How Do I Look, Doc?



Sperry Detector Cars and AAR Detector Cars are regular visitors on Southern Railway System lines. On periodic tours over Southern rails, these coach-like mechanical "detectives" scientifically test the rail for surface and internal defects.

These scheduled trips of the cars over the Southern can be likened to the twice-yearly dental check-ups everyone is urged to have. By having our teeth checked at regular intervals, dentists tell us, minor tooth decay can be found and corrected before major cavities result.

On a section of Southern Railway track between St. George and Reevesville, S. C., a hand test is made to determine the size and type of a detected fault.


"Like teeth, rails can get "cavities," too. Finding them so they can be eliminated before they become troublesome is the job of the Sperry Detector Car .

Owned by the Sperry Rail Service of Danbury, Conn., the Detector Cars are leased to railroads together with the services of trained personnel. A fleet of 17 covers more than 160,000 miles of track every year for railroads throughout the United States and Canada.

Ordinarily traveling at a speed from 6 to 12 miles per hour, the self-powered Sperry Car tests the rail it operates over by a principle of inducing electric cur- rent into each rail. The car generates its own electricity.

Five inked lines on a continuous paper tape in the operating compartment of the Sperry Detector Car show the physical condition of each rail. Normally, these lines are straight and unbroken except as they register rail ends, or joints. However, the smallest defect in a rail, such as a tiny crack, interrupts the physical structure of the rail and als9 the flow of electric current.' This defect records itself on the tape as a break, or wave, in the straight lines.

The physical structure of the rails Sperry Detector Cars travel over is recorded on a continuous paper tape. Keeping a careful watch on the tape, the chief operator will signal for the car to halt for a hand test when a wave in the lines indicates a condition calling for more checking.


The process of locating defects does not end at the tape. An interruption in the flow of electricity through the rail triggers a mechanical device on the car which sprays yellow paint on the rail where the defect appears.

An irregularity on the tape also serves as a signal to the operator to stop the car to permit hand tests on suspected areas to determine the type and size of the defect. These brief tests consist of inducing cur- rent at a localized section of rail where a defect is indicated and noting the reading on a dial connected to the inducting device.

Forces following in a motorcar can easily spot any defective rails that are to be replaced. A small area of the cross tie nearest the defect is painted to identify the location of the defective rail.

While operation of the Detector Car is normally a daytime job, the car can operate at night whenever heavy traffic would make it advisable. Its movements are carefully planned to avoid any interference with regular train schedules. Ordinarily, the car covers nearly 50 miles. of track a day.

A Sperry Detector Car operates under its own power, moving on carefully planned schedules to avoid interference with regular train traffic. (The initials on the front stand for Sperry Rail Service, not Southern Railway System.)


Practical tests have revealed that the induction equipment of the Sperry Detector Car is very efficient. It discloses defects such as fractures, fissures and splits, visible and invisible defects.

Now nearing the end of its third decade of operation, the Sperry Car was first put into commercial use in 1928. Since then the cars have operated over 22 million miles of track for railroads throughout this continent and Europe. Southern began using Sperry Cars for testing rail in 1938.

In 1934, another rail detector car entered the rail- road scene. It was developed by the American Railway Association and its successor, the Association of American Railroads. Like the Sperry Car, the AAR Detector Car also moves under its own power and uses an electronic principle in its operation. Southern began using AAR Detector Cars for testing rail in 1943.

The double-unit AAR Detector Car, developed by the Association of American Rail- roads, is another of the rolling mechanical "detectives" which perform a valuable service for the nation's railroads.


Frequent testing with detector cars, prompt replacement of known defective and, even, "suspicious" rails, and the development and use of improve types of rail are the three elements which are said to have initiated a downward trend in the number and size of defects, with a corresponding increase in the safety of rail travel.

The Southern, as safety-minded as any railroad you'll find, believes in the practical application of all three.