486 REPORT— 1886. 



one I'espect, for there was no provision to prevent the ball from revolving^ 

 whilst its axis of rotation passed through the point of contact made with 

 tlie driven wheel. 



Fisrs. 1 and 2 show a hoist in which this defect was obviated, and which 

 was designed so that the pressure on the driving and driven wheels 

 should vary with the load to be raised. This arrangement ensured a 

 greater efficiency than could otherwise be obtained.' The framing of the 

 hoist was made to bolt to a pair of vertical posts. A drum (m), which 

 replaces the differential arrangement originally used, is cai-ried on one end 

 of a shaft (n), which by means of a wheel (a) placed at the centre of its 

 length receives the motion from the ball (o). The other end of the shaft 

 is held in a bearing {p) ; and therefore, since there is no centre support 

 for it except the ball, the pressure on the ball must be due to the con- 

 stant weight (due to the shaft-wheel, &c.) plus the load multiplied by 

 a constant quantity. The hoist is started, stopped, reversed, or has its 

 speed changed by simply pulling one or other of two ropes which hang in 

 a convenient position. 



This machine has worked most satisfactorily for more than half a year,, 

 and has given no trouble. It works at present thoroughly well, and 

 seems likely to last many years. Experimental data as to its efficiency 

 are given hereafter. 



There is great difficulty in making the framing of these machines light 

 and compact, and at the same time sufficiently rigid to withstand the 

 heavy pressures used. One chief source of difficulty is the part of the 

 frame necessary to carry the pressure-wheel (fig. 1). Figs. 3 and 4 

 show a machine in which this wheel is dispensed with. Two balls are- 

 employed in contact with each other at the point (o). The driving-shaft 

 (a) is of cast iron and is hollow, having two flanges, which at the points 

 {n n) press against the two balls. The drum (b) has also two coiTespond- 

 ing flanges, which touch the balls at the points (J, I). The guide- wheels for 

 each ball are moved simultaneously, so that the axes of the two balls move 

 symmetrically ; hence for each ball there is always the same ratio between 

 the speeds of the surfaces at n, I, and o ; and since the speed at n is the 

 same in each case, the other speeds must also respectively be equal, and 

 therefore all the surfaces roll freely upon each other. 



This machine is extremely compact, and works well. It is now at 

 the Liverpool Exhibition, and with two 6" balls transmits over 2 horse- 

 power. 



2. Special Details of Construction. 



Mode of Preventing Injury to Sphere when its Axis of Rotation passes 

 through a Point of Contact. 



The chief advantage of the sphere and roller mechanism is the power 

 of varying the velocity ratio of the driving and driven wheels by the 

 mere motion of a lever. As is fully set forth in the papers above referred 

 to, this result is obtained by causing the axis of rotation of the sphere to 

 assume different positions relatively to the driving and driven wheels. 

 When, however, the latter is required to move at a very slow speed, or 

 to actually come to rest, the axis of rotation passes so close to the driven 

 wheel that the sphere spins upon the point of contact, and there is con- 



' This machine was briefly alluded to in the paper read before the British. 

 Association, Aberdeen meeting, by Professor Hele Shaw. 



