15 Apr 2002 @ 14:02, by Flemming Funch
Dean Kaman, the inventor who introduced the Segway Human Transporter, a self-balancing motorized scooter, seems to have come up with a way of mass-producing Stirling engines. A Stirling engine can draw its energy from just about anything that can produce heat, and produces next to no pollution. It has so far been extremely expensive to produce and has only been used in places like submarines. See New York Times article (registration required).
A publicity success, the futuristic Segway scooter may be celebrated for its engine
By TERESA RIORDAN
DEAN KAMEN'S motorized scooter, conceived as Ginger and christened Segway, has sparked the public imagination like few other inventions in recent memory. A New Yorker cover recently featured Osama bin Laden making a getaway on a Segway. Last week, the television character Niles rode one on "Frasier."
But recently published patent applications bolster the tantalizing speculation that Mr. Kamen may indeed have something much bigger up his sleeve than the cute scooter, which looks something like a motorized push mower with wheels.
Such speculation has been brewing for more than a year now, fueled in part by remarks made by Robert Metcalfe, a buddy of Mr. Kamen's. Dr. Metcalfe is no slouch himself in the invention department; he created, and made a fortune from, the office network technology known as Ethernet.
Dr. Metcalfe has been quoted as saying that the real "It" - the code name that a journalist, Steve Kemper, used when he sold a book proposal for an insider's account of Kamen's secret new device - is an invention "bigger than pantyhose," "bigger than the Internet" and "almost as big as cold fusion would have been."
Therefore many people were disappointed when the ostensible unveiling of "It" amounted to no more than Diane Sawyer, of "Good Morning America," tooling around Bryant Park on what appeared to be a glorified scooter. Certainly the Segway seems less of a physics-defying concept than Mr. Kamen's iBot, a stair-climbing wheelchair, which he once used to climb a third of the way up the Eiffel Tower.
The importance of "It," however, may have as much to do with the scooter's future engine as with the scooter itself. Last month, the United States Patent Office published application No. 20020029567 - with Mr. Kamen named as one of the inventors - for the manufacturing of a Stirling engine, which can be powered by heat from any fuel and is virtually nonpolluting. Indeed, a profile of Mr. Kamen in the May issue of Vanity Fair says he has produced two small prototypes of such an engine, but offers few details.
Mr. Kamen's wealth and reputation were built on medical patents, but he has patented a wide range of inventions. These include - somewhat improbably, given that Mr. Kamen, in his early 50's, is a lifelong bachelor - a cradle that simulates the experience of the womb and a "catemenial container," essentially a disposable version of a 19th-century menstruation receptacle.
At least three Stirling engine patents have already been issued to one of Mr. Kamen's companies, New Power Concepts, which is based in Manchester, N.H. But the interesting thing about the most recent patent application (and it is only an application; the patent hasn't yet been granted), according to several people familiar with Stirling engines, is that it covers the manufacturing of the engine, not just the design.
"This patent was filed by a person who is going into production," said Brent H. Van Arsdell, president of American Stirling, an educational company that sells nonindustrial Stirling engines to physics professors and enthusiasts. "He's fairly confident of his design. This addresses the question of how can we build this economically and faster and reliably after we already have a prototype that costs us millions of dollars."
The Stirling engine is by no means a new concept. Robert Stirling, a minister in Edinburgh, Scotland, applied for a patent in September 1816 for his "economiser." Over the next two centuries many versions of engines inspired by the Stirling design have been built.
Kockums, a Swedish defense contractor, now produces a Stirling engine for submarines. And NASA is said to be developing Stirling engines for space exploration.
But so far no company has successfully produced a mass-market version, although Philips Electronics tried unsuccessfully about three decades ago to introduce a Stirling car engine.
Why would an inexpensive engine potentially be important? Stirling enthusiasts contend that it might easily provide power for people in emerging economies for water purification or even Internet access. In developed countries it might allow people to go off the electrical grid and even wean themselves from a dependency on foreign oil.
A second pending patent application from Mr. Kamen's company, No. 20010032452, suggests that his engine can run on fuels ranging from cow dung to nuclear material and everything in between, including propane, natural gas, methane, butane and petroleum.
A Stirling is essentially an external combustion engine - as opposed to the familiar internal combustion engines that run everything from automobiles to large factories.
Maureen Toohey, a lawyer for Mr. Kamen, said his company was not yet manufacturing the engines. "We're still in development," she said. But she pointed out that the nonpolluting Stirling engines can be used to power a lot of things other than scooters. "One of the unique things about a Stirling engine is that it's an incredibly versatile platform that one can do many things with," she said.
One of the difficulties in making a Stirling is that its engine cylinder and heat exchangers need to be extremely resistant to high temperatures and thus are usually constructed of the super alloys used in jet engines. These alloys are extremely hard to use in the manufacturing process.
The Kamen engine appears to be not terribly different from other Stirling engines. However, its heat exchanger - which has projecting "fins" that make it look like a riled porcupine ready to attack - has been designed so that it can be cast rather than welded, a key efficiency.
"I can design all sorts of beautiful Stirling engines in my mind," said John Brisson, a professor of mechanical engineering at M.I.T. "The nub of the matter is can you build it so that it operates efficiently, and can you build it cheaply?"
Even if Mr. Kamen is able to produce a low-cost Stirling engine, Professor Brisson warns, the hurdles are many for any disruptive technology. "It would be so radically different that mechanics wouldn't know what to do with it," he said. "The infrastructure is totally different. It has to be better by a factor of 10 than what is out there; otherwise no one is going to make the transition."
April 15, 2002 Copyright 2002 The New York Times Company
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