BLUE BIRD CORPORATION Download PDF Report
Blue Bird Corporation submitted a model Ultra LF, CNG-powered 30 seat/36-foot bus, for a 12 yr/500,000 mile STURAA test. The odometer reading at the time of delivery was 454.0 miles. Testing started on April 15, 2005 and was completed on April 28, 2006. The Check-In section of the report provides a description of the bus and specifies its major components.
The primary part of the test program is the Structural Durability Test, which also provides the information for the Maintainability and Reliability results. The Structural Durability Test was started on August 10, 2005 and was completed on April 7, 2006.
The interior of the bus is configured with seating for 30 passengers including the driver. Free floor space will accommodate 30 standing passengers resulting in a potential load of 60 persons. At 150 lbs per person, this load results in a measured gross vehicle weight of 30,440 lbs. In order to avoid exceeding the GAWR (10,000 lbs) of the front axle, ballast for 5 standing passengers (750 lbs) was eliminated. This reduction from full capacity resulted in an adjusted measured gross vehicle weight of 29,620 lbs and was used for all dynamic testing. The middle segment was performed at a seated load weight of 26,160 lbs and the final segment was performed at a curb weight of 22,160 lbs. Durability driving resulted in unscheduled maintenance and failures that involved a variety of subsystems. A description of failures and a complete and detailed listing of scheduled and unscheduled maintenance are provided in the Maintainability section of this report.
Accessibility, in general, was adequate. Components covered in Section 1.3 (Repair and/or Replacement of Selected Subsystems) along with all other components encountered during testing, were found to be readily accessible and no restrictions were noted.
The Reliability section compiles failures that occurred during Structural Durability Testing. Breakdowns are classified according to subsystems. The data in this section are arranged so that those subsystems with more frequent problems are apparent. The problems are also listed by class as defined in Section 2. The test bus encountered no Class 1 or Class 2 failures. Of the 106 reported failures, 72 were Class 3 and 34 were Class 4.
The Safety Test, (a double-lane change, obstacle avoidance test) was safely performed in both right-hand and left-hand directions up to a maximum test speed of 45 mph. The performance of the bus is illustrated by a speed vs. time plot. Acceleration and gradeability test data are provided in Section 4, Performance. The average time to obtain 50 mph was 39.55 seconds.
The Shakedown Test produced a maximum final loaded deflection of 0.227 inches with a permanent set ranging between 0.000 to 0.005 inches under a distributed static load of 22,500 lbs. The Distortion Test was completed with all subsystems, doors and escape mechanisms operating properly. Water leakage was observed during the test at the top frame of the driver’s window and the top center post of the windshield.
The Static Towing Test was performed using a target load (towing force) of 26,592 lbs. All four front pulls were completed to the full test load with no damage or deformation observed. The Dynamic Towing Test was performed by means of a front-lift tow. The towing interface was accomplished using a hydraulic under-lift wrecker. The bus was towed without incident and no damage resulted from the test. The manufacturer does not recommend towing the bus from the rear; therefore, a rear test was not performed. The Jacking and Hoisting Tests were also performed without incident. The bus was found to be stable on the jack stands, and the minimum jacking clearance observed with a tire deflated was 3.9 inches.
A Fuel Economy Test was run on simulated central business district, arterial, and commuter courses. The results were 0.61 M/lb, 0.78 M/lb, and 1.23 M/lb respectively; with an overall average of 0.77 M/lb.
A series of Interior and Exterior Noise Tests was performed. These data are listed in Section 7.1 and 7.2 respectively.