulled, that air is vented, allowing the air in the reservoir to push the bolt forwards. In a “balanced spool valve” design, the air is rerouted to a small chamber behind the bolt, separate from the reservoir, which then pushes the bolt forward. In either case, the movement of the bolt forward exposes pathways in the bolt or the marker that allow the air in the reservoir behind the bolt to surge forward and fire the paintball.
A typical spool valve has at least one O-ring that undergoes a shear and compression duty cycle for every shot, leading to faster wear and less reliability. Additionally, the necessity of an air reservoir makes them less gas efficient than their poppet-valve counterparts. Since spool-valve markers have no reciprocating mass, other than the bolt, and require little pressure to operate, they have less recoil and are quiet. Examples of markers that utilize this mechanism are the Dye Matrix, Smart Parts Shocker, and Smart Parts Ion.[4]
Tuning the bolt and valve system
In mechanical and poppet-based electropneumatic markers, the valve is usually designed to accommodate a specific operating pressure. Low pressure valves provide quieter operation and increased gas efficiency when tuned properly. However, excessively low pressure can decrease gas efficiency as dramatically as excessively high pressure.
Additionally, the valve must be set to release enough air to fire the paintball. If the valve is not tuned properly, insufficient air to fire the paintball may reach the bolt. This phenomenon, known as “shoot-down,” causes fired paintballs to gradually lose range, and can also occur at high rates of fire. Some markers have integral or external chambers, called low-pressure chambers, which hold a large volume of gas behind the valve to prevent shoot-down.
Tuning can also prevent air blowing up the feed tube upon firing, which disrupts the feeding of paintballs into the marker.
Copy From : http://en.wikipedia.org/wiki/Paintball_marker
