MIL-DTL-11891 Track Shoe Sets, Track Shoe Assemblies, Track Shoe Pads And Track Shoe Bushings, Vehicular: ElastomerizedThis specification identifies the requirements for qualification and production control of track systems supporting U.S. Military Tracked Vehicles. This specification is intended primarily for the qualification of elastomeric compounds used in the fabrication of track and track components and to ensure that the quality and performance established at qualification is maintained throughout production. The contractor is held fully responsible for the entire assembly/component including all non-elastomeric components and fasteners.

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MIL-DTL-11891G(AT)

3.3.3.5 Aged physical properties. Aged physical property tests will be performed on

specimens taken from bushing compounds in accordance with ASTM D573. Accelerated aging

shall be conducted for 166 + 2 hours at 158 + 3.6 degrees Fahrenheit (�F) or 70 to 72 hours at

212�F + 3.6�F. All test results will be reported to the Government. The tolerance for the percent

change of unaged tensile strength to aged tensile strength will not exceed 30 percent during

production. The tolerance for the percent change of the unaged elongation to the aged elongation

will not exceed 40 percent during production (see 4.7.1.4 and 4.7.1.6).

3.3.3.6 Thermogravimetric analysis. This test will be performed in accordance with

ASTM E1131 during qualification to establish requirements for future reference during process

control. All test results will be reported to the Government. The ranges for TGA are as follows

(see 4.7.1.8):

Plasticizer + Residue

+3%

Polymer

+5%

Filler

+5%

3.3.3.7 Vulcanization using oscillating disk cure meter. A curing characteristics curve

(trace) shall be obtained as outlined in ASTM D2084 on the bushing compound being submitted

for qualification. The traces will be provided to the Government. The following tolerances will

be used in production when compared to the charts representing traces of compounds used for

fabrication of components for qualification. Parameter definitions shall be according to

ASTM D2084. Alternative test methods and parameter may be used but must be identified in the

control plan and approved by the Preparing Activity (see 4.7.1.9).

Minimum torque (M): +2 pound-inch (lb-in) [.23 Newton-meter (N-m)]

Maximum torque (M): +4 lb-in (0.45 N-m)

Time to 60 percent of M: T(60) + 0.4 minutes

Time to reach 5 lb-in (0.57 N-m) above minimum torque: +0.4 minutes

3.3.3.8 Bushing adhesion test. Testing apparatus shall conform to ASTM D429,

method B. A hub and spindle assembly is required for mounting the bushing insert (P/N 87565l9)

that shall permit full rotation about a fixed axis. Three complete bushing assemblies (P/N

11678029) shall be selected as the test samples and be of an equivalent state of cure to that of the

bushings submitted for endurance test. Testing shall be conducted on the outer rings of the

bushing assembly (see 4.7.1.10).