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Caterpillar RM500B Rotary Mixer Combines Ease of Use, Superior Performance

The RM500B comes with standard electronically controlled full time all-wheel drive.

Tue March 17, 2015 - National Edition
Construction Equipment Guide

The RM500B combines ease of use, superior performance and high reliability to achieve the most demanding job specifications in both full-depth reclamation and soil stabilization applications. The RM500B replaces the current RM500 Rotary Mixer and offers many new features and enhancements that increase operator comfort and productivity, including a Cat C15 engine with ACERT Technology. Other features include a sliding pressurized cab, an enhanced operator’s environment, automatic rotor depth control, four mode steering, all wheel drive and three rotor design options that provide optimum performance and versatility to meet variations in job requirements. Operating weight for the RM500B is approximately 28 400 kg (62,611 lbs) when equipped with a ROPS, a cab and a universal rotor.


The RM500B features a Cat C15 ACERT engine, a turbocharged, 6-cylinder diesel engine that provides 407 kW (546 hp) of gross power. The engine is designed to meet U.S. EPA Tier 4 Final and EU Stage IV emission standards. Every Tier 4 Final/ Stage IV Cat engine with ACERT Technology is equipped with a combination of proven electronic, fuel, air and aftertreatment components. Applying proven technologies systematically and strategically lets us meet our customer’s high expectations for productivity, fuel efficiency, reliability and service life.

The turbocharged air-to-air aftercooling system provides high horsepower with increased response time while keeping exhaust temperatures low. This generates significant improvements in airflow that increase efficiency and reduce emissions.

The modular stacked cooling system provides cool intake air that helps maximize fuel efficiency and minimize emissions. A variable speed fan draws ambient air from a separate compartment in front of the engine through the cooling package. The exhaust air exits from the front of the machine, providing a cool engine compartment. The cooling fan periodically reverses direction for a short interval during operation. This reversal helps the system shed accumulated dust, keeping the cooling system cleaner. This allows the system to operate at ideal cooling capacity to ensure maximum efficiency.

The RM500B comes with standard electronically controlled full time all-wheel drive. Four independent variable-displacement propel pumps supply balanced oil flow to the front drive motors and the rear drive motors. Two speed ranges allow operation at either maximum torque for work or greater speed for moving around the job site. Gear selection is controlled electronically by a keypad button on the operator’s console. Infinite variable speed control within these ranges is achieved utilizing the propel lever and two buttons on the keypad.

The differential lock feature is absent from the all-wheel drive RM500B. Sensors in the propel system monitor the pressure at each pump, making adjustments to equalize the effort of each wheel for true all-wheel drive traction. This enhancement allows the machine to maintain consistent speed and direction even in severe conditions.

The RM500B is equipped with four mode steering. The microprocessor processes inputs from sensors on the front and rear wheels along with input from the four mode steering selector buttons on the control console keypad. It provides precise simultaneous wheel movement in the crab and coordinated steering modes and automatically realigns the rear wheels to center when the front wheels only steering mode is selected. In the coordinated mode, the inside turning radius is 4.33 m (14’ 2").

Sensors equalize the ground speed and average the readings, which provides more accurate data for the additive metering systems. The end result is greater precision when mixing water, emulsion or both.

The large tires have an aggressive tread and provide a large footprint. Machine weight balance provides stability to the machine when cutting and mixing, resulting in a consistent depth.

Operator’s Environment

The hydraulic sliding cab on the RM500B repositions from side-to-side and can be positioned at any point between the range limits utilizing a keypad button on the side. Placing the cab to the far left or right side of the machine enhances visibility to the front of the machine and provides greater sight lines to the front tire edge. The operator can move the cab quickly during machine operation for faster cycle times and increased production. The cab on the RM500B is fully pressurized to provide a comfortable environment for the operator while keeping noise, dust and the elements out. Features included with the cab are: a rotating, heated, cloth seat with integrated control console and LCD touchscreen, sound absorbing headliner, left and right side lockable doors, tinted glass, air conditioning, heater/defroster and dual front and rear windshield washer/wipers. A sound absorbing floor mat provides sure footing while reducing noise and vibration transmitted to the operator. Four large isolation mounts isolate the cab from the machine frame to reduce vibration transfer to the operator’s station.

A display monitor is mounted to the forward dashboard. Video from remote cameras on the front and rear of the machine is displayed on the monitor, enhances the operator’s view to the front and rear of the machine.

