MAXV
Hand tool sharpener for wildland firefighters
2020-2021
Master's Thesis for Integrated Product Design
Teammates - Sommer Farber, Leora Korn, Jillian Stahl
Background and Need
In 2020, the US saw nearly 60,000 wildfires destroy over 10M acres of land, costing the country $2.3B in suppression efforts alone. The total financial cost of a wildfire season is estimated to be between $130B-$150B, and it is only getting worse.
Fire is natural and necessary, however, climate change and human activity are creating optimal conditions for fast-moving fires that impact areas more frequently and intensely than nature intends. In California, the fire season now runs from June until April, with just one month of reprieve in May. This exhausting season, coupled with low federal support, puts pressure on already strained wildland firefighters. With this in mind, my team’s goal was to make fighting fires safer, easier, and more efficient for the men and women who risk their lives protecting us.
*photos by Leonard Ortiz, AP and USFS
Research
The primary strategy of wildland firefighters is to contain the fires and let them burn out on their own by manually digging breaks in the vegetation called firelines. Firefighters that my team interviewed unanimously highlighted the importance of being as efficient as possible while performing the physically demanding task of creating firelines. There are many ways to improve firefighting efficiency, but our stakeholders drew a key connection between the sharpness of their tools (such as the Pulaski, shovel, and Mcleod), and the ability to complete their tasks quickly and efficiently.
Key Insights
"Efficiency. It's everything." Wildland firefighting is a race against the clock as a fire spreads across terrain. Anything that can improve the speed and ease of a firefighter's job gives a greater chance that they can control the burn before it harms more property, wildlife, or people.
A sharp tool is an efficient tool. Firefighters talked about "making every swing feel like the first swing of the season." Sharp tools allow them to complete their jobs faster, safer, and more effectively.
The effort of sharpening currently outweighs desire. Firefighters know the benefit of sharpening their tools, but the high effort and rudimentary methods of current sharpeners, in the context of a fast-paced environment, means more often than not, they simply have to get by with dull tools.
Design Criteria
Theses insight led to the goal of developing an in-the-field sharpener that would promote more frequent blade maintenance. After multiple interviews and co-creation sessions, we developed the design criteria for our tool:
Able to accommodate a range of blade angles. Different tools have different blade angles.
Multi-directionality. There are a variety of sharpening styles. Some push, some pull, some do both.
Capable of honing as well as sharpening. Honing maintains a blade’s straight edge and ideally is done more frequently, whereas sharpening restores a dull or damaged edge by removing material.
Lightweight, durable, ergonomic. In-the-field blade care requires an extra high standard of performance to weight ratio, reliability, and ease of use.
Prototyping and Testing
We took the goal of being able to accommodate a range of angles as the starting point for our design, and tested possible abrasives and methods of holding them. Diamond coated bits proved most effective for honing as well as most versatile, as they allow for multi-directional use, and a "V" configuration was the natural and best option for honing both sides of a blade at once. We started with a single set of bits in the "V" configuration, but found that adding a second set helped the user maintain the correct orientation of the sharpener in relation to the blade, as well as required fewer swipes.
We continued by refining the angle of the handle in relation to the abrasive head assembly and adjusting it's shape for optimal ergonomics. To reduce risk of injury, we integrated a finger guard in the handle, testing different shapes to accommodate all hand sizes along with gloves.
Ultimately, the tried and true bastard file proved to be the best option for removing bulk material in-the-field, so we integrated a replaceable file into the handle of the tool.
Solution
Our final product, the MAXV, features gear controlled adjustable diamond teeth and an extendable bastard file. Featuring the same simple but robust mechanism used in adjustable crescent wrenches, the worm gear that adjusts the angle of the teeth prevents back-driving, so the angle stays fixed without the need of an additional lock.
The four cylindrical diamond coated teeth are held in with magnets, and have hexagonal shaft, similar to a driver bit. This prevents rotation during use, but also allows the teeth to be removed and rotated to a fresh side, and eventually replaced entirely as the abrasive wears out.
Embedded in the handle is a bastard file with single and double cut sides. The file movement is controlled by a spring loaded slider that connects to a carriage that runs inside an indexable track. This allows the user to select an ideal file length that can for any particular task. Bastard files also wear over time, so when a replacement is needed, the handle disassembles easily, allowing for the used file to be removed from the carriage and replaced with a new one.
Design for Manufacturability
Key design decisions were made to ensure manufacturability and assembly at scale. The head sub-assembly is constructed of aluminum to reduce weight while maintaining durability and mechanical precision. Its complex geometries are achieved with secondary machining operations into diecast components.
The grip of the handle is made of injected molded glass filled polypropylene, chosen for it's combination of durability, low weight, and low cost. The carriage and slider for the file is made from stamped and formed sheet metal.
From the front lines to the front yard
The same versality and robustness that makes the MAXV the perfect in-the-field sharpener for firefighters makes it the stand out within the consumer marketplace. We calculate the per unit cost of manufacturing at quantity to be approximately $11.25, yielding an MSRP of $45. This places it at the premium end of the marketplace, but well within range for prosumers and enthusiasts.