Headstrong: One stubborn puppy, one determined student

UTC mechanical engineering student Connor Mackey hangs out with Wrexham in the Chihuahua’s Chattanooga-area home. Photo by Angela Foster.

The first time Connor Mackey met the 2.5-pound, 10-week-old Chihuahua puppy then known as Niblet, it was love at first sight—for the human.

For the Chihuahua, the feeling hasn’t always been mutual.

“He loves it whenever it doesn’t work and we get to take it off of him,” Mackey said with a laugh.

The “it” in question is a tiny 3D-printed helmet designed by Mackey, a mechanical engineering graduate student at the University of Tennessee at Chattanooga, to protect the puppy’s skull.

Nearly a year ago, a UTC feature spotlighted that puppy, a rescue from the Humane Educational Society (HES) in Chattanooga. The Chihuahua was born with an open fontanelle—the soft spot on the top of the skull where the bone hadn’t fully formed. The condition could make even the simplest household accidents potentially life-threatening for the puppy.

Faced with the severity of Niblet’s condition, HES animal services officers were committed to finding a way to help. That’s when Mackey first laid eyes on Niblet.

Over the past year, Connor Mackey has 3D-printed numerous iterations of the protective helmet.

Today, Niblet is known as Wrexham—a nod to the Welsh football club co-owned by actors Ryan Reynolds and Rob McElhenney—and he’s a rambunctious 14-month-old pup.

Wrexham has grown to 8 pounds. The soft spot has shrunk to a third of its original size. And thanks to a year-long collaboration between Mackey and Wrexham’s adoptive parents, Kay Baker and her husband, Brian MacLean, there’s a working helmet that actually stays on. Mostly.

Mackey learned about the puppy’s condition from his faculty mentor, UC Foundation Associate Professor Trevor Elliott, and ran with the idea of designing a 3D-printed helmet. His design work was done from his home at his own expense.

His first helmet design wasn’t perfect but it bought the puppy time.

“It kind of did what it needed to do, which is prevent it from euthanasia,” said Mackey, who received a bachelor’s degree in mechanical engineering from UTC in May 2024. “But a more refined helmet design was needed for future use and for him to be able to move around and live with it.”

The helmet journey quickly became a passion project. Mackey tried everything, from adjusting existing 3D models of Chihuahua heads to experimenting with computer-aided design programs to build models from scratch. He even bought a 3D scanner and used a mobile phone app to capture the shape of Wrexham’s head.

“Getting dimensions in general was a challenge,” he admitted. “I think I printed off 20 at one point, just trying to get even the infill for the 3D print to see how squishy we wanted it and how flexible we wanted it.”

He began visiting with Wrexham and the adoptive parents every few weeks to test new prototypes. Each visit brought them closer to a helmet that was both functional and tolerable.

“The first design was like a football helmet,” Baker recalled. “It was really thick and a little heavy. But we told Connor what we thought and he came back with another version. And then another.”

MacLean showed off 16 different designs that Wrexham had sampled.

“I mean, you can see how different they all look,” Baker said.

“And then we had success,” MacLean said.

The final design is sleek and open around the ears, Mackey explained. It’s lighter, thinner and more flexible than any of the earlier versions.

Instead of using custom-made straps, he incorporated Apple Watch bands into the design, leveraging their comfort and ease of adjustability.

“That was a very last-minute design change,” Mackey said, “but it made it a lot better.”

Wrexham, Connor Mackey, Kay Baker and Brian MacLean

Truth be told, Wrexham doesn’t wear the helmet every day. In fact, he wears it only when necessary. And when he has it on, he typically wants to be held by Baker.

Around the house, he’s playful and relaxed, especially when running around the backyard. Baker said she’s more cautious and puts the helmet on when they’re heading into public spaces because the soft spot, while small, still exists.

“We don’t take him to dog parks, so from a safety perspective, I don’t think he really needs to wear it all the time,” said Baker, who is a former HES board member and longtime volunteer. “He’s done a lot without it and he’s been fine.”

Baker credits Mackey’s persistence and generosity for giving the couple peace of mind.

“If it weren’t for Connor, we would just have that original helmet and that would be it,” she said. “Now we know we have one that—if we feel like he really needs to wear it—we have one that fits correctly. And that’s because of Connor.”

It’s not just the design that impressed Baker and MacLean. It’s the student behind it.

“Connor is just delightful and really kindhearted and spent a lot of hours just messing with it on his own time,” Baker said. “Brian and I are both just so grateful for Connor caring so much about a dog that’s not even his. He didn’t have to do this.”

Mackey called the year-long trial-and-error process a “test of problem-solving under constraints” and a lesson in design thinking that he’ll carry forward into his engineering career.

“It just kind of shows that if you want something great, it’s going to take a long time,” he said. “I’ve learned that the goal sometimes is for a year from now, but we still need to step on the gas the entire way. That’s what got it built.”

These days, Wrexham lives with four other dogs—Annabelle, Agent Gibbs, Ziggy and his “best buddy” Zoey, who weighs 7 pounds. Baker said he is “as spirited” as any puppy, but his parents keep a close eye on playtime.

“We’re always monitoring,” she said. “We don’t want one of them to accidentally put their paw on his head.”

And what happens when Connor stops by?

“Wrex is not crazy about it at first,” Baker said. “Wrex likes him, but he knows what it means when he sees Connor. He knows it means there’s going to be a helmet on his head, at least briefly.

“But by the end of the visit, he’s taken treats from Connor and even lets Connor hold him.”