20 



THE INDIA RUBBER WORLD 



[OciuuER 1, 191 y. 



(d) The usual inc-thods of inspection used by tire companies in com- 

 mercial practice to discover defects in each roll of cord fabric shall be 

 employed, and tests to determine the tensile strength of cords shall be made 

 in ten individual cords taken from each roll. These tests shall be made in 



The individual cords shall be tested in a fabric testing machine in which 

 the distance between grips is approximately 10 inches, which grips separate 

 at the rale of 20 inches per minute. Th 

 standard specification of the individual i 



(e) Beads shall be constructed with wire strands 

 as in standard commercial practice. Tensile strength 

 as used by the individual tire manufacturers in the 

 will be satisfactory in so far as they are sufficient to preclude any chance 

 of a bead stretching or blowing off the rim when under pressure. 



(f) Two chafing strips of fabric weighing not less than 8 ounces per 

 square vard shall be used. Each chafing strip must extend up«-ard on 

 each side of the tire at least 1% inches from the heel of the bead. One 

 chafing strip shall extend at least 3/16-inch from the other. 



(k) There shall be a cushion or rubber compound applied over the 

 cords which shall be wider than the breaker. The minimum gage of this 

 cushion shall be .0625-inch. . 



(h) Over the cushion there shall be at least one breaker strip of open- 

 wcavc fabric such as is used in standard commercial practice, coated r 

 both sides with a rubber compound having the physical 



e ■ ------ »--» *i — cusnvon anu 



width 



effected, 

 of 3; 



Egyptian cotlon. or its pnysicai t 

 10 ounces per square yard. 



(i) The tread of the tire shall 

 3/16-inch of which shall be the 

 tread under the middle of the no 



(j) The sidcwall of the tire : 



:id chemical prop- 

 between the cushion and tread 

 strip shall have 



not be less than 7/16-i-nch thick in 

 minimum thickness for the part 

 n-skid portii 

 hall have a 



urn thickness of .0625- 



AND Tests, (a) Cross sectional diameter 

 o the recommended weight and load sched- 

 r.. siiaii uc ix^L less than 5.2 inches, 

 shall be capable of withstanding water P/^essure^ o 350 pounds 

 square inch without apparent injur 

 cretion of the itispector 



— -x Measurements 



of each tire inflated according 

 ule of the S. A. E. shall be i 



(b) - 



be made 



(c) 



m strength 



ngth factor" is the produc 



' - -=ght angles to 



at the tread 



the 



if the tire shall be 2,500 pounds. This 

 „, of the number of cords per inch measured 

 :o the cords; times strength of individual cord 

 times the number of plies. 



union between breaker and tread and between 

 erage 32 pounds 



(e) Strength of the 

 14 pounds, or more, per 



(f) Strength of 



more, per inch, using the 

 shall average 



The strength of the 

 breaker and cushion shall a 



.-»..nrt.ir.l frirtion lest. . , ,, , 



between sidewall and 

 r iin.il using the standard friction test. 



union between sidewall and plies shall average 16 

 h, using the standard fricti ' ' 



lent busii 

 (b) Ko 



be prepared 

 to be given 



product a;; 1 



see that l ■ 

 (d) A .- 

 •he Govcriimciil str.tnig 

 cates in construction an 

 properly and a sufficient 



Service, at least 



- I I iv an affidavit before delivering tires to 

 ■ tires' to be delivered are practically dupli 

 ■lal of tires which he has previously 



of tires s.".tisfactory to the Motor Transpoj 

 g averaged on the re 



ted 



vlieels at least 5;000 



side of each tire shall be properly lined in accordance 



ctice of tire manufacturers. 



of the size 35 by 5 shall be furnished with each tire, 

 IS 1.. .,iandard commercial practice. 



