August 1, 1921 



THE INDIA RUBBER WORLD 



829 



Society of Automoti\e Engineers Specifications for Insulated Cables' 



Electrical Equipment Division Report 



THE Electrical Equipment Division's recommendation that the 

 present S. A. E. standard for insulated cable be revised to 

 conform to the accompanying specifications for insulated cable, 

 was approved. Although the proposal does not as yet include 

 electrical tests, it is desired by the cable manufacturers that the 

 manufacturing specifications be adopted and published without 

 delay so far as they have been completed. 



The electrical tests for high-tension ignition cable will be in- 

 cluded in the standard at a later date, as no entirely satisfactory 

 tests have yet been developed. The electrical tests included in 

 the present standard, although used considerably in general power- 

 cable testing, are not considered satisfactory for automotive high- 

 tension ignition cable. 



The proposed revision is submitted as a practical and satis- 

 factory specification founded on the best commercial e.xperience. 

 It embodies many points in common with government specifica- 

 tions which have been generally approved and will be used by 

 manufacturers in producing high-grade insulated cable. 



INSULATED CABLE 



I. GENESAL SPECIFICATIONS 



Conductors. Conductors shall be bunched or stranded as 

 specified in each section and shall be annealed copper wire in ac- 

 cordance with Specification No. B3-15 of the .'\merican Society 

 for Testing Materials. .\11 wires shall be thoroughly tinned and 

 must withstand the tinning test as specified in Section II, Tests. 

 All tests of copper conductors shall be made before stranding 

 or insulating. 



Cotton Separ.^tors. Material for separators, where specified, 

 shall be of good grade cotton and shall be closely and tightly 

 applied. 



Rubber Insul.\tion. Rubber insulations shall be homogeneous 

 in character, properly vulcanized, and placed concentrically about 

 the conductors. Rubber insulations shall adhere closely to, but 

 shall strip readily from, the conductors, leaving them reasonably 

 clean. Rubber insulations used on cables covered by these speci- 

 fications shall contain not less than 20 per cent (by weight) of 

 good grade Hevea rubber which has not been previously used. 



V.ARNISHED Cambric Tape. Varnished cambric tape shall be 

 made from a good grade cotton fiber treated with multiple coats 

 of insulating varnish. The instantaneous puncture voltage shall 

 be not less than 750 volts per mil of thickness tested in accordance 

 with the standards of the American Institute of Electrical Engi- 

 neers. Varnished cambric tape shall be not less than 0.005-inch, 

 nor more than 0.013-inch thick. 



Braids. Braids shall consist of closely woven cotton yarn, and 

 shall not be less than 1/64-inch thick. Braids shall be impreg- 

 nated with at least two coats of properly dried, heat, oil and water 

 resisting insulating varnish or impregnated with black weather- 

 proof compound which has an even and smooth finish, .\djacent 

 layers of cable, when wound on the reel, shall not stick to one 

 another at any temperature under 105 degrees F. (40 degrees C). 



Armor. Armor shall be of either galvanized or sherardized 

 soft steel, soft brass, aluminum or copper and applied in a close 

 helix. Successive turns shall not overlap. Armor dimensions 

 shall be as given in Table 1. 



Table 1. Armor Thickness and Width Di.mensions 



Thickness, In. 



Armor Min. 



Small 0.014 



Large 0.01" 



NoM. 

 0.017 

 0.020 



Max. 



0.020 

 0.023 



Min. 



0.045 

 0.095 



WIDT.H, In. 

 — ■ r«- 



9Hom. Max. 



n.050 0.055 



0.100 0.105 



'The Journal of the Sncicty ef .\utomolive Engineers, July, 192L Pages 



.■\rnior shall be solid "D" shaped, unless otherwise specified 

 by the purchaser. The large armor is recommended for use on 

 all cables e.xceeding yi-inch diameter underneath the armor. 



II. TESTS 

 Tinning Test. For this test, samples of the bare wire before 

 being stranded or insulated shall be properly selected to secure an 

 average grade of tinning. The wires shall be thoroughly cleansed 

 by means of ether, benzine, gasoline, naphtha, caustic alkali solu- 

 tion, alcohol, or hot water and soap, whichever may be found 

 necessary to thoroughly clean the wires. 



The wires shall then be rinsed in clear water and wiped dry 

 with a soft cotton cloth. The wires shall then be immersed for 

 one minute in a solution of hydrochloric acid having a specific 

 gravity of 1.088 at 70 degrees F. (21 degrees C), and then rinsed 

 in clear water and wiped dry as above specified. The wires shall 

 then be immersed for 30 seconds in a solution of sodium poly- 

 sulphide which contains an excess of sulphur and which has suffi- 

 cient, strength to thoroughly blacken a piece of clean untinned 

 copper wire in 5 seconds. 



The complete cycle of operations shall then be repeated, com- 

 mencing with the immersion in hydrochloric acid and ending with 

 the immersion in the sodium polysulphide solution. 



Tests of tinning shall be made on not less than 10 sets of 

 samples of reasonable length. All wires shall withstand one 

 immersion in the hydrochloric acid without blackening in the 

 sodium polysulphide solution, and 75 per cent of the wires shall 

 withstand three immersions in the hydrochloric acid without 

 blackening in the sodium polysulphide solution. .-MI tests shall 

 be conducted with the solutions at a temperature of 70 degrees F. 

 Physical Tests. A test specimen of rubber insulation which 

 has not previously been handled, not less than 6 inches long 

 shall have marks placed upon it 2 inches apart. The sample shall 

 then be stretched at the rate of 12 inches per minute until these 

 marks are 6 inches apart, and then immediately released. Thirty 

 seconds after being released the distance between the marks shall 

 not exceed 2'/l inches. The test specimen shall then be stretched 

 until the marks are 7 inches apart before it is ruptured. 



The ultimate tensile strength of rubber insulation shall not be 

 less than 600 pounds per square inch. The tensile strength shall 

 be calculated upon the original cross-section of the test-specimen 

 before stretching. 



Physical tests shall be made at a temperature of not less than 

 50 degrees F. (10 degrees C), nor more than 90 degrees F. (32 

 degrees C). 



For the purpose of these tests, care must be used in cutting to 

 obtain samples of uniform cross-section and no manufacturer 

 shall be responsible for results obtained from samples imperfectly 

 cut. 



The above physical tests shall not apply to wires or cables hav- 

 ing a wall thickness of less than 0.04S-inch. For wires and 

 cables having a wall thickness of less than 0.04S-inch the initial 

 and ultimate stretch shall be 5 and 6 inches, respectively, and the 

 tensile strength not less than 500 pounds per square inch. 



Miscellaneous Tests. The following tests apply to high- 

 tension (secondary) ignition cables only. 



Oil Test for Braided Cables. A sample of cable shall be im- 

 mersed in a mixture of equal parts of machine oil and gasoline 

 for a period of 24 hours without allowing the ends of the sample 

 to become submerged, .^fter this immersion the impregnating 

 varnish should not show signs of softening or absorption, and 

 when the braids have been peeled oflf, it should be shown that 

 no oil has penetrated to the rubber insulation. 



