.May 1, 1921 



THE INDIA RUBBER WORLD 



577 



BUREAU OF AIRCRAFT PRODUCTION, UNITED 

 STATES ARMY 



SPECIFICATIONS OF ELASTIC CORD FOR HOLT FLARE BRACKET 



TENSION STRAP 



Specification No. 26,603, November 14, 1918 



GENERAL 



1. This specification covers the requirements of the Bureau of 

 Aircraft Production for an elastic cord for Holt flare bracket 

 tension strap. 



MATERIAL 



2. The elastic cord shall be made of multiple strands of rubber 

 tightly encased within two layers of cotton braid. 



Braid 



3. The inner braid shall consist of from 30 to 40 white threads 

 with a soft finish of 16/4 ply or equivalent. 



4. The outer braid shall consist of from 30 to 40 white threads 

 with a hard finish of 16/4 ply or equivalent. 



5. Both the inner and outer braids shall be w'rapped over and 

 under with two or three threads. 



Rubber 



6. The cord strands shall be made of a compound containing 

 not less than 90 per cent of the best Para rubber. 



MANTJFACTUEE AND TOLERANCES 

 * Strands 



7. The rubber strands shall be square. In a given cord the 

 strands must be of the same size in cross-section. This size shall 

 be between O.OS and 0.035-inch. 



8. The strands shall be thoroughly treated with soapstone or 

 talc to prevent them from adhering to each other in the finished 

 cord. 



Cord 



9. The diameter specified is the overall diameter of the braid 

 with rubber strands inclosed. A tolerance of minus zero or plus 

 3/64-inch will be allowed on the overall diameter. 



TESTS 



10. The extension of a rubber strand at breaking load must 

 not be less than 700 per cent. Tlie measurement shall be made on 

 a two-inch length. 



11. A specimen of each finished cord shall be tested by stretch- 

 ing to double its normal length. The braid must show no evidence 

 of failure under this test. The load required to produce this ex- 

 tension must not be less than that given in Table 1. This test 

 shall be made on a specimen with a gage length of six inches on 

 specimen, at a temperature of 60 to 75 degrees F. 



12. One test specimen shall be tested for each 50O feet of fin- 

 ished cord unless in the judgment of the inspector the uniformity 

 of the cord can be ascertained with fewer samples. 



Table 1 



Lo.vDS FOR mo Peb Cent Exten.^ion 

 Dianieter of finished cord. Load to give 100 per cent extension, 



pounds 



inch 



25-35 



MARKING 



13. Each roll of finished cord shall be plainly marked with the 

 date of manufacture of the cord, preferably on a tag of permanent 

 nature fixed to the cord. 



INSPECTION 



14. Elastic cord shall not be used for making Holt flare bracket 

 tension straps after six months from the date of its manufacture. 



15. Materials and finished cord shall he subject to inspection 

 by the Inspection Department of the Bureau of Aircraft Produc- 

 tion under its Manual of Inspection. 



16. The Bureau of .\ircraft Production inspector shall have 

 full and free access to all parts of the manufacturer's plant con- 

 cerned in the manufacture of the elastic cord. 



EXERCISER ELASTIC CORD FOR AIRPLANE TYPES A AND B 

 FLEXIBLE GUN MOUNTS 



Specification No. 26.502. November 7, 1918 

 GENERAL 



1. This specification covers the requirements of the Bureau of 

 .Mrcraft Production for elastic cord to be used on airplane types 

 A and B flexible gun mounts, to counteract the weight of one or 

 two flexible guns. 



MATERIAL 



2. The elastic cord shall be made of multiple strands of rubber 

 tightly encased within two layers of cotton braid. 



Braid 



3. The inner braid shall consist of from 36 to 48 white threads 

 with a soft finish of 16/4 ply or equivalent. Single threads must 

 have a tensile strength of four (4) pounds. 



4. The outer braid shall consist of from 60 to 80 white threads 

 with a hard finish of 16/4 ply or equivalent. Single threads must 

 have a tensile strength of five and one-quarter (5J4) pounds. 



5. Both the inner and outer braids shall be wrapped over and 

 under with three or four threads. 



Rubber 



6. The cord strands shall be made of a compound containing 

 not less than 90 per cent of the best Para rubber. 



MANTJFACTUflE AND TOLERANCES 

 Strands 



7. The rubber strands shall be square. In a given cord the 

 strands must be of the same size in cross-section. This size shall 

 be between 0.05 and 0.035-inch. 



8. The strands shall be thoroughly treated with soapstone or 

 talc to prevent them from adhering to each other in the finished 

 cord. 



Cord 



9. The overall diameter of the braid with rubber strands in- 

 closed shall be 7/16-inch. A tolerance of minus zero or plus 1/16- 

 inch w'ill be allowed on the overall diameter. 



TESTS 



10. The extension of a rubber strand at breaking load must not 

 be less than 700 per cent. The measurement shall be made on a 

 two-inch length. 



11. A specimen of each finished cord shall be tested by stretch- 

 ing to double its normal length. The braid must show no evi- 

 dence of failure under this test. The load required to stretch a 

 7/16-inch cord from normal length of 12 inches to 18 inches shall 

 be from 18 to 24 pounds. 



12. One test specimen from each 500 feet of finished cord shall 

 be tested unless, in the judgment of the inspector, the uniformity 

 of the cord can be ascertained with fewer samples. 



13. Each roll of finished cord shall be plainly marked with the 

 date of manufacture of the cord, preferably on a tag of permanent 

 nature fixed to the cord. 



INSPECTION 



14. No elastic cord shall be used for making flexible gun 

 mounts after six months from the date of its manufacture. 



15. Materials and finished cord shall be subject to inspection 

 by the Inspection Department of the Bureau of Aircraft Produc- 

 tion under its Manual of Inspection. 



16. Tlie Bureau of .Mrcraft Production inspector shall have 

 full and free access to all parts of the manufacturer's plant con- 

 cerned in the manufacture of the elastic cord. 



Communications regarding all technical matters pertaining to 

 specifications should be addressed to the Specification Section, 

 Bureau of Aircraft Production, United States -\rmy, Dayton, 

 Ohio. 



SPECIFICATIONS OF THE BUREAU OF AIRCRAFT 

 PRODUCTION, UNITED STATES ARMY 



RUBBER BAGS FOR GASOLINE TANKS 



Specification No. 16,024, October 30. 1918 



GENERAL 



1. This specification covers the general requirements of the 

 Bureau of Aircraft Production for rubber bags for gasoline 

 tanks. 



2. Production engineering drawings for each size bag shall 

 form a part of this specification, and may be obtained on applica- 

 tion to the Instrument Department. Production Engineering. 



3. Bureau of Standards Circular No. 38, on "The Testing of 

 Rubber Goods," shall form a part of this specification. 



4. Use, The bags are for use nn airplane gasoline tanks to 

 catch and conduct away gasoline which may leak from punctures 

 in the tank. 



5. Durability. The bags must withstand the weather condi- 

 tions encountered at varying altitudes and their life must be such 

 as is indicated by the nature of the ruliber compound. 



6. Dimensions. The bags shall conform to the dimensions 

 called for on the drawings or in the order. 



