We have all seen the headlines.
Fundamentally, students are not safe. There is little in place, whether legislation or school security, to protect them from these types of events. Teens know it. Surveys show over half of them are worried about events like these happening at their school (source).
Losing a friend in a mass school shooting launched me into this project. I want students to know they are safe from these events while in school.
Mantis's design objective is to provide an instant response to stop a school shooting within seconds of its start. This response needs to be powerful enough to deter would-be shooters from attempting an attack in the first place due to the presence of the system. The goal of this project is to demonstrate that the technology for such a system certainly exists today and to develop it to a mature implementable form.
Read the second half of Log #6 to get an idea of how Mantis would be built into a school.
Mantis Prototype 1 Design
Goal of initial prototype was to demonstrate proof-of-concept capabilities of the system.
- Vision recognition and tracking
- Aiming at target
- Effectiveness of molten wax spray
Going into the project I knew the single most difficult problem I would face in the design was finding a method of actually stopping or impeding the assailant. It should be obvious that lethal weaponry would be wildly inappropriate for an automated system like this in a school. Other options such as tasers and kinetic energy (rubber bullets) “less-lethal” weapons are still off the table.
I realized method of stopping the assailant needed to conform to the following criteria:
- Cannot cause serious injury
- Precise, only affects the assailant, doesn’t impede people trying to escape
- Has a range approaching 30ft
- Is inexpensive
- Stops or seriously impairs the assailants despite their knowledge that the system is in place
Pepper spray fails the 2nd and 5th requirement as it would affect nearly everyone in a room and pepper spray resistant masks exist.
The concept behind a wax spray being used to blind an assailant is simple. A wax would be stored as a liquid at a temperature above its melting point (waxes exist that have melting points of ~110F). The wax would be fired at the assailant's face using pressurized air. The liquid wax spray would solidify on the the assailant's face, making it difficult to remove. The spray would remain effective regardless of whether the assailant wears googles or a helmet.
The core of the mechanical design is a rotating gimbal carrying the spray gun. The gimbal is powered by two brushless motors via Servocity gears. The structure of the gimbal was cut from birch plywood with a cnc laser at a local makerspace and painted black. Part of the original design (see Project Log #3) was a mechanism that loaded paintballs into the barrel of the launcher from the side via a cog rotating around the barrel. This loads the paintballs regardless of the position of the gimbal. Two aluminum tubes support the gimbal and electronics. The CAD is available on Onshape via this link: https://cad.onshape.com/documents/ac8b725e62c16dcfa55febf4/w/1b3f44837eb8cf66650975b8/e/ea8d60ad8c8b8706f7aef81b
The electronics are powered by a 12V DC power supply. I used an Odrive (a previous Hackaday Prize entry) to control the motors. Brushless motors controlled by Odrive are mind-blowingly quick, precise, and powerful, perfect for this application. An Arduino will control power to the the loading system and paintball launching...Read more »