Clutches and brakes are a mainstay in motion designs that need to stop, hold, or index loads.
Especially over the last five years, a technology trend towards application-specific designs has quickened as several industries are pushing the performance envelope of stock components. So, we recently asked six industry experts for comments on this and other trends spurring clutch and brake innovation.
Jean-Paul Beyak | Regional representative — Nexen Group Inc.
David Ebling | President of the Altra Electric Clutch Brake Group — Warner Electric, Matrix International, Inertia Dynamics | Altra Industrial Motion
Rich McConkie | National accounts manager of Wichita & Industrial Clutch | Altra Industrial Motion
Jürgen Schwär | Product manager, Stieber Clutch of Altra Industrial Motion
Naytoe Aye | Business manager of industrial products — Formsprag & Marland Clutch of Altra Industrial Motion
Mike Travis | Sales and marketing manager — Formsprag & Marland Clutch of Altra Industrial Motion
Here’s what they had to say.
What technological advances have improved clutches and brakes over the last few years?
Ebling: Thanks to friction-material improvements, there are now torque-dense clutches and brakes that perform better than ever in high-temperature applications. Thanks to design software, lead times are now shorter for application-specific components. Consider the latest wrap-spring clutches, which work better at lower speeds and loads than previous designs. This is an example of repackaging a mature technology to meet modern application requirements and cost constraints—in this case, to let designers sometimes pick this clutch over costlier servosystems.
Beyak: Technological advances improving clutch and brake performance are longer life and reliability and lower overall cost of ownership for air-actuated types; and clutches and brakes optimized for specific markets (which have the necessary specifications at moderate cost). For example, some conveyor clutches now generate higher torque. Some improved facing material eliminates dust while delivering torque more smoothly.
Ebling: Clutch and brake friction materials continue to evolve with new material science—for higher and more consistent coefficients of friction, as well as slower wear for longer service life. For example, it’s now cheaper to manufacture Neodymium magnets, so they’re increasingly common in safety brakes (for holding and emergency or e-stops), which makes for smaller and more reliable brakes. Other improvements in magnet wire, lead wire, and connection insulation now lets users run brakes and clutches at higher temperatures than before, for broader application performance, longer useable life, and improved reliability.
McConkie: We’ve focused on improving corrosion-resistance, friction material stability, weight and performance tolerances—specifically, narrowing minimum and maximum torques to let designers reduce their service factors.
Travis: There’s an uptick in end-user requests for product monitoring, so now we offer to mount temperature and vibration probes to low-speed backstopping clutches and other types. Over the last five years, there’s also been more demand for larger backstops to meet new conveyors drives—with combined horsepower requirements exceeding 14,000 hp. So in 2010, we began making a low-speed backstop with a torque capacity of 1,200,000 lb-ft, followed in 2012 by units with torque capacities of 1,600,000 and 2,100,000 lb-ft. Safety factors are included in the torque ratings.
What industries are spurring clutch and brake design changes or increased use?
Ebling: Machine-safety regulations have driven use of electromagnetic and pressure-operated power-off brakes, while market demand for increased automation (and reduced labor costs) continues to fuel requirements for small and cost-effective clutches and brakes. Many designers are replacing hydraulics with electromagnetically operated clutches and brakes to boost efficiency and avoid leakage problems.
Beyak: Some industries are using more spring-engaged brakes than ever, and safety is a big driver … as is the aim to prevent lawsuits. Increased focus on efficiency will continue driving brake and clutch use over the next decade, as clutches can improve system efficiency by eliminating the need to start and stop motors.
McConkie: In oil and gas, widespread conversion to ac drives for many applications has driven use of high-horsepower, spring-applied e-stop and parking brakes.
Schwär: In the mining industry, loads steadily increase as drivetrain dimensions shrink. More specifically, power requirements are now 3,500 kW at 1,800 rpm in the standby-generators or uninterruptible-power-supply industry.
Travis: The mining industry also needs more performance monitoring so operators can schedule clutch replacements and get earlier warnings of premature drive-component failures. So, we’ve incorporated mounting provisions for both temperature and vibration probes into our product designs.
Aye: We’ve seen more petrochemical-market interest in overrunning clutch technologies. This market’s worldwide growth is increasing demand for overrunning clutches to isolate multiple drivers.
