TIN

although deposits of tin are widely dis- tributed, the two areas of chief importance are the asiatic depos- its, comprising malaya, siam and china, and those of bolivia. these two areas provide about 85° of the world’s total output. until 1916 the british empire production exceeded that of foreign countries; but since that date, owing to the enlarged output from bolivia and the dutch east indies, the production of foreign countries has been the larger. in 1925 the world's most impor- tant producer of tin was still the federated malay states where the alluvial deposits of the kinta valley form the richest tinfield. the methods of working are ground sluicing and hydraulic min- ing; open cast-workings; underground workings and dredging. in burma the most important occurrences of tinstone are in the bawlake state of karenni, at the mawchi mines, in the amherst district (a) at belugyum, (4) east and west of the seludang range; and in the thaton, tovoy and mergui districts. the burmese mineralised belt continues southwards through the f.m.s. to the islands of singkef, banka and billiton in the dutch east indies, thus forming the world’s richest tin-producing area. in 1924 1t supplied over 60% of the world’s total output; and the dutch east indies alone contributed no less than 23-2% of the world’s production. it was, however, stated in 1925 that within 12 years the bulk of the rich secondary deposits of dutch east indies, of malaya, of siam and of lower burma will have been exhausted. other asiatic occurrences of tin are those of french indo-china in the province of tongking; in china, in the provinces of yunnan, kwangsi, hanan, kwangtung and fukien; tires and in japan in (a) the akenob district, tajima province, (d) the taniyama mine, satsuma province, (c) the kiura mine, bun- go province, (¢) mines near takayama and hirukawa, mine province. in north and central america cassiterite is known to occur in very small quantities, also in canada, united states, mexico and british honduras. the most important producer in south america is bolivia, whose tinfields supplied 21-4 % of the world’s total output'in 1924. the chief mines occur in la paz, cocha- bamba, oruro and potosi. the most important point about the bolivian deposits is that they are primary, and lode-mining is much more likely to yield larger outputs over a longer period of future years than is the case with the asiatic deposits. tin 1s widely distributed in australasia—all the states of the common- wealth of australia and also new zealand produce the mineral— but in 1923 the whole area yielded only 23° of the world's total production. in the continent of africa the most important tin producer is nigeria (bauchi plateau), followed by the union of south africa and swaziland. other contributing countries are the gold coast, nyassaland, belgian congo, portugese east africa, south west africa and rhodesia. in 1924 the continent of africa produced 5°47% of the world’s production of tin for that year, of which 4°47% was contributed by nigeria. in europe the chief producing countries are great britain, czechoslovakia, germany, portugal and spain. with regard to the mines in cornwall and devon, during the so years ending 1800 the output varied between 2,000 and 3,500 tonsa year. the maximum output during the war was 6,537 in 1914. by 1922, when so few mines were working, the production was only 370 tons. by 1924, owing to the greatly improved conditions, the fig- ure had risen to 1,725. in 1925 about 95% of the production oc- curred in the camborne-redruth area. the following table gives the world’s production, in long tons, of tin ore for 1913, 1918 and 1923. 1913 1918 1923 united kingdom 5,288 bos 1 1,021 nigeria . 3;872 5,904 5,860 swaziland . 270 358 107 union of s. africa 2,251 1,422 918 india (burma) : : 303 647 1,400 straits settlements . ’ : 7 22 6 federation of malay states 50,125 | 37,360] 37,643 unfederated malay states 1,241 2,720 l727 australia : ; 2 7,780 4,747 3,283 approx. total 71,100 | 57,100 | 52,000 bolivia : : 26,327 | 29,104 | 29,767 dutch east indies 20,541 | 19,200 | 31,019 siam. : : 6747 8,835 6,334 china . ; 8,408 8,730 8.727 other countries . 200 226 1,740 approx. total 62,000 | 66,100 | 78,600 world’s total (approx.) 133,200 | 123,200 | 130,600 the 1924 total was approximately 137,860 long tons. bribliograppity.