3 °
RECEN T LOCO MO LIVES.
carriages, increased on specially busy days to 22, 24 and even 26 vehicles,and, therefore, the difficulties of designing an engine capable of starting onsuch an incline and running economically at high speed were considerable.
Under these circumstances Mr, Bromley-designed the engines whichwe illustrate and are about to describe, and the success of the design maybe judged from the fact that they have conveyed 26 carriages up this in-cline without assistance, and can start on the gradient with 20, or the usualmaximum load. When we bear in mind that the larger train equals thelength of a goods train of 45 wagons, the feat is evidently one of no ordi-nary magnitude, and shows what can be done by a single pair of driving-wheels.
The engines, which were built by Messrs. Dubs, of Glasgow , com-menced running in May last, and have horizontal outside cylinders, 18 ir*diameter and 24 in. stroke. The driving-wheels are 7 ft. 6 in. diameter andall the other wheels, of both engine and tender, are 4 ft. diameter. Theleading end of the engine is carried by an Adams bogie, with a 7-ft. wheel-base. The boiler pressure is 140 lbs. to the square inch, and the tractiveforce per pound average pressure on the pistons is nearly 87 lbs. The en-gine and tender are fitted with the Westinghouse automatic brake, blocksbeing applied to all except the bogie wheels. The tender is carried on sixwheels, with a base of 12 ft., the tank holding 3,000 galls, of water. Theheating surfaces and weights, in complete running order, areas follows :
203 i^-in. tubes, .... 1,097 sq. ft. (external)-
Fire-box, - - - - in sq.ft, (internal).
Total, .... 1,208 sq. ft.
Grate area, - - - - 17.1 sq.ft.
Weight on bogie, - - - - - 17 tons 5 cwt.
Weight on driving-wheels, - - - 15 tons.
Weight on trading-wheels, - 10 tons 10 cwt.
Total, - - - - - - 42 tons 15 cwt.
The engine has two features which are almost peculiar to Americanpractice. The slide-valves, lying horizontally on the top of the cylinders,are worked by rocking-shafts, and the cab has a large door in front on theleft hand or fireman side, enabling the men to walk around the engine incomparative safety; for to clamber around the outside of a cab, encum-bered with a lamp, a spanner and an oil can, is at the best of times anoperation demanding more foothold than a 2 )4 in. angle-iron affords. Asthe trailing-wheels require no splasher, the door is of a good height, ex-tending from the foot-plate to the roof, and is a convenience that needsonly to be seen to be appreciated. No door is placed on the driver’s side,the space being occupied by the reversing-screw inside the cab and theWestinghouse pump outside.
The boiler barrel is 11 ft. 5% in. long and 4 ft. 1 in. internal diameter.The plates are of Yorkshire iron, )4 in. thick, butt-jointed throughout, thelongitudinal seams being double-riveted and formed by inside and outsidebutt-straps. The circumferential seams and smoke-box angle-iron ringsare in accordance with Great Eastern Railway practice of late years, madeof steel rolled like a tire in the form of a ring, thus making a particularlyneat and strong job. The hole cut in the barrel for the dome man-hole isstrengthened by a )4 in. plate riveted around it—a very necessary precau-tion often omitted in locomotive boilers. The boiler rivets are if in. diam-eter, except those in the smoke-box angle-iron, and foundation and fire-holerings, which are fa in. diameter. The holes in the plates were specified tobe punched, and those in the angle-irons drilled, but Messrs. Dubs invaria-bly drill all the holes in the boilers of the engines they make. The tubesare precisely like those of the Mogul engine—fig. 161. They are No. 11B. W. G. thick at the fire-box end and taper to No. 13 at the smoke-boxend, and are composed of a mixture of 70 per cent, of best selected copperand 30 per cent. Silesian spelter. They are fixed in the tube-plates byDudgeon’s patent expander, the fire-box ends being in addition flanged overand ferruled. The fire-box casing is 6 ft. long and 3 ft. n in. wide, thethroat-plate and the sides and top (which latter are made in one piece) are-j'f in. thick, while the back plate is )4 in. thick.
The inside fire-box tube-plate is fa in. thick, all the other plates being-jSg- in. Much diversity of opinion exists as to the proper thickness of fire-box plates when new. Some boiler-makers have found that fas in. standthe longest, presumably because they most readily conduct the heat, butthis does not at the best present any great margin for safety; an fa in. wearreduces the thickness to % in., below which few practical men would careto run fire-box plates. On the other hand, very stout copper plates areused in Germany with great success, and we have seen cases where 180 lbs.pressure has been carried for many years without either leakage or wastingaway of the plates, possibly because they were nowhere less than fa in.thick, the tube-plates being 1 y in. and ryf in. in different engines.
The whole subject of copper plates for fire-boxes is one that demandscareful study; fire-box repairs form a heavy and increasing item on almostall lines, and the secret of making a durable and trustworthy fire-box ofsteel plates seems difficult if not impossible of discovery, and though steelis largely used in the United States , our higher pressures would not admitof such thin plates, while the smaller durability of the cheaper material,apparently entailing frequent and costly repairs and renewals, renders itsuse, in the long run, anything but economical.
