10 



THE INDIA RUBBER WORLD 



[October 1, 1920. 



inflammable motion picture films. All tlie processes so far 

 perfected have been protected with patents. Incidentally it has 

 been found that ocoiillo fiber is even stronger than ramie. Dr. 

 Weisgcrbcr has had two tires made of such fabric, well fric- 

 tioned witli gum, and which are still good after 22,000 miles' 

 use on a heavy sedan run mostly in a rough country. 



Ocotillo, diminutive of "ocote," a kind of Mexican pine, and 

 which is one of the candlewoods of the great arid region of 

 the Southwest, known botanically as Fouquieria splendens, is a 

 shrub with naked, wandlikc, thorny branches, which, usually in 

 February, after a brief rainy season, puts forth foliage and 

 clusters of bright scarlet flowers. The stems have long been 

 used for poles and wired for fencing. The plant is usually 

 ten feet tall. The supply is practically inexhaustible. Soon 

 after it is chopped ofT close to the root it starts to sprout again. 

 While lying in heaps in the yard, even three months after cut- 

 ting, it often puts forth its flowers. The Mexicans say that it 

 has more lives than a cat, and that the only way to kill it is 

 to burn it, root and branch. Officials of the company say that 

 there is enough ocotillo within a fifteen-mile radius to keep their 

 plant running at full capacity for fifty years. 



Nor is the company satisfied with its present achievements. 

 It is also experimenting with the species of cactus known as 

 the "saguaro" (Cereus gigaiiteus), from which it is predicted a 

 yield of 11 to 12 per cent of rubber will be readily obtained. 

 The saguaro, the largest of the cacti family, often attaining 

 a height of sixty -feet, is an arborescent plant growing abun- 

 dantly in Arizona and New Mexico, with sparse, candelabrum- 

 like branches, bearing yellow flowers and edible fruit. 



The company's plant is located in a plain, which for heat 

 and aridity during the long summer is said to be rivalled only 

 by Death Valley, California. A temperature of 132 degrees F. 

 is often reached. Water is to be had only from deep-driven 

 wells. It is described as a country of almost endles's sunshine, 

 burning alkali sand, rank thorny growths, vipers, lizards, Gila 

 monsters, scorpions, rattlesnakes, tarantulas, stinging flies and 

 poisonous beetles. Yet the workers manage to adapt themselves 

 fairly well to the unfavorable natural surroundings, and the com- 

 pany considerately makes the hours of labor as few as possible 

 in the more torrid season. 



RUBBER TECHNOLOGISTS FOR THE BUREAU OF STANDARDS 



The United States Civil Service Commission announces open 

 competitive examinations for the positions of associate tech- 

 nologist in rubber, textiles and other subjects, salary $2,000 to 

 $2,800 a year, and assistant technologist $1,400 to $1,800 a year. 

 Vacancies in Washington and elsewhere are filled from these 

 examinations. 



The Bureau of Standards covers a wide field of work in phys- 

 ics, chemistry, engineering and industrial technology, including 

 research and standardization, and offers valuable experience in 

 these professions, combining as it does theoretical, experimental, 

 and practical work. The duties of the appointee will be in con- 

 nection with original investigations in some field of the Bureau's 

 work. The chances for advancement arc good. Experience in 

 the Bureau is considered an admirable training for scientific 

 work, and its close connection with the industries makes it par- 

 ticularly valuable as a training in industrial research. 



Competitors will not be required to report for examination at 

 any place, but will be rated on the required subjects, such ratings 

 being based upon the competitors' sworn statements in their ap- 

 plications and upon corroborative evidence adduced by the Com- 

 mission. Papers will be rated promptly and certification made 

 as the needs of the service require. 



Applicants should apply for Form 1312, stating the title of the 

 examination desired, to the Civil Service Commission, Washing- 

 ton, D. C. 



THE MEASUREMENT OF CRIMP U4 YARNS AND 

 FABRICS' 



By .1. N. Gadsby and E. D. IValcn- 



IN THE PROCESS of Weaving any fabric the raising and lowering 

 of warp threads causes them to bend around the filling 

 threads and assume a wavy shape. The filling threads are also 

 bent out of their natural straightness by the pressure of the 

 warp threads. The relative amount of waviness in warp and 

 filling depends upon the nature of the threads, the method of 

 interlicing and the subsequent treatment of the woven material. 



In fabrics used for structural purposes, such as tire fabrics, 

 the absolute and relative amounts of the waviness in two sys- 

 tems of threads becomes a consideration of much practical im- 

 portance. The elastic properties of the fabric depend not only 

 upon the yarns used, but also upon their interrelation. The 

 purpose to be constantly kept in mind is to attain the condition 

 that all parts of the material shall be affected by the stress of 

 working conditions in proportion to their ability to withstand 

 that stress. The relative elasticity of the fabric in warp and 

 fining directions tends to determine the distribution of the 

 stresses. 



There seems to be some lack of clearness as to the meaning 

 of the term "crimp," owing to confusion with the shortening of 

 yarns during weaving, commonly called "take-up." The stresses 

 of weaving, the retention of the yarns in a distorted position, 

 and the treatment wliich they may receive while in that position, 

 all help to alter the yarn permanently ; so that, from the point 

 of view of the fabric, the original properties of the yarn are not 

 those which need be considered. 



As applied to tire fabrics, crimp should be considered as the 

 difference in distance between any two points on a yarn in a 

 fabric and between the same two points after the yarn has been 

 removed and straightened. The diflference between crimp and 

 take-up consists of the permanent elongation of the yarns inci- 

 dent to the processes of weaving and finishing. It is impossible 

 to make a determination of take-up from an examination of the 

 finished material. This term should only be used in connection 

 with calculations involving the length of yarn required for a 

 piece of cloth, the yarn being as received from the spinning or 

 twisting machinery. 



The determination of crimp involves making two measure- 

 ments, first, in the fabric, and then after removing and straight- 

 ening. The only difficulty met in making this determination, is 

 that of producing straightness without also producing elonga- 

 tion due to the use of tension. The method commonly used is 

 the crude one of holding the yarn fast at one end and passing 

 the thumb over it toward the other end. This method is so 

 obviously inexact and dependent upon the identity of the oper- 

 ator that it requires no further comment. 



Another method suggested and frequently used is to apply 

 a definite tension on one end, by the use of a spring, a weight, 

 or other means, holding the other end fast. The objection to 

 this method is that the load is arbitrarily selected and that it is 

 by no means certain whether the crimp has been completely re- 

 moved and whether no elongation has taken place. As no two 

 yarns stretch the same amount when subjected to the same load 

 under like hygroscopic conditions, crimp determinations upon 

 different yarns, using a constant load method, are not compar- 

 able. 



Since it seemed likely that a yarn would stretch under any 

 tension, it was decided to make a study of its behavior under 

 various tensions and to deduce from this the length of the yarn 

 when straight and under no tension. .Accordingly the instrument 

 shown in Fig. 1, was constructed. 



In using this instrument the yarn is securely clamped in a jaw 



* Publistied by courtesy of the American Society for Testing Materials. 

 Paper rend at the annual meeting of the Society at Asbury Park. New 

 Jersey, June 22-2-1, 1920. 



- Formerly assistant i>hysicist and laboratory assistant, respectively, of 

 the Bureau of Standards. Washington, D. C. 