—j. m. ifill, “ tin: its political and commercial control,” fug. and mining journ., vol. 109 (1920); e. f. kern, “electrolytic refining of tin,” trans. aimer. eleciro-chem. soc., vol. 38 (1920); a. c. vivian, ‘' tin—phosphorus alloys,’' journal inst. metals, vol. 23 (1920); g. p. baxter and h. w. starkweather, * electrolytic estimation of tin,"’ journal amer. chem. soc., vol. 42 (1920); j. d. falconer, ‘‘ the geology of the plateau tin fields,” geol. surv. nigeria, bull. t (1921); n. m. penzer, tin resources of the british empire (1921), containing a full bibliography of works published from 1912-20; w. r. jones, tinfields of the world (1925). (nw wl pe.) tires (sce 26.1006).—structurally tires are divided into two main classes: solid rubber and pneumatic. the cushioning prop- erties of solid (american) or band (british) tires come from the elasticity of the rubber and the depth of the tread. there is a sub-class of solid tires, designated by the name of cushion tires. in pneumatic tires compressed air serves both as the cushioning and load-supporting medium. the rubberised fabric structure 781 of the casing in this case serves as a flexible, yielding container for the compressed air. | history.—in 1910 the motor-vchicle industry used the ‘clincher ” or “ beaded edge’ pneumatic tire constructed with square woven fabric. these tires in 1910 averaged only 3,000 to 4,000 m. of service. the clincher design of the rim and bead com- bination (fig. 1) as a method of attachment of tire to the rim had its limitations, particularly in the larger sizes, so that progress in improving the service of tires of this type was discouraging. the principle of the bead of the dun- lop-welch wired-on bicycle tire was then developed and intro- duced under the name of the “straight-side” bead. this idea first became practical for motor-vehicle use in 1907, when an american manufacturer (the goodyear tire and rubber co.) offered to the american public its “‘ detachable ”’ straight-side rim and tire (fig. 2). its progress was slow because of competitive hindrances, but by roro the merits of the detachabie rim obliged the clincher tire manufacturers to furnish some sort of a detach- able tire. the result was the ‘f quick-detachable ” (q.d. clincher), a tire fitting a detachable clincher rim and having its beads shaped like the regular soft bead clincher, but with an inextensible wire bead core like the straight-side tire. during this period of de- velopment, the q.d. clincher served as a transition type. the merits of the straight-side construction, however, grad- ually made it more popular than the q.d. clincher, with the re- sult that the last q.d. clincher rims were made in 1916. in the meantime the european demand continued to be for the clincher type exclusively, while they were discontinued in american production except for the use of clinchers in the ford sizes. progress in details of design, materials and methods of manu- facture was very gradual, the general idea being always to build a “ balanced ” tire, that is, one in which all parts were equally durable. the straight-side tires of square woven fabric of 1920 averaged 5,000 to 6,000 m. of service and required air pressure ranging from §5 to 75 pounds. about 1912 electric automobiles in america created a demand for ‘‘ power saver ” tires, to which tire plies inner tube fic. 1.-—cross section of clincher bead on rim. breaker fabric straight side rim fic. 2.—perspective of straight-side tire on rim. the tire makers responded by offering special casings of “ cord ” fabric structure for which exceptional resiliency and lack of internal friction were claimed. this tire was not at all durable at first, but as it was gradually perfected, the leaders of the in- dustry became convinced that it (what is now called the “ high- pressure " cord tire) was to be the quality tire of the future (fig. 3). phe cord tires —ydly separation and fabric breaks in cord tires are effectively prevented because the cords, being com- pletely insulated from each other, provide a flexibility of the ‘carcass’ without chafing, that greatly reduces injury from under-inflation and overloading.’ the two-ply “ cable ” cord 782 construction was the initial form, and the “ multi-ply ” con- struction (the goodyear co.’s contribution) soon followed. in 1920 the merits of the multi-ply construction had prevailed to such an extent that the cable cord was no longer made. after the world war european tire manufacturers began to duplicate 3 fic. 4.