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Thread: Shake, Rattle and Roll

  1. Default Shake, Rattle and Roll

    When you buy a new truck (or your fleet does), you want to be confident that it will perform as intended. That means hitting potholes, going over railroad tracks, climbing or descending long, steep grades, traveling on the worst roads America has and possibly delivering to off-highway locations, all without damage or maintenance issues. Truck manufacturers want the same thing, because if your truck doesn’t operate as advertised, they pick up the repair cost under warranty.

    Think about all that goes into a new truck, all the components, all the processes and all the stresses and strains under which they operate. It’s a minor miracle of modern engineering that they function as well as they do. Much of it has to do with computer aided design and engineering, but that very design and engineering is dependent on human input. When there is human involvement, you have room for error. Manufacturers need to test the vehicles before they get into customers’ hands to prove that they will perform as intended. If they don’t, manufacturers need to be able to quickly make repairs and design revisions, and then test to be sure that the changes work.

    In the earliest days of commercial vehicles, trucks were simple and straightforward, and often over-built. Just a few thousand miles of driving on the typical crude roads of the day were enough to cause weak items to fail.

    The first attempt at an automotive proving ground later became the Indianapolis Motor Speedway. It was a 2.5 mile track paved with bricks, having four distinct corners. It was built in 1909 when Indiana was the center of American auto manufacturing.

    World War I demonstrated that cars and trucks needed to be tested more severely, in less time. That’s when the concept of proving grounds arose.

    In 1926, the Studebaker Corporation developed 840 acres near their South Bend, Ind., factory into a facility for testing its vehicles, including Army trucks. In addition to workshops that are still in use today, there are three general areas. On level ground, there is a high speed oval with a large skid pad for brake testing. The brake test area has varied surfaces with different coefficients of friction.

    Inside the complex, a hilly, wooded off-road course once tested tanks. It is now used to test the HMMWV (Humvee) and military trucks. A fairly long and steep climb leads to the torture track sections. Here trucks navigate cobblestone (Belgian block) surfaces, simulated pot holes and undulating surfaces that will take a truck from full bounce to full rebound and back. Diagonal concrete pads twist the chassis from full left twist to full right twist and back many times each run.

    The concept is simple. Stress trucks beyond what they will encounter in years of service, and do it repeatedly. Development engineers speak of acceleration factors up to 100:1. That means that one mile of test equals 100 miles of real world experience. In 10,000 miles of 24-hour-a-day driving, a million miles of experience can be gained, often under conditions far more demanding than anything encountered on the road.

    Today, every truck maker and many major component manufacturers operate their own proving ground. Many also rent track time and facilities from established proving grounds. Among the major independent facilities, Ohio’s Transportation Research Center (TRC) shares space with NHTSA and is home to a great deal of truck brake research. The Nevada Automotive Test Center was established after the U.S. Army Corps of Engineers defined an area in northwest Nevada that had terrain similar to almost every kind in the entire world. Its altitude ranges from a modest 3,900 ft above sea level to as much as 11,000 ft. Terrain ranges from desert to mountains, with grades from 3 to as much as 75 percent, three feet vertical for every four feet of horizontal travel.

    Tire companies have their own facilities. I’ve been at Bridgestone Firestone’s desert track in Fort Atkinson, Texas, when it hadn’t rained in 13 years, and Goodyear’s in San Angelo Texas, where it had. I also toured Goodyear’s Akron, Ohio, facility. Tire makers have their own tests for tires, including Goodyear’s torturer that grabs a tire right on the truck and turns the tread 45 degrees or more. If a tire can survive that, it can probably stand up to severe curbing. All tire tracks have glass plates with dyed water. They enable engineers to observe the tread as it rolls over the glass under load.

    While tire companies need hot climates for testing (excessive heat destroys tires), truck and accessory makers also need cold climates to test winter operations. Bendix operates a proving ground in Houghton, Mich., where I got to drive on ice and packed snow testing ABS-6 Advanced with ESP. Even on split surfaces, with different traction left and right, I could brake and accelerate without jackknifing or spinning out. Without the room afforded by the proving ground, I wouldn’t have tried.

    I visited a number of proving grounds and drove trucks on a few of them. Perhaps the most interesting was back at the Studebaker grounds, now operated by Bosch. Freightliner leases facilities there, and they gave me the opportunity to drive a Western Star for several laps on the most torturous portions of the course.

    Experiencing the forces first hand made me appreciate how a truck can receive 100 miles or more of punishment each and every test mile it travels. It also made me appreciate the skills and stamina of the engineers and technicians who apply the equivalent of a million miles in just a few weeks of continuous driving.

    By Paul Abelson

  2. #2
    Accremonious Guest

    Default Computer Assisted Designing

    What the advent of the Personal Computer, LAN networking and Computer Assisted Design has done is allow the engineers to slim down designs to only what is just needed for the individual parts need to function plus refine the designed life times of parts. Conventional light bulbs for example can now be designed for say a 100hour life time use expectancy. The manufacturing quality assurance now ensures that 99% of those bulbs will last 100hours + or - one hour! Likewise the major automotive/truck components can now be manufactured to very precise life times. What happens is that you only get what you pay for and the energy efficiency pressures are driving this to very slim margins!
    We can build exhaust systems that will out last the vehicle's life time but the amount of Nickle, Chromium, and other alloying metals would drive the price up astronomically! hence the competitve pressures of the manufacturerers peers keeps the price down and the metal selection is often carbon steel or cast iron with very minimal alloying if at all!
    These are just a few facets of the complexity that industry has evolved to. The trend to plastics, and composites will continue for over all weight reduction, noise reduction, temperature/environment control, etc.
    One Mechanical Engineer that I worked near told me one day in the steel mill, "remember all bearings are designed knowing that they are all going to fail at some date in the future regardless of design". With proper maintainence most will last close to or exceed their design life. (the environment of a steel mill is highly dosed with the second best natural grinding compound = iron oxide! Aluminum oxide being the best of the commonly available with out resorting to exotics (ceramics).
    Now next door my retired GMC Purchasing type tells me that if they had their way, there would be no trucks and truck drivers delivering parts to the assembly centers, only enclosed conveyors! We are viewed as an unreliable link (necessary evil) in the process when it may in fact be traffic, weather, accidents, road designs/rush hours and scheduling of runs and routes that are physically an impossibility! Just remind the next smart ass executive that 10% of North America lives in a big truck on the freeways making sure his product's parts are available, the finish product moved to market, and some of which is purchased by those same truck drivers! Never mind the food, gasoline, clothes to wear, etc. The railroads are not efficient at keeping our "just not enough time" society supplied. What they do best is move large quantities of bulk goods on a less than instantaneous demand schedule.
    (We have been neighbors for 36 1/2 years!)

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