TUBES 1037 



and a new surface is exposed to be operated upon. The next operation after ' floating ' 

 is polishing, which is either effected by hand with list passed round the tube, the 

 tube being lubricated with rotten-stone and oil, or (in the finish of large-sized 

 tubes) an internal buff or hole lined with list or felt, revolves by machinery: 

 the tube being passed in, is polished by the revolution of the buff; the final 

 polish is given by dry list, with powdered dry rotten-stone. Brass tube when 

 finished by burnishing is floated, then scoured with wet pounded clay crucible; 

 then burnished by steel burnishers, gall being applied to hinder their scratching. 

 The last method gives the most brilliant style of finish ; by either mode of finish, 

 they are protected from oxidation by a lacquer applied with a camel's-hair brush when 

 the tube is heated, which is done either by laying the tube to be lacquered on a hot 

 iron plate, or by passing through its interior a jet of steam. On cooling, the protec- 

 tion is perfect and the finish completed. 



Solid Brass Tube, i.e. brass tube drawn without seam, as used for locomotive- and 

 marine-boiler purposes, &c. 



In 1780, Matthew Bolton suggested the introduction of tubes into steam-engine 

 stationary boilers. Trevithick in 1815, in his experiments on engines for locomotive 

 purposes, suggested and applied pipes or tubes, but placed them perpendicularly. 

 Gurney, Summers, and Ogle, in their experiments used also tubes ; and George 

 Stephenson in his ' rocket ' engine, adopted the almost present arrangement of the 

 tubular boiler. By the ordinary, or soldered brass-tube process, the tubes so produced 

 not unfrequently leaked at the joint or seam from imperfect running of the solder, 

 and the production of a ' solid ' or seamless tube became a desideratum. Iron tubes 

 speedily become corroded by the surrounding water in the boiler, and the necessity 

 for finding a substitute in a tube of a material not liable to oxidise and of sufficient 

 strength to resist the exigencies of wear and tear, became a desideratum. Economi- 

 cally, also, the brass tube is in the end cheaper, as the old tubes are taken back by the 

 manufacturers in exchange for the new at a trifling advance in order to cover expense 

 of re-manufacture. Up to the year 1838, tubes for locomotive- and marine-engines 

 were either formed of welded iron, or of brass tube produced by soldering at the 

 joints. In that year, however, Mr. Green of Birmingham conceived and carried 

 into practice the production of seamless brass tubes, in a manner akin or similar to 

 that already described in the production or manufacture of lead and block-iron tube ; 

 i.e. he cast the brass or copper ' billet,' from which the future tube was to be made 

 in moulds, inserted a mandril" into the aperture produced by the sand 'core,' made 

 an alteration in the drawbench, increasing its strength, and operated on its motion 

 by reducing the speed, thereby increasing its power, in order to overcome the stubborn 

 nature of tho brass or copper billet operated upon. By reference to cut of drawbench, 

 Jig. 2025, the large wheel is not operated upon in the manufacture of solid brass tube, 

 by a pinion as shown, but by an endless screw which worked into corresponding 

 threads on the outer surface of the large wheel, and the die was formed not of one, 

 but four parts, i.e. as four revolving pulleys placed at an angle to each other, forming 

 a round hole or die in the centre ; the brass billet or copper with its mandril similar 

 in form to that already shown. It was then subjected to the action of the drawbench, 

 and gradually reduced by the action of the four-roll tool to the desired external size 

 and the strength of metal desired. Eepeated annealings are required in the process 

 of drawing, in order to restore the ductility of the metal of the partially-drawn billet, 

 which is eventually converted into the finished locomotive tube. The metal or brass 

 of which these tubes are composed is made from the best copper and zinc or spelter, 

 as such tubes are replaced every three years ; when worn out they are sold to manu- 

 facturers for reconversion into similar tubes, or command good prices for raw material, 

 to be used for other purposes in the brass foundry trade. 



Another method or process for the manufacture of solid brass tube is also in use, 

 which was introduced in 1852 by G. F. Muntz, junior, and made from the metal 

 familiarly known as ' Muntz's ' metal, which possesses the property of being worked, 

 rolled, or manipulated at a low red heat. (See MTTHTZ METAL and SHEATHING.) In 

 this, as in Green's process, the raw material is presented in ' billet ' form for manu- 

 facture into finished tube. This process may be described as follows : 



Tho ' billet ' out of which the future tube is intended to be made is cast in an iron 

 mould with a sand-core : the billet is oval in form, the metal being thickest on the two 

 largest surfaces of the oval. The billet being cast, and the sand removed from its 

 interior, the interior is coated with a wash of lime-water and salt. This prevents the 

 adhesion of the interior surfaces of the metal together in the process of rolling the 

 billet to the length of the intended tube. This is effected by means of rolls grooved in 

 their circumference. In the ordinary process of rolling metal, it will be observed that 

 it is simply elongated by the thickness being reduced, but its breadth is not increased ; 

 the thickness of the metal of the ' billet' in the upper and under side therefore provides 



