PART V. MECHANICAL EQUIPMENT 



CHAPTER XXIII 



PRINCIPLES OF MACHINES 

 FUNDAMENTAL DEFINITIONS 



Machine. A machine is a device for doing work when 

 some source of power is applied by means of an inclined 

 plane, a lever, a pulley, or a combination of the three. The 

 wedge, screw, wheel and axle, and pulley are usually called 

 simple machines, but the principles involved in them are 

 covered in the lever, inclined plane, and pulley. All machines, 

 no matter how complex, may be reduced to these three simple 

 elements. 



The word "machine" is applicable to any device with one 

 or more moving parts, and tool to one that has no moving 

 parts; but in common usage of the terms this distinction is 

 not always observed. Devices with moving parts are fre- 

 quently called tools. This is especially true when some 

 simple device has been replaced by a machine. Many of the 

 hand tools used in the trades have been replaced by mechani- 

 cal devices which increase the ease and speed of an operation, 

 but the word "tool" is still applied to the collection of 

 devices that make up the individual working outfit of that 

 trade. The only equipment for haymaking, at one time, 

 was the scythe and hand-rake, which were properly called 

 tools. While these tools have been replaced by the mowing 

 machine, self -dump rake, and other mechanical appliances, 

 all of which are machines, the term "haying tools" is still 

 applied to them. The term "farm implement" is applicable 

 to any equipment used in the performance of farm work. 



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