930 Transactions of tee American Institute. 



article, hoping, with them, tliat out of this great field of promise -vre 

 may some day soon pluck flowers of comfort. 



A New Dynamic Indicator. 



The following pnper contributed by Mr. C. P. Leayitt, on the 

 " Perpetual Dynamic Indicator," was then read by the secretary : 



The object of the djmamic indicator is to register the average 

 amount of power transmitted from a motor to a revolying shaft, and 

 is intended to supersede the ordinary dynamometer where great 

 accuracy is required. Unlike the ordinary form of dynamometer, in 

 the use of which the force and velocities of the motor must remain 

 nearly constant, in order to arrive at reliable results, this instru- 

 ment is not aft'ected by changes in the power which it is intended to 

 rejrister : but shows by the number of revolutions of a countershaft, 

 the average power which it has transmitted in a given time ; and by 

 the speed of that countershaft, the power which it is transmitting at 

 any particular moment of time. This result is accomplished in the 

 following manner : 



To a shaft which is to be driven, a pulley is fitted to revolve loosely 

 I)etween two collers. Firmly secured to the shaft is a pile spring, 

 the extremities of which connect with the pulley by a proper articu- 

 lation, so that such power as may be applied to the pulley must be 

 transmitted thi-ough the spring. Any variation of the force applied 

 to the pulley will thus cause it to slightly move upon the shaft. 

 Outside of the hub of the pulley, a x'adial bar is firmly attached to 

 the shaft, which extends nearly to the face of the pulley, where it 

 forms a fulcrum for a swinging bar, also radial. The short arm of 

 this swinging lever is made to press, by means of a light spring, 

 .against a piece of steel fitted to the edge of the pulley ; which piece 

 of steel is properly inclined to the plan of revolution, so that as the 

 pulley turns upon the shaft, the swinging lever shall make a coi'res- 

 ^onding motion parallel to the shaft. The lower end of the swing 

 lever connects with a sliding boss upon the shaft, which rerolves with 

 it. A circular disk of rubber is fitted to this sliding boss, and it is 

 turned to a very fine edge where it presses against, and rotates a 

 small light cone, which is adjusted with one of its sides, parallel to 

 the shaft, in such a manner that as the boss is moved by the variation 

 of power to different positions upon the shaft, the disk of rubber 

 shall act upon corresponding diameters of the cone, and thus move 

 it with corresponding velocities.. In this manner, the number of 



