Still higher speeds, up to 75 or even 80 m.
For speeds over six knots a 14-second glass is employed, and the speed indicated by the log-line is doubled.
Or more which are now performed by several railways in Great Britain, and on which average speeds of 54 or 55 m.
Steam at high pressure exhausting into the atmosphere is still commonly used, but the great power required for raising heavy loads from deep pits at high speeds has brought the question of fuel economy into prominence, and more economical types of the two-cylinder tandem compound class with high initial steam pressure, superheating and condensing, have come in to some extent where the amount of work to be done is sufficient to justify their high initial cost.
4), a taffrail one, which, however, is not as a rule used for speeds over 18 knots.
The duty of a railway with deficient plant or facilities would seem to be to make up for their absence by moderating the speeds of its trains, but public sentiment in America appears so far to have approved, at least tacitly, the combination of imperfect railways and high speeds.
The high and heavy cars, the high speeds, the severe weather in the northern states in winter, the fluctuating nature of the business, resulting often in the employment of poorly qualified men and in other irregularities, are among the causes of this state of things.
Such trains, therefore, range in weight from 600 to 1800 tons or even more, and the journey speeds from terminus to terminus, including stops, vary from 15 to 30 m.
Again, low speeds, light stock, less stringent requirements as to continuous brakes, signals, block-working and interlocking, road-crossings, stations, &c., tend to cheapness in working.
Hittorf (1853) to the unequal speeds with which he supposed the two opposite ions to travel.
For other speeds the power varies as the cube of the speed.
Generally: (I) At speeds less than 25 m.
Several stars appear to have speeds exceeding Ioo m.
Per second; several stars (Groombridge 1830 among them) have radial speeds of this amount.
Trans., 1894) investigated the question for the cases of loaded and unloaded shafts, and, owing to the complication arising from the application of the general theory to the cases of loaded shafts, devised empirical formulae for the critical speeds of shafts loaded with heavy pulleys, based generally upon the following assumption, which is stated for the case of a shaft carrying one pulley: If Ni, N1 be the separate speeds of whirl of the shaft and pulley on the assumption that the effect of one is neglected when that of the other is under consideration, then the resulting speed of whirl due to both causes combined may be taken to be of the form N1N2~!
The agreement between the observed and calculated values of the critical speeds was in most cases quite remarkable.
Speeds can be regulated to a nicety for each separate machine, and any machine can be set in motion by pressing a button.
The obstacles are (I) the smallness of the waves, and (2) the changes which occur at speeds too rapid for the eye to follow.
The eruptive prominences, called also metallic, because it is they which show at their bases a complete bright line spectrum of the metallic elements, rush upwards at speeds which it is difficult to associate with transfers of matter; the velocity often exceeds loo m.
A common arrangement for driving a lathe spindle, in either direction at several definite speeds, is to provide a countershaft on which are mounted two fixed pulleys and two loose pulleys to accommodate two driving belts from the main shaft, one of which is open and the other crossed.
The sea pierces the islands in deep fjords, or separates them by narrow inlets through which tidal currents set with great violence, at speeds up to seven or eight knots an hour; and, as communications are maintained almost wholly by boat, the natives have need of expert watermanship. There are several lakes in which trout are abundant, and char also occur; the largest is Sdrvaag Lake in Vaagd, which is close to the sea, and discharges into it by a sheer fall of about 160 ft.
Fresnel showed that rotary polarization could be explained kinematically by supposing that a plane-polarized stream is resolved on entering an active medium into two oppositely circularly polarized streams propagated with different speeds, the rotation being rightor left-handed according as the rightor left-handed stream travels at the greater rate: The polarization-vector of the primitive - stream being = a cos nt, the first circularly polarized stream after traversing a distance z in the medium may be represented by = a cos (nt - k i z), ni = a sin (nt - kiz), and the second b z = a cos (nt - k 2 z), n2= - a sin (nt - k2z).
Since the two circular streams have different speeds, Fresnel argued that it would be possible to separate them by oblique refraction, and though the divergence is small, since the difference of their refractive indices in the case of quartz is only about o 00007, he succeeded by a suitable arrangement of alternately rightand left-handed prisms of quartz in resolving a plane-polarized stream into two distinct circularly polarized streams. A similar arrangement was used by Ernst v.
But no increase in the coefficient of friction had been detected at slow speeds, until the experiments of Prof. Fleeming Jenkin (Phil.
Instead of science proceeding at the slow speed of time, the only limit on its progress will be processor speed—and those two speeds hardly can be compared.
To "heave the log," a man holds the log-reel over his head (at high speeds the man and portable reel are superseded by a fixed reel and a winch fitted with a brake), and the officer places the peg in the log-ship, which he then throws clear and to windward of the ship, allowing the line to run freely out.
With increase of speeds this matter has become important as an element of comfort in passenger traffic. As a first approximation, the centre-line of a railway may be plotted out as a number of portions of circles, with intervening straight tangents connecting them, when the abruptness of the changes of direction will depend on the radii of the circular portions.
In this case electricity was to be the motive-power, and speeds exceeding ioo m.
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.
Aspinall on the Lancashire & Yorkshire railway to ascertain the resistance of trains of bogie passenger carriages of different lengths at varying speeds, and the results are recorded in a paper, " Train Resistance," Proc. Inst.
This formula is valid between speeds of 37 and 77 m.
Any modification of the design which will reduce the resistance to the flow of steam through the steam passages at high speeds will increase the piston speed for which the indicated horse-power is a maximum.
In all countries passenger trains must vary in weight according to the different services they have to perform; suburban Weight trains, for example, meant to hold as many pas ah d sengers as possible, and travelling at low speeds, do not weigh so much as long-distance expresses, which include dining and sleeping cars, and on which, from considerations of comfort, more space must be allowed each occupant.
An hour; while usually the fastest express trains maintaining inclusive speeds of say 45 m.
But isolated examples of high speeds do not give the traveller much information as to the train service at his disposal, for on the whole he is better off with a large number of trains all maintaining a good average of speed than with a service mostly consisting of poor trains, but leavened with one or two exceptionally fast ones.
High speeds are often attained.
In deep shafts hoisting speeds of 3000 or 3500 ft.
Though it is small and simple in construction for light work, for heavy hoisting at high speeds massively framed towers, often 80 to ioo ft.
The friction of water, investigated for slow speeds by Coulomb, was measured for higher speeds by William Froude (1810-1879), whose work is of great value in the theory of ship resistance (Brit.
Heliometer, completed in 1887 for the Royal Observatory at the Cape of Good Hope, Repsolds, on Gill's suggestion, introduced the following improvements: (a) Four different speeds of motion in position angle were provided.
The pins in the two rollers oppose each other, those of the workers being "back-set," and this arrangement, combined with the relative angle of the pins, and the difference in the surface speeds of the two rollers, results in part of the fibre being broken and carried round by the worker towards the stripper.
The ratio of the surface speeds of the drawing roller and the feed roller is termed the draft: surface speed of drawing roller _ draft.
Or less up to 1200 m., and the speeds relative to the spot range up to 2 or 3 m.
At high speeds the centrifugal tension of the belt or rope, of amount wv 2 /g, may be considerable, and must be subtracted from the end tensions.
These logs were towed from the ship, but with quick passages and well surveyed coasts, the need arose for a patent log which could be readily consulted from the deck, and from which the distance run under varying speeds could be quickly ascertained.