Downloaded from https://www.everyspec.com MIL-STD-81OC 4.6.12.1 Part 1 (Former 4.16.1) DISCONTINUED 4.6.12.2 Part 2, bounce, loose cargo 4.6.12.2.1 Purpose. To determine that the equipment, as prepared for field use, shall be capable of withstanding the vibrations normally indui- ed during combat transportationas loose cargo. Equipment in this class is normally transported in a transit case, combination case, or special container from which it is removed just prior to use, e.g., ammunition or missiles. 4.6.12.2.2 Apparatus. A package tester capable of 1 inch (double ampli- tude) displacement and of suitable capacity for testing military equipment. 4.6.12.2..3 Test conditions.
The test bed of the package tester shall be covered with a panel of l/2-inch plywood, with the grain parallel to the drive chain. The plywood shall be secured with six-penny nails, with top of heads flush with or slightly below the surface. Nails shall be spaced at 6-inch intervals around all four edges. If the distance between either pair of fences is greater than 24 inches, the plywood shall also be nailed at 3-inch intervals in a 6-inch square at the center of the test area.
Using suitable wooden,fences, constrain the test item to a horizontal motion of not more than 2 inches in a direction parallel to the axes of the I axes of the shafts, a distance more than suffici~nt to insure the test item A will not rebound from fence to fence. For large items, care should be taken to avoid potential air-cushioningeffects which may exist between the surface of the package tester and the test item. 4.6.12.2.4 Performance of test. The test item, as secured in its transit case, or combination case, or as otherwise prepared for field transportation, shall be placed on the package tester within the constraints outlined above. The test item will not be operated during vibration.
The package tester shal1 be operated in the synchronous mode with the shafts in phase. (In this mode any point on the bed of the package tester will move in “a circular path in a vertical plane perpendicular to the axes of the shafts.) The package tester shall be operated at 1-inch double amplitude and 284 rpm *2 rpm for a total of 3 hours. At the end of each l/2-hour period, turn the test item to rest on a different face, so that at the end of the 3-hour period the test item will have rested on each of its six faces (top, bottom. sides, and ends). At the end of the 3-hour period, the test item shal1 be operated and inspected and results obtained in accordance with General Requirements, 3.2.
The package tester shall be operated in the vertical linear mode (straightup and down in the vertical plane) instead,of in the synchronousmode when one of the f01lowing conditions occurs: a. Bouncing of the test item is very severe and presents a hazard to personnel. i METHOD 514.2 514.2-18