BMT line #7 "Green Hornet," 16 is the MS car, 1 is the D-motor. MT "D Motor" Triplex Car - courtesy Richard Dornhelm.

Millions of people in this country have hobbies. There’s stamp collecting, role playing games, beer making -- you name it, it’s out there.

And then there's my dad, Richard Dornhelm. He grew up in New York City in the 1940s and '50s and fell in love with the city's trains -- especially the ones running underground.

"I'm a civil engineer by training," he says now. "And I'm a Brooklyn boy by birth. We never had a car; we had a subway. We took the subway to my grandma’s house or we took the subway to museums. Took the subway to Coney Island. We took the subway pretty much everywhere we went."

When he was little, Dad and his brother Mark always stood at the front of the first car, where they’d stare out the huge front window as the trains barreled down the track.

[Listen to the audio version of this story at KQED]

"There wasn’t much to see in a tunnel," Dad says. "So it was really the anticipation that this train would take you somewhere and you’d come out of this hole in the ground and be in a very different place. A different world."

Dad grew up in Brooklyn -- near the Church Avenue station, on the F line -- and stayed there until he finished college. He eventually landed in California where he met my mom, who also grew up near the Church Avenue stop. When I was growing up, he only rode the subway when we went back East to visit family.

And then 15 years ago, he went to a railway museum in Rio Vista, a river town near Sacramento. And there he found some of the original 1880s steam-powered cars that once ran on Manhattan’s elevated tracks.

The two cars survived because they'd been sold for use in the Kaiser Shipyards in Richmond -- across the bay from San Francisco. After seeing them, my dad went home and started thinking about how to build replicas by hand, remembering subway modeling he’d done as a teen. And then the project just sort of took off.

One car led to another, and one subway line led to the next -- the old BMT, the Independent, and so on. You can see where this is going.

"I never intended to end up with 100 cars," Dad says.

But he did. And now my parents' living room in what is otherwise a simple 1970s tract home in Walnut Creek looks like a New York City rail yard. Dad's hand-crafted cars are about a foot long, of all colors, from all eras. They've won awards and run in holiday shows at Manhattan's Grand Central Station. There are antique-looking ones with paneled wooden sides and tiny bare lightbulbs. And there are shiny new stainless steel.

My dad allows that other people "don't look at subways the same way I do." Asked to explain, he adds: "I think they’re a marvel of ingenuity and even if they are a hole in the ground, it still has really produced enormous benefits for the people in the cities.”

My own kids have love for Dad's trains, too, driving them on a mock elevated track he's built. They can't really understand the hundreds of hours of work these incredibly detailed, built-from-scratch trains represent.

There are turquoise-and-white cars, replicas of cars built for a World's Fair. There's the 1930s “Green Hornet,” originally made of aluminum and shaped like a BART train, but scrapped because of World War II. And then there's the bright orange refrigerator car, something he remembers from the 1950s.

"The doors would open and people from the neighborhood would go up and buy crates of wine-making grapes," Dad remembers. "It was largely an Italian neighborhood. I remember I first heard about California because those orange refrigerator cars were from this place called California. Wonderful place I thought. Too bad the subway doesn’t go there."

Over the holidays, I watched my Dad sanding wood in his workshop, which used to be my room.  His father was a toolmaker and my Dad uses some of those tools as he works.

I’m struck by how much these models bring together: My dad and his father. Our families in California and Brooklyn. My dad’s childhood with his grandkids’. I can’t help but admire the cars' artistry as we look at them. He reminds me some of them will be mine someday.

“You don’t have to keep them all," he says. "You can just pick a few. And remember the subway… and remember me. What else can I say?"

To see more photos head over to KQED's The California Report where this article originally appeared. There's also a charming video of a model train pulling into a model El station and passengers "get on" the train with no seeming human hand at the puppet strings. Or go see the real things at the NY Transit Museum.