Line Cutterz Auto Glass Breaker – 2023

In 2019, we designed a fishing line cutting tool for Line Cutterz that enjoyed great success in the angling market. For their next product, they asked us to adapt their patented blade design for the automotive world. We designed a seat belt cutting, auto glass breaking multi-tool that clips to car visors as a visible easy-to-grab emergency escape device. Multiple prototypes and testing rigs informed our design and engineering process, resulting in a refined and effective tool.

We began with sketch ideation; experimenting with blade placement, accommodating the glass breaker assembly, and exploring human factors of product use and placement in the vehicle. In an emergency, it’s critical that the tool is readily accessible and clearly and naturally communicates function. With this in mind, along with considerations of ergonomics, manufacturability, and engineering, we arrived at a concept that places the two main functions along the same axis as each other, facing opposite directions. Flip one way for glass breaking, the other for seatbelt cutting. In this configuration, the space required for the pin and spring of the glass breaker serves as a perfect grip area, which we clad in a textured rubber overmold. On the pull-out blade guard we placed a ring for attaching the tool to a keyring.

Design and Engineering

With our design direction distilled, we made further concept developments in 3D CAD. As with any tool, it’s critical to use CAD at the right point in a product development cycle. Too early can inhibit exploration and creative problem solving. Too late can needlessly stall a project when precision and accuracy are required to realistically assess the viability of ideas. Now on the computer, we could develop the exact design and placement of components and work on specifics of the housing construction.

The housing is primarily held together with friction pins that snugly join one half of the shell to the other. A single screw is hidden below a magnet to ensure the housing never comes apart. This assembly is very effective, economical, and eliminates the need for unsightly screw holes on the backside of the product.

We also engineered the glass breaking mechanism. Opposing springs automatically fire a steel striker at the window once pressed down far enough on the glass. We refined this mechanism with several physical prototypes to guarantee the device would be strong enough to break a window on the first try and robust enough to work every time.

We made multiple high-fidelity engineering prototypes until we got the design of the glass breaker just right. To make sure the device would never fail in the field, we performed a litany of glass breaking and seatbelt cutting tests. Line Cutterz even assisted by testing the glass breaker on a range of car windows at a scrapyard.

It was also critical that we ensured the device wouldn’t fly out of its visor clip in the event of a crash. We created a crash-testing rig with an accelerometer to simulate the g-forces experienced in a crash from several directions. To this we attached the visor clip and gathered testing data to quantitatively assess our design.

The final product is an attractive, reliable, and robust tool that’s easily within reach in an emergency. It fits stylistically with the Line Cutterz brand and builds their product portfolio of specialty cutting devices.