Disc attached to Drive Shaft

Driver

Type 631-BL S T R O B O T A C ®

Range: 600-14,400 rpm direct reading, useful from 60-100,000 rpm.

Accuracy: ± 1 % of dial reading over most of the range. .

Flash Duration: 10-4ÛMsec.

Power: Operates from normal 115v, 60-cycle lines.

Portability: 75/β χ 9 χ 10 inches, 9'/2 lbs.

*ieo. Photo Courtesy Towmotor Corporation

Horsepower = Tx2n How to make reliable horsepower measurements without resorting to expensive

equipment? This is a problem that confronts many engineers. The Towmotor Corporation of Cleveland utilizes a fundamental physical principle and the G-R Strobotac to perform this work.

Measurement of engine horsepower is accomplished with a hydraulic power-absorption stand and the G-R Strobotac. Fitted concentrically over a drive shaft is a cylindrical sleeve that has a low-inertia disc at one end and is attached to the drive shaft at the other end (see sketch). Parallel to the low-inertia disc and securely con­nected to the drive shaft is another disc.

When the driver is operating, the drive shaft twists and there is a relative dis­placement between the two discs that is proportional to the TORQUE applied. However, since the whole assembly is whirling around, little can be seen. It is neces­sary to "stop" the motion to determine the displacement — this is done accurately and conveniently with stroboscopic light, supplied by the Strobotac. This instrument simultaneously gives the SPEED of the rotating shaft on its calibrated dial. Since HORSEPOWER is proportional to the product of TORQUE and SPEED, the job is done.

The G-R Strobotac is ideally suited for this type of work or, for that matter, for any measurement of speed of rotating, reciprocating, or other cyclic motion. The instrument is an ideal design, production, or maintenance tool. Its high-intensity, short-duration pulses of light "freeze" rapidly moving parts or processes, making possible detailed examination of the action while at full speed. There is no physical connection between Strobotac and the device under test — no drag whatever to

affect the operation under investigation.

Broad Avenue at linden, Ridgefield, N. I. NEW YORK ARE* 1000 N. Seward St. IOS ANGELES 31 8055 13th St. Silver Spring, Md. WASHINGTON, D. C. 1150 York Road, Abington. Pa. PHILADELPHIA 1182 Los Altos Ave., Los Altos. Calif. SAN FRANCISCO 6605 W. North Ave.. Oak Park, III. CHICAGO

In CANADA: 99 Floral Parkway. TORONTO IS

are now covered by a

2-year Warranty

VOL. 49, NO. 12 · DECEMBER 1957 6 1 A

Low Inertia Disc Attached to Cylindrical Sleeve

Load

STROBOTAC Manufactured Exclusively by

GENERAL RADIO Company 275 Massachusetts Ave., Cambridge 39, Mass.

All G-R Products