—cross section of balloon tire. fic. 3.—cross section of high- pressure straight-side tire. american multi-ply cord construction in their millimetre beaded- edge sizes. the cord tires of 1920 averaged 7,000 to 8,o00 m. of service and required air pressure of 45 to 65 pounds. the balloon tire—the next major development in automo- bile tires came with the introduction of the balloon tire. this type was first developed, perfected and put on the market by the firestone tire and rubber co., the fundamentals underlying this development being, first, to make it possible to owners to use air pressure ranging from 2s to 35 \b.; second, to use a much larger cross section of tire in combination with a smaller diameter of rim so that the overall height of the tire would remain the same; and third, to use only four plies of cord in the carcass con- struction in order to give the extreme flexibility which would be necessary for use with low pressures, and at the same time to secure the durability which the public demanded (fig. 4). by way of example in showing the relationship between high- pressure cord tires and the balloon type, the following table is included to give typical examples: high-pressure tires ralloon tires sedan - no. proper ,; no, proper models size plies | pressure ize plies | pressure i | | et ford zox3i | 4 55 lb 4-40-21 4 30 ib. fab. cl. buick 31x4 5 60 ib 5:25~-21 4 34 [b. dodge 32x4 6 60 |b 5:77-20 4 35 ib. willys- knight } 32x43 6 60 |b 6-20-20 4 30 ib. paige . | 33x43 6 65 ib 6-75-21 4 34 ib. packard 33x5 8 65 |b 7-30-20 4 30 ib. the improved riding comfort secured from the use of balloon tires brought them into general use very rapidly; the first being sold for change-overs and put on cars by manufacturers as orig- inal equipment in the early autumn of 1923. by the autumn of 1924 they were used as original equipment on nearly all cars except fords, and the ford co. adopted them to replace the clincher fabric tires early in 1925. in 1925 the high-pressure cord and balloon tires reached such perfection that the cord tires averaged from 12,000 fo 14,000 m. and the balloon tires between 16,000 and 18,000 miles. to summarise the progress of pneumatic tire development over the period of 1910 to 1925 from a dollar-and-cents stand- point, we find that the tire cost per mile on a medium size car diminished as follows: the balloon tire development in america was entirely on straight-side rims with the standard flat base design. the dun- lop rubber co. in england simultaneously developed balloon period iqio—2 1913-5 1916-8 | i9gig-21 | 1922-5 tire mile cost $o.0112 | $0.0055 | $o0.0041 | $0.0030 | $0.0016 tires tires similar to those used in america, with rims worked out in the straight-side type with the drop centre design, as on the old dunlop-welch wired-on bicycle tire. tires for motor trucks. —in tots the goodyear co. started actively to develop large, heavy construction pneumatic tires for use on motor-trucks. beginning with 1916 all activities in this line were confined to the cord construction which gradually developed in 6, 7, 8, 9 and 10 in. sections, ranging from 10 to 16 plies, and employing from 90 to 130 lb. of air. tocarry the load, in some cases, it was necessary to use the tires in dual or twin application on the rear wheels. the use of these tires was very limited, however, until the period of motor-bus expansion which began in 1921, so that truck or bus tires, as they were called, came into large production by 1925 in both single and dual applica- tion. the average mileage of these tires on buses varied over a wide range due to the different classes of service; in some local- ities as low as 12,000 m. while in other places as high as 25,000 miles. in 1925 the balloon-tire principle was introduced into bus application by the firestone co., by bringing out what was known as “ balloon bus tires,” designed to run with from 45 to 50 ib. of air. solid tires-——the typical solid tire of 1910 was the british “ pressed-on ” band tire (fig. 5), then in use in europe and soon to be duplicated in america. these tires were fitted to the wheels by simply forcing or pressing on with a special press, but in the absence of conveniently located tire presses, some american manufacturers adapted the metal-base idea to a “‘bolted-on”’ design (called “‘ demountable ’’), having bevels