The pipes are best supported on rollers which allow of movement without straining the joints.
The motion communicated to rollers by the pencil serves to cut resistance in or out of the two line circuits which are connected to the rollers, and thus two independent variable line currents are obtained.
CoRACIAE.-Either (I) with long spina externa sterni, Coraciidae, rollers, Old World.
Speed to 60 fathoms for 20 knots, the pull of the line and rotator is borne by coned rollers, having their outlines tapering to a common point in their rotation, thus giving a broad rolling surface.
The bearings and rollers are lubricated with castor oil every twelve hours through holes in the sliding case E, and can be examined by unscrewing the case E and the eye M.
Cuckoos are abundant, some of them of lovely plumage, also rollers, kingfishers and hornbills.
In time it became a common practice to cover them with a thin sheathing or plating of iron, in order to add to their life; this expedient caused more wear on the wooden rollers of the wagons, and, apparently towards the middle of the 18th century, led to the introduction of iron wheels, the use of which is recorded on a wooden railway near Bath in 1734.
He had, however, the courage to act up to his own professions in collocating the rollers (Coracias) with the beeeaters (Merops), and had the sagacity to surmise that Menura was not a Gallinaceous bird.
It consists essentially of two rollers either both of wood, or one of wood and one of iron, geared to revolve in contact in opposite directions; the seed cotton is fed to the rollers, the lint is drawn through, and the seed being unable to pass between the rollers is rejected.
The coagulated rubber separated from the watery fluid is cut up into small pieces and passed through the grooved rollers of the washing machine, from which it issues in sheets, long crinkled ribbons or " crepe," which are then dried in hot air chambers or in a vacuum dryer, by which means the water is dissipated at a lower temperature.
The softened slices are now repeatedly passed between grooved rollers, known FIG.
As washing rollers (fig.
Another very excellent method of vulcanizing cut sheet goods consists in placing them in a solution of the polysulphides of calcium at a temperature of 140° C. Rubber employed for the manufacture of cut sheets is often coloured by such pigments as vermilion, oxide of chromium, ultramarine, orpiment, antimony, lamp black, or oxide of zinc, incorporation being effected either by means of the masticator or by a pair of rollers heated internally by steam, and so geared as to move in contrary directions at unequal FIG.
Most of the rubber now manufactured is not combined with sulphur when in the form of sheets, but is mechanically incorporated with about one-tenth of its weight of that substance by means of the mixing rollers - any required pigment or other matter, such as whiting or barium sulphate, being added.
Air goods, such as cushions, beds, gas bags, and so forth, are made of textile fabrics which have been coated with mixed rubber either by the spreading process above described, or by means of heated rollers, the curing being then effected by steam heat.
Rollers are made to adhere to their metal spindles by the intervention of a layer of ebonite, and after vulcanization they are turned.
It is usually made by incorporating about 40% of sulphur with purified Borneo rubber by means of the usual mixing rollers, shaping the required articles out of the mass thus obtained, and heating for six, eight or ten hours to from 135° to 150°.
For example, Wilde produced copper printing surfaces for calico printing-rollers and the like by immersing rotating iron cylinders as cathodes in a copper bath.
The rope is carried on rollers between the rails.
The ropes are supported between the rails and guided on curves by rollers and sheaves.
There are two modes of installing the system: either the rope passes above the cars and is carried by them, resting in the clips, or it is carried under the cars on rollers, the cars being attached by clips or a gripcarriage.
Rollers up to 5 tons in weight are employed and are now generally driven by power.
The more elaborate patterns found on what is known as " figure rolled plate " are produced in a somewhat different manner; the glass used for this purpose is considerably whiter in colour and much softer than ordinary rolled plate, and instead of being rolled out on a table it is produced by rolling between two moving rollers from which the sheet issues.
In the Paris Exhibition of 1900 a cane-crushing mill was shown with three rollers 32 in.
