If fleet managers could have one wish granted, what would it be?
According to a recent "wish list" compiled by fleet members of The Maintenance Council (TMC), some ideal changes include a reduction in the price of LEDs, advances in connector mechanisms and an industry-wide standardization of inwire coding. Like the lengthy Christmas lists of hopeful children, TMC's wish list also is long and includes such items as: defect-free truck tires; fastener systems that will ensure adequate torque retention; a longer life-span for water and fuel pumps, radiators and injectors; adequate sensors for electronic engines; improved visibility; more effective mirrors; equipment geared for vibration and various temperatures; longer-lasting cabs; and vast improvements in frames, transmissions, axles, drivelines, suspension systems and brakes.
In 1985, fleet members of TMC reported which design and engineering changes would be necessary to successfully operate and maintain vehicles in the times ahead. In 1987 and 1993, other papers reported on the progress of the previous requests and added new ones. These papers, which were compiled by a wide spectrum of for-hire and private fleet managers, intended to bridge the gap between truck component engineers and truck users. After all, when assessing a vehicle's effectiveness, there is no better source for information than equipment users who know a vehicle's utility and performance level.
The refuse industry's presence in TMC is represented by 24 fleet maintenance managers from Waste Management Inc. in Oak Brook, Ill., and Browning-Ferris Industries, Houston. In addition, an approximate 24 city fleet managers are members, along with representatives from a few small waste haulers.
Electronics, Tires, Wheels The electrical and instrumental system requires the most maintenance and is most frequently repaired. According to users, significant improvements in the headlamp's design have extended the lamp's life. For example, headlamps which were originally installed by OEMs have an average life of 200 days and the replacement lamps last approximately 540 days. On the other hand, while incandescent lamps require 10 times the amount of amperage as a yellow LED lamp, fleet managers cannot economically justify the cost of LEDs.
Further, TMC survey respondents reported that headlamp connectors are their foremost connector problem; connections at the starter are another top concern. In addition, wiring systems need to be protected. An overwhelming 98 percent of fleet managers surveyed want an industry-wide standardization of inwire coding to properly diagnose electrical failures.
On the average, tires represent the highest single cost of total vehicle maintenance costs (approximately 20 percent). While manufacturers have successfully responded to many issues raised in the 1980s, others still need to be addressed.
In general, users want truck tires to be defect-free and to age well, or to be manufactured with improved compounds that protect the sidewall against ozone degradation. In addition, tread compounds must wear longer and accept several retreads to achieve the desired 1-million-mile life. A run flat capability can extend tire life and polymers can improve air retention, extend tire life and make up for less-than-optimum tire maintenance.
Smaller tires that will maximize cube are very desirable, according to the fleet managers. The new 19.5, 70 series low-profile tires perform adequately from a downsized brake and dissipate heat from a smaller wheel envelope. But more work needs to be done to improve tire mileage, integrity and the load carrying capacity of smaller diameter tires.
Tire repair limits and repairability have remained unchanged during the last five to 10 years and no noticeable improvements have been made in steel wire corrosion resistance. Retreading has remained unchanged; the average number of retreads on standard and low-profile tires today is 2.1, which is essentially the same as about 10 years ago. The trend towards constructing tires with only three full belts has made tires more vulnerable to penetration. On average, more than 50 percent of the today's retreaded tires require repair; this is up from five years ago, when only 35 to 40 percent of the tires required repair work.
Users want all manufacturers to have the same overall and buffed dimensions for matching and retreading purposes. Tire OEMs have not addressed the need for an industry standard in tire sizing and consequently, vehicle tires are often mismatched. For example, vehicles may have similar tires with slightly different sizes or tires of the same size but different dimensions.
Users report that the hub-piloted disc wheel system has a superior fastening system, but rust and difficulty in maintaining fastener torque are a continuous problems. Current systems require the wheels to be retorqued between 50 and 100 miles after installing a wheel. As a result, managers want fastener systems that ensure adequate torque retention. Although a wheel may attain a 10-year life, it requires too much maintenance to keep it operating for that long.
Engines Despite improved durability, serviceability, efficiency and costs, TMC's survey indicated that engines can still be improved since they have the highest maintenance costs.
For example, 36 percent of survey respondents feel that today's cooling systems are less durable than those of five years ago. Managers expect a radiator for Class 6 trucks to last 5 years or 250,000 miles. For Class 7 and 8 trucks, the radiator is expected to last 5 years or 700,000 miles.
Water pumps have a low satisfaction level among equipment users. In 1987, a request was made for a B-5 life of 300,000 miles. The 1993 survey noted that 43 percent of the responding fleets have not reached that level. The 1987 paper also requested a B-5 life of 600,000 miles for the rest of the cooling system, hoses, thermostats and radiator caps, but by 1993, 43 percent of the responding fleets had not achieved this life.
The greatest advancement in engines has been the electronics which control and monitor many of its functions. Electronics increased fuel mileage, decreased diagnostic time and, through higher efficiency, have also contributed to lower operating and maintenance costs. On the other hand, an electronic engine with a faulty sensor will confuse both the driver and the mechanic.
