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BUSRIDEMAINTENANCE.COM

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Brake function, safety and maintenance


Table of Contents Corporate overview

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Advantages in brake design

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By Jerry Thompson

Bus calipers: Why rebuild? Better ask: Why not?

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By John Kirkpatrick

Advanced engineering and materials for foundation brake performance and longevity

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By John Campo

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Corporate Overview ProTec Friction Group is a US-based worldwide producer of reliable braking solutions for the most demanding friction applications and environments. We are dedicated to making our customers’ business easier through product innovation, rapid response, reliable supply and the best prices in the business. ProTec is proud of its offerings to both the coach bus and municipal transit markets. Our aftermarket and OEapproved linings, pads, and rotors are manufactured to the highest global standards in our world class and ISO certified facilities. Our bus and light rail customers rely on our brake products to provide safe and dependable stopping power, significant noise reduction, and a longer pad and rotor life.

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FOCUS ON: BRAKES

Advantages in brake design By Jerry Thompson

to install. It is also serious because a worn and The philosophy of ProTec Friction Group / or grooved rotor negatively affects braking is that all the elements of a brake system must quality and precipitates early pad wear out, work together. A braking system is a holistic noise and caliper damage. entity, requiring a combination of research The downside of rotor wear is certainly a and science with on-the-street experience reason to evaluate another option and ProTec in order to generate breakthrough safety and has that option. We invite you to track rotor lifespan solutions. wear in your fleet and prove our claim for Managers and maintenance personnel in the yourselves. What we do in our test vehicle coach bus and municipal transit sector have program is to observe regularly, through the always been interested in improved safety, wheel slots, the rotor face condition. The extended mileage, and reduced road calls for pads keep the rotor at a lightly burnished state brake-related service. ProTec is working to free from grooving and scoring. At regular redefine “quality” in friction materials. We intervals the wheels are removed and the have recently determined that transit and ProTec brakes are constructed with fibrillated aramid fibers in a rotors measured. coach bus friction materials currently on the branched structure that creates By cleaning off a spot on the outer edge of market generate excessive heat. millions of microscopic air pockets the rotor (just beyond the pad contact area) Engineers and physicists agree that a moving which absorb significant heat and with a scouring pad or crocus cloth, the new vehicle requires a certain amount of counter- cool the friction interface. rotor thickness is exposed. We measure that energy to stop. It has always been assumed that the amount of energy generated was theoretically the same thickness slipping a micrometer or caliper in beside the caliper. By sliding the instrument a little toward the center of the rotor irrespective of brake material. Recently, however, we have found it is not quite true. There are we pick up the wearing surface thickness. The difference, of various other efficiencies to be considered. Different materials course, is the wear the rotor has experienced. Using this method follow different energy trajectories. The generation of heat at ,it is easy also to track a system using conventional components the friction material / mating member interface depends on the and establish your own baseline. Nothing drives home a product surface conditions of both components. Just running your hand improvement like evaluating it in your own application. In addition to the harvest of significantly lower lifecycle across a piece of paper and then a sheet of sand paper will help you to understand how surface conditions affect a brake system’s costs, there exists a positive “green effect” from the reduced consumption of cast iron drums and rotors which waste useful life. This has led us to create a new family of friction materials huge amounts of energy to extract the iron ore, manufacture, for the bus vehicle market that allow a cooler running brake transport and replace. Our more advanced pads eliminate brake interface, which in turn lessens lining, drum and rotor wear, dust completely and absorbs all noise such that no shim, chamfer while maintaining stopping distance. In addition to using more or other noise suppression hardware is needed. advanced synthetic and organic fiber combinations for superior If you are still reading this article: reinforcing, insulating and wear life properties, we also A. You probably own, operate or manage a motorcoach fleet or utilize high temperature lubricants. Finally, we compression public transit authority. mold at significantly higher pressures than all other brake B. Accordingly, you have an interest in safely and cost-effectively manufacturers in order to achieve unparalleled friction contact extending brake system life. with drums and rotors. C. You’re scratching your head and wondering if the author This strengthened hyper-compacted surface structure spreads is just fantasizing about dramatic improvements in brake heat energy/thermal loading more evenly across the lining surface. performance, or in touch with the future of bus brake systems. The result is that the friction runs dramatically cooler. More For more information, contact ProTec Friction Group at uniform contact makes both the friction material and the mating member last longer by reducing the tendency of a lining to develop 914-244-3600 or visit their website: www.protecfriction.com. and spread “hot spots” which lead to premature brake wear. Our tests show that our most advanced friction pads will virtually eliminate brake rotor wear. Field trials are currently underway in order to precisely quantify and document this effect. The ProTec claims regarding brake rotor life are pretty serious – serious because rotors are both expensive to buy and expensive 4