Ebling: There are several more examples. The outdoor power-equipment industry has given more attention to safety and better operator experience in the form of shorter mower-blade stop times and improved engagement characteristics. In contrast, the marine industry needs rugged drivetrains that can survive severe impact and torque-reversal loads. Here, friction clutch-brake products excel, thanks to high torque transfer with slip capabilities that protect drivetrains.
In the food-processing industry, there’s constant push for more reliable washdown components with stainless-steel housings … particularly in meat processing, where clutch-brake components work with motors and gearboxes.
In mobile-power equipment, including hybrid vehicles and agriculture, turf and garden, and off-highway construction equipment, there’s need for high-torque clutches and brakes with relatively low cycle rates. Here, electronic controls (in lower-cost processors and smart chips) are making efficiently controlled electric clutches and brakes more common. Controlled acceleration and deceleration of operating loads is a core clutch-brake function, but it’s the flexibility and capabilities of today’s mobile-power equipment that necessitates precise transmission control in the form of starting, stopping, and holding torque.
Perhaps the most significant power-transmission trend is the rise of ultra-efficient electric-motor drives, including those in hybrid vehicles. On one hand, electric vehicles can remove the need for selective driveline coupling … but sometimes, efficient drives don’t have adequate starting torque. Here, a clutch can help the drive get to operating torque before it’s loaded. But even the highest-tech motor drives need a mechanical device to stop and hold position.
In energy generation, wind in particular is driving development of power-efficient holding brakes — pitch brakes for turbine blades, for example. Again, technology driven improvements in friction systems and control capabilities allow more use of clutch-brakes as cost effective solutions.
Safety requirements also continue to evolve, necessitating responsive e-stops with failsafe clutch-brake products. Sophisticated friction materials and controls help today’s brakes and clutches work better than ever in everything from absolute position control for robotic servodrives (where brakes do emergency dynamic stopping and load holding) to sophisticated safety stop on garden-tractor mower lades, concrete saw blades, or stump grinders.
How will the focus on efficiency change the use of brakes and clutches?
Ebling: Efficiency demands from customer applications are driving a trend towards efficient clutches and brakes with integrated circuitry, reduced current draw, lower rotating-component inertia, and lighter assembled weights. Clutches and brakes that smoothly disconnect parasitic losses can maximize driveline efficiency, not to mention operator experience … for example, to connect and disconnect radiator fans (to displace viscous clutches) or even drives (such as electric motors in hybrid powertrains) to alternative power sources. A recent example is the new use of clutches to control cooling-system fans on medium and heavy-duty trucks.
Schwär: Efficiency is getting more important, and we think business will evolve to more customer-specific solutions in the next decade. Even requirements within an industry and application are often similar but not identical. Here we predict more use of custom overrunning clutches, which have more than 99% efficiency in torque transmission.
Aye: Demand for higher-efficiency hydraulic power-recovery turbines has led us to develop larger, faster overrunning clutches … in turn making the turbines that much more practical.
We see more application-specific (and custom) clutches and brakes than ever.
Beyak: There is a trend in clutches and brakes toward applications-dedicated and fully-custom components built for increasingly specialized designs — for example, fully enclosed designs; fully integrated feedback; specialization for vertical applications, and brakes and clutches for underwater applications. Here, we customize standard products to meet unique customer needs without having to design completely new and expensive product.
Ebling: We see a continuing trend toward custom-designed products. Designers work to differentiate themselves from competition with unique designs, and that affects partner suppliers … so now, the trend is toward integrated features on components to simplify final assembly and reduce overall supply-chain base. Designers that push the envelope of productivity and efficiency usually need something more than a catalog or production component. In fact, we are working on selling more complete drive-system offerings. In some cases, our designers look to us for the expertise to design and provide the complete drive package including the motor, gearing, mechanical drive components, and couplings. We can draw upon the other brands to design comprehensive drivetrain solutions, so designers get single-source convenience, from engineering through invoicing.
McConkie: Almost without exception, our new market sales in the past several years have all been unique configurations tailored to specific needs. Monitoring sensors, fully enclosed housings, extreme-temperature and saltwater-splash resistance, calibrated torques, multiple actuation and redundant actuation systems, and controlled stopping are just some of the demands.
