S11 Low Floor

SUPREME CORPORATION Download PDF Report

EXECUTIVE SUMMARY

Supreme Corp. submitted a model S11 Low Floor, diesel-powered 14 seat (including the driver) 28-foot bus, for a 10 yr/350,000 mile STURAA test.  The bus is built on a Ford Motor Co. F-450 XL Super Duty chassis.  Testing started on November 9, 2009 and was completed on June 28, 2010.  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 25, 2009 and was completed on June 21, 2010.

The interior of the bus is configured with seating for 14 passengers including the driver.  Free floor space will accommodate 20 standing passengers resulting in a potential load of 34 persons.  At 150 lbs per person, this load results in a measured gross vehicle weight of 18,240 lbs.  In order to avoid exceeding the GAWR (7,000 lbs) of the front axle, ballast for all 20 standing passengers and 2 seated passengers was eliminated.  This reduction from full capacity resulted in an adjusted measured gross vehicle weight of 15,060 lbs and was used for all dynamic testing.  The middle SLW segment was performed at the same 15,060 lbs.  Ballast for 2 seated passengers was eliminated to avoid exceeding the GAWR (7,000 lbs) of the front axle.  The final segment was performed at a CW of 13,400 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.

Accessibility, in general, was adequate.  Components covered in Section 1.3 (repair and/or replacement of selected subsystems), with the exception of the 2 alternators, along with all other components encountered during testing, were found to be readily accessible and no restrictions were noted.  The alternators were stacked in the engine compartment in limited space.       

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 twenty-three reported failures, sixteen were Class 3 and seven 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 14.49 seconds.

The Shakedown Test produced a maximum final loaded deflection of 0.921 inches with a permanent set ranging between -0.005 to 0.010 inches under a distributed

static load of 12,750 lbs.  The Distortion Test was completed with all subsystems, doors and escape mechanisms operating properly.  Water leakage was observed during the test at the cab/body interface and the emergency escape hatch.  All subsystems operated properly. 

The Static Towing Test was performed using a target load (towing force) of  16,080 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 3.0 inches.

A Fuel Economy Test was run on simulated central business district, arterial, and commuter courses.  The results were 5.71 mpg, 6.11 mpg, and 11.48 mpg respectively; with an overall average of 6.81 mpg.

A series of Interior and Exterior Noise Tests was performed.  These data are listed in Section 7.1 and 7.2 respectively.