His cranberry fields flooded with 6 inches of water, Dan Brockman drives his new harvesting machine — romantically named the ruby slipper — through the vines. Steel, finger-like rods submerged in the chilly waters quietly nudge and shake the plants.

Berries float to the surface, a sea of red forming behind Brockman's tractor as he drives.

His invention — five years in the making — promises a much faster way to harvest the popular fruit that is a staple of Thanksgiving Day tables and a $200 million-a-year industry.

"If it works as well as it appears it does, yes, it will revolutionize cranberry harvesting," said Teryl Roper (search), a fruits crop specialist and professor of horticulture at the University of Wisconsin-Madison (search). "I don't know why no one thought of it before. It is elegantly simple."

The ruby slipper (search) is an alternative to expensive mechanized water wheel beaters (search) that have been used for decades each fall to harvest cranberries.

Brockman's invention has no movable parts other than spring-loaded arms upon which metal finger-like rods are mounted. As the device is pulled or pushed through flooded cranberry vines with a tractor, the arms follow the contour of the ground and the rods shake off the berries — much like someone shaking a small apple tree so the fruit rains down.

The berries float to the top of the water, where workers gather them together and pump them into trailers and trucks for processing into juices, sauces and other products.

By comparison, the self-propelled machine now used throughout the industry features a rotating beater similar to rotating cutters on old push lawn mowers that knocks the berries from the vines as the harvester slowly drives down flooded fields.

Brockman, 47, invested $30,000 developing his ruby slipper. A patent is pending.

"I didn't build it with the concept that I am going to build something that everyone wants to buy. I was building it so I could harvest my crop better and more efficiently and it just happened that a groundhog finds an acorn," Brockman said, laughing.

BDT Inc., a Wisconsin Rapids manufacturing company that bought the rights to build the machine from Brockman, has sold eight ruby slippers so far — costing from $7,000 to $9,000 depending on the width — and all the customers are happy with the results, engineer and co-owner Dave Dix said.

It's the biggest technological development for the cranberry industry in 20 years, Dix said.

Many larger growers now use three workers each operating a self-propelled water wheel beater, some costing up to $40,000 each, Dix said.

BDT's testing shows Brockman's invention can do the same amount of harvesting in the same amount of time with one operator, Dix said. The machine can harvest four acres of vines in an hour, which is extremely fast.

"That's crazy," said Dix. "You are going to see beaters going up for sale."

Dix predicts 500 to 1,000 ruby slippers could be sold in the next five years.

According to Roper, there are about 1,200 cranberry growers in the United States and Canada. Wisconsin produces more than half of the estimated 575 million pounds of cranberries Americans consume each year, according to the Wisconsin State Cranberry Growers Association (search).

Wetherby Cranberry Co. in Warrens, Wis., which has grown cranberries for 100 years, bought a ruby slipper and expects to harvest up to half of this fall's 125-acre crop with it, co-owner Nodji VanWychen said.

The early results are promising. The new tool is faster and more efficient and growers are excited about the machine, she said.

"What is so amazing to me is to see how rapidly the slipper goes through the [cranberry] beds. We are running the tractor at about 6 mph. That is just whizzing right along," VanWychen said. "The fruit is not harmed, that we know."

What's left unanswered yet is whether the machine damages the vines to the point of harming production next year, she said.

If not, it will be the new harvester for most of the industry, VanWychen predicted.

Jeffrey LaFleur, executive director of the Cape Cod Cranberry Growers Association (search) in Massachusetts, had not heard of the ruby slipper, but he expected his growers would be interested in it.

Brockman spent six years working in a paper mill before returning to the cranberry farm his father started in 1946. The idea for the ruby slipper came during hours of idle thinking while riding tractors or sitting in the silence of a stand while deer hunting, he said.

"I always approach just about everything with the idea that there's a better way to do it. You just need to find it," Brockman said. "I started cutting and welding and building. The first three machines didn't work at all."

He kept tinkering, developed a prototype two years ago and tested it in bogs. His father was dumbfounded.

"He is just a shaking his head: 'I can't believe that thing works. It is way too easy. How did you ever think of that?'" the son recalled.

Brockman picked two fields with the ruby slipper and the next year the crop came back even better. He hired a consultant who found evidence the return crop was 17 percent to 24 percent better than areas harvested with a conventional beater, suggesting his invention did less damage to the plants than conventional beaters.

As for how he came up with the name of his machine, Brockman had hunted in the Ruby Mountains in Nevada and thought Ruby was an attractive name. His invention quickly got to be called a stripper or picker, but he definitely didn't want it known as a stripper.

His machine slips through the vines of ruby-colored cranberries — thus the ruby slipper.

"I am not a mad scientist. I just make things out of necessity to make my life easier. I always say if you want to find the best way to do something, get a lazy guy to do it. I guess I am lazy," the cranberry grower said, laughing again.