All cylinders drive on one crank-axle with three cranks at 120°.
The horsepower available at the driving-axle, conveniently called the brake horse-power, is from 20 to 30% less than the indicated horse-power, and the ratio, B.H.P./I.H.P. =E, is called the mechanical efficiency of the steam engine.
This disk is carried on an axle inclined to the line of draught, and also to a vertical plane.
There are two soft iron tongues, n, s, fixed upon and at right angles to an axle a, which works on pivots at its ends.
16, which shows in a diagrammatic form a wheel and axle connected to the framework of a vehicle, in the way adopted for railway trains.
In the second case every axle in the train may be made a driving-axle if desired, in which case the locomotive as a separate machine disappears.
If T is the mean torque, the work done on the crank-axle per revolution is 27rT.
This is done by the little crank B on the axle of the fly-wheel, acting through the rod C, and the bent lever D, which forms a toggle-joint at E with the vertical piece of metal below it.
When portable cranes are fitted with springs and axle-boxes, drawgear and buffers, so that they can be coupled to an ordinary railway train, they are called " breakdown " or " wrecking " cranes.
Let a couple be applied to the axle tending to turn it in the direction shown by the arrow.
Assuming the wheels to roll along the rail without slipping, this couple will be equivalent to the couple formed by the equal opposite and parallel forces, F 1 acting in the direction shown, from the axle-box on to the frame, and F 1 =µ0, acting along the rail.
The couple T is necessarily accompanied by an equal and opposite couple acting on the frame, which couple endeavours to turn the frame in the opposite direction to that in which the axle rotates.
Motors may be applied to every axle in the train, and their individual torques adjusted to values suitable to the weights naturally carried by the several axles.
V hen the train is started and is moving slowly, the toroue acting on the driving-axle may be estimated as that due to about 85°/, of the full boiler pressure acting in the cylinders.
This would be distributed between three coupled axles giving an average of 1.38 tons per axle, though the distribution might not in practice be uniform, a larger proportion of the weight falling on the driving-axle.
Engines of this class, with 78-inch driving wheels and the leading axle fitted with Webb's radial axle-box, for many years did excellent work on the London & North-Western railway.
(4) " Four-coupled " three-axle type, with trailing axle, 0-4-2.
The advantages claimed for it are: short coupling-rods, large and unlimited fire-box carried by a trailing axle, compactness, and great power for a given weight.
(5) " Four-coupled " type, with a leading bogie truck and a trailing axle, 4-4-2.
Occasionally a somewhat similar type is designed with the bogie under the fire-box and a single leading axle forward under the smoke-box - an arrangement in favour for suburban tank engines.
(8) " Six-coupled " type, with a leading axle, 2-6-0.
Occasionally the American eight-coupled type has a bogie instead of a single leading axle (4-8-0), and is then termed a " Twelve-wheeler," or " Mastodon."
(11) " Ten-coupled " type, with a leading axle, 2-10-0.
It is used to a limited extent for mountain-grade goods traffic, and has the advantage over the " Consolidation " or eight-coupled type of lighter axle loads for a given tractive capacity.
In both the four-wheeled and the six-wheeled types the axles were free to rise and fall on springs through a limited range, but not to turn with respect to the body of the carriage, though the middle axle of the six-wheeled coach was allowed a certain amount of lateral play.
Gauge, and laid with rails weighing from 50 to 70 lb per yard; a flat-footed 60 lb rail, with the axle load limited to 14 tons, has the advantage for such lines that it permits the employment of a proportion of the locomotives used on main lines.
The orders actually granted have allowed 50 lb, 56 lb, 60 lb and 70 lb rails, with corresponding axle loads of 10, 12, 14 and 16 tons.
0.5 in.); weight of rails, 12 (26.45 lb) to 20 (44 lb) kilos; mean load per axle, 6 tons; minimum curve, 70 m.
4.85 in.); locomotives, maximum weight per axle 6 tons, rigid wheel base 1 .
The power is applied by steam acting directly on a crank at one end of the axle, and the diameter of the fan may be 40 ft.
By numerous guide blades, dividing it up into a series of rectangular tubes of diminishing section, attached to a horizontal axle by cast iron bosses and wrought iron arms. The tubes at their smallest part are connected to a cast iron ring, io ft.
The pulley E is driven from an axle of the carriage.
The gear operating the paper roll is driven from the axle of an inde pendent wheel which is let down into contact with the rail when required This wheel serves also to measure the distance travelled.
36 gives the loads per axle and the distribution of loads in some exceptionally heavy modern British locomotives.
When the agreed-on weight is on the drum, the silk is drawn across the face of the drum parallel with its axle, and pulled off in form of a sheet, and is called a lap. This lap is thin, but presents the fibres of silk now joined and overlapped in a continuous form, the length measured by the circumference of the drum.
The motion of the rod consequent to a motion of the case is modified by the projecting axle of the stationary mass, and after much magnification is recorded on a sheet of smoked paper.