Wide, comfortable steps with non-skid surfaces are placed to provide access to the operator’s station from either side of the machine. The steps and handrails are recessed within the overall machine width to minimize exposure to obstacles. The top deck is flat, providing good access to either side of the cab.

The comfortable and durable seat has a standard in-seat heater and provides adjustments for maximum comfort. The seat features an integrated steering handwheel and side control console with LCD touch screen. The seat rotates 90 degrees from center to the right or left to further enhance operator comfort. The seat also includes a 75 mm (3") wide seat belt.

The integrated control console and handwheel steering controller move and rotate with the seat. The control console features a padded arm rest, a controller keypad, the propel lever and the LCD touchscreen controller. The propel joystick has six thumb buttons that allow the operator to conveniently control certain rotor functions.

The LCD touch screen display features a large, easy-to-read interface, function indicators and warning indicators to keep the operator informed of machine operation and vital systems. The large display panel shows information selected by the operator such as rotor depth, propel speed selection, steering modes, rotor speed and various other functions. Information is easily visible in direct sunlight or low light conditions. Functional switches are also positioned within easy reach of the operator on the keypad.

The electronic monitoring system is designed to warn the operator of system faults utilizing a three-level warning system. The warnings are based on the severity of the problem. A level one warning represents the least severe problem, while a level three warning represents the most severe.

The speed control function allows the operator to set the maximum propel speed attainable at the fully forward or rearward position of the propel lever. This standard feature is especially useful when the machine is started and stopped frequently.

On-board microprocessors monitor operating conditions, receiving input signals from sensors in the engine, propel, steering and rotor drive systems. Self-diagnostic programs provide information for troubleshooting and alert the operator of potential system problems. If a machine fault occurs, a code is displayed on the LCD display to alert the operator and assist in troubleshooting.

Cutting/Mixing System

The large, variable-volume mixing chamber is mounted mid-point between the front and rear tires. When the rotor cutting depth is deep, the effective volume of the chamber increases to allow for the increase materials. When the rotor is set at a lower depth, the rotor itself occupies the space within the chamber, making it effectively smaller in volume.

The machine is able to work in both forward and reverse due to adjustable front and rear doors on the mixing chamber. The heavy-duty front door is powered with two hydraulic cylinders for raise and lower. The front door raises parallel to the cutting surface to prevent the door from plowing material in harsh soil stabilization conditions. This is ideal for peak efficiency on soil stabilization, bio-remediation or during mixing passes on full depth reclamation.

The rear door is also hydraulically operated. The operator can control the sizing of the material by adjusting the rear door opening. The narrower the opening, the longer the material is processed in the rotor chamber, and the finer the sizing.

Automatic rotor load control enhances machine productivity. The on-board microprocessor constantly evaluates engine RPM and propel speed as required to maintain peak performance. The microprocessor matches propel speed of the machine to the load on the engine and adjusts propel speed so that engine speed does not drop below 1,950 RPM. The operator can activate the automatic load control with button on the control console keypad.

The RM500B provides three modes of rotor depth control. During operation, the microprocessor receives input from the rotor position sensor, rotor mode buttons (on propel joystick) and rotor raise/lower buttons on the propel joystick or on the LCD touchscreen display. The three modes of rotor depth control are:

Travel Mode: When the TRAVEL position is selected, the rotor moves to a factory-calibrated full-up position and remains there. This provides clearance for moving the machine over obstructions or traveling between job sites.

Manual Mode: In this mode, the operator controls the position of the rotor by using the RAISE/LOWER buttons. A visual depth gauge is positioned on each rotor lift cylinder so the operator can precisely control the cutting depth of the rotor from the operator’s station.

Automatic Mode: Selecting the AUTOMATIC position provides automatic rotor depth control. In this mode, the microprocessor maintains rotor depth at the position set by the operator. Rotor depth can be displayed on the LCD display panel. The numbers will show in either inches or millimeters.

A plus sign (+) means the rotor is above ground, a minus sign (-) means the rotor is below ground. A graphic on the LCD display indicates the position of the rotor.

The rotor drive system operates directly through a Cat Powershift transmission and drive axle. The mechanical rotor drive system allows efficient and reliable transfer of engine power to the rotor and is sized to handle tough cutting and deep mixing. A keypad button on the control console is used to engage or disengage the rotor transmission.

