The idea began with a foosball table. Some years ago Dr. Chris Ross decided to share one of his favorite hobbies in medical school with his kids. But when he thought more about it, he realized that his youngest son, at age 4, would not be able to play.

Ross bought a pinball table instead. And the collection began.

Over the years the emergency room physician and his wife, Jean, have transformed their McCordsville basement into a subterranean arcade of sorts with half a dozen machines lining one wall.

For Paul Earwood, the pinball preoccupationstarted with a single machine. Since he bought the 200 to 300-pound diversion about a year ago, he has cycled through a number of others.

The Brownsburg resident now owns 11 pinball machines. Some he keeps at his house. Others he stores at Mind over Mash, a brewery in Brownsburg. Of course.

The two men have never met. But this weekend they are pooling some of their machines, along with some others, at a fundraiser to help fight dementia.

The two-day gathering is the brainchild of Chris' wife Jean, a volunteer with Dementia Friends Indiana, an initiative of CICOA Aging & IN-Home Solutions that runs programs for seniors with dementia and aims to raise awareness about the problem.

Participants can try their hands, and supple wrists, on at least 17 pinball machines of various vintages, ranging from the '70s to today. The event will take place 11 a.m. to 11 p.m. Friday and Saturday at Books and Brews on Shelby Street on the south side.

Ross will bring the Spiderman machine that introduced his family to the joys of hitting metal balls with rubber flippers.

He also will bring the second machine he bought, one with a more adult Metallica theme. He bought this machine, which plays classic hits from the heavy metal band, for himself.

Thus he was hooked on what he calls the “retro and upcoming hobby of pinball.”

Next came an NBA Fast Break machine. Before he knew it, a handful of machines lined the wall of his basement.

Since then he has bought and sold a number of machines — some when he mastered them, others for more mundane reasons. Tales of the Crypt left because his son found it too scary to play.

“Pinball is lots of fun to play, but each machine has a different style of play, different shots, different goals,” Ross said.

For Earwood, the appeal is not just about playing pinball or owning the machines but tinkering with them, too.

Over a year ago he owned none. But then a friend of his mentioned that he had a machine he was looking to store, and Earwood recalled how much he had enjoyed playing pinball at the arcade across from his high school in Washington state.

He bought an F-14 Tomcat machine and spent the next few months tracking down more machines. Some he would buy and then trade. Others he kept.

Often the challenge lies as much in bringing somnolent machines to life.

Many of the machines he owns date to the 1970s.

“It’s not that the new toy is the cool one. It’s what do I enjoy playing, and it varies,” he said. “I enjoy new machines with all the ramps and, at the same time, enjoy playing older ones. It’s single ball, and it plays a little slower and you can potentially play for a longer time. But you need to pick your shots. You can’t just hit the ball randomly.”

Earwood saw a message that Ross posted in a Facebook group of arcade game enthusiasts, asking whether other pinball machine owners would lend their machines for the fundraiser.

Having lost his mother to Alzheimer’s, Earwood did not hesitate.

He plans to rent a box trailer and bring as many machines as he can get working to this weekend’s event. One of those, Time Warp, is one of only two machines designed with curved flippers, he said.

Another highlight of the event will be two NBA Fast Break machines linked to one another so two opponents can play at the same time, Ross said.

He also plans to bring his newest and current favorite machine, Total Nuclear Annihilation.

Pinball may have hit its heyday in the '80s or '90s, but Ross is hoping to make the fundraiser an annual event. For this first year there are 150 tickets available, and Ross is hoping it will sell out.

Contact IndyStar reporter Shari Rudavsky at 317-444-6354 or shari.rudavsky@indystar.com. Follow her on Facebook and on Twitter: @srudavsky.