All aboard! Exploring a toy train empire. For 25 years, Adolf Arnold has been a relentless collector

``Good afternoon, welcome aboard,'' booms Adolf Arnold, owner, conductor, and engineer of the A&D Toy Train Village and Railway Museum. The two women he's greeted look faintly bemused, as their children scurry from one display to another bellowing, ``Look Mommie - elves, Santa, trains!''

Dozens, hundreds of trains.

An 1860s smoke belcher circles a Western town; a diesel pulls a long string of tank cars past a refinery; an intricately detailed steam locomotive guides its passenger coaches through a Bavarian village. Most of the trains chug into action at the push of a button by an entranced child, or adult.

Christmas themes are here and there, but the festive air comes primarily from the whirring and clacking of the tiny engines themselves - tapping out the enduring allure of railroading and the ever-popular toys it spawned.

Acquiring miniature trains has been Mr. Arnold's preoccupation for the past quarter century. And not just electric trains. ``There's no end to it - trains made out of wax, sugar, chocolate, paper, you name it.''

He even has a colorful ``spit-ball'' train crafted on a sheet of construction paperyears ago by his son Douglas (the ``D'' in ``A&D''). Over 2,000 trains in all, from 21 countries.

``Whatever looks like a train, is a train, runs, stands still, is pretty - I take it!'' proclaims Arnold with a guffaw. He doesn't care much about authenticity and prototype operation - obsessions with ``serious'' model railroaders. With rare exceptions, his exhibits all came ``out of a box'' at some point. They were sold off a toy store shelf - from the vintage 1850 tin wind-up locomotive to the shiniest new Lionel.

A portly, grandfatherly man whose robust voice carries the inflection of his native Germany, Arnold began collecting as a respite from the pressures of his advertising business. But the hobby soon oustripped his home.

He recalls the point at which his wife, Virginia - a patient, understanding woman who for the most part has supported his toy train empire - rebelled. ``The living room was full, the bedrooms, the dining room, and my wife said, `No, no more!'''

So the search began for some kind of building to contain the flood of rolling stock and locomotives.

After a number of real estate deals fell through, Arnold happened on the Middleboro site - an abandoned supermarket in this rural, somewhat nondescript corner of southern Massachusetts. Three months and a big chunk of capital later, the outside of the old market had been tranformed. But the inside, says Arnold, ``was a big mess, with boxes everywhere.''

About then, he continues, eyes twinkling, ``the miracle happened.'' He and a friend had taken the first, faltering steps towards turning the barnlike structure into a museum that would reflect its founder's passion for toy railroading. It was ``a very hot evening, and we were sweating, putting up walls,'' Arnold remembers.

Suddenly, people started dropping in. One was a carpenter, another a electrician. All were friends or friends of friends. All had heard about the project and wanted to lend a hand. Some were model train enthusiasts; many weren't.

``The volunteers made it all possible,'' says Arnold, a note of emotion in his voice. He figures some 4,300 hours were donated. ``And now here's something that many people are proud of,'' he adds, sweeping his arm to encompass the attractive display cases, the 34-foot-long master layout, abuzz with a dozen trains running at once, and the trolleys and locos clicking along on overhead rails.

Arnold estimates he's had 50,000 visitors during the two years the museum has been open. Some have come from such far-off places as Spain, Saudi Arabia, and Germany. Today, a young couple from London, the Riches, are visiting, having seen a listing in the Boston Globe. Their blond little boy, William, peers intently at a freight train rounding a bend inches from his nose. ``We knew he would like it, and the adults would too,'' says his mother, with a smile.

That kind of response, says Arnold, is all the reward he needs.