LSHT Motor Drives Tough Industrial Shredder

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Unsorted debris from construction or demolition sites, railroad ties, and many types of mixed industrial waste can be costly to transport and difficult to recycle or deposit in landfills unless it is shredded to reduce its volume and shape. The high-speed horizontal grinding systems used to produce biomass fuels, landscape mulch, compost, and animal bedding are not effective in reducing these challenging materials. A slow-speed shredder that provides much higher torque is a better solution for commingled, contaminated waste streams such as municipal solid waste (MSW), and pliable synthetic materials like rubber tires and carpeting, which will not fragment easily in a high-speed grinding system.

Rotochopper Inc., St. Martin, Minn., set out to design a new line of industrial slow-speed shredders to pre-process these difficult materials and integrate them with the company’s grinders to provide a single-pass solution for processing contaminated waste. Rotochopper’s engineers knew they needed a powerful motor that could withstand torque spikes and drive the shredder reliably for many years. Although they considered gear drives, customer feedback showed that, under these conditions, gear drives often failed after approximately 5,000 hours of shredding. To achieve a longer life and protect users of their new machine from costly rebuilds and downtime, the engineers sought a better alternative.

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The Rotochopper TS-2 slow-speed shredder incorporates an Eaton Hydre-MAC low-speed, high-torque radial-piston hydraulic motor that withstands torque spikes and delivers reliable performance up to six times longer than gear drives while shredding tough, commingled materials.

Based on experience as a longtime customer of Eaton Hydraulics, Rotochopper selected the company’s Hydre-MAC low-speed, high-torque (LSHT) motor. The direct-drive, radial-piston motor delivers more than 1,000,000 lb.-in. of torque and is better able to tolerate torque spikes than geared drives because it has no gears to wear down or fail under the stress. Compared to the typical 5,000-hour life of a geared drive in high-torque shredding applications, the Hydre-MAC radial-piston motor is expected to last more than 30,000 hours. Another advantage for Rotochopper is that Hydre-MAC motors are designed and manufactured in the United States.

Built to Handle Tough Materials

After choosing the radial piston hydraulic motor, Rotochopper’s engineers completed development of the TS-2, the first model in the company’s line of industrial slow-speed shredders. The TS-2 features a user-friendly design that keeps the shredder in sync with other processing equipment. Built to simplify operation, improve uptime, and reduce maintenance costs, the high-torque shredder helps customers minimize the costs of turning challenging feedstocks such as railroad ties or construction and demolition debris (C&D) into compact waste or diverse end products that may include compost, landscape mulch, and boiler fuel.

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Eaton’s Hydre-MAC direct-drive radial-piston motor can deliver 900kW of power and more than 1,000,000 in.-lb. (280,000 Nm) of torque at maximum pressures up to 350 bar, with efficiency greater than 94%.

During prototype testing, the Rotochopper’s TS-2 quickly laid waste to a complete washing machine. In additional testing, the powerful machine has shredded and separated railroad ties and other tough feedstocks. Check out this video:

One of the toughest is C&D waste, which is generated from construction, renovation, repair, and demolition of houses, large buildings, roads, bridges, piers, and dams. C&D waste may include such diverse mixed materials as wood, steel, concrete, gypsum, masonry, plaster, metal, and asphalt.

The new shredder supports the manufacturer’s commitment to “Perfect in One Pass” product solutions. Vince Hundt, co-founder and international sales manager at Rotochopper, says, “The introduction of the TS-2 is the completion of a long-term Rotochopper plan and promise to provide our customers with a complete line of grinders from hammer-mill to hi-torque. Eaton’s Hydre-MAC motor provides the torque we needed to help the new TS-2 shredder effortlessly process C&D, railroad ties, and other contaminated materials.”

The TS-2 shredder is available with diesel or electric power units from 400 to 630 hp, in stationary, portable, or track-mounted configurations. The shredder also integrates with other Rotochopper products to create a multi-stage fiber sizing system, where raw waste goes in and a finished product—even fine textured fibers—comes out.

High-Torque Motor Meets Demands

The performance characteristics and rugged construction of the hydraulic motor made it the logical choice for the demanding requirements of Rotochopper’s shredder application. During operation, the motor generates little heat and wear because its symmetrical 18-piston/roller-assembly design does not undergo side loading. Moreover, its large inlet and outlet ports minimize pressure drop at high power.

Eight hardened cam lobes deliver 144 power strokes per revolution and provide long life. If maintenance is ever necessary in the field, all of the motor’s load-bearing surfaces are completely serviceable. Eaton reports that operating efficiency is greater than 94%.

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LSHT radial-piston motor’s symmetrical design incorporates18 piston/roller assemblies that ensure even loading, with eight flame-hardened cam lobes that provide 144 power strokes per revolution.

The motor includes a standard hollow shaft with shrink-disc coupling and several optional features, including shaft encoders, integral multi-disc brakes, and internal or external spline shafts. Eaton also offers standard torque arm kits for all motor sizes.

The heavy-duty Hydre-MAC motor is based on the same principles as the partially discontinued Hagglunds Marathon motor and was developed in partnership with MacTaggart Scott. This makes it a direct, drop-in replacement for the Marathon motor. Because it uses the same shaft and mounting hardware, the costs of switching motors during replacement are a non-issue.

Eaton’s Hydre-MAC hydraulic motors are a radial-piston, cam-lobe design. The housing is stationary and can be mounted using a mechanical flange, foot, or torque arm arrangement. Pressurized fluid, entering one or both of the inlet ports, is directed through the manifold housing through a series of passageways and a valve plate to sealed pistons, which are located in a rotating block (known as the rotor or cylinder block). Fluid entering into the piston chamber (cylinder) pushes the piston radially outward. The piston, in turn, pushes against a guide block (crosshead assembly), which has two rolling-element bearings located on either end. These bearings roll down the cam slope, causing the shaft to rotate. As the bearings roll down the cam slope, a reaction force is exerted upon the guide slot in the rotor through replaceable low-friction plain bearing surfaces.

At the end of the pistons’ extension stroke, the cam profile returns them to the starting position, and the oil flows outward from the pistons through the valve plate and manifold and out the return port. The rotor is connected to the shaft, and as cam reaction forces cause it to rotate, the output shaft transmits rotational power to the machine shaft. Output torque is proportional to system pressure. Drain ports are supplied to allow leakage oil to exit the motor from the highest point, ensuring that all bearings remain bathed in lubricating oil.

The Hydre-MAC direct-drive, radial-piston LSHT motor is available in eight sizes, from 13 to 50 l/rev. Each motor delivers constant power over a range of torques depending on the speed of the machine. Eaton says the Hydre-MAC motor can transmit up to 900 kW of power and up to 280,000 Nm of torque at pressures to 350 bar.

Lyle G. Meyer is global product manager, industrial drives, at Eaton Hydraulics, Eden Prairie, Minn.