It is driven by a powerful engine through triple gearing of 42 to 1, and speeded to have a surface velocity of rollers of 15 ft.
In Louisiana two mills, set one behind the other, each with three rollers 32 in.
Long, and driven by one engine through gearing of 15 to 1, are speeded to have a surface velocity of rollers of 25 ft.
Passing the canes through three consecutive sets of rollers, in order to extract everything possible of extraction by pressure) is employed.
To prevent this various implements, such as disk harrows and specially constructed rollers, may be used to consolidate the upper stirred portion of the soil and place it in close capillary relationship with the lower unmoved layer.
This method is rarely practised except by the rollers of zinc. A certain amount of refined zinc can be dipped from the furnace; a further amount, nearly free from iron, can be liquated out of the ingots cast from the bottom of the bath in a subsequent slow remelting, and it is sometimes possible to eliminate a zinciferous lead which collects in the sump of the furnace.
The slides are kept firmly down to their bearings by the rollers r, r, r, r, attached to axes which are, in the middle, very strong springs.
The arrangements for this purpose vary, of course, with the amount of work to be done with one fixing of the machinery; where it is likely to be used for a considerable time, the drum and brake are solidly constructed, and the ropes of steel or iron wire carefully guided over friction rollers, placed at intervals between the rails to prevent them from chafing and wearing out on the ground.
Anthracite coal in Pennsylvania is subjected to breaking between toothed rollers and an elaborate system of screening, before it is fit for sale.
At the centre, spaced by distance pieces nibbed into the plates at the centre and by rollers at the ends.
The draw-bar is connected to the buckle, which is carried on rollers, the ends of the spring resting J on plates fixed to the under-frame.
The chains pass over lofty piers on which they usually rest on saddles carried by rollers, and are led down on either side to anchorages in rock chambers.
Some suspension bridges have broken down in consequence of the oscillations produced by bodies of men marching in step. In 1850 a suspension bridge cable was carried on a separate saddle on rollers on each pier.
There are wrought iron saddles and steel rollers on the piers.
On either side from the towers the chains are carried over similar saddles without rollers, and thence at 45° with the horizontal down to the anchorages.
For spans over 75 ft., expansion due to change of temperature is provided for by carrying one end of each chain girder on rollers placed between the bearing-plate on the girder and the bed-plate on the pier or abutment.
The pressure on the rollers is limited to about p= 600 d in lb per in.
The arch rests on rollers and is narrowest at the crown.
The axis has eight bearings, consisting of rings of live rollers 4 i 7 zin.
In some cases hauling tackle is used, in others power is applied by levers and ratchets to the rollers on which the girders travel.
This was passed again and again between gradually approximated rollers, with occasional annealing, until the desired thickness had been attained.
This fric tion has been greatly re duced by making the draw doors, or sluice-gates, slide on each side against a verti A cal row of free-rollers sus pended by an encircling / chain; and the working .%i/ is much facilitated by FIG.
The barrage at the head of the Nile delta, and the regulating sluices across the Nile at Assiut and Esna in Upper Egypt below Assuan, are examples of draw-door weirs, with their numerous openings closed by sluice-gates sliding on free rollers, which control the discharge of water from the river for irrigation.
The silk to be opened is placed on a latticed sheet or feeder, and thus slowly conveyed to a series of rollers or porcupines (rollers set with rows of projecting steel pins), which hold the silk firmly while presenting it to the action of a large receiving drum, covered with a sheet of vulcanized rubber, set all over with fine steel teeth.
The silk drawn by the rows of teeth on the drum through the porcupine rollers (or porcupine sheets in some cases) covers the whole of the drum, hooked at certain intervals round the teeth; and when a sufficient weight is on the machine, it is stopped, and an attendant cuts, with a knife, the silk along the back of each row of teeth, thus leaving a fringe of silk hooked on the pins or teeth.
The frame is capable of being raised into contact with travelling combs, affixed to an endless belt placed round two metal rollers about 6 ft.