The main frames of the engine have a peculiarity which we believewill be new to most of our readers. A difficulty often arises as to themeans of providing clearance for bogie wheels, particularly when they areof large diameter, and the leading wheels especially having a very con-siderable lateral or rather radial movement, a considerable amount of roomis required. Some engines simply have the frames so cut away that thewheels pass clear underneath them. This answers well enough for wheelsup to 3 ft. 3 in. diameter, when the frame must be cut away up to a heightof 3 ft. 7 in. from the rails, or say 2 in. above the centre line of thebuffers ; but it i evident that to cut away the frame still more would seriouslyweaken it, and therefore, to accommodate 3 ft. 6 in. wheels the frameshave often been set in, a lap weld being made, sometimes, in front only ofthe cylinders, and sometimes both before and behind them, thus giving asmall offset to clear the trailing wheel of the bogie, and a larger to clearthe leading wheel, which has, of course, the most motion. In some cases,a massive forging, some 4 in. square, has been carried over the frontbogie-wheel like a splasher, welded to the main frame just in front of thecylinders, and at the other end carrying the buffer-beam. A simpler,cheaper and we think better plan has been adopted by Mr. Bromley toovercome this difficulty. The frames have simply been inclined inwardfrom the motion-plate to the cylinders, whence they continue parallel tothe buffer-beams, where they are 3 ft. 4% in. apart, thus (as they are 1 fain. thick) permitting a side play of 5)4 in. each way to the leading bogie-wheel. As the frames are firmly braced and bound together at the anglescaused by the bends, there is not only no tendency to change of form, buta species of diagonal is introduced which materially stiffens the frame.
The driving and bogie horn-blocks are of cast-steel, the former beingsecured to main frames by sixteen i-in. bolts. The wear between the driving-axle box and the horns can be taken up by a wedge, which is tapered 1 in10, and is not only prevented from slacking back by the screw and checknuts which set it up, but is also clamped to the horn-block by a i-in. boltin a manner first introduced, we believe, on the Great Southern & Westernof Ireland . The wedge being thus firmly and doubly held, no knock cantake place between it and the horn-block, and practice has shown that thisimprovement, trifling as it appears, is of considerable value. The driving-horn stays are flat pieces of wrought-iron, checked into suitable flangeson the horn-blocks, and held to their work by i-in. studs. Weight isput on the driving-wheels through the medium of volute springs of thesame size, and arranged in the same manner as those so successfully used onthe Brighton and North British railway.
The valve-motion is so clearly shown in the drawings that a detaileddescription is hardly necessary. It will be noticed that the top arm of therocking-shaft is the longer, thus increasing the travel of the valve. Therocking-shaft bracket is particularly well secured. We understand none ofthe rocking-shafts in these engines have ever given the slightest trouble,and do not show any signs of knocking. The valves are circular, as in theMogul engines. The eccentric-straps are of wrought-iron with brassliners.
All the tires are of the same width and thickness on tread, 5 fa in., and3 in., respectively, and are fastened in the same way and are of the samerolled, but not of the same finished, section. The driving and middle tenderwheels are parallel on the tread and have % in. thinner flanges than theremaining wheels, which are tapered as is usual, 1 in 20. A safety tire fasten-ing, consisting of two Mansell rings, is being applied on the Great EasternRailway to all wheels, whether for engines, tenders, carriages or wagons, aparticularly neat-looking section having been adopted for the two formerclasses of rolling-stock. The side strain caused by the pressure of theflange against the rail is taken by a plain lip on the tire, which is mani-festly safer than trusting to the tensile strength of the transverse countersunkrivets, which at the junction of each spoke in the rim hold the two Mansellrings together. The rings have then only their proper duty to perform, tokeep the tire from flying off the skeleton, should the former break. Thedriving-wheel has 22 spokes, measuring 4 in. by i)4 in. at the boss, and 3)4in. by 1 )4 in. at the rim. All the other wheels have 10 spokes each, meas-uring on the tender 3)4 in. by 1 fa in. at the boss, and 3 in. by 1 y in. atthe rim, the engine wheel spokes being of the same thickness but havingfa in. greater depth. All the tires and the engine-axles are of cruciblesteel. The driving-axles are 7 fa in. diameter in the centre, while thebearings are 11 in. long x 8 in. diameter, and the wheel-seat measures 8 in.long x 9/4 in. diameter. The bogie and trailing-axles are 5)4 in. diameterin the centre, and have bearings 9 in. x 6 in. The tender axles are ofYorkshire iron and are 6 in. diameter in the centre, 6)4 in. in the boss ofthe wheel, and have outside journals 9 in. long and 5 in. diameter. All theaxle-boxes are precisely similar to those used in the Mogul engine, andtherefore we need say little about them here. The under sides of thejournals are oiled by means of pads pressed up by springs, and the recessesat the top of the boxes are supplied with suitable syphons, so that two in-dependent systems of oiling are provided. *
The connecting-rod is of great length, measuring 7 ft. 6 in. betweencentres. The big-end bearings are 5 in. x 5 in., and the small-end 3)4 in.x 3)4 in. Small ends are now very commonly fitted with a plain brassbush, and the plan has many advantages, the first cost is not great, andthe end can be got up nearly wholly by machine work, and while it is im-