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|  MIL-S-62549(AT)
3.4.13.5 Articulation (wheels). Sufficient articulation shall be provided on each wheel under
each of the following conditions and with the full payload on the roadbed of the semitrailer.
Allowable load variation at each wheel from the mean or uniform loading is 30% when the axles
are articulated as follows:
a. With first and third wheels on one side and center wheel on opposite side, elevated
four inches above remaining wheels.
b. With any pair of opposite wheels elevated four inches above remaining wheels.
c. With any two pairs of opposite wheels elevated four inches above remaining pair.
3.4.14 Brakes. The brakes shall be of the full-air internal expanding type and shall conform
to FMCSR 393.45, 393.46, and 393.52 and FMVSS 121. The brake system shall include piping,
hose connections, gladhands, spring loaded dust covers or dummy gladhands equipped with
security chains, air reservoirs (with remote operating control for the drain valve positioned above
the bottom of the frame rail), automatic slack adjusters, brake chambers, relay emergency valve,
and all other parts and connections required for a complete air-brake system. All brake linings
shall be constructed from non-asbestos materials. Location of air fittings shall be near the front of
the gooseneck and shall be recessed in the gooseneck to preclude damage. All components of the
braking system shall be installed above the bottom of axles to provide adequate road clearance
when traveling over uneven or rough terrain. No part of the foundation brakes shall extend below
the bottom of wheel rims.
3.4.14.1 Parking brakes. The semitrailer shall be equipped with a minimum of two spring
actuated parking brakes that shall hold the semitrailer, heading up or downhill with rated payload,
on a 10% grade despite the depletion of the compressed air supply. The parking brakes shall be
automatically applied upon disconnection of the emergency air line and under emergency
conditions. The parking brakes shall conform to FMCSR 393.41.
3.4.14.2 Gladhands/coupler. The semitrailer shall be equipped with connectors for service
and emergency air in accordance with SAE J318 or MS35746. The service brake connector shall
be yellow and the emergency red. The location of the connectors shall be as specified in
SAE J702. Gladhand tags conforming to MS53007-1, "service", and -2, "emergency", and
dummy coupling assembly conforming to drawing 7411021, shall be furnished and properly
installed.
3.4.14.3 Brake chambers. The semitrailer shall be equipped with commercial heavy duty
spring applied type brake chambers with environmental covers, boots and diaphrams of a type
unaffected by environmental conditions specified in 3.2.2. A manual means of disengaging the
spring actuated parking brake independent of any power source shall be provided to allow
emergency operation of the semitrailer. A means for manual lubrication and adjustment of the
slack adjusters shall be provided.
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