protoTYPING: Heated Lacrosse Stick Scores Big

Enventys Partners team helps teen inventor through prototyping process

Both the weather and unsatisfactory results on the field were leaving her cold, and high school lacrosse player Samantha Wolfe felt she had to do something about it.

During the winter, the native New Yorker found her hands would get cold to the point that they would lose dexterity and her game would suffer. “I tried different gloves, but nothing seemed to keep my hands warm,” she says. “Whether it was during a game or practice, I was not able to play to my full potential as the numbness in my hands was hindering my playing.”

There was nothing on the market to help. So with the help of her father, Bruce Wolfe, they decided to create a heated lacrosse stick. Because they did not have much experience with product development, they reached out to Enventys Partners in April 2015 to help bring it to life. The result has been a pre-production prototype that is being tested at the highest levels of the women’s game.

Samantha Wolfe, inventor of the Finger Fire, can keep her hands warm on the field now.

From blank canvas to progress

The product was loosely defined at the beginning of the project. Samantha had a great idea but had never made a prototype. The only requirements for the stick were that it heat up to about 90 degrees Fahrenheit in a few minutes, that the mechanism be as light as possible and fit completely inside the stick, and that it stay hot for 90–120 minutes of a typical practice or game. Because we were not locked into a particular technology or existing patents, the team had a blank canvas to build it from the ground up.

The process began by researching different heating methods. Heating the stick electrically was an obvious path, but we were concerned about how power-hungry heaters tend to be and were worried we would not have enough battery life. We also looked into chemical and phase change heating technology as alternatives.

Early sketch renderings of different technology.

To evaluate the different technology, we bought a variety of heating products, took them apart, and measured their heating capacity and power use. The main findings were that chemical heating means were not effective, and there were plenty of low-voltage heating devices that seemed feasible.

We measured the temperature rise of a heated mouse.

It was time to make a proof of concept prototype of the stick. My favorite heater from our research was a resistive copper film we found. This seemed to have plenty of heating capacity with just a few volts of electricity and could be rolled up to fit inside the stick. We sourced a small-diameter, high-powered lithium battery that would fit inside the stick and wired in a mini-USB lithium charger. Using two of the heating elements, we wired it up and slid the assembly inside the stick so that one heater would be near the center of the stick for the player’s upper hand while the other was wrapped around the batteries at the butt end to heat the lower hand.

The prototype worked well right away. Despite not having any microcontroller to monitor and throttle the temperature of the heating element, it warmed quickly to a comfortable temperature. The only problem was that because there was no regulation of the battery power, the heaters were running at 100 percent power all of the time generating only about 45 minutes of battery life.

The first concept model.

Fine-tuning a solution

At this point, I solicited the service of our electronics guru. I showed him the prototype and the issues I was having. We decided to change the heaters to a ceramic unit and mounted them on aluminum sleds with wings that would spring tightly against the inside of the stick to get maximum heat transfer and keep them from sliding.

We designed a new circuit board with a microcontroller and temperature sensor so we could monitor the heaters and throttle the output for better battery life. Then we designed a plastic part that would fit into the butt end of the stick and put the PCB in place while giving us access to the charging port. We made two of these prototypes, one for an aluminum stick and one for a carbon fiber stick. With a little bit of tweaking, both sticks worked great and we shipped them to Samantha for field testing.

The next-gen prototype featured a custom circuit board and updated heating elements.

The sticks worked well, and she got some great feedback from other high school players. She also continued to work on her business by trademarking the name FingerFireTM for the product and receiving a patent for the technology.

Though high school players loved the product, she knew the concept needed validation from elite players. She began reaching out to college teams to see if they were interested in her idea and got two of the best Division I teams — Syracuse and Johns Hopkins — to agree to test them. Each school sent five sticks to EP office to get retrofitted with the technology.

In order to make assembly easier and more robust, we designed a thin plastic chassis to hold the batteries and mechanically bridge the upper and lower heaters. We 3D-printed the new chassis and made more heater sleds and PCBs. After a small issue with the charging circuit on the PCB we got the problem solved, and the sticks were sent to each school before the weather warmed up this past spring.

Prototype stick with custom butt cap

Higher-level approval

Samantha attended the training sessions and got real-time feedback on the sticks from the teams. Though the sticks were programmed to heat to about 90 degrees, both teams mentioned that they wanted more heat in the next generation.

Samantha (center) poses with members of the Johns Hopkins women’s lacrosse team.

Fall is right around the corner and Samantha is starting her first semester at Hamilton College in Clinton, New York, but refinement of the concept continues. The EP engineering team is making changes to the prototypes to get more heat without hurting battery life, and the updated prototypes will be delivered back to the teams in the fall to get a full cold-weather season of testing. Samantha has also received inquiries from 2017 national champion University of Maryland, and we will be making sticks for the Lady Terrapins.



Originally published at Edison Nation Blog.