Babbet's anti-friction metal, to be used somewhat after the manner of tin, for the bearings of machinery, is thus described: -
Tin or compounds like the above used alone, owing to their softness, spread and escape under the superincumbent weight of locomotive engines, and other heavy machinery; and therefore brasses or bearings are employed under this patent to support the softer metal, but the brasses are made larger in diameter, and with internal fillets that almost touch the axles, so as to prevent the thin lining of the anti-friction metal from spreading and being pressed out.
The brasses are first cleaned and tinned, and an exact iron model of the axle baring been turned, the parte are heated, put together in their relative positions, luted with plastic clay, and the fluid anti-friction metal is poured in, which then becomes of the required form, and effectually soldered to the brass. The anti-friotion metal scarcely appears to suffer from wear, and owing to its unctuous greasy nature, requires much lees oil than other metals and alloys used for bearings.
See Letters Patent granted to Wm. Newton, 15th May, 1843, for "Certain improvements in the construction of boxes or axletrees of locomotive engines and carriages, and fur the bearings or journals of machinery in general, and also improvements in oiling or lubricating the same. Being a communication, &c"
Note X, page 285, at foot, and 802. - Before "The Palladiumizing process."
(Cranfurd's Patent for Galvanized Iron.)
At the time the author inserted in his former volume the account of Mallett's process for coating iron with one and palladium, be accidentally overlooked a previous patent granted to Mr. Henry William Craufurd, April, 1887 (and described in the " Repertory of Patent Inventions," Vol. ix, New Series, page 289), he will now proceed to supply the deficiency; and also to give some particulars of another method by which iron that has been previously tinned is also coated with zinc.
In Mr. Craufurd's patent, sheet iron, iron castings, and various other objects in iron, are cleaned and scoured by immersion in a bath of water, acidulated with sulphuric acid, heated in a leaden vessel, or used cold in one of wood, just to remove the oxide. They are then thrown into cold water, and taken out one at a time to be scoured with sand and water with a piece of cork, or more usually a piece of the husk of the cocoa nut, the ends of the fibres of which serve as a brush, and the plates are afterwards thrown into cold water.
Pure zinc covered with a thick layer of sal-ammoniac is then melted in a bath, and the iron, if in sheets, is dipped several sheets at a time in a cradle or grating. The sheets are slowly raised to allow the superfluous zinc to drain off, and are thrown whilst hot into cold water, on removal from which they only require to be wiped dry.
Thick pieces are heated before immersion in a reverberatory furnace, to avoid cooling the zinc. Chains are similarly treated and on removal from the zinc require to be shaken until cold to avoid the links being soldered together. Nails and small articles are dipped in muriatic acid, and dried in a reverberatory furnace, and then thrown altogether in the zinc covered with the sal-ammoniac, left for one minute, and taken out slowly with an iron skimmer; they come out in a mass soldered together, and fur their separation are afterwards placed in a crucible and surrounded with charcoal powder, then heated to redness and shaken about until cold, for their separation. Wire is reeled through the zinc, into which it is compelled to dip by a fork or other contrivance.
It is to be observed that the zinc is melted in a bath or crucible just a little beyond the point of fusion, and is always covered with a thick coat of sal-ammoniac, both to prevent the waste of the zinc, and further to prepare the metal that is to be zinced. Cast-iron baths or vessels, such as are used for melting tin or pewter, were first employed, but sine acta very rapidly upon the cast-iron, unites with it, and falls in a granular state to the bottom of the vessel; therefore an earthen lining of fire brick, luted with clay, was, with some difficulty and lost of heat, maintained in the cast-iron vessel, to defend the same from the action of the zinc.
(Craufurd's patent, 1837.) Now, however, wrought-iron baths welded at the angles are used without the clay lining (Morewood & Rogers's patent, 1841), as the deterioration both of the zinc and of the vessel are then less rapid, and the process succeeds better than when cast-iron baths are employed. The spoiled granulated metal, which is only considered to contain about five per cent. of iron, is ladled out and returned to the zinc manufacturers for purification or re-manufacture.
Note Y, page 285, at foot, and 302. - Before "The Palladiumizing process" (Morewood and Rogers's Galvanised Tinned-iron.)
Mr. Edmund Morewood's process is different, and is declared in his patent dated 1841 - "to consist in tinning the metals to be preserved from oxidation as aforesaid, in the ordinary manner of what is called tinning, and then, in what I call zincing the said tin, so that the external surface may be zinc, placed in such relation with the tin, and the metal to be preserved from oxidation, as that both the said tin and zinc should have a united or combined influence in preserving the said metal." See "Repertory of Patent Inventions," New Series, Vol. xviii. page 170.
The present practice is, however, different from the above, as the iron is covered with tin by a galvanic deposition, as in the electrotype process, and is afterwards zinced in a bath of the fluid metal. The following is the practice, which is secured by subsequent patents, enumerated further on.