424 



THE INDIA RUBBER WORLD 



Makoh 1, 1921 



In repairing a blow-out it is usually necessary to make a lay- 

 back of the tread and make the step-offs on the outside as far as 

 can l>e cured in a ;-4-circIc mold to insure the repair. In curing 



Showing Mechanical Construction of the Adjustable Mold 



a casing in which the non-skid design has not worn to any great 

 extent, fill up these designs with a soapstone mash, place the 

 tire in the mold with steam on, set the bead plates, put a slight 

 pressure on the bag, and after the moisture in the soapstone 

 mash has been allowed to evaporate put the necessary air in 

 the bag to make the cure. This will prevent squeezing the mash 

 out at the ends of the molds and mashing down the design. 



Don't forget that it is necessary in curing built-in sections to 

 cure from both sides ; that is, use steam in the bag for a part 

 of the cure as specified in the chart. It is impossible to cure a 

 shoe on the inside of a tire with heat from the molds only, and 

 much time is saved by using a combination steam and air bag 

 and curing the shoe at the same time the section is being vul- 

 canized in the mold. 



Either use new cord patches, or make them out of successive 

 plies of cords. Take care to see that the reinforcing cords run 

 in the same manner as those which they replace. Different manu- 

 facturers build the tires in different w-ays, some building them 

 in groups ; that is, having several plies of cords run in one di- 



Giant Read Spreader 



rection and then have the same number running in the other 

 direction, while other manufacturers cross each successive ply. 

 In removing one group only from the outside of a casing, built 



by the former method, take care to see that the majority of the 

 plies reinforcing the inside run in this same direction. 



Do not neglect the small nail holes or tread cuts in a tire 

 which comes in for a repair. "Large blow outs grow from little 

 tread cuts," therefore, look carefully for smaller defects. 



Use a rat-tail rasp in cleaning out the tread cuts or puncture 

 so that the cement will adhere. Use plenty of cushion gum next 

 to the cement. Cushion gum has a great deal to do with holding 

 the repair, and the size of the casing must be taken into con- 

 sideration and several plies used where only one would be used 

 in a passenger tire. 



It is often easier in curing a tread cut or sectional repair, 

 where only a small part of the design must be reproduced, to 

 put in a sufficient amount of rubber and pack the cure with soap- 

 stone, afterwards carving out the design with a knife and buffing 

 it rather than making expensive impression pads from rubber and 

 fabric. 



Inside fabric breaks may usually be repaired by cord patches 

 il they extend through several plies. However, it is necessary 

 to build an inside section into the tire. Use the awl in finding 

 out the fabric depth before determining what kind of repair to 

 give it. 



Place the coated side of the fabric down in rebuilding sections. 

 In rebuilding a section where the cords run in groups, it is well 

 to use a ply of 1/32-inch cushion gum between each group to 

 prevent friction where the cords cross. Use plenty of soapstone 

 liefore placing the bag inside the tire, to prevent it from sticking 

 to the tire. 



Allow the stem opposite to the one which the steam hose is 

 connected to remain slightly open during any cure w^here steam 



Flexible Shaft-Buffing Outfit 



is used in the bag, closing it tight when air is used. In making 

 a lay-back of a tread, cut across the lowest or thinnest part of 

 the tread design, even if this makes the cut run in an irregular 



dircctiiin, as it will make a neater and more substantial joint. 



Italy's exports of rubber, gutta percha, and their manu- 

 factures for the period January-June, 1920, were valued at 89,077,- 

 950 lire (provisional returns), as against 21,885,550 lire for the 

 corresponding period in 1919. Normally the lira is worth $0,193; 

 present exchange value is $0,034. Par value is used in these 

 computations. Similar imports into Italy during the January- 

 June period of 1920 were 81,322,960 lire, as against 92,944,700 lire 

 in the corresponding period of the preceding year. 



Rubber scrap exports to the United States from the Bristol, 

 England, consular district in 1919 were valued at $3,464, as against 

 $9,733 in 1918. From the port of Hull, 1,049,007 pounds of crude 

 rubber, valued $342,716, were exported to the United States in 

 1919. as against 119,594 pounds, valued $49,690, in 1918. 



