JuLV 1. 1920.] 



THE INDIA RUBBER WORLD 



653 



First, the standardization of existing machines, which prac- 

 tically means only one make, one capacity and the same dimen- 

 sions of the same moving parts; otherwise there will still exist 

 confusion of results caused by the testing of materials on ma- 

 chines having different machine characteristics. 



Second, the redesign of the principle of the recording head of 

 the testing machine, so that the results obtained are independent 

 of the machine. The second consideration is practically as easy 

 to effect as the first, and has the advantage of being based on 

 sound mechanics. 



It may be asked why the Bureau of Standards has recom- 

 mended that a particular make and size of inclination balance 

 testing machine be used by the military departments during the 

 present crisis. The military departments, such as 

 the Quartermaster's Department and Signal 

 Corps, were confronted with the problem of 

 checking large deliveries immediately. Under 

 these conditions the Bureau of Standards recom- 

 mended one size of test specimen, one speed of 

 operation, one make, and one capacity of inclina- 

 tion balance testing machine, regardless of 

 whether any one condition of the test was funda- 

 mentally sound. The main object was to obtain 

 uniform test methods at once. 



For investigational work such as Committee 

 D-13 contemplates, however, the testing machines 

 used should be fundamentally correct. 



The requirements of a testing machine are: 

 (1) rigidity: (2) as nearly automatic operation 

 as is possible; (3) recording head free from ob- 

 jectionable characteristics caused by (a) prin- 

 ciple, (b) mechanical design, 

 p " The Bureau of Standards has been e.xperiment- 



T E s T I N G- '"? with a testing machine which as a whole has 

 Mac hine, no value as a commercial machine, but which has 

 TuREAu OF shown itself to be reasonably constant and free 

 from machine characteristics. It is constructed 

 on the constant-increment-of-stretch principle 

 and has a recording head of a suspended spiral 

 spring and oil dash pot to take care of recoil. 

 The head is illustrated in Fig. 3. 

 ''•■ ^'■'"'"^- From the results obtained with this machine the 



Bureau is redesigning the present testing machines along these 

 lines, with the addition of a temperature correcting device and an 

 individual test result totalizer. The construction is rigid and sim- 

 ple, and the operation a little quicker and as automatic as that 

 of any existing machines. 



Standards. 



Piston Yoke; 



PROPOSED TENTATIVE SPECIFICATIONS FOR 

 ADHESIVE INSULATING TAPE.' 

 Issued, 1920. 

 1 These spECiFiCATinNs cover a friction tape composed of 

 ' • cotton sheeting impregnated with an adhesive insulating 

 compound. 



I. MANUFACTURE. 



2. The cotton sheeting layer shall be made from a sheeting 

 evenly and firmly woven from good cotton, and as free from 

 unsightly defects, dirt, knots, lumps, and irregularities of twist 

 as is consistent with the best manufacturing practice. The 

 threads shall run in straight lines without waving, so as to re- 

 duce to a minimum the raveling of the cloth when cut into tape. 



3. The frictioning compound shall be an adhesive and in- 

 sulating compound practically free from free sulphur (not over 

 0.05 per cent) or other substances which would have a deteriorat- 

 ing effect on copper or other metals or on the fabric. 



on Rubber 



4. The fabric shall be thoroughly impregnated and evenly 

 covered on both sides with the frictioning compound. 



5. The thickness of the tape shall I)€ not less than 0.013 nor 

 more than 0.017-inch; when measured with a rubber spring mi- 

 crometer with 0.4-inch diameter foot. 



6. The compound shall adhere firmly to the fabric and shall 

 not pull away from the fabric so as to leave bare spots when 

 adjacent thicknesses of the tape are separated. 



n. PHYSICAL PROPERTIES AMD TESTS. 



7. When the tape is held before a strong light, the number of 

 pin holes noted per linear yard of tape. 34-inch wide, shall not 

 exceed two. 



8. The tensile strength per .}'4-inch width shall be not less than 

 30 pounds. The initial distance between the jaws of the testing 

 machine shall be 12 inches, and the rate of separation of the jaws 

 shall l)e 20 inches per minute. 



9. When wrapped on a clean, smooth copper rod and baked 

 at 100 degrees C. for 16 hours, the compound shall not discolor 

 the copper. 



10. (a) The adhesion of the friction coat of compound between 

 the plies shall be such that when a strip of tape 2 feet long and 

 ^-inch wide is taken from a roll and wound upon a 1-inch 

 mandrel under tension of 7J^ pounds at the rate of 30 inches per 

 minute, a weight of 3 pounds shall not cause the plies to separate 

 at a greater rate than 30 inches per minute. 



(b) After a strip has been exposed to dry heat at 100 degrees 

 C. for 18 hours and then cooled to room temperature, a test 

 specimen shall withstand the test prescribed in the paragraph 

 (a), except that the weight applied to unwind the tape shall be 

 1 pound instead of 3 pounds. 



11. The test for dielectric strength shall be made as follows: 

 The tape shall be spirally wound with one-third lap on a smooth 

 metal rod. 1 inch in diameter, for a distance of 6 inches. Two 

 inches in the center shall be covered with tin foil and bound 

 down securely with tape, and an alternating potential of 1,000 

 volts, of a frequency of not over 65 cycles, shall be applied for 

 five minutes between the metal rod and the tin foil without 

 puncture. 



12. One y^-pound roll for each 250 rolls shall be selected at 

 random for the various tests. At least two feet of the outer 

 layers shall be removed and one specimen taken for each test. 

 If the tape fails in any one test, two additional specimens shall 

 be taken. If the tape fails in either of these two additional tests, 

 the material shall be rejected. 



III. STANDARD WEIGHT, DIMENSIONS AND VARIATIONS. 



13. The net weight of the tape, ^-inch wide, shall be not less 

 than S ounces per roll, exclusive of core, wrapping, and box. 



14. The length of ■>4-inch tape shall be not less than 55 yards 

 per pound. 



15. The width sliall not vary from that specified more than 

 ±0.03-inch. 



IV, PACKING AND MARKING. 



16. Each roll shall be wrapped in oiled paper or metal foil 

 and enclosed in a suitable box. The wrapping shall be secure 

 and shall thoroughly protect the contents. 



17. Each box shall be marked with the name of the manu- 

 facturer or trade-mark, and the nominal widtli and weight of 

 the tape. 



V. INSPECTION. 



IS. The tape shall be tested and inspected within four weeks 

 of date of delivery. 



In the Dutch East Indies there are now about 12,000 motor 

 cars. Practically all imported since 1915 are of American manu- 

 facture. Previous to that Italian and French cars predominated 

 and manufacturers in both countries are trying hard to regain the 

 Dutch East Indian market. 