on the inside edges of the steel band so arranged that hoop- shaped “ wedges ”’ could be fitted to mount the tire, the whole assembly being bolted in place with “ side flanges.” early metal base tires in america failed prematurely from fracture of the exposed hard rubber at the edge of the base band due to rough strects. to remedy this the band was made in “ channel ” form and the hard rubber protected by the side of the channel (fig. 6). in 1913, as an experiment, a “ channel base ” tire was tried, made to press directly on the s.a.e. (society of automotive engineers) standard wheel without traction plate or staples, previously considered necessary. the experiment was successful, and this new type, being much simpler and less expensive, rapidly superseded all other types in america. in 1915 wide single solid fig. 5.—perspective of solid (european). tires (fig. 6) were introduced in america (8 in., ro in., 12 and i4 in. wide) on the rear of heavy trucks in place of dual or twin tires. in 1920 wide singles and duals were almost equal in pop- ularity. the principal development in the period from 1920 to 1925 was the much wider demand for non-skid treads (fig. 6) on solid tires and the development of the cushion tires of the hollow type; that is, having a circumferential cavity extending around the tire inside. the growth of pneumatic tire production in the united states is shown by the following figures, those for 1913, i915 and 1925 being estimates:— 1913 6,588,000 1922 . 40,930,000 ios . 12,840,000 1923 - 45,245,000 1920 . . 32,400,000 1924 . 51,633,000 1921 . 27,297,000 1925 » 53,900,000 tires structure, materials and manufacture —in designing pneumatic tires, five major forms of tire troubles must be kept in mind by the manufacturer: (a) possibility of premature tread wear; (6) breaks in fabric structure; (c) bead troubles; (d) loosening of the tread from the carcass; (e) separation between the plies of cord fabric. the proper resistance to tread wear is provided by using a very high quality of stock as a tread material, combined with suitable thickness and tread pattern. fabric breaks are guarded against by using a high grade cotton in the cord struc- ture and in suitable quantity so that the factor of safety is at least seven against bursting clue to air pressure in the tire. the other three items are functions of the flexing, and to develop further the principles underlying tires, the balloon tire will be taken as an example. low-pressure air in any tire means a rel- atively large area of contact. a large area of contact means a greater flattening out (or greater vertical deflection). flattening out means flexing and working of the carcass, particularly the fic. 6.—perspective of solid (american giant). sidewall, a condition which, carrie to an extreme, may easily lead to premature failure in circumferential flexing breaks in the sidewall or tread separation or ply separation. the importance of flexing problems may be seen from the following considerations: for every single revolution of the wheel, the tire carcass from bead to bead and completely around the circumference has to flex, so that if the tire is run soft, the degree of flexing is much more exaggerated than if run properly inflated. a tire which renders 15,000 m. revolves 10,000,000 times. to give this mileage, every part of the carcass must flcx 10,000,000 times and not fail. manifestly, if a great many mil- lion flexes must be provided against without failure, the major problem is to prevent excessive flexing and introduce qualities into the tire to make it still more proof against flexing failures. the component parts of the straight-side pneumatic tire are shown in figs. 7 and 8. the bead portion has embedded in it a circular inextensible wire core, usually of many strands in the form of braid, cables or coils (to give a certain amount of flexibility}. this wire anchors the tire to the rim, prevents it from blowing off, and gives enough ngidity to prevent the tire from creeping on the rim when inflated. the body or “ carcass ” of the pneumatic tire consists of bias “ plies ” of cotton fabric impregnated with adhesive rubber “‘ friction,” insulated from each other by a thin “ skim coat ” of the rubber, and having the edges of the plies folded or “ tied in ” alternately over and round the wire bead core (see fig. 7 showing detail of a typical bead “ tie-in ”’). since