MIL-S-62549 Semitrailer, Low Bed, 40 Ton Nominal Payload For Transportation Of Heavy Engineer Construction Equipment, M870A2This specification covers a level frame, low bed semitrailer equipped with a folding gooseneck for front loading and movement of heavy engineer construction equipment.

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MIL-S-62549(AT)

3.4.1.1 Interchange coupling. The interchange coupling dimensions specified below shall be in accordance with SAE J701:

a.	Minimum support clearance radius	88 in
b.	Maximum swing radius	84 in
c.	Range of kingpin setting	16-30 in
d.	Upper fifth wheel plate	65 ± 1 in
	height, loaded

3.4.2 BII.

3.4.2.1 Wrench. A tire lug wrench shall be provided.

3.4.2.2 Highway warning kit. A highway warning kit including three emergency reflectors and four red flags shall be furnished and shall conform to FMVSS 125 and FMCSR 393.95. The kit shall be in a metal or plastic box and located in the tool box of the gooseneck.

3.4.2.3 Pocket for equipment record folder and manuals. A pocket for the vehicle operation manuals and the Government furnished log book shall be furnished and stowed in the tool box located under the floor of the gooseneck.

3.4.3 Screw threads. Unless otherwise specified (see 6.2), all screw threads shall be in accordance with FED-STD-H28.

3.4.4 Frame splices. Where frame members are spliced, joints shall be reinforced to fulfill the static loading requirements of 3.2.1 and the dynamic loading requirements of 3.4. Frame splices shall be included with technical proposal and shall be designed to avoid stress concentration. All splice welds shall be continuous.

3.4.5 Chassis. The semitrailer chassis shall have sufficient rigidity and strength to withstand both unloaded and fully loaded semitrailer in the operations of loading, unloading, and dynamic transport.

3.4.6 Frame assembly. Level with folding gooseneck. Main frame members shall be braced with a sufficient number of cross-members to insure stability. The Rear cross-members shall extend the full width of the semitrailer. The main structural members of the frame assembly shall be manufactured from low alloy high strength steel. All parts of the frame shall be electric-arc welded. When the semitrailer is loaded with rated payload, the maximum fiber stress in any frame member shall be no greater than 33 percent (%) of the frame material yield strength. The semitrailer shall be equipped with rear loading beavertail to sustain repeated loading as specified

in 3.5.8.