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98 Custom - 2006
By Bill Mills - Photos By Dawn Mills - July 2006

Overview - How It Works - Disassembly - Testing - Raw Test Data

HOW IT WORKS

The Tippmann 98 Custom is a blowback driven semi-auto paintgun, with an electronic trigger option.  The core of the 98 is Tippmann’s CVX valve.  The CVX valve is a poppet style design.  The hammer strikes the valve, opening it and releasing a burst of gas through channels that route it to the breech, and a smaller burst back at the hammer, recocking it for the next shot.  The CV in CVX stands for Constant Velocity, referring to the fact that in addition to the valve spring, gas pressure helps hold the poppet valve closed.  This means that velocity spikes from rises in gas pressure are reduced, because as the gas pressure rises, the valve becomes harder to open.

At rest, between shots, the bolt of the 98 Custom is open, and the hammer (rear bolt in Tippmann terminology) is in the rear position, compressing the mainspring.  A hardened steel latch, called the sear holds the bolt back.  The bolt is attached to the link arm, which sits in a slot in the hammer.  The ACT spring keeps the link arm pressed against the front end of the slot.

When the trigger is pulled, the hammer is released, and the mainspring decompresses, slamming the hammer forward.  At the same time, the ACT spring pushes the link arm forward, closing the bolt as the hammer strikes.

If there is a partially fed paintball blocking the breech, the bolt stops against the obstruction, with only the pressure of the ACT spring against it.  If however, there is no obstruction, the bolt (and the paintball it is pushing into back of the barrel) moves forward, and the link arm shifts downward, locking into a hole in the hammer. 

With the hammer and bolt solidly linked together, they continue forward, until the breech is sealed and the hammer strikes the valve core.  The impact of the hammer on the valve core presses it into the valve.  This allows gas to flow through a pair of channels in the sides of the valve body, forward to the power tube, which routes the gas through the center of the bolt and into the breech where it launches the paintball. 

At the same time, a small amount of gas escapes around the sides of the valve core into the space between the valve and hammer.  This space acts as a piston and pushes the hammer back, recompressing the mainspring.  When the hammer flies back, the front of the ACT slot pulls on the link arm, bringing the bolt to the rear position with the hammer, and compressing the ACT spring.

Once the hammer comes back far enough, it catches again on the spring loaded sear, to await the next shot.

Electronic triggered versions of the 98 Custom operate in exactly the same way.  With the mechanical trigger, an arm extending from the back of the trigger pushes upward on the sear, which pivots like a see-saw, releasing the hammer from its back end.  With the E-Trigger, the trigger instead trips an electronic switch.  Then, a microprocessor detects that the trigger has been pulled, and acts based upon its programming – this may include firing a single shot, a burst, or fully-automatic fire.

In order to fire the 98 Custom, the microprocessor delivers an electrical charge to a compact solenoid.  The solenoid is a coil of wire that produces a magnetic field when it is energized.  The magnetic field pulls on a metal core.  The result is that an electrical signal is converted into a short amount of mechanical movement.

That movement is applied to a stainless steel rod, which trips the front of the sear, just as a mechanical trigger would.  Electronic triggering offers a couple of significant advantages over mechanical triggering.  The first of these is the availability of multiple modes of fire.  Rather than needing to design complex latching and sear systems, functions like 3-round burst are merely a matter of writing a subroutine in the microprocessor’s software.  The second advantage is of benefit even when, like at most paintball fields, players are limited to semi-auto mode only. 

When using an electronic trigger, the player’s finger must merely do the work of activating a microswitch.  This means that the trigger pull can be made to be shorter and lighter than if the trigger had to directly push the sear against the pressure of the ACT spring and mainspring.  A shorter and lighter trigger pull makes well aimed single shots easier to take, and makes higher rates of fire easier to achieve.

Set up of the 98 Custom for review was straight forward.  A HALO B loader was fitted into its feedneck, and a Crossfire high output screw-in HPA tank was installed in the ASA.  It should be noted that the 98 was cocked before screwing in the air system, as hammer pressure could hold the valve open before gas pressure has a chance to build up in the valve.   

Older Tippmann E-Triggers utilized a rotary selector switch to turn the electronics on or change the mode, and a variable resistor to dial in the maximum rate of fire.  In contrast the newer WAS Equalizer E-Triggers feature a single power and programming button, along with a bi-color status LED.  This arrangement provides a wider range of user adjustability, but lines up with the same holes in the grip frame making it backward compatible with earlier 98 Custom receivers.

The power/programming button must be accessed with a hex wrench, or other similar shaped tool pressed into the hole in the grip frame.  While this may seem an inconvenient way to turn the marker on and off, it means that modes cannot be changed without a tool – a feature that is required for paintball tournaments and most paintball fields.

Just a press of the button for half a second was all that was needed to turn the 98 on.  This resulted in the LED lighting orange and then briefly flashing red to indicate that the electronic trigger system was on, and configured for use with a 98 Custom.  A brief green flash would indicate set-up for use in an A-5.

The Equalizer board supports five different firing modes.  Semi-auto is a traditional semiautomatic mode in which one shot is fired for every complete pull and release of the trigger.  Three shot ramping mode fires as a semi-automatic for one two, or three shots in a row.  If three shots are fired in a row, each following trigger pull will result in up to three shots being fired, until the trigger is released and left unactivated for a short period of time, after which the three rapid shots will once again be required in order to activate the three shot bursts.  Three shot full auto mode acts similarly, after three rapid trigger pulls, the trigger can be held down, and the 98 will fire repeatedly until the trigger is released.  Auto response mode fires two shots per trigger pull – one when the trigger is pulled, and another when it is released.  If the trigger is pulled and held for a quarter second or more, no shot will be fired on trigger release, as a safety feature.  The final mode, turbo fires as a normal semi-auto when the trigger is pulled at low cyclic rates.  When the trigger is pulled at a rate of more than 4 times a second, turbo mode fires on both the pull and the release of the trigger.

In addition to setting the mode, there are three more settings which can be adjusted in the Equalizer electronics.  Dwell time sets how long the solenoid is actuated for each shot.  Decreasing the dwell time can extend battery life, but it must be kept long enough to reliably trip the sear every time.  The debounce setting is used to tell the microprocessor how intensely to discriminate between the long (relatively) steady electrical connection made by the trigger switch closing its contents, and the short signal spikes generated by switch noise.  Tweaking this value can result in increased rates of fire, but setting it too low will result in the electronics counting switch noise as trigger pulls, and that can lead to penalties where play is restricted to true semi-auto mode.  The final setting is a rate of fire cap, which can be set for use at fields or tournaments which allow only a maximum rate of fire.  It should be noted, that technically many mechanical paintguns are illegal at such events, because they do not feature a way to limit their rate of fire (even though the average user can not pull their trigger as fast as the limit) but the introduction of electronics allows a straightforward way to restrict rate of fire.
While powered on, the Equalizer board blinks its LED green.  Pressing and holding the power button about a half second causes the LED to flash red, and the circuit board to power down.
 

Continue to Disassembly

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