MIL-S-46777 Semitrailers, Dump, Commercial, General Specification ForThis specification covers various sizes of rear dump semitrailers. The dump semitrailers are operated by the truck-tractors hydraulic system, unless the self-contained engine driven hydraulic option is required.

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MIL-S-46777C

3.1.2 Towing compatibility. Unless otherwise specified, the semitrailer shall be compatible for coupling, towing, maneuvering, spotting, and dumping under all conditions specified herein when coupled to a commercial truck-tractor that is unmodified, except for installation of power hoist components. Commercial truck-tractors shall include those specified in KKK-T-2108,

KKK-T-2109, and MIL-C-52895, MIL-T-52901. The empty height of the underside of the upper

fifth wheel plate above level ground, when the semitrailer is level, shall coincide with the height of the truck-tractor, having a rating equal to or exceeding the gross combination weight rating (GCWR) of the truck-tractor and semitrailer with payload. Each semitrailer shall be compatible with fore and aft rocking lower fifth wheels. When and as specified by the procuring activity (see 6.2, 4.5.2.5, and 6.4):

(a) The dump semitrailer shall be matched to the user's prime mover (truck-tractor) to insure complete, compatable, powered combination vehicle(s); or

(b) The dump semitrailer shall be furnished coupled to a new prime mover as a complete, compatable, powered combination vehicle package.

3.1.3 Material design criteria. The stresses in the load carrying members of the semitrailer, with the payload as specified in table I and the applicable specification sheet, shall not exceed

33 percent of the yield point (YP) strength under static conditions. A calculated stress analysis

of the semitrailer shall be furnished. This analysis shall include calculations and diagrams for the following:

(a) The GVWR load distribution diagram of the semitrailer.

(b) The vertical shear diagram for the length of the semitrailer.

3.1.4 First-article semitrailer. The contractor shall furnish a semitrailer of each size for examination and test within the time frame specified (see 6.2) to prove that his production methods and choice of design detail will produce semitrailers that comply with the requirements of this specification. Examination and tests shall be as specified in Section 4, and unless otherwise specified herein, all examinations and tests shall be conducted by the contractor subject to surveillance and approval by the Government (see 6.3). When specified (see 6.2), the Government will conduct any or all of the first-article examination and tests, as specified

(see 6.2).

3.2 Special requirement. Semitrailers shall meet the following special requirements as specified herein.

3.2.1 Electromagnetic interference. When specified (see 6.2), semitrailers supplied with an auxiliary engine (see 3.8) shall have electronmagnetic interference emission and susceptibility characteristics conforming to SAE J551.

3.2.2 Treatment, painting, and data plates. As specified by the procuring activity for the appropriate service (see 6.2), treatment, painting, and data plates shall be in accordance with MIL-STD-1223 and as specified herein. Inaccessible areas of the semitrailer, and truck shall be