Max-D valves (short for Maximum Distance valves), like pinch trigger valves, pull valves, and ball valves, are devices for controlling water flow through a water blaster with the use of a trigger mechanism. Akin to pinch trigger valves and ball valves, Max-D valves can allow water (or air) to pass through the valve in either direction unhindered. The purpose of this valve is not to control flow direction; it is simply for controlling whether flow should occur or not, allowing the water (or air) to move in the direction from highest to lower pressure. Operation of Max-D valves is akin to ball valves as they use a rotating ball with a passage to control flow and are not as affected by the amount of internal pressure. However, they have some additional parts which increase their effectiveness at getting the best stream pushed through the nozzle.
Parts of the Valve:
A Max-D valve is comprised of several (eight or more) parts:
- trigger - where the user's finger contacts the system
- wire/trigger rod - transferring the force of the pull from the trigger to the valve
- lever #1 - amplifies the force from the spring to rotate the ball in order to open or close the valve
- lever #2 (Max-D lever) - this lever is rotated by the finger-pulled trigger to extend or release tension on the spring
- toggle-wire - this short piece of wire bridges lever #1 with lever #2 and controls when the main lever can actually rotate
- ball (with hole) - this rotatable part serves as the gating device for the valve
- spring(s) - there are typically two springs: one is used to push/pull the lever back to the closed position and the other secondary spring helps to push the trigger back to its at-rest position
- housing - holds the other pieces in place and creates the water tight seal about the ball, preventing flow until the ball is rotated into the right position
Water Blasters that Use This Valve:
Some blasters that use Max-D valves include*:
* Note: water blasters that use standard ball valves (a simpler version of the Max-D valve) are not included in the above listing
When there is no significant pressure on the trigger (either from internal or external force), the spring pushes (or pulls) the trigger forward and pulls lever #1. This, in turn, rotates the ball such that the open passage through the ball is not in line with the entry and exit ports of the valve. Akin to regular ball valves, since rotating the ball valve to the open position requires a rotary force, no amount of increased internal pressure will cause the valve to open (unlike pinch trigger valves). As such, some sort of pressure relief valve at another point in the internal tubing assembly is highly recommended for, without one, it would become possible for too much pressure to be pushed into the water blaster, resulting in structural failure at some point of the assemble (typically at tubing connection joints)
Partial Pull (still closed):
This pseudo-step is where Max-D valves differ from standard ball valves. While pulling the trigger a little will partially open a standard ball valve, pulling a trigger only part-way causes Lever #2 to rotate, stretching the spring between Lever #1 and Lever #2. However, due to the angle of the wire also bridging Lever #1 and Lever #2, Lever #1 does not rotate during a partial pull, leaving the ball part of the Max-D valve still in its closed position. The wire between Lever #1 and Lever #2 acts as an small energy hurdle, forcing the spring to build up more energy as Lever #2 stretches it further from Lever #1.
Valve Snaps Open:
Once Lever #2 reaches a critical point, two things happen. First, the spring linking Lever #1 and Lever #2 has enough stored energy to pull Lever #1 and rotate the inner ball. Secondly, the long hole in Lever #2 where the wire bridging Lever #1 and Lever #2 ends up at the right angle such that the end of the wire in contact with Lever #3 can slide freely. Both these events occurring together causes the Max-D Valve to snap to the open position with the wire between the two levers suddenly slipping, allowing Lever #1 to experience the force stored in the spring and quickly rotate.
Being a little more engineers than the regular ball valve, Max-D valves are designed to be more-or-less perfectly aligned when Lever #1 snaps the ball to the open position. Like ball valves, when fully open, Max-D valves offer straight flow through the system. In most cases, however, the diameter of the hole through the ball is slightly smaller than the inner diameter of the entry and exit ports, thus slightly reducing maximum possible flow rates.
In an analogous way to what happens when the trigger is partially pulled, the initial or partial release of the trigger will allow Lever #2 to rotate towards its initial Closed Position location, but Lever #1 and the ball will remain in their fully open position. This is in part from the angle the wire bridging Lever #1 and Lever #2 is as well as the angle the spring between Lever #1 and Lever #2 is making in the partially-released position.
Valve Snaps Close:
Once Lever #2 reaches a critical point, two things happen. First, the spring linking Lever #1 and Lever #2 is in the right position with enough stored energy to pull Lever #1 and rotate the inner ball. Secondly, the long hole in Lever #2 is in position to allow that end of the wire to slide. Both these events occurring together causes the Max-D Valve to snap to the clsoed position with the wire between the two levers suddenly slipping, allowing Lever #1 to experience the force stored in the spring and quickly rotate close.
