Mav 1, 1920. J 



THE INDIA RUBBER WORLD 



513 



THE BUNSEN BURNER IN RUBBER REPAIR. 



By Arthur C. Squins. 



EvKKv RUBBER MAX knows that melting rubber spoils it. 

 whether the rubber is vulcanized or not, but, like many 

 other rules conserving rubber, there are exceptions. A well- 

 known case in point is the sticking of the iron shafts into rubber 

 wringer rolls. This has .been done successfully for years by 

 heating the shaft red hot and forcing it through the rubber roll. 

 The hot iron melts the rubber that it comes in contact with and 

 forms a tenacious film that is tremendously adhesive. Indeed, 

 it is one of the strongest bindings known. 



Along the same line is the melting of a vulcanized rubber sur- 

 face for patching. This has also been done witli a hot iron, but 



surface treated with the tlame of the burner. The \ ulcanized 

 rubber is semi-devulcanized and its surface rendered very sticky. 

 After it is applied as a new tread and vulcanized it forms a 

 vcrj- tenacious and durable stock at a small cost. 



Prep 



Tire for Retreading by the Blue-Flame Process. 



a better way is to use a controlled blue flame ; for this the 

 Bunsen burner or blow-torch is ideal. A quick searing of a 

 rubber surface — being careful not to scorch the fabric — effects a 

 semi-devulcanization of the rubber surface and melts some of 

 the rubber. A patch cemented on this never lets go. Hof water 

 bottles, which are most difficult of repair, respond to this method 

 better than to any other. So, too, mner tubes are exceedingly 

 well mended by the blue-fiame method. The applicability of it to 

 auto tires has also quite lately been thoroughly demonstrated. 

 Even auto tires which have been worn down nearly to the fabric 

 (if the carcass are being successfully semi-devulcanized and re- 

 treaded by this new method. 



It is not necessary to file, roughen or clean the worn parts 

 of a tire, as has been customary. The blue flame removes all 

 foreign tnatter, sulphur bloom, and moisture, leaving a clean, 

 sticky surface. This is covered with a solution consisting of 5 

 per cent pure rubber dissolved in 95 per cent of carbon 

 tetrachloride or benzol and given time to dry. 



.\ new tread is best constructed by applying 2-inch-wide strips 

 of unvulcanized tread stock to the sticky tread surface and 

 stitching the strip smooth and fast all around the face of the 

 tire. The new tread is formed of strips of semi-devulcanized 

 stock cut to the desired width and thickness of the tread, super- 

 posed and stuck fast on the unvulcanized strip. Next a 

 strip of unvulcanized tread stock cut wide enough to cover and 

 overlap the built up tread completely around the circumference 

 of the tire completes the assembly that is now ready to be cured 

 in a sectional vulcanizer or retreading mold. 



A complete new tread built en a tire 4^ by 35 inches requires 

 2;/ pounds of new unvulcanized stock and 714 pounds of vul- 

 canized tire strippings. The weight of the retread stock used 

 in retreading a tire should be known. This fact can be ascer- 

 tained by vulcanizing a foot length of standard retreading stock 

 in the mold free from contact with the tire. 



The semi-vulcanized stock mentioned is tlius prepared. Tread 

 strippings from worn tires are cut to the proper width and the 



ALUMINUM IN THE RUBBER INDUSTRY. 



Cteel and iron mandrels, molds and cores have been and still 

 •^ are very generally used in many branches of the rubber in- 

 dustry. Similarly maple forms or lasts have been the rule in the 

 manufacture of rubber boots and overshoes. Steel, iron and 

 wood leave much to be desired in the way of adaptability, though 

 from differing ctuses. 



Mandrels, molds and cores are not only heavy to handle, but 

 used in connection with the process of vulcanization are more or 

 less seriously subjected to rusting and pitting, thus transferring 

 rough and discolored surfaces to the rubber cured in contact with 

 these defects. 



Boot trees and lasts for large overshoes where made of maple 

 wood are subject to deterioration by the heat of vulcanization and 

 undergo a slow carbonization with the result that when continu- 

 ously handled, as they are, the sharp angles wear away rapidly, 

 thus changing the form and fit of the goods made upon them. 



These defects have been very completely removed by the intro- 

 duction of aluminum alloy to replace steel, iron and wood, par- 

 ticularly for the places indicated. A few facts with regard to 

 aluminum will be of interest in this connection. 



INNER TUBE MANDRELS AND CORES. 



In the first place sulphur has no effect on it at all: further, it 

 is light, having little more than one-third the weight of iron. 

 This is important for the men who handle the mandrels. .\ two- 

 inch aluminum tube _ 

 ten gage and ten 2HK ^ i^. ..^'^'^'"^"^i^taiLvi 

 feet long will weigh 

 about nine pounds, 

 while the same man- 

 drel in iron will 

 weigh twenty - si.x. 

 This makes con-^id- 

 erable difference in 

 the speed with 

 which the mandrel 

 can be handled. The 

 illustration shows a 

 couple of tube man- 

 drels used in an English tire factory and in accordance with 

 their usual practice they are curved to the form of the tire. 

 Still it is found that the rubber tube is quite easily peeled off. 



Aluminum cores are also used for outer covers, but in the- 

 shape of a closed circle the joint in the metal being carefully- 

 welded. Tube mandrels are, of course, made of smaller tube in. 

 straight lengths, but whereas a steel one will weigh a hundred 

 pounds the same apparatus in alumintnn will only weigh thirty. 



LABELS FOR BRANDING HOSE, TIRES, ETC. 



.-\luniinum can be rolled very thin, in fact, nearly as thin as 

 gold, and there is a great demand for strip about ten one-thou- 

 sandths of an inch thick for brands. When a pattern or lettering 

 has to be stamped on a rubber hose or tire it is, of course, neces- 

 sary to intcrpo.sc a thin strip of metal bearing the lettering or 

 design to be impressed in the rubber. Some rubber manufac- 

 turers use tin for this purpose, but tin is more than three times 

 as heavy, and although it costs more to the pound, aluminum is 

 at least seventy-five per cent cheaper, because of the greater area 

 due to its lesser gravity. 



ALUMINUM TIRES AND LASTS. 



Riibl'cr boots and overshoes are now made on aluminum lasts 

 of a special alloy devised by a British company for this purpose- 

 This metal pours freely into the mold, and is strong and easily 



.Aluminum 



