How Water Blasters Work

The Motorized Water Gun

In the last section, we saw that the basic squirt gun uses a simple piston, a cylinder pump and two one-way valves. Since the pump is activated by moving the trigger back and forth, this design is fairly limited in the size, range and duration of its bursts.

One easy solution to this problem is to increase the size of the pump cylinder and the trigger. This is the basic idea behind classic water bazookas like the one shown below. In this design, the trigger mechanism isn't really a trigger at all -- it's more like a syringe. Essentially, you hold the piston in one hand and the cylinder in the other. To suck water in from the reservoir, you pull the piston and cylinder apart. To expel the water, you push them back together.

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This gives you much more water to work with in each shot. If you push the piston into the cylinder with great force, you can shoot the water a good distance. If you push it more slowly, you can expand the duration of the blast. Some water bazookas don't have an attached water reservoir: To load them, you must suck in water through the barrel, as you would fill a syringe.

Obviously, this design requires a lot more work from the shooter than the conventional squirt gun, so it's not particularly user-friendly. The 1980s saw the arrival of a new sort of water gun that did almost all the work itself. You can see in the diagram below that these guns work in basically the same way as the conventional squirt gun, except the pump is powered by a small motor rather than by the trigger. The trigger is only a switch that completes an electrical circuit so that the battery can power the motor. The motor moves a series of gears, which move a small cam. The rotating cam has an extended lever that catches the piston, pulls it back and then releases it, allowing a spring to push it forward. In this way, the motor moves the piston in and out of the cylinder, drawing water in from the reservoir on the upstroke and driving it down the barrel in the downstroke.

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Since the pump is activated by a turning motor rather than a trigger, the design can have a slightly expanded cylinder size without making it more difficult to shoot. This extends the blast range somewhat. But the real advantage of this design is that the shooter doesn't have to keep pumping the trigger to continually shoot water. If you hold down the trigger, the motor keeps pumping, emitting a rapid series of bursts, like the continual fire of a machine gun.

Both of these gun designs are a substantial step up from the ordinary squirt pistol, but they still have significant limitations. Blasting the bazooka requires a good bit of muscle power from the shooter, and the motorized gun's water stream is still fairly weak. In the next section, we'll look at the water-gun design that revolutionized the industry, building blasts that reach 50 feet (15 m) or more.