KKK-B-1579 Buses, Motor: School, With High Headroom, 20-, 28-, 36-, 44-, 58- Passenger, Two-Wheel DriveThis specification covers gasoline and diesel, engine driven, high headroom, two wheel drive school buses. Buses shall have an engine mounted partially \(snub nose\) or completely forward of the windshield. Vehicles procured under this specification are commercial items which shall be warranted \(by a single prime contractor\) as specified in 6.4 or in procurement documents.

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KKK-B-1579B

3.2.8 Accessibility. The design of the vehicle and optional equipment shall permit ready

accessibility for routine servicing and shall permit accessibility for replacement and adjustment

of component parts and accessories with minimal disturbance of other components and systems.

3.2.9 Materials. The materials shall be new or new reclaimed material, not less than the

quality conforming to current engineering and manufacturing practices. Materials shall be free

of defects, suitable for the intended service.

3.3 Performance.

3.3.1 Speeds and gradeability. High and low speed requirements shall be met with the

bus loaded to specified GVW.

3.3.1.1 High speed gradeability. The vehicle shall ascend a 1.75 percent grade at

50 miles per hour (mph). Gradeability shall be verified with calculations in accordance with

SAE J688 (see 6.3).

3.3.1.2 Low speed. Low speed of a unit with a manual transmission shall be calculated

with the engine operating at not less than 35 percent of recommended governed speed and shall

provide a vehicle speed not greater than 4 mph. Low speed of a unit with an automatic

transmission shall not exceed 12 mph at manufacturer's recommended governed speed.

3.3.1.3 Maximum geared speed. The maximum geared speed at engine governed speed

shall be not less than 58 mph. Conformance to geared speed specified shall be determined by

calculating in accordance with the following formula:

Maximum geared speed (mph)=

Governed speed (rpm)

Total gear reduction x tire factor (see 6.3)

3.3.2 Turning radius. The turning radius, defined as the distance from the turning center

of the centerline of the tire describing the largest circle while the vehicle is executing its sharpest

practicable turn, shall be not greater than 30 feet for type I; 34 feet for type II, VI, and VII; and

45 feet for type III, IV, and V.

3.4 Chassis components.

3.4.1 Engine.

3.4.1.1 Gasoline engine. When specified (see 6.2), the engine shall be a liquid cooled,