SUPREME CORPORATION Download PDF Report
Supreme Corp./Startrans Bus submitted a model Senator HD Cutaway, CNG-powered 29 seat/32-foot bus, for a 7 yr/200,000 mile STURAA test. The odometer reading at the time of delivery was 8,499 miles. Testing started on October 15, 2010 and was completed on March 29, 2011. 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 November 3, 2010 and was completed on January 7, 2011.
The interior of the bus is configured with seating for 29 passengers including the driver. (4 seats stow away to accommodate 2 wheelchair positions). Free floor space will accommodate 15 standing passengers resulting in a potential load of 44 persons. At 150 lbs per person and 600 lbs per wheelchair position, this load results in a measured gross vehicle weight of 20,500 lbs. Note: at Gross Vehicle Load (GVL) the weight of the rear axle 684 lbs over the rear GAWR and 1,000 lbs over the GVWR. The first segment of the Structural Durability Test was performed with the bus loaded to a GVW of 20,500 lbs. The middle segment was performed at a seated load weight of 18,350 lbs and the final segment was performed at a curb weight of 13,520 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 is provided in the Maintainability section of this report.
Effective January 1, 2010 the Federal Transit Administration determined that the total number of simulated passengers used for loading all test vehicles will be based on the full complement of seats and free-floor space available for standing passengers (150 lbs per passenger). The passenger loading used for dynamic testing will not be reduced in order to comply with Gross Axle Weight Ratings (GAWR’s) or the Gross Vehicle Weight Ratings (GVWR’s) declared by the manufacturer. Cases where the loading exceeds the GAWR and/or the GVWR will be noted accordingly. During the testing program, all test vehicles transported or operated over public roadways will be loaded to comply with the GAWR and GVWR specified by the manufacturer.
Accessibility, in general, was adequate. Components covered in Section 1.3 (repair and/or replacement of selected subsystems), were found to be readily accessible and no restrictions were noted with the exception of the auxiliary battery. Access to the auxiliary battery was hindered due to the location of the CNG tanks. The only other accessibility issue encountered during testing was difficult access to the diagnostic interface connector due to the location of brackets for the A/C compressor.
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, 2, or 4 failures. Of the 2 reported failures both were Class 3.
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 17.92 seconds. The Stopping Distance phase of the Brake Test was completed with the following results; for the Uniform High Friction Test average stopping distances were 27.79’ at 20 mph, 55.75’ at 30 mph, 94.84’ at 40 mph and 126.57’ at 45 mph. The average stopping distance for the Uniform Low Friction Test was 24.33’. There was no deviation from the test lane during the performance of the Stopping Distance phase. During the Stability phase of Brake Testing the test bus experienced no deviation from the test lane but did experience pull to the left during both approaches to the Split Friction Road surface. The Parking Brake phase was completed with the test bus maintaining the parked position for the full five minute period with no slip or roll observed in both the uphill and downhill positions.
The Shakedown Test produced a maximum final loaded deflection of 0.282 inches with a permanent set ranging between 0.001 to 0.005 inches under a distributed static load of 16,200 lbs. The Distortion Test was completed with all subsystems, doors and escape mechanisms operating properly. Water leakage was observed during the test at the lower right corner of the windshield. All subsystems operated properly.
The Static Towing Test was performed using a target load (towing force) of 16,224 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 6.7 inches.
A Fuel Economy Test was run on simulated central business district, arterial, and commuter courses. The results were 0.55 M/lb, 0.98 M/lb, and 1.40 M/lb respectively; with an overall average of 0.79 M/lb.
A series of Interior and Exterior Noise Tests was performed. These data are listed in Section 7.1 and 7.2 respectively.