Teen builds baseball-throwing prosthetic arm for father injured during Iraq tour

Rob Frei created the prosthesis as part of his senior thesis in high school.

For the first time in 16 years, Jason Frei can throw a baseball with his right hand.

"It was really amazing," Jason Frei said of the new ability. "To have that chance again ... was a really special thing."

And, he has his son Robbie Frei to thank for it.

"Every time, it was the same response: 'I would need two hands for this,'" Robbie Frei said. "I don't know if he felt left out or not."

So in the fall of 2017, Robbie Frei, a senior at Priory High School in Missouri and captain of the school robotics team, created a 3-D video-game one-arm adapter for his father. He got help from his team, as well as the school's engineering team, and used the school's resources, including 3-D printers.

And when it came time to decide on a senior thesis, Robbie Frei stuck with the prosthesis but challenged himself to give it a different function: throwing a baseball.

"He did all of the math and all of the design to use it to play baseball. ... I can throw a baseball with my left hand, I learned to do that, but I wasn't able to do it with my prosthetic. ... He really kind of crossed the bridge. It was a great project," Jason Frei said.

The new prosthesis is modeled after Jason's working hand. To create the prosthesis' baseball-throwing motion, Robbie said he used a video of himself throwing a ball, and then analyzed that video on a computer to come up with the geometric model and speeds.

"Seeing it [in] real life -- and fit right -- it was just incredible," said Robbie Frei. "From a more emotional standpoint, I was absolutely blown away that I was creating something that I could use in the real world to help people."

Jason Frei, who now works at Boeing, said his son's project lives up to the company's standards when building airplanes.

"It was really cool to see him come to that process and to see him when he printed the final product, how good it really was because of all the testing he did," Jason Frei said. "That was neat."

Robbie said he'd been involved in robotics since the seventh grade. He's now wrapping up his sixth year on the robotics team and plans to continue studying robotics in college.

In the meantime, he and his father plan to continue improving the prosthetic hand. They have plans to add a rotating wrist and perhaps make adjustments to the thumb joint.

"It's a really evolving process," Robbie said. "Hopefully, by the end, by the time I go off for college, I'll have a really nice arm that he can keep for a long time."