By Jerry Thompson
Originally published in in BusRide Maintenance Magazine, January 2015
The philosophy of ProTec Friction Group is that all the elements of a brake system must work together. A braking system is a holistic entity, requiring a combination of research and science with on-the-street experience in order to generate breakthrough safety and lifespan solutions.
Managers and maintenance personnel in the coach bus and municipal transit sector have always been interested in improved safety, extended mileage, and reduced road calls for brake-related service. ProTec is working to redefine “quality” in friction materials. We have recently determined that transit and coach bus friction materials currently on the market generate excessive heat.
Engineers and physicists agree that a moving vehicle requires a certain amount of counterenergy to stop. It has always been assumed that the amount of energy generated was theoretically the same irrespective of brake material.
Recently, however, we have found it is not quite true. There are various other efficiencies to be considered. Different materials follow different energy trajectories. The generation of heat at the friction material / mating member interface depends on the surface conditions of both components. Just running your hand 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 useful life.
ProTec brakes are constructed
with fibrillated aramid fibers in a
branched structure that creates
millions of microscopic air pockets
which absorb significant heat and
cool the friction interface.
This has led us to create a new family of friction materials for the bus vehicle market that allow a cooler running brake interface, which in turn lessens lining, drum and rotor wear, while maintaining stopping distance. In addition to using more advanced synthetic and organic fiber combinations for superior reinforcing, insulating and wear life properties, we also utilize high temperature lubricants. Finally, we compression mold at significantly higher pressures than all other brake manufacturers in order to achieve unparalleled friction contact with drums and rotors.
This strengthened hyper-compacted surface structure spreads heat energy/thermal loading more evenly across the lining surface. The result is that the friction runs dramatically cooler. More uniform contact makes both the friction material and the mating member last longer by reducing the tendency of a lining to develop 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 to install. It is also serious because a worn and / or grooved rotor negatively affects braking quality and precipitates early pad wear out, noise and caliper damage.
The downside of rotor wear is certainly a reason to evaluate another option and ProTec has that option. We invite you to track rotor wear in your fleet and prove our claim for yourselves. What we do in our test vehicle program is to observe regularly, through the wheel slots, the rotor face condition. The pads keep the rotor at a lightly burnished state free from grooving and scoring. At regular intervals the wheels are removed and the rotors measured.
By cleaning off a spot on the outer edge of the rotor (just beyond the pad contact area) with a scouring pad or crocus cloth, the new rotor thickness is exposed. We measure that thickness slipping a micrometer or caliper in beside the caliper. By sliding the instrument a little toward the center of the rotor we pick up the wearing surface thickness. The difference, of course, is the wear the rotor has experienced. Using this method, it is easy also to track a system using conventional components and establish your own baseline. Nothing drives home a product improvement like evaluating it in your own application.
In addition to the harvest of significantly lower lifecycle costs, there exists a positive “green effect” from the reduced consumption of cast iron drums and rotors which waste huge amounts of energy to extract the iron ore, manufacture, transport and replace. Our more advanced pads eliminate brake dust completely and absorbs all noise such that no shim, chamfer or other noise suppression hardware is needed.
If you are still reading this article:
- You probably own, operate or manage a motor coach fleet or public transit authority.
- Accordingly, you have an interest in safely and cost-effectively extending brake system life.
- You’re scratching your head and wondering if the author is just fantasizing about dramatic improvements in brake performance, or in touch with the future of bus brake systems.
For more information, contact ProTec Friction Group at 914-244-3600 or visit their website:
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.