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Jerry Thompson is the director of Engineering Services at ProTec Friction Group where he oversees the departments responsible for research & development, application engineering and technical consulting. This follows a successful technical career General Motor and Raybestos. Now a member of the exclusive Road Racing Drivers Club and the Corvette Hall of Fame, Jerry is an active racer and avid ambassador for the sport.

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FOCUS ON: BRAKES

Bus calipers: Why rebuild? Better ask: Why not? By John Kirkpatrick

In this era of throwaway parts and appliances that cost more to fix than to replace, the repair and remanufacturing of otherwise perfect goods has become somewhat of a lost art. In the case of brake systems for buses, calipers are safety components which must meet strict quality standards. For all practical purposes, remanufacturing automotive parts is very much like assembling new parts – except that some of the components are taken from used parts, especially the housing. A quality rebuild includes these steps: •E  ach used caliper is stripped fully. The core is checked for physical damage, wear, cracks and excessive rust. •A  ll cores and reusable parts are sand shot blasted with a specialized process that preserves threads. •C  ores are painted with a controlled thickness layer of black or gray anti-corrosion paint. • All calipers are fitted with guide pins and seal kits. • All bushings and bearings are replaced 100 percent. • All seals and boots are replaced 100 percent. • Calipers are inspected throughout the build process, followed by final quality and pressure testing. There are two main reasons to consider caliper remanufacturing: Savings and Sustainability Savings “A properly rebuilt part is virtually indistinguishable from a new part,” says Steve Yelencsics, president of Raritan Valley Bus Service, Edison, NJ, noting that his company saves money every time. “However, a rebuilt part normally costs us 50 percent to 75 percent of the cost of a comparable new one, and carries the same warranty.” Let’s run the numbers for a motorcoach bus with six calipers installed.

A new brake caliper from the manufacturer costs a fleet approximately $975. The cost of an equivalent re-manned part is $475: a savings of $500 X six calipers (or $3,000) savings per bus. For a fleet with 50 buses that replaces its calipers every two years, the savings over just four years will be noteworthy. Two periodic replacements multiplied by $3,000 savings/ bus by 50 buses adds up to a total savings of $300,000.

We have found that having our calipers rebuilt is a cost effective and eco-friendly direction.

— Hugh Dowling, Parts Manager, Mears Transportation

Sustainability Bus operators are increasingly concerned with reducing negative environmental impact by investing in new fuels, better tires and lighter vehicles. And, they wish to communicate their environmental actions to riders, government agencies and the general public. “We are doing our part, in ways big and small, to contribute to a healthier planet,” says Charlie Konieko, maintenance manager for Peter Pan Bus in Secaucus, NJ. “Purchasing remanufactured parts is in line with our core mission.” A typical motorcoach caliper weighs 70 pounds and each threeaxle bus has six calipers, equaling 420 pounds per bus. Over the 10-year lifespan of a bus, calipers may be replaced four times. Four replacements at 420 pounds equals 1,680 pounds per bus. For a fleet of 100 buses, this represents 168,000 pounds of saved iron use per fleet According to the International Energy Agency, the greenhouse gas of most relevance is carbon dioxide (CO2). On average, 1.8 tons of CO2 are emitted for every ton of iron produced. Even accounting for a 30 percent recycle factor, the positive environmental impact of widespread bus industry remanufacturing would be a reduction of over 60 million pounds of CO2 over 10 years. Using remanufactured calipers requires virtually no time and no additional investment. The carbon savings and benefits are immediate. To learn more about caliper remanufacturing and determine whether a reman program is right for your fleet, contact John Kirkpatrick of ProTec – TDIR division at 908-370-8890. John Kirkpatrick, serves as vice president of sales for ProTec – TDIR division. ProTec is a U.S.-based worldwide producer of reliable solutions for the most demanding friction applications and environments, including on/off highway, agriculture, construction, oilfield, marine, mining, railroad, assembly line and specialty applications. Visit www.protecfriction.com and www.protec-bus.com.

