April, 1888.] 



ELLIOTT SOCIETY. 



203 



AN ELECTEICAL SPEED INDICATOR. 



BY r. W. SCHLEPEGRELL, A. M. 



In wood- working and other high speed machinery, it is of vital importance 

 that the number of revolutions per minute should be kept at the rate for which 

 the machine was built. When saws and planer knives are running at their 

 normal speed, the cutting surface acts like a chisel, cutting its way through the 

 wood. When, however, it is below that rate, the cutting surface no longer 

 makes a clear smooth cut, but drags and tears its way through the wood, not 

 only doing less work, but doing it in an inferior manner. On the other hand, 

 when machinery is run above its normal speed, it is compelled to do work be- 

 yond its capacity, and breaks down in its weakest parts, besides endangering 

 boxes and journals from over heating. The diminution of the speed may be 

 caused by the fall of the steam-pressure in the boiler, slipping of belts, &c. , 

 while the irregular working of the governor, or the breaking or slipping of the 

 governor belt is the principle cause of an increase of the speed. 



A simple device by which the increase or diminution of speed in machinery, 

 above or below its normal rate, may be indicated electrically, is here illustrated. 



ELECTBICAL SPEED INDICATOK. 



The indicator shaft, arranged to receive motion conveniently from the ma- 



