Impulses are prie examples of an electropneumatic conversion from a mechanical stacked open bolt blow back to an electropneumatic version. It consists of two bores in the body: one for the firing assembly and one for the bolt. The design employs a pneumatic piston which drives a hammer forward. Other markers that share a similar design include the ICD Bushmaster series, Bob Long Intimidator series of markers, Tribal series of markers, MacDev Cyborg, and others. The AKALMP Viking and WDP Angel series of markers are also very similar to the Impulse in design.
Impulse Design and Layout:
As said, housed within the top bore in the body is the marker's bolt, the bolt's connectino to the firing assembly, and the barrel. The bolt is just a piece of aluminum (the stock bolt, anyways), and it is held into the hammer through a pull pin (frequently called the bolt pin), which protudes out the top of the body. The bolt is removeable by pulling the bolt pin up and out of the bolt, which will allow it to slide out the back of the body. The Impulse uses Impulse-threaded barrels (except for the pre-productions, which used modified Shocker-threaded barrels).
The lower bore houses the components of the firing assembly: the piston, hammer, and valve. The piston is simply a pneumatic device which moves back and forth according to which end is pressureized. It is connected to the hammer via the ram, and in front of the hammer is the valve, and a large spring is placed in front of the valve to close it between firings. The hammer is shaped so that the bolt pin fits into it, so the bolt will move forward and rear whenever the hammer does. The valve is removable by unscrewing the front endcap and loosening the set screw on the underside of the body. Pressureized air enters the marker through the area occupied by the valve spring.
Located within the body is also a small bore that runs the whole length like the other two. It is the main air distribtion manifold, and feeds the various parts of the marker with presurized air. Specifically, it allows the soleniod (located at the back of the body) to have access to the pressure stored at the front of the marker. Note that there is a small plug on the side of the body; this is simply a port that was drilled between the manifold and the solenoid, and then needed to then be sealed off from the atmosphere. There is never any need to remove this screw; if you do so then apply some strong loctite (red or green) and put it back in.
Attached to the underside of the body is a standard, four-way pneumatic solenoid. The soleniod's function is to pressurize the desired end of the piston to fire and recock the marker. This area is enclosed within the solenoid housing (aka. circuit housing). The soleniod is connected to the marker's board by two small wires (positive and negative). The marker's boards are also housed within the solenoid housing. In Impulses not equipped with the Vision anti-chop eye, only a single circuit board operates the marker. In Vision-equipped Impulses, however, there is also a smaller board (the Vision daughterboard) which the soleniod firsts connects to, and then connects to the main board.
The grip frame houses the battery and trigger. The trigger assembly is the same as the ones found in 2000-2002 Shocker Sports. It is held in place by two horizontal pins, one to pivit over and one to act as a pre and post-travel stop. The Impulse also features a standard bottomline screw pattern and a .45 grip frame.
Firing Cycle Synopsis:
While the Impulse rests idle, the forward chamber of the piston is pressureized, which keeps the hammer back. Because the hammer is back, so is the bolt because they are connected via the bolt pin. There is ideally a paintball in the chamber, ready to fire. If there is not and Vision Mode is activated, the marker will not fire until one is loaded.
Assuming that a paintball is in the chamber (or Vision Mode is not active), when you pull the trigger you switch the solenoid valve so that the rear section of the piston becomes pressureized. This quickly moves the hammer forward, along with the bolt to close the breech and push the ball into the barrel. When the hammer moves forward far enough, it pushes forward a pin on the back of the valve, which opens the front of the valve to the pressureized air stored in front of it. This air is then shunted in through the valve and up through the air transfer port, and into a newly-exposed hole on the bottom of the bolt which then transfers the pressure into the barrel to propel the paintball. Milliseconds later, the solenoid switches back to move the hammer back away from the valve (this amount of time is known as dwell, and is anywhere between four and 14 milliseconds with the stock board). When the hammer retracts, the valve spring will close the valve and stop pressure from flowing through it, and it will also retract the bolt to allow the next round to be loaded. The Impulse is now ready to fire again.
It is also important to mention that with a stock Impulse, the solenoid actually dosen't play much of a role in recocking the bolt / closing the valve. In this case, what is commonly refeered to as back pressure from the bolt is created by a paintball when it fires. This is actually what pushes the bolt back, and it pulls the hammer along with it. If you want to know, this is Newton's third law of motion (with every action there is an equal and opposite reaction), also known as the action/reaction law. It depicts that when you push against a wall, the wall actually pushes back. If it does not, you would move the wall. When you push a book across a table, you are excerting more force on the book than it is excerting back on you, thus it moves. The Impulse's bolt works the same way: if you removed the bolt pin and closed the breech with the bolt so the marker will fire, and pull the trigger, the bolt will fly backward (warning: if you do this, be prepared for the bolt to fly out the back of the body). So basically what happens is a very small amount of force is used to push the bold back enough to close the valve, then after that has happenned the solenoid will be able to pull the hammer the rest of the way back. Read the later section, Air Restriction Modifications, for more detail is you so desire.
