Accession Number : ADA307520

Title :   Broad Temperature Range Obturator Pad Materials.

Descriptive Note : Technical rept.,

Corporate Author : WATERVLIET ARSENAL NY

Personal Author(s) : Montgomery, R. S.

PDF Url : ADA307520

Report Date : 27 JAN 1975

Pagination or Media Count : 73

Abstract : It is important that obturator pads seal satisfactorily over a wide range of ambient temperatures. This is difficult to achieve at very low temperatures, where the elastomeric pad materials become stiff and fail to transmit pressure hydrostatically as they must for effective obturation. Furthermore, since the coefficient of thermal expansion of an elastomer is about 10 times that of steel, the pad shrinks much more than does, its cavity in the breech assembly as the temperature falls. Methods were developed for evaluating these characteristics of candidate materials simply and inexpensively. The most promising elastomer was the castable polyurethane made from Adiprene L-42. This elastomer retains excellent flexibility to temperatures below -65 F and pads with very little change in the important diametral direction with temperature can be made by incorporating 1/4 in. glass fibers in the formulation. Adiprene-fiber glass pads have sealed well in both the l75mm Gun M-113A1 and the 155 mm Howitzer M-185 from 125 deg down to a temperature of -50 deg F in climatic firing tests at Aberdeen Proving Grounds which corroborates these ideas on the design of obturator pads and the shop methods of evaluation.

Descriptors :   *OBTURATION(BALLISTICS), LOW TEMPERATURE, FIRING TESTS(ORDNANCE), ELASTOMERS, THERMAL EXPANSION, GLASS FIBERS, RANGE(EXTREMES), BREECH MECHANISMS, POLYURETHANE RESINS, SEALS(STOPPERS), SEALED SYSTEMS, CASTINGS, COLD WEATHER TESTS, CARTRIDGES(PAD), HOWITZERS.

Subject Categories : Guns
      Ballistics

Distribution Statement : APPROVED FOR PUBLIC RELEASE