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730 " tubing " machine, and the bead wires are padded with rubber and frictioned fabric and cold pressed into shape. (See RUBBER for stock preparation.) " Building " the tire is the next step. A " core " in shape and size like the inside 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 in 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. During the decade 1910-20 tire building changed from all hand work to a combination of hand and machine building. In addition to saving labour, the machines turn out more perfect work. The final step is the vulcanizing or " curing." Fundamentally this is simply the processes of subjecting the " uncured " tire to a definite degree of heat for a definite length of time while the tire is confined under pressure in a strong iron " mould " (with an iron " curing core " or inflated " air bag " inside the tire). The heat effects chem- ical changes in the rubber compounds just as in cooking. Quality in a tire is very dependent on the curing. Not only must there be an optimum cure but the mould pressure must not disturb the fabric lest " buckles " or " mould pinches " be formed. This last is so important that many manufacturers resort to the more expensive double cure process the carcass is semi-cured to " set " the rubbers and fabrics with much less danger of fabric displacement, after which the tread is cemented in place and the cure finished.

Tire Troubles. For the purpose of general analysis in pneumatic tire service, five major tire troubles are recognized. They are: (i) unsatisfactory tread wear; (2) separation either (a) between plies of fabric or (6) of tread from carcass; (3) fabric ruptures; (4) bead troubles; and (5) tube troubles. In each case it is possjble to classify pretty completely the origins of the mischief. Of course, many instances of premature tire failure are due to defects of design, materials or manufacture; on the other hand, by far the more frequent cause of tire trouble is abuse in the hands of the user as outlined below:

Abrasion

Wheels out of alignment Too much power Improper use of brakes Skidding

Abrasive road surfaces Under-inflation Sharp stones cutting tread Deterioration from oil

Excessive flexing

Riding under-inflated

Riding car tracks

Overloading

Riding flat

Abuse of rough roads

Cuts

Heating from speeding

Water-soaked fabric

Overload

Over-inflation

Under-inflation

Stone bruises

Premature ply separation

Cuts

Exposed fabric water-soaked

Speeding on rough roads

( Bent rims

\ Under-inflation

Unsatisfactory Tread Wear

Separation

(a) between plies

of fabric (6) of tread

from carcass

Fabric Ruptures

Bead Troubles

caused by

caused by

caused by

caused by

Riding flat Leaky valves Puncture

Tube Troubles \ caused by Heating from speeding

Pinching under bead Tears from rough handling Neglect of spare tube Solid tire troubles are confined to premature wear in the form of cutting, chipping, and breaking large chunks out of the tread; dis- integration in the heart of the tire due to the accumulation of the heat of internal friction on long trips (rubber is such a poor conductor that heat is not adequately dissipated by windage) ; and separation of the whole mass of the tread rubber from the steel base-band. This last is a defect in materials or manufacture except in cases where external abuse fractures the hard rubber. In order to cushion a specific load properly a tire must not have too high air pressure; on the other hand, under-inflation results in excessive flexing which in turn brings on premature ply separation and fabric breaks. Ex- perience has demonstrated that a pneumatic tire should not flex more than 11% (for large tires) to 15% (for small tires) of the section diameter of the tire. Recommendations designed to advise vehicle manufacturers and users as to the proper conditions under "which the tires should be used are given in their "carrying capacity" schedules, as indicated in the following table.

Carrying Capacities and Inflation Pressures of Pneumatic Tires S.A.E. Standard.

For passenger cars

For commercial vehicles

Tire Size

Fabric tires

Cord tires

Cord tires

Max'm load per tire Ib.

Air

pressure Ib. per sq. in.

Max'm load per tire Ib.

Air pressure Ib. per sq. in.

Max'm load per tire Ib.

Air

pressure Ib. per sq. in.

il ti 1

9

10

375 570 815 1,100 1,500

45 55 65 75 85

400 600 850 1,200 1,700

40 5 60 70 80

850 1,200 1,700 2,200 3,000 4,000 5,000 6,000

"

70

75 80 90

100 IIO I2O 130

(J. E. HA.)

TIROL (see 26.1010), an Austrian Territory, divided by the Treaty of Peace of St. Germain into two separate parts Northern Tirol and the district of Lienz. Northern Tirol is bounded on the E. by Salzburg, on the N. by Bavaria, on the W. by Vorarlberg and Switzerland and on the S. by Italy (German Southern Tirol). It lies mostly in the valley of the Inn, the northern part in the Kalk-Alpen and the southern in the schists and the central zone of the eastern Alps. The southern frontier almost coincides with the watershed between the Inn and the Adige. In the N., Tirol extends into the basins of the Lech and the Isar. The " Fohnstrasse " of the Brenner renders the cultivation of maize possible in some parts of the Inn valley. The new Territory has an area of about 4,787 sq. m. and its pop. was in 1910, 304,713, in 1920, 306,156 (64 per sq. mile). The area of the Lienz district is about 763 sq. m.; pop. in 1910 about 29,000.

The population is almost entirely German and Roman Catholic (1910, 98-9%). The proportion of males to females in 1910 was as 1,000 to 981 but in 1920, 1,000 to 1,053.

For administrative purposes Northern Tirol is divided into seven districts and the autonomous city of Innsbruck, the capital (pop. in 1920 55,659). Lienz is a district of itself. Other important places besides Innsbruck are Holting bei Innsbruck (pop. 9,503), Schwaz (pop. 7,385), Hall (pop. 6,984), Kufstein (pop. 6,662), Lienz (pop. 5,756), Worgl (pop. 4,030), Landcck (pop. 3,919).

Agriculture and Forestry. In 1910, 23-7 % of the present Tirol was unproductive. Of the productive areas (1910), 5-9% was arable, 0-2% gardens, 7-4% meadows, 41-5% pasturage (almost entirely high summer grazing lands) and 44-9% forest.

Cattle-raising ana farming on the high lands are well-developed industries, although less care is bestowed on them than in Switzer- land. But in 1918 there were only 159,398 head of cattle (of which 91,219 were cows) and 24,421 swine. The Tirolean breeds of cattle are highly esteemed. Forestry also holds an important place among the industries of this Territory.

Minerals. The salt mines yielded 15,000 tons in 1915 (9% of the whole Austrian output) at Hall bei Innsbruck. The production of jignite, 40,000 tons in 1915 (scarcely 2% of the Austrian output), is chiefly from Haring in the Unter-Innthal. Copper, lead, zinc, antimony and sulphur and asphalt are also mined.

Manufactures. Industry is still little developed although the use of the abundant water power is rapidly increasing; there are electrical stations at Innsbruck and elsewhere. Mention should be made of the wood, iron, textile, earthenware and glass industries. Innsbruck is as yet hardly an industrial city but has commercial importance and is visited by great numbers of tourists.

Communications. Mountain railways from Innsbruck to the Stubai-Thal and to Mittenwald, the junction for Munich, have led to a great development of tourist traffic and are of marked impor- tance for trade and industry.

REFERENCES. Norbert Krebs, Landerkunde der oslerreichischen Alpen (1913); Jos. Blaas, Geologischer Fiihrer durch die Tiroler und Vorarlberger Alpen (1902); H. v. Fickcr, Klimatographie von Tirol und Vorarlberg (1909) ; Widmann, Geschichte von Tirol; The Unity of Tirol (Memorandum of the Academic Senate of the university of Innsbruck, 1919).

TIRPITZ, ALFRED VON (1840- ), German admiral and politician, was born at Kiistrin March 19 1849. He entered the Prussian navy in 1865, and by 1890 had risen to be chief-of-staff of the Baltic station in the Imperial navy. In 1892 he was in