A Catechism of the Steam Engine

by C. E. John Bourne

656. Q.--What are the dimensions of the boiler?

A.--The interior of the fire box is 3 feet 7-1/4 inches wide by 3 feet 5-1/2 inches long, measuring in the direction of the rails. The area of the fire grate is consequently 12.4 square feet. The bars are somewhat lower on the side next the fire door than at the side next the tubes, and the mean height of the crown of the fire box above the bars is 3 feet 10 inches. The top edge of the fire door is about 7 inches lower than the crown of the fire box. The fire box is divided transversely by a corrugated feather or bridge of plate iron, containing water, about 3-1/2 inches wide, and of about one-third of the height of the fire box in the centre of the feather, and about two-thirds the height of the fire box at the sides where it joins the sides of the fire box. The internal shell of the fire box tapers somewhat upwards to facilitate the disengagement of the steam. It is about 2 inches narrower and shorter at the top than at the bottom; the water space between the external and internal shell of the fire box being 2 inches at the bottom and 3 inches at the top.

657. Q.--Of what material is the fire box composed?

A.--The external shell of the fire box is formed of iron plates 3/8ths of an inch thick, and the internal shell is formed of copper plates 1/4 inch thick, but the tube plate is ¾ inch thick. The fire grate is rectangular, and the internal and external shells are tied together by iron stay bolts 3/4 inch diameter, and pitched about 4 inches apart. The roof of the fire box is stiffened by six strong bars extending from side to side of the fire box like beams, and the top of the fire box is secured to these bars, so that it cannot be forced down without breaking or bending them.

658. Q.--What are the dimensions of the barrel of the boiler?

A.--The barrel of the boiler is 3 feet 7-1/2 inches in diameter, and 10 feet long. It is formed of iron plates 3/8ths of an inch thick, riveted together. It is furnished with 181 brass tubes 1-7/8 inch diameter and 10 feet long, secured at the ends by ferules. The tube plate at the smoke box end is 5/8ths of an inch thick, and the tube plates above the tubes are tied together by eight iron rods 7/8ths of an inch thick, extending from end to end of the boiler. The metal of the tubes is somewhat thicker at the end next the fire, being 13 wire gauge at fire box end, and 14 wire gauge at smoke box end. The rivets of the boiler are 3/4 inch diameter and 1-1/2 inch pitch. The plating of the ash pan is 5/16ths of an inch thick, and the plating of the smoke box is 3/16ths of an inch thick.

659. Q.--Will you describe the structure of the framework on which the boiler and its attachments rest, and in which the wheels are set?

A.--The framework or framing consists of a rectangular structure of plate iron circumscribing the boiler, with projecting lugs or arms for the reception of the axles of the wheels. In this engine the sides of the rectangle are double, or, as far as regards the sides, there are virtually two framings, one for the reception of the driving axles, and the other for the reception of the axles not connected with the engine. The whole of the parts of the outer and inner framings are connected together by knees at the corners, and the double sides are elsewhere connected by intervening brackets and stays, so as to constitute the whole into one rigid structure. The whole of the plating of the inside frame is 3/4 inch thick and 9 inches deep. The plating of the outside frame is of the same thickness and depth at the fore part, until it reaches abaft the position of the cylinders and guides, where it reduces to 1/2 inch thick. The axle guard of the leading wheels is formed of 3/4 plate bolted to the frame with angle iron guides. The axle guards of the trailing wheels are formed of two 1/2 inch plates, with cast iron blocks between them to serve as guides. The ends of the rectangular frame are formed of plates 3/4 thick, and at the front end there is a buffer beam of oak 4-1/2 inches thick and 15 inches deep. The draw bolt is 2 inches diameter. There are two strong stays on each side, joining the barrel of the boiler to the inside framing, and one angle iron on each side joining the bottom of the smoke box to the inside framing.

660. Q.--Of what construction are the wheels?

A.--The wheels and axles are of wrought iron, and the tires of the wheels are of steel. The driving wheels are 6 feet 6-1/2 inches in diameter, and the diameter of crank pin is 3-1/2 inches. The diameter of the smaller wheels is 48-1/2 inches. The axle boxes are of cast iron with bushes of Fenton's metal, and the leading axle has four bearings. The springs are formed of steel plates, 3 feet long, 4 inches broad, and 1\2 inch thick. The axle of the driving wheel has two eccentrics, forged solid upon it, for working the pumps.