Because the depressureization/repressureization of the piston is the only event driving the firing of the marker, the Impulse is allowed to sustain very high rates of fire, unlike the Shocker Sport which preceeded it. And because it is such a clean, efficient method of firing, the addition of the Vision sytem was the next step. Most Shockers can only fire 14-bps (the boards are capped lower then this, though); this is actually a drawback of the design of their fill poppet assemblies if you want to know...basically it's just a design restriction implicated on the marker by the unique method by which it fires. Impulses, on the other hand, use a simpler method to fire, like other markers with a hammer.
Below are several animations of Impulses in operation.
Air Restriction Modifications:
As said, there is a small chamber on the right side of the receiver the runs the entire length of the body. Gas enters the manifold from the large air chamber in the front of the body and uses the manifold to get to the soleniod at the rear of the body. The problem is this (as was hinted to earler by the explination of Newton's third law): when the solenoid fires, a much larger amount of pressureized air begins to be blown through the valve at the front of the receiver. When this happens, the solenoid will not be able to gather enough pressureization to switch the hammer back to close the valve. An example of this would be when the toilet is flushed in your bathroom while the shower is running: the water grows very cold very suddenly, because the toilet uses it up temporarily. Unlike a toilet, however, the solenoid will not automatically switch back without the proper amount of pressure. This is where an air restriction mod takes into effect. An Impulse without an air restriction mod will not be able to dry fire because back pressure is required to push the bolt backward. This actually recocks the marker, not the solenoid in Impulses without an air restriction mod as was explained earler.
There are two types of air restriction mods: restriction mods, which seperate the manifold from the air chamber through a small plug inserted through the manifold itself, and isolation mods, which completely seperate the manifold from the air chamber effectively on the outside of the marker, specifically in the vertical adapter. Isolation mods aren't always applicable because the Impulse has to be pre-drilled fto accept them, however many Private Label Imps have this porting as well as Impulses with lower serial numbers.
Air restriction mods are also known as solenoid optimizers, because that's basically what they do. That is, they prevent the air chamber from steaking away pressure from the manifold like your toilet steals away cold water away from your shower (at least they prevent it from happening to such a large degree). This makes it so the Impulse can be dry-fired. So basically they allow the solenoid to be operated using a seperate source of pressureized air. Which brings me to my next point...
If you have an LPR on your Impulse, you'll notice that its output plugs into the manifold through a tapped solenoid optimizer, specifically a restriction mod. This allows the manifold to only feed the solenoid with air, and because the solenoid dosen't require as much air to complete its task, air in the restricted manifold can be regulated down to a lower pressure than that of the air chamber. So you use an LPR output pressure to control the pressure of the solenoid (pneumatics pressure), you use the Max-Flo to control the pressure of the air chamber (operating pressure). And because the manifold is regulated to a lower pressure than the air chamber, when you regulate the Max-Flo the pressure fo the manifold remains constant (unless you lower the Max-Flo past the LPR's setting, which you can't do).
There are two places for an LPR to tap off the Max-Flo's output pressures: through a hole in the front of the valve endcap (which you may not have), or through the PRV output on the vertical adapter. I suppose you could also tap it directly off the Max-Flo, but that would require a long macroline and be kindof unconventional. The brass PRV is not needed while using an LPR.
Assorted Technical Specifications:
· Body manifold threads: NPT ports, 1/8"
· Feed tube threads: 32-tpi, 0.807" major diameter
· Trigger return spring set screw: 1/4"-28 (1/8" allen wrench)
· Piston housing hex wrench size: 7/8"
· Valve set screw threads: 7/16"-20
· Valve endcap threads: 1"-16
Electronic Components' Specifications:
· Green/amber board Intellifeed connector: JST Connector wire-to-board crimp connector, eBH series
· Green/amber board power switch: ITT/Cannon part# GT12MAKE
· Green/amber board microporcessor: 2-MHz Microchip PIC16LC72A
· Cricket board microprocessor: Atmel ATMEGA8L
· Trigger Microswitch: subminiature snap action lever switch, Omron part# D2F-01L (80-g) or D2F-FL (25-g)
· Solenoid lead connector: JST wire-to-board crimp connector, part# S2B-PH-SM3-TB.