Nerf Guns, or “blasters,” can be great fun for kids or around a busy office. Although you usually know when you’ve been hit by one, they generally don’t hurt, so shooting one is a more acceptable prank than, say, soaking your coworker’s pants with a medicine syringe… not that I’ve ever done anything like that.
Once the immediate fun wears off, you might wonder how it works. In the case of the 3-barreled multi-blaster featured in the video below, the mechanism is quite interesting. The basic premise is that a piston on the bottom of the gun is pulled out to cock the “weapon,” and when the trigger is pulled, it releases this piston to push a dart out of the gun with a blast of quickly moving air.
This is easy enough to understand, but what is really interesting is that these darts can be fired sequentially, and the gun is “smart” enough to know if it has a dart in the chamber or not. This is accomplished by using each of the darts to switch a spring-loaded valve when they are pushed into the chamber. After one chamber is fired, air bypasses it on the next shot, which instead flows to the next loaded dart position.
It’s a clever and simple way to accomplish the task. As Bill “the Engineer Guy” Hammack puts it, “This blaster is the epitome of good engineering.” He even references the mechanism’s patent, in which it’s described as “simply constructed, structurally robust, compact, automatically operated, and relatively inexpensive.”
His video explains things nicely, but, as credited there, it’s based on this “Steve Crayons” clip. Check that out for a slightly different take on this concept.