Bob Nepper's North St. Paul basement is littered with strange-looking tools, some of them hand-made on his metal lathe. His garage is filled with an assortment of devices he created to make household chores easier.
But inventing is more than just a hobby for Nepper. He and his friend Bill Stevenson of Lake Elmo have created a device that may help relieve the cholera epidemic in Haiti.
The invention is a solar-powered water pasteurizer that can cheaply and easily clean water.
Missionary groups from Indiana and South Dakota took a few of the pasteurizers to Haiti after the catastrophic earthquake in January, but the devices were held up in customs and sat idle at a dock. Now a Florida missionary group has bought another of the pasteurizers and plans to take it to Haiti.
Contaminated drinking water has been the main cause of the cholera outbreak that has killed more than 2,200 Haitians in the past few months.
The pasteurizers are a perfect fit for Haiti, Nepper said, because they require only sunlight to remove the bacteria from the water. One pasteurizer can purify 30 gallons of water a day.
"I have great sympathy for the Third World and children," Stevenson said. "If they had good water, they wouldn't be in the hospital. It's so easy to fix."
Nepper and Stevenson, retired 3M engineers, didn't know each other before a mutual friend introduced them about 12 years ago. They hit it off right away and began to create a handful of homemade devices, some more successful than others.
They built a self-driving lawnmower and a sound-emitting device to keep woodpeckers from destroying telephone poles. But neither project garnered as much attention as the solar water pasteurizer.
The pasteurizer is a large, metal-clad rectangular box. Dirty water is dumped into a bucket at the top, where it is filtered through a cloth and runs into a feed tube at a tilted plastic solar panel. Once the water reaches the bottom of the panel, it runs up a hundred plastic tubes in the panel, which is painted black to capture as much heat as possible.
The panel is encased in a metal frame, insulated with reflective material and covered with a clear plastic sheet to prevent the wind from taking away the heat.
When the water reaches about 160 degrees —- pasteurization temperature — a thermometer releases it into a bucket.
Nepper and Stevenson used plastic tubing instead of copper to cut costs, and sell the pasteurizers for $300 to $350, which Nepper thinks is the cheapest on the market.
The road to invention of the water pasteurizer began about two years after Nepper and Stevenson met. That's when another 3M retiree, John Roche, director of the Solar Oven Society in Minneapolis, approached them. Roche's nonprofit organization builds solar cookers for use in countries with abundant sunlight but little clean cooking fuel.
Roche knew that Nepper had a knack for building things and suggested that he make water-pasteurization indicators — known as WAPIs — inch-long plastic tubes containing a special wax that melts when water has been pasteurized.
The WAPIs Roche was interested in were being made by sealing the ends with the flame of a Bunsen burner, which caused leaks.
Stevenson came up with a design that calls for hammering the ends instead. In Nepper's basement, the two use custom-made tools to make parts for the WAPIs, including a device to cut the plugs to the exact lengths and a custom spindle that cuts wires.
"Those two accomplish more in one day than anyone I've ever seen," Roche said.
Most of the assembly, which takes about three minutes and can be done with a hammer, takes place outside Nepper's basement. Kits are sent to high school and college students who build the WAPIs for a little cash.
Nepper said that since 2006 he and Stevenson have sold 20,000 of the latest version of the WAPIs. Most are sold to solar-oven cooking organizations across the country, who package the WAPIs with their ovens before shipment.
"A lot of people are stopping by and thinking we're making a high school science project," Nepper said of the solar water pasteurizers. "They don't realize we're making an actual product."
Nepper has several ideas for who could use the pasteurizers, such as the Federal Emergency Management Agency. Nepper said he and his friend are getting too old to start a company to mass-produce their invention, and seek someone to license the product to be made in other countries.
"We're two legs, but we need a third leg to make marketing work," Nepper said. "We know how to build things but don't know how to sell them."
For now, the two humanitarian engineers will continue to do whatever they can to help those who need clean water.
Nepper has found a project he finds more fulfilling than the average retirement activity.
"This is my boat, my fishing line, my tackle, my fishing license," Nepper said pointing to the lathe. "This is what I do. I think it's stupid to sit there and bob that thing up and down."