TKANSACTIONS OF SECTION A. 553- 



More detailed infoi-mation in regard to tlie l^ehavioiir of certain of the above 

 metals may be found in articles before published by the author, and in one which 

 probably appears in the current number of the ' Philosophical Magazine.' 



6. On a Dynamometer Coupling. By Professors W. E. Ateton, F.B.8., 



and John Peery, B.E. 



The instrument exhibited to the Section is one of a complete set of instruments 

 designed by the author for measuring purposes in electric lighting, and in the trans- 

 mission of power. The other instruments belonging to the set are — 1st. A dead-beat 

 Galvanometer or Am-7neter, which measures accurately a strong electric current 

 in amperes. It gives an immediate measurement of a rapid alteration in the 

 current ; when wound somewhat differently, this becomes the author's Volt-meter, 

 which measures instantaneously an electromotive force in volts. 2nd. A rhotometer, 

 which ogives the strength of a light in standard candles, and which enables the 

 measuring operation to be performed in a veiy small room. 3rd. An Ergo- 

 meter, which gives at one reading the horse-power which is being expended 

 pn an electric arc or in an incandescent lamp, or in any other electric circuit. That 

 is, it gives in one reading the product of electro-motive force into current. The 

 authors have called the instrument a Power-meter, but Sir William Thomson has 

 given te it the name Ergometer. 4th. The present instrument; a Dynamo- 

 meter, which measures the horse-powei- transmitted from one length of shafting 

 to another in a factor^-, or the power given up to any machine. 



Various dynamometers, as is well known, are in existence, but however suited 

 they may be to laboratory conditions, they cannot be regarded as suitable for 

 workshop use. In fact, they are to be called arrangements of scientific apparatus 

 rather than dynamometers. The dynamometer described by the authors in their 

 paper read before the Society of Telegraph Engineers last session may be seen in 

 use by the students of The City and Guilds of London Technical CoUege at 

 Fmsbury. It is capable of more general application than this, because it is used 

 in the belting which drives a dynamo or any other machine. Although the 

 principle of construction of this instrument is the same, they think it worthy of 

 notice from its being capable of taking the place of an ordinary shaft coupling, 

 and froni its not being much more expensive than an ordinary shaft coupling. 

 In fact, it consists of the two halves of an ordinary coupling, onekeyed to each of 

 the shafts which are to be coupled. The shape is slightly different from what is 

 usual, and allows the connection of the two halves by means of the spiral springs. 

 Now it is evident that if one shaft turns the other, it can only do so by pulling 

 the springs, and the movement of the turning couple is proportional to the 

 lengthening of the springs, that is, to the angidar advance of one half of the 

 coupling before the other half. Here are two light levers, by means of which this 

 relative motion of the two halves produces a radial motion of a silvered bead, 

 and the distance of this bead radially from the shaft, can be read off on a scale. 

 The scale reading, midtiplied into the number of revolutions per minute, gives at 

 once the horse-power transmitted through the coupling. The whole arrangement 

 would appear to be nearly as small and insignificant as an ordinary coupling were 

 it not for the disc of sheet iron, with its marginal flange, which is used to protect 

 the levers and the bead. Everytliing except the bead is painted dead-black. The 

 instrument exhibited has been designed to couple a Brotherhood Engine and a 

 Brush Machine, and w^hen the bead is close to the sliaft and the speed is 800 

 revolutions per minute, tlie coupling transmits 18 horse-power. In the present 

 position of the bead the springs are unstrained, and tliis is the case when no 

 power IS being tran.smitted. It is the authors' intention to attempt to introduce these 

 couplings into every line of shafting in manufactories, so that the stream of power 

 along every shaft may be measured and visibly made known at any distance from 

 which tlie bead may be distinguished. 



