Miniature steam engines run in the family.

ost steam engines have disappeared from use or been put in museums, but after 60 years in the business Thomas Jensen continues to build and sell working miniature models, some of which weigh as little as 2 lbs. Sales of the tiny machines have supported him and his family since the 1930s. Now,

Jensen, a Danish-born mechanical engineer, admits that he is most content in his machine shop, a small garage-like building almost invisible to passersby. Inside, between 3000 and 5000 tiny machines, about % the size of full-scale steam engines, are churned out each year.

His company, Jensen Manufacturing Company Inc. (Jeannette, Pa.), is very much an extension of its founder. Jensen's son, Tom Jr., is president of Jensen Manufacturing. He too is a mechanical engineer, as is Tom Jr's son, John, who works for the Norfolk Naval Shipyard (Portsmouth, Va.) and plans to one day take over Jensen Manufacturing and carry on the tradition of steam engine making in the U.S. well into the next century. (John has been a member of ASME since 1990. His interests are in design engineering, and fluid power systems and technology.)

The low profile the senior member of the Jensen family, Thomas, has kept throughout his life has underplayed his career's achievements. "Everything is carried out totally incognito--that's my dad's style," said Betty Meil, Jensen's daughter, who herself is the mother of two electrical engineers. However, Jensen's achievements haven't always gone unnoticed. President Bush recently wrote a congratulatory letter to Jensen for his 91st birthday. Jensen's efforts have "inspired those around [him] and have set an example for others to follow," the president said.

Humble Ingenuity

Many in the miniature steam engine fraternity are surprised at the ingenuity that underlies some of Thomas Jensen's creations. But to him there is nothing wondrous about much of what he does; whether that be machining within tolerances of [+ or -] .0005-inch or making boilers that last for decades. For one particular part of the manufacturing process, Jensen built a tube-cutter that saws off small brass boilers to length from the inside. "That's very simple, there's nothing special about it," he insisted. But according to miniature steam engine hobbyists, the cutter is rare for the manner in which the tubes are sawn off. In this case, the use of multiple steel cutting wheels spinning around both the inner and outer circumferences of the tube reduce the chances of part deformation.