8 Compound (ai The tread shall be made from and have the char- 

 acteiistics of a compo-.tnd containing at least ?0 per cent by volume of the 

 best new rubber. Content of sulphur shall not exceed 8 per cent by wejght 



viNG. The ir 

 standard pra 

 A flap 



the 



.^pound shall 



e strength of 

 inch ard shall have a minimum set of 25 per e 

 by stretching 2 to 10 inches and holding for 10 

 10 minutes and then measuring the per 



laimed rubbe 



be 2,600 pounds per square 



;nt. Set test shall be made 



minutes, resting sample for 



of elongation over the original 



tha 



n — These shall be made fr 

 ;ontaining at least 85 per 

 plantation rubber. Sulp! 

 nt by weight of new rubbe 



sed. 



volume of the 

 ent shall not 

 No reclaimed 



rubber shall be 



(e) Sidewall— The sidewall shall be made 

 teristics of a compound containing a minimum 

 the best qualitv new wild or plantation rubbe 





weight 



vulcanized 



from and have the charac- 



of 65 per cent by volume of 



r. Sulphur content shall not 



rubber used. No reclaimed 



minimum tensile strength of 



■e inch and a minimum elongation of 450 per eeiit 



maximum set of 25 per cent. Tlie compound shall 



known to the rubber trade as "oil substitutes." 



ir in any of the above compounds shall not exceed 8 



of new rubber used except as follows: if the manu- 



sulphur-bearing mineral fillers, thereby causing the 



total sulphur m be over 8 per cent of the weight of new rubber ■-- 



do so but shall submit for analysis a sample of the finished 

 stock. Such stock shall not show a sulphur content in 

 of over 8 per cent of the weight of new rubber used. 



9. Inspection. The Motor Transport Service reserves the right to make 

 any inspection or test or analysis necessary to insure the product meeting 

 all' reqnire-nents of this specification. 



10. Packing. All tires shall be spirally wrapped according to standard 

 practice and properlv labelled on the outside showing size, type, name of 

 manufacturer, serial'number and marked with either tag or label in colors 

 of red, white or blue which will denote as follows: red, first four months of 

 calendar year; white, second four months of calendar year; blue, last 

 four months uf calendar year, years to be designated by square, triangle 

 and round labels or tags, tags or labels to be approximately 2 inches in 

 diameter. Tires shipped for original equipment of cars shall be packed as 



lAll sections for approval must be sent to Lieutenant George B. Wells, 

 Engineering Division, Motor Transport Corps, 358 Union Station, Washing- 

 ton, District of Columbia. 



specified by customer. In the case ot oversea sliipniciils, iiie specincniiuns 

 covering this shall be applied. 



SPECIFICATIONS FOR PNEUMATIC AUTOMOBILE TIRE 



CASINGS, SIZE 36 BY 6. 



.Specification No. 1070. 



coed construction. 



1 General, (a) Pneumatic automobile tire casings manufactured in 

 •-ccordance with this specification shall be of cord construction of the size 

 known to the trade a? 36 by 6 inches. 



(b) The tire must give satisfactory service under a load of 2,000 pounds, 

 when inflated to 90 pounds per square inch. 



(c; Tires to be free from all defects and fully guaranteed as to mate- 

 rial and workmanship. . , , . , ^ 



(d) Tires shall be of the standard commercial non-skid design of the 

 manufacturer furnishing the same, or of rib tread design as specified on 

 :hc order. In the case of a manufacturer using more than one non-skid 

 tread design, selection of the design to be adopted is at the option of the 

 Motor Transport Corps. A small section of the tire shall be submitted 

 for approval before contract is let.' 



(el --Ml tires shall be plainly marked with manufacturer's name and 

 the size of the tire and marked with either tag or label in colors of red, 

 white or blue, which shall denpte as follows: red, lirsl four months of 

 calendar year; white, second four months of calendar year; and blue, last 

 four months of calendar year. Years to be designated by square, triangle 

 and round label or tags— tags or labels to be approximately two inches in 

 diameter. 



(f) As soon as possible it is desired that all tires be marked with the 

 equivalent millimeter sizes as recommended by the Society of Automotive 



2. Type. All tires manufactured in accordance with this specification 

 shah be of the straight side rim of the size 36 by 6 inches. 



3. Construction. (a) Carcass of tire shall consist of no less than 

 four and no more than twelve separate plies of cord applied in such a 

 manner that an equal number of plies shall run in each diagonal direc- 



(b) All cord material to be of the best quality, combed Sea Island or 

 Egjptian cotton, or ils phvsical equivalents. 