In addition, respondents are disappointed with the life span of the injector and fuel pump. In the next five to eight years, fleet managers would like to get 500,000 miles from injectors and to purchase fuel pumps that will last the engine's life.
Overall, the durability of today's engines have reached the 600,000-mile mark set in the 1987 TMC "Tomorrow's Truck" paper. With technology rapidly emerging, users expect engines to average 1 million miles by the year 2000.
Cabs And Controls Vision accounts for 90 percent of the information a driver receives. In general, fleets need 360-degree visibility and dry roads, or clear day visibility in all weather conditions. Improved visibility, fewer blind spots, more effective mirrors and improved defrost and defogging capability, especially for side and rear windows, have recently been requested.
In addition, vibration and temperature affect drivers. The natural frequency of the seated body is between four and six Hz while truck seat vibration frequencies fall mainly in the two to 10 Hz range. As a result, people who spend more than 50 percent of their working time driving are three times more likely to have herniated discs. In addition, 50 percent of U.S. truck drivers have lower back pain (versus 20 percent of jet pilots) and experience decreased visual acuity.
Further, drivers in cabs with hot temperatures committed significantly more moving violations, and even a moderate heat change from 21 degrees Celsius to 27 degrees Celsius degraded driver performance.
In terms of overall cab construction, previous papers indicated that cabs should have a 10-year life span (1 to 1.2 million miles). Fleet managers report that manufacturers have been most lax in this area (see "Cab Construction" table on page 52).
Chassis Suggestions emphasize the need for standardized brake systems. Goals include easily recognizable component identification to ensure long-term system integrity, and color-coded air lines to assist mechanics in troubleshooting and maintenance.
Waste haulers and other fleet managers listed future challenges, including:
* Standard color coding of air lines;
* Improved methods of brake inspections;
* Suspensions that allow constant vehicle cushioning in all degrees of multi-directional movements;
* Electronic traction control for differentials, allowing the function to be fully automated;
* Increased durability, reliability and compatibility in automated lubrication devices to justify the cost of their use;
* Disc brakes. Continued research of this reliable method is needed to maximize braking and minimize costs;
* Vehicle alignment problems. Currently, these problems cannot be corrected without unnecessary expense and downtime. Reference points for quick alignment may solve this. Available technology allows optical distance sensors to be mounted on the vehicle's chassis. These sensors could automatically measure the distance between points and input this data into a driver information system. The driver information system would, in turn, calculate the vehicle's alignment and inform the driver of any necessary adjustments;
* Ride quality. Cost reductions for air ride suspensions have increased their use. Adding a servo or an active, low-cost and low-maintenance suspension with greater dampening effect would help. Replacing the equalizer bushing assemblies currently used with assemblies that use roller bushings with sealed bearings (using no grease fittings) also would bolster ride quality and extend the life of both air and spring suspensions;
* Rust. Electrolysis, caused by dissimilar metals, remains a concern. Cost-effective composite materials would help;
* Wheel ends. Manufacturers of wheel ends, axle spindles, axle nuts, wheel bearings and oil seals must standardize one system of securing wheels and axles. This system must follow a standardized procedure for wheel bearing adjustment and proper clearance or preload pressure;
Total Vehicle Electronics Self-diagnosis strategies need to emphasize fault isolation. For example, the system should point out the faulty component so that the mechanic has to conduct fewer checks.
On-board trend analysis would assist in troubleshooting performance complaints and preventive maintenance scheduling would prevent trucks from being removed from service for subjective reasons.
All engine manufacturers have adopted standardized messages for reporting on diagnostics to the hand-held or scan tools. Fleets also need a standardized, universal, hand-held diagnostic tool with a five-year life to reduce initial costs as well as mechanic training costs. Currently, three engine manufacturers and all OEs of ABS and transmissions use one tool with proprietary cartridges, but standardization is still a problem.
Diagnostics systems need to provide better detection and isolation of intermittent and real versus perceived faults. However, the various OE cartridges are not always interchangeable with the current generic diagnostic readers; their OE cartridges offer less diagnostic ability than the OE proprietary tool.
Fail-soft procedures are used by most engine OEs in the event of failure in injectors, sensors and wiring harnesses. When a sensor failure is detected, the software substitutes a default value to the sensor, which in some instances degrades engine performance. The Environmental Protection Agency requires that degradation from emissions-related failures will force the vehicle to undergo maintenance. Typically, engine protection sensor (or harness) failures will not cause a hard shutdown of the engine.
Further, the users said electronic component design life should be 10 years or 1 million miles, with less than a 1 percent failure rate during a two-year period.
Another series of user requests and suggestions will be presented to the SAE in November 1995. If you are a municipal solid waste fleet manager and would like to submit design requests for future vehicles, please contact: World Wastes Truck Editor, 41 Preston Ave., White Plains, N.Y. 10604.