We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
1949 HALF-MILLION IMAGES PER SECOND 485
MOTIVE POWER AND ROTOR DYNAMICS
During early operation of the camera, motive power was supplied by an air turbine constructed at the University of Virginia.8 The 5-ounce camera rotor was supported by the upper end of the same piano-wire shaft, 0.039 inch in diameter, that served the turbine itself. Two babbitt journal bearings were used, one below the turbine rotor, the other between the turbine rotor and the camera rotor. The upper bearing served to seal the evacuated rotor chamber from the atmospheric pressure existing within the air turbine.
The camera rotor, as seen in Fig. 4, has the appearance of being mounted to spin about an axis that makes a considerable angle with its own natural axis. At first sight many engineers therefore assume that the rotor cannot be balanced properly. The rotor is approximately a right prism of hexagonal cross section, with the prism axis intersecting the axis of spin at about 15 degrees. It is well known, however, that the inertial characteristics of any spinning body may be represented by those of an equivalent ellipsoid. It is also well known that the fundamental requirement for static and dynamic balance is that the body must be mounted to spin about one of the principal axes of the equivalent ellipsoid. Moreover, the equivalent ellipsoid for any right prism of regular polygonal cross section is a spheroid whose major or minor axis coincides with the prism axis. By pure coincidence the prismatic camera rotor, designed on the basis of optical considerations alone, has almost exactly the correct length to make its equivalent spheroid a true sphere. It may, consequently, be mounted and balanced to spin about any axis that passes through its center of gravity without changing its appearance appreciably.
The balancing of such a body, however, proved exceedingly difficult. The difficulty lay in the facts that the near-spherical body involves extremely high critical speeds, that the true axis of balance of the nearspherical body may make a large angle with the axis of spin even though the unbalance at speeds below 500 revolutions per second is barely detectable, and that shaft failure at the critical speed is certain if the angle between the true axis of balance and the axis of spin exceeds the greatest angular deflection that can be tolerated by the shaft.
After numerous shaft failures at a critical speed of about 1200 revolutions per second, a better understanding of the problem was gradually obtained and it was finally possible to spin the rotor with