A choice of three rotor speeds permits working in a wide range of materials, depths and applications. First speed is used primarily for pulverizing the material. Second or third rotor speeds can be used in blending or mixing passes. The rotor speed selection buttons are located on the control console keypad.

The rotor is driven on both sides by single strand, high strength drive chains which are contained in heavy-duty chain cases partially filled with oil. A shear disc or optional torque limiter protects the rotor drive components from shock loads.

Three rotors are available for the RM500B:

The universal rotor can be used for either full depth reclamation or soil stabilization and is equipped with 200 point-attack carbide-tipped tools mounted in drive-in, knock-out, bolt-on tool holders and arranged in a chevron pattern for maximum breakout force.

The point-attack type tools have long been the standard selection for reclamation applications. The rotor ends are equipped with triple-tree tool placement that provides optimum tool spacing to clean up loose material and reduces drum wear when maneuvering in the cut. Cutting width is 2438 mm (96") wide. Maximum cutting and mixing depth is 406 mm (16"). In Europe, the universal rotor has a maximum cutting and mixing depth of 457 mm (18").

The soil rotor is used for a variety of soil mixing and stabilization applications and blends additives with semi-cohesive or granular materials. The rotor is equipped with 238 point-attack, carbide-tipped tools mounted in drive-in, knock-out, weld-on tool holders and arranged in a chevron pattern for maximum breakout force. Replaceable end rings protect rotor mandrel from wear. The rings are hard-faced for extended service. The rotor has a cutting width of 2438 mm (96") wide, and a maximum mixing depth of 508 mm (20").

The combination rotor is designed primarily for use in soil stabilization applications in cohesive materials, but also works well for light asphalt reclamation. The rotor is equipped with 114 point-attack, carbide-tipped tools mounted in drive-in, knock-out, bolt-on tool holders and arranged in a chevron pattern for maximum breakout force. Its versatile design is intended for applications where material gradation is of less importance and where higher working speeds are desired. Replaceable end rings protect rotor mandrel from wear. The rings are hard-faced for extended service. The rotor has a cutting width of 2438 mm (96") wide, and a maximum mixing depth of 508 mm (20").


Accessing major service and maintenance points is easy on the RM500B. Daily service points are accessible from ground level and are grouped at certain points around the machine. Large doors provide access to the engine. Hinged ground level side panels provide access to engine components and the cooling system.

The hydraulic rotor hood rotates forward to allow service access to the rotor and cutting tools and is held securely in the service postion with a heavy duty locking pin that slides easily into position. Ground level side access doors on the rotor hood provide convenient access for easy cutting tool removal and replacement.

The rotor drive-chains self-lubricate in sealed chain cases partially filled with oil. A lubrication reservoir for the stub shaft bearing is mounted on the front of the hydraulic tank. The reservoir has two separate chambers providing oil to each stub shaft. Oil level is easily monitored from the operator’s station, providing quick visual verification of sufficient oil levels for each stub shaft.

Other features that make servicing simple include leak-resistant O-ring face seal hydraulic fittings, grouped quick-connect hydraulic test ports, S•O•SSM ports, visual site gauges and remote grease points.

Hydraulic hoses are held neatly in place with polyurethane routing blocks. The blocks prevent hoses from rubbing against one another, extending the service life and reliability of the hose.

Wiring for the electrical system is protected by nylon-braided wrap. All-weather connectors ensure electrical system integrity. Electrical wiring is color-coded, numbered and labeled with component identifiers to simplify troubleshooting.

Two maintenance-free Cat batteries power the 24-volt electrical system and are specifically designed for maximum cranking power and protection against vibration. The batteries are mounted on the side of the machine and are accessible from ground level. The machine is equipped with a 150-amp alternator.

The machine is Product Link™ wire-ready. The Product Link option ensures maximum uptime and minimum repair costs by simplifying tracking of equipment fleets. It can provide automatic machine location and hour updates. Product Link can be obtained through your local Cat dealer.

Options include: a Roll Over Protective Structure (ROPS), a Falling Object Protective Structure (FOPS), a road operation light package, a warning beacon light, a mirror package, a bolt-on counterweight, a remote camera facing the rear chamber door, a folding push bar, an emulsion spray system and a water spray system.

For more information on the new RM500B Rotary Mixer, contact your Cat dealer. For more information,

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