MIL-DTL-11891G(AT)
4.7.1.13 GC mass spec. This test shall be performed to the requirements of 3.3.3.11.
During production, the test shall be performed on unvulcanized rubber sampled at the frequency
established by the Government. The results will be compared to the established test results
obtained at qualification.
4.7.1.14 Bushing fill. To determine conformance to 3.5.4, the contractor shall test each
mold cavity as specified herein. Every time a mold is reworked, or a new mold is produced, each
cavity shall be tested. Prior to initiation of production, each mold shall have each bushing cavity
tested for minimum and maximum fill by use of the approved compound in the following
procedure:
a. Mold one set of bushing to pin or sleeve, without bond (do not use bonding agent)
for minimum fill in accordance with 4.7.1.14.1, and maximum fill in accordance
with 4.7.1.14.2. Another set of bushings which shall be bonded may be used for
maximum fill determination in accordance with 4.7.1.14.3 in lieu of 4.7.1.14.2.
Record mold position of each bushing. Record the outside diameter of each pin or
sleeve of the unbonded set in inches to three decimal places.
b. Ensure skin coating between or beyond rings and flash is not in excess of
0.031 inch.
c. Record from track shoe drawing the following dimensions in inches:
(1) Maximum and minimum diameter of bore in shoe body.
(2) Average length of bore in shoe body. NOTE: On the boss and bushing sleeve
combination where the bushing sleeve is shorter than its mating boss, use the
bushing sleeve length as the determining factor).
4.7.1.14.1 Minimum fill determination. Using the unbonded bushing, the following
procedure shall be completed:
a. Slide bushing elastomer off pin or sleeve.
b. Immerse elastomer in graduated cylinder of water. Water and bushing shall be at
the same temperature of 80 + 20°F. Record volume of water displaced in cubic
centimeters.
c. Apply data from drawings and recorded bushing sleeve diameter in the following
formula:
Vcc = 12.227 (Do2 - Di2)L
Where:
Do = maximum diameter of bore (inches)
Di = recorded diameter of pin or sleeve (inches)
L = average length of bore or sleeve (inches)
Vcc = volume of cavity for bushing
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