THE INDIA RUBBER WORLD 



[August 1, 1920. 



Rubber Armor for Airplane Gasoline Tanks. 



RUBBER was long ago suggested as a possible defensive 

 armor for battleships, the idea being that many projectiles 

 would not penetrate it owing to rebound and deflection, 

 and that holes made by those which did pierce the rubber would 

 quickly and almost completely close again. While this dream 

 has never materialized, one of the most vital, vulnerable and 

 dangerous parts of airshijjs is now being protected on the same 

 principle \v i t h 

 much success, and 

 an added meas- 

 ure of safety 

 and endurance 

 has been given 

 to Uncle Sam's 

 b i r d-m e n by 

 rubber. 



Gasoline tanks 

 on United States 

 .Army airplanes 

 are being equip- 

 ped with rubber 

 and fabric cover- 

 ings in order to 

 prevent leaks in 

 case the tank is 

 penetrated b y 

 bullets and thus 

 the fire hazard is 

 reduced. There are two types of these leak-proof coverings, de- 

 tachable and fixed, the former being furnished whenever prac- 

 ticable. 



The tank or tank form is first covered with tire breaker fabric 

 with the coated face outside. A 1/16-inch ply of pure, first-grade 

 washed and dried smoked sheet rubber is then applied over the 

 breaker fabric. Over the crude rubber is applied a f^-inch layer 

 of rubber compound, and the three layers are rolled down into 

 close and uniform contact over the whole surface of the tank, 

 when the completed covering on the tank or form is vulcanized 

 and the accessory fittings for filling the tank are installed. The 

 coverings conform to government dimensions and a tolerance 

 of plus %-inch is permitted on overall height, breadth and length. 

 No minus variation in the thickness of the walls is allowed. All 

 openings for accessory fittings are reinforced with fabric strips 

 or washers. 



Coverings of the detachable type have four triangular end flaps 

 laced together which permit insertion or removal of the tank. 

 Attached along the edges of these flaps before vulcanization are 

 strips of 17j4-ounce tire duck. These fabric strips are to re- 

 inforce the edges which hold the lacing eyelets, which are stand- 

 ard brass grommets. 



The rubber compound from which the main body of the rub- 

 ber covering is made contains not less than 92 per cent by weight 

 of new washed and dried, hard fine Para, or the highest grade 

 only of new Hevea plantation rubber, 6 per cent by weight of 

 sulphur, and not more than 2 per cent by weight of magnesium 

 o.xide. 



The utmost precautions are taken to safeguard the quality of 

 the materials and workmanship. The required tensile strength of 

 the compound is at least 1,800 pounds per square inch. The 

 elongation of a two-inch section at the breaking point is at 

 least 700 per cent. When the specimen is stretched from two 

 to fifteen inches, held in the stretched position for ten minutes 

 and then released for ten minutes, the permanent elongation must 

 not exceed 12^ per cent. Great care is exercised during the 



whole manufacturing process to exclude grit, dust or foreign 

 substances from the interior of the tank. 



Tensile test specimens of the rubber compound are cut with a 

 die from samples furnished by the manufacturer, or from a 

 sample covering. Samples are required to be approximately 3/32 

 or ?/^-inch thick with the constricted portion of the specimen 

 ^4-inch wide and having smooth edges. 



Manufacturers 

 are required to 

 furnish, at their 

 own expense, with 

 each heat of tank 

 coverings, a sam- 

 ple eight inches 

 square of the 

 covering made up 

 as applied to the 

 !ank. It must be 

 vulcanized at the 

 same time and 

 under the same 

 .-onditions as the 

 coverings it rep- 

 resents, and be 

 g u a r anteed 

 to consist of the 

 same materials. 

 All materials 

 and finished coverings are subject to inspection by the Inspection 

 Section, Procurement Division, of the Air Service, and acceptance 

 or approval of the materials in process does not infer acceptance 

 of the finished product. All accepted coverings are plainly 

 marked with the official acceptance stamp of the Air Service. 

 The manufacturer's name or trade-mark, the Air Service produc- 

 tion order number, style of covering and the date of manufac- 

 ture are permanently impressed on the outside of each rubber 

 covering, and the coverings or covered tanks are packed for 

 shipment as directed by the purchaser. 



The Air Service reserves the right of free access for its in- 

 spectors to all parts of the manufacturer's plant concerned in 

 the manufacture of these coverings ; also of adequate facilities 

 for determining that the materials and coverings conform to 

 specification, and of the opportunity to check and mark all 

 materials in process or in stock. 



The information and illustration used in this article were sup- 

 plied by the Specifications and Standards Section, Engineering 

 Division, Air Service, United States Army, Dayton, Ohio. 



\iRrL.\ 



ADJUDICATED PATENTS. 



Elyria N.\tion.\l Rubber Heel Co. vs. I. T. S. Rubber Co. 

 United States Circuit Court of Appeals, Ohio. 



The Tuflford reissue patent. No. 14,049, for a rubber heel, held 

 not infringed on review of an order granting a preliminary in- 

 junction. ("Federal Reporter," volume 263, page 979.) 



ST. LOUIS AS A MANUFACTURING CENTER. 



The St. Louis, Missouri, Chamber of Commerce is circulating 

 very convincing literature telling manufacturers who are con- 

 templating a change of location, or the establishment of a 

 branch office, just why St. Louis should be chosen. 



The city's recent successes in inducing large business concerns 

 to come there are chiefly due to central location, favorable trans- 

 portation facilities and rates both by land and water, available 

 lis, and the excellent living and housing conditions. 