the function of the carcass is to serve as a strong yet flexible container for the inner tube with its charge of compressed air, the specifications covering the fabric call for great strength, uniformity of weight, freedom from grit and the best grades of long staple cotton. ‘‘ cord” ply-fabric is pri- marily a warp composed of parallel cores of combed arizona high-quality cotton resembling fish line and weighing 11 to 15 oz. per sq. yard. each cord (23s-5—3), cabled yarn, has a tensile strength of 16 1o 20 pounds. in cord tires the cords of each ply must cross those adjacent, consequently the direction of the 783 bias is reversed in the successive plies. the bead “ tie-in ” around the rubberised wire bead “ core ” also includes narrow reinforcing strips of srictioned fabric (see figs. 7 and 8). the outermost of these is named the “ chafing ” strip. the outside of the carcass is entirely covered with rubber; the sides with a 3 tire plies inner tube reinforce strip fic. 7.—cross section of straight-side bead on rim. “sidewall ” layer, 1-16 in. thick, and at the tread portion with “cushion stock,” “‘ breaker fabric,” “undertread ” and “ tread.” the tread is the thick, tough, firm, wear-resisting face of the tire which is in contact with the road surface. the forces and stresses of vehicle operation are so severe in their tendency to tear the tread from the carcass that the tire makers have found it impracticable to attach the tread directly to the carcass, and have interposed the soft, elastic, adhesive “ cushion ” and open mesh “ breaker fabric ” to taper off the severity of the shearing stresses that would loosen the tread. another very important function of the cushion and breaker is to prevent fabric rupture of the carcass by softening and spreading the intensity of impact of rough roads. the design and quality of the tread rubber must be worked out to wear at least as long as any other part of a balanced tire. the physical properties most desired are toughness, to resist cutting and chipping, and attrition resistance to provide against abrasion from road surface friction. inner tubes.—there are no particular differences of design for the inner tubes; nearly all makes resemble each other very closely, highest quality rubber, with little or no compounding except sulphur, is used for grey tubes (see rupbeer). the best red tubes are compounded with antimony sulphide. to be tread breaker fabric cushion tire. plies reinforce strips oft 5 fic. 8.—perspective of step down section of balloon tire. satisfactory the tube must hold air; not crack or check in storage; not stretch out of shape; not stick to the casing; not split or tear easily; not be affected by heating; and must be repaired easily. “ flaps,” made of inexpensive rubberised fabric, are used in straight-side tires to prevent the tube from being pinched or nipped under the edge of the bead, and to keep water and rim rust away from the tube. manufacturing processes —only general ideas of manufactur- ing can be mentioned. first, there is ‘‘ stock preparation;” the rubber and “ compounds ” are mixed, the fabrics “ fric- tioned ” and “skimcoated ” with rubber, gauged to a very exact thickness, the frictioned fabric cut to proper widths on a 784 machine called the “ bias cutter,” the cushion, undertread, and sidewall stocks sheeted out and cut to width on the calender, the tread rubber prepared either in the calender or the “ tubing ” machine, and the bead wires padded with rubber and frictioned fabric and cold pressed into shape (see rubber). “ building ” the tire is the next step. a ‘ core,” in shape and size like the in- side of a finished tire used as a building form, is mounted on a stand which permits the core to revolve. the tire plies are drawn taut around the core and rolled down smooth one after another, and at the proper time the bead is put into position. after the last ply is in place, the tie-in at the bead is made; the building is finished by adding the sidewall, cushion, breaker strip and tread. the final step is the vulcanising or “ curing.” fundamen- tally this is simply the process of subjecting the “ uncured ” tire to pressure in a strong iron “ mould ” with an inflated “air bag ” inside the tire. the heat effects chemical! changes in the rubber compounds just as in cooking. quality in a tire is very dependent on the curing. (see also moror vehicles.) (j. e. h.4)