354 SECTIONAL TRANSACTIONS.— G. 



of cleaning, feeding and milking of 150 cows can be accomplished by three men, as 

 against the fifteen normally needed. A central hydro-manure plant to distribute the 

 manure over the farm hydraulically saves a lot of labour, both of men and horses. 

 Over eight tons of produce have to be transported on a farm per arable acre, plus 

 3£ tons of milk per cow, and at least another nine tons of manure per acre has also 

 to be carried and spread. This means a total of 8,152 tons to be transported annually 

 on a farm with 420 acres of arable land — no mean proposition. Hence the importance 

 of modern electro-mechanical means of transport. 



Mr. H. W. Swift. — The Transmission of Power by Belts. 



The fundamental principles of the operation of a driving belt are still incompletely 

 understood ; in particular, opinion on the mechanism of creep and slip is still divided, 

 and relations obtained by causing a belt to move slowly over a stationary pulley are 

 still applied to running conditions. 



Discussion of the transfer of power by an extensible belt shows that so long as the 

 tension ratio (Tj/Tj) is less than that (en P) corresponding to the limiting co-efficient 

 of friction and angle of embrace, relative motion on either pulley will only occur over 

 the ' active ' arc of embrace which extends back from the point of leaving through 

 an angle (3 where T l /T i =e , 'P. The successful operation of crowned pulleys and 

 twisted drives depends on this fact. Preliminary experiments demonstrated that 

 ' static ' tests do not enable the running characteristics of a belt to be predicted. 



A new plant for the testing of belts under running conditions is described, by means 

 of which the speed, power and mean tensions can be controlled and measured and the 

 loss of speed and power determined. Power is obtained from a variable speed motor, 

 and may be returned mechanically by means of a return belt which permits greater 

 powers to be transmitted by the belt under test than can be obtained from the driving 

 motor. 



A series of tests carried out under constant mean tensions at a low belt speed 

 (1000 f.o.m.) show that the creep-power characteristic can generally be predicted 

 with some confidence from the known elastic properties of the belting, and that serious 

 bodily slip occurs at a value of the tension ratio which corresponds tolerably well 

 with that obtained from a ' static ' test. The characteristics for various classes of 



T — T 



leather and fabric belting are compared, and the ratio -- 1 — — 2 , defined as the ' Co- 



-M 



efficient of Performance,' is proposed as a useful criterion of the effectiveness of a 

 driving belt. 



The practical conditions of operation at constant centre distance are discussed ; 

 changes in mean tension with power transmitted are examined for horizontal drives 

 and the results of experiments are given to confirm the results obtained. 



Afternoon. 



Visits to works in Hunslet district : — 



(i) Airedale Foundry. — Messrs. Kitson & Co., Ltd. 



(a) A Kitson-Still Locomotive — a combination of an internal combustion and 



steam engine : as applied to a locomotive this is a new departure. 



(b) Three engines for Western Australia. 



(c) Special foundry work in connection with complicated cylinders for locomotives. 



(d) Surface combustion appliances applied to furnace work, heating, cremation, 



and cooking. 

 (ii) Steam Plough Works. — Messrs. J. Fowler & Co. 



(a) Cultivating machinery (cable-drawn implements, forest clearing engines, 



steam and motor tractors). 

 (6) Road transport machinery (steam wagons, traction engines, &c). 



(c) Road-making machinery (rollers, sprayers, gritters, scarifiers, &c). 



(d) Construction machinery (concrete mixers, &c). 



(e) Light railway machinery. 

 {Hi) Hunslet Engine Works. 



(a) A series of engines for Ceylon. 



(b) Shunting engines of latest L.M. & S. Rly. type. 



(iv) Midland Engine Woeks. — Messrs. J. & H. McLaren. 