Schwär: We see the same emphasis on specialization. Together with end users, we’re developing more complete custom solutions … with some 4,000 special designs already for specific applications.
Travis: Yes, even though our application engineer group has developed over 3,000 overrunning clutch design variations, we still have a monthly average of more than 20 new designs processed through our engineering department.
Tell us about an application unlike anything possible 10 years ago.
Beyak: An industrial-manufacturing customer needed a brake to offset a high torque requirement to hold a large ballscrew-backdriving force. This force was three times the output servomotor force needed to move the product into place for processing.
The brake also had to engage during any power losses. Because internal servomotor brakes typically only have 50% of the stall torque of the servomotor, the servomotor and brake would have been massive and cost prohibitive. Plus, internal servomotor brakes aren’t well-suited for e-stopping. So, we modified a servomotor brake to have 200% of the stall torque of the servomotor (from 150% for a standard product) and the engineer stacked two brakes inline to boost the safety factor.
Ebling: Recently, we supplied electric-brake systems to replace hydraulic brakes on several military applications. They included a power-off brake, a power-on friction clutch, a permanent magnet tooth brake, and gearing all in one system. The switch from hydraulic to electric was thanks in part to reduced service requirements and increased safety.
Another example is a stump-grinder application we helped improve. Old versions coasted to a stop when mechanically disengaged from the engine and gearbox drive. Now, a dynamic brake stops the cutter head almost instantly, for more safety for the operator.
McConkie: In a fairly unique application, we developed stainless-steel friction wear surfaces for a brake going in a saltwater environment. Years ago, we would have been limited to using only coatings on exposed surfaces, and would’ve been unable to protect actual friction wear areas. The problem was that pitting and corrosion of wear surfaces destroy torque calibration and can cause the brake to deliver torques far above the planned specification. That in turn leads to gearbox, coupling, bearing, and cable failures. But recent breakthroughs in friction materials let us design a brake with all the normal torque characteristics of a standard brake that is capable of running if occasionally submerged in saltwater.
Schwär: A major gearbox OEM needed a load-sharing releasable backstop for use on a new incline conveyor system at a Pennsylvania coalmine.
Unlike other backstops that offer limited reverse rotation after being engaged, the new system can execute a controlled release under load and rotate backwards for maintenance and clearing work (in the event of a blockage, belt jam, or overload). Here, high-speed backstops with internal torque limiters go on the intermediate shaft (a high-speed shaft) of the multi-drive system’s driving unit; two or more backstops share the reverse load. With a maximum torque capacity of 180,000 Nm, some have up to 3.5 times more torque capacity than traditional backstops and up to 15 times more energy dissipation.
The friction linings work in an oil bath, so the unit can function after long periods of nonuse.
Travis: The fan market aims to conquer windmilling—when unpowered fans rotate in the wrong direction because of wind. To help, our engineers developed a low-cost fan backstop that doesn’t need controls or a shaft key. That simplifies installation.
How has manufacture or distribution changed over the last few years?
Ebling: 3D solid modelling, lean manufacturing, and overall globalization of suppliers have evolved clutch-brake products and applications.
Consider how we can efficiently design and simulate magnetic circuits with computer-aided magnet analysis. That’s let us quicken the redesign of components to boost efficiency and lower cost — on large two and four-pole one piece slotted rotors.
Years ago, we standardized on stampings and consolidated designs so we’d get volumes to justify capital expenses. Today, rapid 3D design and 3D manufacturing let us machine unique parts to satisfy unique customer needs without huge capital investment. Together with quick setup practices and single-piece flow-assembly methods, the part-volume consideration is mostly irrelevant.
Case in point: Recently, we worked with mudboat maker to engineer and build a driveline-reversal mechanism. It uses low-cost, high-volume clutches re-engineered into a custom brake.
Beyak: We use lean manufacturing and improved machine tools and plant layout, because it lets us make higher-quality products in a fast and efficient manner. We’ve seen designers convert from electric brakes and clutches to pneumatic products where demands have increased and electric products can’t meet those demands.
Travis: We see all sales-channel segments looking for shorter manufacturing lead times to keep inventory down. So we use lean manufacturing to reduce lead times — and have even reduced clutch lead-time overruns 50% over the last three years.