LOCOMOTIVE ENGINE. 



465 



FIG. 46. 



FIG. 46. 



have not the inner ones ; and instead of them a strong iron frame is placed imme- 

 diately within the wheels, bearing upon the axles, and having the whole engine 

 resting upon it ; this gives the engine a lighter appearance, as the wheels are quite 

 on the outside. But the outside frame adds considerably to the stiffness of the engine, 

 and is of great utility in that respect, particularly when the engine gets thrown off 

 the line, as happens occasionally; when the outside frame serves materially to 

 protect the machinery. It has also an advantage in enabling the engine man to 

 have access to any part of the engine whilst it is working, as the wheels and the 

 space between them are covered over by the splashers, and can be readily passed over; 

 this is very useful, as the working parts frequently require examining and replenish- 

 ing with oil whilst running. The friction is less when there is no outside frame, as 

 there are but two bearings on the cranked axle instead of five ; but they have to 

 be the full size of the axle, as they are inside the wheels, which much increases the 

 friction of each, and renders the whole but little less than in the other plan ; the axle 

 is also not held so steadily as with the middle inside bearings. 



WHISTLE. Z' (Plates LXXXIX., XC.,and XCII.,) is a steam whistle used for the 

 purpose of giving warning of the approach of the engine when running ; the con- 

 struction of it is shewn to one quarter size, or four times the scale of the engravings., 

 in figs. 45 and 46. It is all of 

 brass, and the foot, A, is cast 

 hollow, with a flanch, B, at the 

 bottom to bolt it upon the fire- 

 box ; it has a cock, C, placed in 

 it, with the handle D, and screw 

 E, to keep it tight, the handle 

 projecting out to allow firm hold 

 to be taken of it. The cup F, is 

 fixed upon the foot A, by screw- 

 ing the piece G, upon it, and both 

 are turned truly at their outer edges, 

 leaving a very narrow passage, //, 

 four inches diameter, between them all round. The piece G is hollow, having 

 holes, H, in its sides ; and a pillar, K, stands upon its centre, on which is screwed 

 the bell L L, the thin edge of which is brought just over the opening /, and half an 

 inch above it. When the cock is opened, the steam enters the cup F, through 

 the holes H, and rushes out at the narrow slit /, striking the thin edge of the bell L, 

 in a similar manner to the action in organ pipes, and producing an exceedingly shrill 

 sound ; some holes, M, are made in the top of the bell, to allow the steam to pass 



3 N 



