Arizona republican., 1921-02-06

vision to make sure that materials are not spoiled during the process. TO illustrate the necessity of this super vision it is necessary only to point out that a single drop of moisture in the rubber or fabric will, when the tire is subjected to heat in the vulcanizer, turn to steam and expand into "blisterp that will ruin the tires sale ability.
 Among the most important parts of the equipment are the big tanks III which the tires get their heat bath After the tire is built it is placed in steel mould weighing from 800 to 5000 pounds. Putting the tires into these InouIds and taking them out again, and transporting the moulds about the factory requires an amount of labor that is an important item in the cost of tire
 When the building of the tire has been completed and it has been placed in the mould, it goes into the vul- canizer-a big hollow tank capable of holding a dozen or more tires of aver age size. When the tires are in place in the vulcanizer. the lid is screwed down and the steam turned in The temperature rises gradually for 0 minutes when a temperature Of about 2s6 degrees Is reached. The tire re- mains at this temperature for about
 
 off. After fifteen minutes of cooling the moulds are taken out and the tires removed. and stripped from the cores on which they were built.
 If everything has been done right the tire is a good one. but If there nave been errors or sltp-shod work, the tire Is spoiled. Once tire has been vulcanized it cannot be changed. It Is like a jar in pottery, until it is baked anything can be done with it, but once baked it's form becomes per- manent and changes cannot be made. The task of regulating the degree of cure Is matter for the expert. It took the inventor of vulcanizing six years after he had discovered the right theory to reach by endless ex- perimentation the point where he lcould give the rubber just the cure that was needed.
 l Tire building is not hap-hazard, | easily acquired art. It requires in- finite pains and cease1ess vigilance. | If a tire is imperfect in any particular it cannot go on the market except as a second In the factories of the l United States Tire company this re- quirement for care at every step has resulted in the establishment of a rigid system of inspection so complete that every operation is carefully super vised by trained men. When the tire | goes into the vulcanizer,. it is as per | feet as human eyes and hands can make it. So efficient has this system | proved that the number of imperfect | tires has dropped to an average o1 one in thousand.
 | Once properly cured a tire canno, be subjected to further curing without producing an "overcure," condition which results ip rapid deterioration o1 1 the rubber. It is for this reason that | so many re-treading processes have | proved unsatisfactory. The new tread must be vulcanized to the old car. | cass. and a certain amount of re-yuI. l caniZation of the carcass takes place l causing such an overcure as to talk, 1 the life out of the rubber in the car. | cass. While in the vulcanizer the rubber melts and runs together. st 1 that the various parts that enter int the structure become firmly fused to- gether in one piece. The ordinar, rubber boot of commerce is one in separable piece, welded and moulded together by vulcanization. Yet wher it went into the vulcanizer it was 3s separate pieces anyone of which migh have been easily removed from tn, rest.
 To secure permanent union of on, piece of rubber with another, vulcani zation is necessary It is for thi. reason that small vulcanization outfit. are found in every tire repair shop In view of the intricacies of, the vul. canization process it is remarkable t, what degree of efficiency many o these repairmen have attained.