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FOCUS ON: BRAKES

Advanced engineering and materials for foundation brake performance and longevity By John Campo As an accompaniment to Jerry Thompson’s article “Advantages in Brake Design” in the January 2015 edition of BUSRide Maintenance, this article addresses the drum and rotor side of the friction-couple equation. In his article, Thompson highlighted some of ProTec Friction Group’s state-of-the-art friction materials and how they manage inevitable heat generated during braking cycles. He described the significance of the surface conditions and the friction materials used when it comes to directing “energy trajectories” and reducing brake component wear. Similarly extreme demands are placed on brake rotors and drums.

D

uring the past decade, significant technological advances have found their way into the light, medium and heavyduty brake markets. More recent innovations like engine brakes, transmission retarders and regenerative brakes are assisted by electronic and computer-based systems to improve brake performance and safety. A field once dominated by mechanical engineers now shares responsibilities with electrical and software engineers, who are developing advances in antilock braking systems (ABS), stability control, collision mitigation and adaptive cruise control, to name just a few. Today, stopping distance is sometimes dependent as much on lines of code as on the characteristics of disc pads clamping to a rotor. And while such smart innovations may greatly improve the brain of a braking system, its backbone remains the foundation brakes – namely the drums, shoes, rotors and disc pads. Perhaps these same innovations help foster the prevailing “conventional wisdom” that foundation brake materials are about as good as they are ever going to be. Indeed, competing manufacturers offer an array of choices when it comes to varying designs and chemistries in friction materials, rotors and drums which are largely distinguished by their price point. However, the general perception is that, for the most part, these different materials have plateaued and operate within a narrow spectrum of conventional friction and mating surface technology. Like so much conventional wisdom, nothing could be further from the truth. Two companies, ProTec Friction Group and Power Brake, are collaborating on the manufacturing and marketing of the bestperforming and longest-lasting foundation brakes ever seen. Of course, when it comes to slowing or stopping a moving vehicle, no one is suggesting that ProTec/Power Brake have discovered a way to defy the physical laws of conservation of energy and momentum. It just seems that way. In a typical closed braking system where the energy of motion is exchanged for heat energy, how this heat is managed is the crucial element determining the brake’s life and performance. ProTec/Power Brake’s specially-engineered rotors and drums consist of materials that optimize the forces and energies present at the friction couple interface during and after a brake cycle. Simply stated, when the vehicle’s brakes are applied, the disc

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pads or brake shoes clamp against a rotor or drum. The friction resisting the motion of the rotating wheel converts kinetic energy into thermal energy which is then conducted primarily through the cast iron rotor or drum. In many cases specially designed rotor and drum fins, vanes, grooves, holes or vents generate air movement to finish the job by dissipating the heat via the process of convection. Any remaining heat is transferred through the friction surfaces and other components in the brake system. Through a proprietary manufacturing process using extreme force, hardening alloys are introduced into the surface of the cast iron rotor or drum. It is not a coating or plating. These elements actually coalesce with the cast iron, reducing latent stresses and creating a much more “friction friendly” environment… without sacrificing brake torque. The cast iron becomes less of a “heat sink” and more of a “heat mirror,” thereby reducing the residual heat gain in the wheel end. Because of this, rotors and drums are less subjected to warping, scoring, heat-checking, hot-spotting and cracking. Additionally, because they are stronger (higher yield and tensile strength per ASTM test E8) and harder (Vickers hardness test), rotors and drums retain their original configuration, allowing for a more complete and uniform contact of friction to cast iron. Because cast iron fretting corrosion is minimized in a ProTec/Power Brake drum or rotor, when brake pressure is released the uncoupling is clean, with no temperature-increasing drag. It cannot be overstated that the quality and condition of the mating materials of friction to cast iron is a key component to promoting an efficient brake. Employing advanced materials allow for a greater surface contact of the materials at the friction couple. Optimum brake torque can be achieved with the least amount of pressure. Therefore an efficient brake is a higher-performing, cooler-running and longer-lasting brake. PowerBrake longevity drum, rotor and friction products for private coach, school bus and paratransit fleets are available from ProTec Friction Group. John Campo is a heavy-duty brake and suspension professional for Power Brake LLC, St. Petersburg, FL. Visit the company online at www.powerbrake1.com. Visit ProTec Friction at www.protecfriction.com and www.protec-bus-com.

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Brake function, safety and maintenance  

BUSRide presents "Brake function, safety and maintenance," an educational eBook from ProTec!

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