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

TABLE III.  Semitrailer specifications (continued).

VMRS No.                         Feature                                                      Requirements

Min. 8-in. travel range from compression to rebound each axle. Cushioning bumper stops, anti-sway components linking

road-side and curbside, and heavy duty shock absorbers

dampening ride.

Provide positive cushioning stops other than shock absorbers to

halt rebound and withstand min. 2-g unsprung weight deceleration, typical of lowering the semitrailer with a crane. Air spring suspension of trailing member type, having piston or multiple bellows per SAE J551, internal bumpers.

Provide air pressure protection valve, air controls, and air-tight plumbing.

Plumbing of flexible hose and reusable swivel fittings, same as for air braking system.

Ride frequency max. 130-CPM at center of dump body.  Height

control valves, closed center time delay type protected from road splash, debris, and obstacle damage.

Time delay limits min. 3-sec. to max. 8-sec.

Guarded driver over-ride air control on roadside front for

selection of (1) high, maximum suspension height, (2) average, normal automatic height, and (3) low, depleted-air height.

VMRS 17-001-001

Tire - New.

Tires comply with TRA Year Book and DOT FMVSS for

highway speeds and 50 mph for ML tires.

Tires at least 100 level quality intended for use on powered units.

Provide all tires with traction-road-lug type tread.  Unless otherwise specified, provide 2-ea. widebase single tubeless tires on each axle, min. size 18-22.5 ML, min. LR-H (16 PR).

When specified (see 6.2), furnish 4-ea. conventional radial dual

tubeless tires on each axle, min. size 12R22.5 min. LR-G (14PR).

When specified (see 6.2), furnish 4-ea. conventional bias dual tube-type tires on each axle, min. size 11.00-22 min. LR-G

(14PR); provide heat resistant radial type inner tubes, tire flaps, and multi-piece rims with the wheels.

When specified (see 6.2), furnish 1-ea. inflated spare tire and wheel assembly with each semitrailer.

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