Читать книгу Inventors at Work, with Chapters on Discovery - George Iles - Страница 23

Table of Contents

It was a memorable day when first a round log or stick was thrust under a burden, easing its motion and leading to the wheel by piecemeal improvements. A section cut off from the end of a round log is to-day the wheel for ox-carts in China and India. In its crudest form a roller enables a man to drag a load instead of carrying it, and he can readily drag much more than he can carry. Wheelwrights of old soon found that a wheel need not be solid, that strong spokes, a sound rim, and a metal tire embody the utmost strength and lightness. Roller and ball bearings much extend the benefits of simple wheels; they lessen friction in the best typewriters, bicycles, and elevators; in wagons, carriages, and automobiles roller bearings are so helpful that their use should be universal. Of notable efficiency is the Hyatt bearing, formed by winding a steel strip into a spiral roller. This device has a flexibility which enables it to conform to irregularities of motion much better than can a solid cylinder.

Bullock cart with solid wheels.

For machinery the wheel is indispensable. The hand does its work chiefly in moving to and fro, as in sawing and whittling. Machines outdo manual toil by moving swiftly and continuously in a circle: instead of the smoothing iron we have the mangle, boards are planed by rotary knives, timber is divided by circular saws, and the steam turbine is displacing the steam engine which every moment has to check the momentum of huge reciprocating masses. Noteworthy in this regard is the perfecting press which prints a newspaper from a continuous roll, as contrasted with the old machine which demanded for each impression a distinct series of to and fro movements. The Harris Rotary Press for job printing is of like model. It feeds itself with 6,500 sheets an hour, printing from a stereotype or an electrotype curved upon its cylinder. The lathe, simple enough a century ago, has been developed into machines of great complexity, power, and variety, all with the original rotary mandrel as their essential feature. Milling machines, steadily gaining more and more importance, employ rotary cutters which dispense with the manual chipping and filing of former days.

Section—A B

Ball thrust collar bearing.

Ball Bearing Co., Philadelphia.

Rigid bearings for driving axles of automobiles.

Ball Bearing Co., Philadelphia.

Hyatt helical roller bearing.

Hyatt rollers supporting an axle.

Treads and risers joined by curves.