As can be seen illustrated in the diagram above, there is a direct path through the ball valve when it is fully open. While there still is a partially open state when the ball is being rotated, the time is takes to rotate the ball thanks to the spring and geometry of the system is much shorter than than of a manually operated ball valve. In all practical sense, this is a binary valve with two main states: open and closed. As such, the stream that enters the nozzle does so at maximum force (pressure) available as opposed to having a slight lag/ramp up time as experience in standard ball valve activation. It is this which allows Max-D valves to allow streams to truly achieve their maximum distance based on the pressure available.
For Max-D valves, the holes through the ball tend to match the entry and exist ports quite closed. As with normal ball valves, if the hole through the ball is smaller than that of the entry and exit ports, it would reduce the possible flow rate had the valve not been present. If the inner diameter of the hole through the ball portion is less than the connective tubing, that, too, will introduce some turbulence into the flow path.
Again, as with standard ball valves, even when the hole through the ball is more-or-less identical to the entry and exit ports, since this also means part of the outer sphere is missing, there are some resulting gaps/indents between the housing and the ball that will add in some turbulence to the flow (albeit only minor amounts). Compared to pinch trigger valves and pull valves, however, Max-D valves offer superior laminar flow when done properly.
Strengths and Limitations:
The Max-D valve is only found on various Super Soaker and Nerf Super Soaker-brand blasters. It does offer some advantages over its standard ball valve counterpart as well as other valves. Unlike the pull valve, the Max-D valve does not get harder to operate as the internal pressure within a water blaster increases. Like the pull valve, since it will not open with increased internal pressure, a pressure relief valve is needed to prevent over-pressurization and possible structural failure of a pressurized water blaster system.
As can be seen by the Max-D valve diagrams, the amount of contact area between the ball and the housing in the ball-valve is fairly substantial. While this can help prevent undesired leakage of pressurized water and air around the ball, it also means that if the ball is damaged or not properly lubricated, it can end up becoming very difficult to operate or even lock up altogether. A good waterproof, non-petroleum-based lubricant is highly recommended to be applied to ball in Max-D valves in order to keep them moving smoothly through repeated use.
One advantage to Max-D valves are their ability to permit very good laminar flow through them when fully open. Unlike pull valves, water can flow linearly from entry to exit ports of the valve. However, due to the geometry involved, as one attempts to increase the inner diameter of the hole through the ball, a significantly larger overall ball is required in order to maintain the seal when the valve is intended to be in its off position. After a point, it actually becomes more costly from a materials standpoint to create a large-opening ball valve versus a pull valve with similar maximum flow rate. While the flow lamination from the pull valve will not be as good as that of the ball valve, lamination can be corrected after the valve through use of a flow lamination device (to be discussed in another article). Thus, the cost effectiveness of Max-D valves lies within a limited range of optimal flow rates and amount of material needed to build all the parts of the valve.
Beyond cost of materials, as a ball gets larger if more direct flow is desired, this also increases the amount of surface area around the ball that must be kept water tight. As the amount of contact surface area of the ball with the housing increases, more force becomes necessary to rotate the ball into its open and closed positions. This, too, becomes a limiting factor since MAx-D valves rely on both manual, finger-pull triggers as well as their spring bridging Lever #1 and Lever #2 to operate. A high amount of needed force would make larger ball (and necessarily larger spring) too difficult to manually operate for the typical user. This can be offset, in part, by having longer levers attached to the ball. However, a longer lever would both have to be strong enough to withstand the forces applied as well as require a longer distance for the trigger to move in order to rotate the ball far enough to open and close properly.
The biggest problem with Max-D valves results from their added complexity. Since there are more parts that move more forcefully, Max-D valves high a higher chance of having a part fail, resulting in loss of function. One common point-of-failure is regarding the spring between Lever #1 and Lever #2. In some cases, the spring loses some level of its elasticity, meaning it ends up no longer being able to store enough force to rotate the ball valve open or closed. In other cases, the attachment points for the spring to Lever #1 or Lever #2 may fail. Beyond this, since both levers are under constant pressure from the spring, there are reports of one or the other lever deforming or breaking after awhile. Thankfully, since Max-D valves are basically ball valves with a more complex trigger mechanism, the valve can be made operational again simply by attaching the trigger wire to Lever #1; while this removes its Max-D functionality, this switch ends up converting the Max-D valve back into a standard ball valve. While most Max-D valves seem to have a good amount of useful life, the fact that they require more parts to operate does mean that there are simply more things that can go wrong in time.
Overall, Max-D valves offer the smoothest laminar flow when fully open, but have a practical size limitation when one needs to factor in cost and strength required to operate. Their increased complexity also means there are more potential points of failure, but operation of the valve can be restored with a little time and skill.