TABLE OF CONTENTS In studying the construction of machinery, it is necessary, or at least convenient, to have an understanding of its basic principles. This chapter therefore includes a brief review of a few of the laws of physics involved in machinery construction and operation.
There are a number of parts or assemblies such as gears, brakes, and clutches that are common to machines of widely different types. These are described together for convenience of reference, and to avoid complicating the descriptions in the following chapters.
Speed and Force. An engine usually turns its crankshaft too fast and with too little force (torque) for the machine it powers. This speed can be reduced and the force increased in the same proportion by the use of gears, levers, pulleys, and other devices. Explanation of how this is done can best be started by referring to some basic laws of physics.
Conservation of Energy. The first law is that of conservation of energy that energy cannot be created or destroyed, only changed from one form to another. In machinery, speed and force are applied by the engine. Some of this energy will be transformed by friction into heat and wasted, but most of the rest may be converted from speed to power, or power to speed, and back again.
Levers. The oldest and simplest converter is the lever, which may be divided into three types. Figure 12.1(A) shows a first-class lever, consisting of a crowbar with its business...