(c) All cord fabric must be thoroughly dried according to standard 

 manufacturing practice, before it is started through the operations of 

 rubberizing. 



(d) The usual methods of inspection used by tire compannies in com- 

 mercial practice to discover defects in each roll of cord fabric, shall be 

 employed, and tests to determine the tensile strength of cords shall be 

 made on ten individual cords taken from each roll. These tests shall be 

 made in the following manner: 



The individual cords shall be tested in a fabric testing machine in 

 which the distance between grips is approximately 10 inches, which grips 

 separate at the rate of 20 inches per minute. The results shown must 

 be up to the standard specifications of the individual manufacturer. 



(e) Beads shall be constructed with wire strands in the same manner 

 as in standard commercial practice. Tensile strength tests for wire strands 

 as used by the individual tire manufacturers in the construction of beads 

 will be satisfactory in so far as they are sufficient to preclude any chance 

 of a bead stretching or blowing off the rim when under pressure. 



(f) Two chafing strips of fabric weighing not less than 8 ounces per 

 square yard shall be used. Each chafing strip must extend upward on 

 each side of the tire at least lyi inches from the heel of the bead. One 

 chafing strip shall extend at least ^:i-inch above the other. 



(g) There shall be a cushion of rubber compound applied over the 

 cords which shall be wider than the breaker. The minimum gage of this 

 -ushion shall be .080-inch. 



(h) Over the cushion there shall be at least one breaker strip of open- 

 weave fabric such as is used in standard commercial practice, coated on 

 both sides with a rubber compound having the physical and chemical 

 properties of a nature to form a perfect union between the cushion and 

 tread when the cure is effected. This breaker strip shall have a minimum 

 width of 4^ inches and shall be cut on a 45-degree bias. Breaker shall 

 be made from the best quality Set Island or Egyptian cotton or its 

 equivalent and should weigh not less than 10 ounces per square yard. 



(i) The tread of the tire shall not be less than 9/16-inch thick, 7/32-inch 

 of which shall be the minimum thickness for the part of the tread under 

 the middle of the non-skid portion. 



(j) The sidewall of the tire shall have a minimum thickness of .0625- 



4. Physical Measurements and Tests, (a) Cross sectional diameter 

 of each tire inflated according to the recommended weight and load sched- 

 ule of the S. A. E. shall be not less than 6.2 inches. 



(b) Tires shall be capable of withstanding water pressure of 350 pounds 

 per square inch without apparent injury. This test to be made at the 

 discretion of the inspector. 



(c) The minimum strength of the tire shall be 3,000 pounds. This 

 "strength factor" is the product of the number of cords per inch meas- 

 ured at the tread at right angles to the cords; times strength of individual 

 cord as taken from the cord tire; times the number of plies. 



(d) The strength of the union between breaker and tread and between 

 breaker and cushion shall average 32 pounds or more per inch, using the 

 standard friction test. 



(e) Strength of the union between sidewall and plies shall average 14 

 pounds or more per inch, using standard friction test. 



(f) Strength of the union between cushion and plies shall average 26 

 pounds or more per inch, using the standard friction test. 



5. Road Tests. Any manufacturer bidding on orders for the govern- 

 ment business must be prepared to meet the following testing conditions: 



(1) No tires are to be given consideration by the Government unless 

 the company submitting the bid tenders an affidavit stating, that they main- 

 tain and nroperly check up tests on cars to properly test their pneumatic 

 tire product and that these cars deliver an average of 8,000 tire miles weekly. 



(2) The ears, speeds, loads, and road conditions must be such that the 

 tires are properly tested and the Government may appoint an inspector to 

 see that the above conditions are complied with. 



(3) A successful bidder must supply an affidavit before delivering any 

 tires to the Government stating that the tires to be delivered are practieallv 

 duplicated in construction and material of tires which he has previously 

 tested properly and a sufficient number of tires satisfactory to the Motor 

 Transport Service, at least six tires, have averaged on the rear wheels at 

 least 5.000 miles. 



6. Lining. The inside of each tire shall be properly lined in accordance 

 with the standard practice of tire manufacturers. 



7. Flaps. A flap of the size 36 by 6 shall be furnished with each lire 

 as in standard commercial practice. 