Corn is threshed by a norag, a machine resembling a chair, which moves on small iron wheels or thin circular plates fixed to axle-trees, and is drawn in a circle by oxen.
The siphon is supported on a vertical axle carrying two armatures which are acted upon by two electromagnets.
An axle carrying four cams is normally at rest, but it is thrown into gear with the mechanism when the armature rises, makes one complete revolution, and comes to rest ready for the next signal.
The rate at which work is done on a particular axle is measured by the product where T is the torque or turning moment exerted on the axle by the motor or mechanism applied to it for this purpose, and is the angular velocity of the axle in radians per second.
The journal of the axle A, is carried in a bearing or axle-box B, which is free to move vertically in the wide vertical slot G, formed in the frame and called generally " the horns," under the control of the spring.
The weight W 1 carried by the part of the frame supported by the wheel (whose diameter is D) is transmitted first to the pins P 1, P2, which are fixed to the frame, and then to the spring links L 1, L2, which are jointed at their respective ends to the spring S, the centre of which rests on the axle-box.
If the speed is given in miles per hour, S say, V =1.466 S (6) The revolutions of the axle per second, n, are connected with the radians turned through per second by the relation n =w/27r = w/6.38 (7) § 2.
Every axle of an electric locomotive may thus be subjected to a torque, and the large weight which must be put on one pair of wheels in order to secure sufficient adhesion when all the driving is done from one axle may be distributed through as many pairs of wheels as desired.
The fundamental difference between the two methods is that while the mechanical energy developed by a steam engine is in the first case applied directly to the driving-axle of the locomotive, in the second case it is transformed into electrical energy, transmitted over relatively long distances, and retransformed into mechanical energy on the driving-axles of the train.
7 he torque exerted on the driving-axle by the steam engine just at starting may be that due to the full boiler pressure acting in the cylinders, but usually the weight on the coupled wheels is hardly sufficient to enable advantage to be taken of the full boiler pressure, and it has to be throttled down by the regulator to prevent slipping.
It has many advantages for heavy high-speed service, namely, large and well-proportioned boiler, practically unlimited grate area, fire-box of favourable proportions for firing, fairly low centre of gravity, short coupling-rods, and, finally, a combination of the safe and smooth riding qualities of the fourcoupled bogie type, with great steaming capacity and moderate axle loads.
(io) " Eight-coupled " type, with a leading axle, 2-8-0.
In most of the systems that have been proposed this result is attained by electrical regulation; in one, however, a mechanical method is adopted, the dynamo being so' hung that it allows the driving belt to slip when the speed of the axle exceeds a certain limit, the armature thus being rotated at an approximately constant speed.
Electricity is applied through a separate locomotive attached to the head of the train, or through motor carriages attached either at one end or at both ends of the train, or by putting a motor on every axle and so utilizing the whole weight of the train for traction, all the motors being under a single control at the head of the train, or at any point of the train for emergency.
With rows of coarser straight teeth, each row set parallel with the axle of the machine.
By an invention probably due to Humfray Cole and published in 1 578 by William Bourne in his Inventions and Devices, it was proposed to register a ship's speed by means of a "little small close boat," with a wheel, or wheels, and an axle-tree to turn clockwork in the little boat, with dials and pointers indicating fathoms, leagues, scores of leagues and hundreds of leagues.
Hence if all the energy supplied to the train is utilized at one axle there is the fundamental relation RV (I) Continuing the above arithmetical illustration, if the wheels to the axle of which the torque is applied are 4 ft.
The low-pressure cylinders drive on the leading crank-axle with cranks at right angles, the highpressure cylinders driving on the trailing wheels.
(3) " Four-coupled " three-axle type, 2-4-0.
Apart from this general meaning of the word, the chief transferred use is that for a piece of wood used for various specific purposes, as a framework, bar, &c., such as the tree of a saddle, axle-tree, cross-tree, &c.
Diamonds are now employed not only for faceting precious stones, but also for cutting and drilling glass, porcelain, &c,; for fine engraving such as scales; in dentistry for drilling; as a turning tool for electric-light carbons, hard rubber, &c.; and occasionally for finishing accurate turning work such as the axle of a transit instrument.
The substitution of steel for iron as the material for rails which made possible the axle loads and the speeds of Lto-day, and, by reducing the cost of maintenance, contributed enormously to the economic efficiency of railways, was one of the most important events in the history of railways, and a scarcely less important element of progressive economy has been the continued improvement of the steel rail in stiffness of section and in toughness and hardness of material.
The relation between the b.h.p. and the torque on the driving-axle is 55 o B.H.P. =Tu., (9) It is usual with steam locomotives to regard the resistance R as including the frictional resistances between the cylinders and the driving-axle, so that the rate at which energy is expended in moving the train is expressed either by the product RV, or by the value of the indicated horse-power, the relation between them being 55 0 I.H.P. =RV (Io) or in terms of the torque 55 0 I.H.P.X€=RVe=TW (II) The individual factors of the product RV may have any value consistent with equation (to) and with certain practical conditions, so that for a given value of the I.H.P. R must decrease if V increases.