Three-Ton Brain

To have the public's first look at the biggest and keenest mechanical brain in the world, a total of 6.000 persons one day last week trooped down into a basement of the University of Pennsylvania's Moore School of Electrical Engineering in Philadelphia. There they found a new differential analyzer even more formidable than its name--a maze of delicate mechanisms united in a 28-ft. monster weighing three tons (see cut). They saw innumerable gears mesh silently, shafting turn on jeweled bearings, operators carefully adjust hand controls; they heard five small motors tranquilly purr. On the "answer table" they saw a metal arm bearing a stylus make a curved graph on white paper.

"What can it do?" someone asked.

"Well, it's like this," answered Irven Travis, young Moore School instructor who designed the machine. "Suppose you're firing a salvo from a battleship. . . ."

In long-range gunfire nine or ten factors might be taken into consideration for computing the most accurate possible trajectory: speed of battleship, speed of enemy ship, drift of waves, wind velocity, shape of shell, muzzle velocity of shell, atmospheric humidity, even the rotation of the earth. Naval engineers might wrestle with their ballistics equations for months to correlate these factors. The machine can do in five minutes what it takes five naval engineers four months to do on paper.

One problem which the machine actually worked on last week was the Vanderpoel equation for activity of vacuum tube oscillators. The originator of the equation found it possible to work out one solution every two days. It takes a long, while to set the machine for this problem, but, once set, it whips out solutions at the rate of four per hour. Mr. Travis thinks the machine may solve astronomy's knotty "three-body problem."* Professor Charles DeVan Fawcett, the machine's enthusiastic impresario and financial nurse since its inception, believes it will calculate the factors of maximum efficiency in airplane stabilizers, automatic temperature control, radio, television, "wirephotos," high-speed induction motors.

Reduced to simplest terms, the machine has ten "integrators," each of which is set by a hand dial to compute the effect of a variable quantity on the problem to be solved. Each dial sets two movable parts --an 8-in. stainless steel disk, mirror-smooth, and a smaller wheel with a knife edge in contact with the disk. Governed by precisely controlled friction, the speed of the small wheel is the crucial factor in solving any problem. A bevel gearing delivers that factor to the "answer table" where the factors from all the integrators are combined and the final solution appears with a maximum error of .01%.

Inspired by the pioneer "brass brain'' designed by M. I. T.'s Dean Vannevar Bush,/- young Engineer Travis dreamed for years of building a bigger one. was stopped by lack of funds. Finally Professor Fawcett persuaded FERA to grant $40,000. The University contributed $10,000. During the 15 months of manufacture and assembly, a total of 115 FERA-paid mechanics, mostly skilled toolmakers, have worked on the machine. The U. S. Army, interested from the start and ready to commandeer the machine in case of war, is now building an exact duplicate on its ordnance proving grounds at Aberdeen, Md.

*Three-body problem: Project three bodies of known masses into space in three directions. At any subsequent time, calculate their positions, allowing for their gravitational effects on one another.

/-Smaller than the Moore School monster, Dr. Bush's machine has six integrators.

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