Tandem Vibratory Roller

Overview

A tandem vibratory roller is a self-propelled compactor with two smooth steel drums mounted in line, one at the front and one at the rear. It is used to consolidate hot-mix asphalt, granular base layers and soil on roads, car parks, airfields and similar paved areas. The machine combines static weight with dynamic vibration: the dead weight of the Articulated Frame presses the drums onto the surface while rotating eccentric weights inside each drum add a high-frequency impact force that drives air and voids out of the material. In a tandem configuration both drums are driven and both vibrate, so each pass compacts twice and the machine maintains traction on grades and on freshly laid mat.

The two frame halves are joined at a central Articulation Joint that provides both the steering pivot and an oscillation axis. Articulated steering keeps the rear drum tracking exactly in the path of the front drum, which avoids leaving uncompacted strips and lets the operator follow tight radii. The oscillation axis lets the two halves twist relative to each other so all four drum edges stay in contact when the ground is uneven.

Articulated frame and steering

The Front Frame Weldment and Rear Frame Weldment are welded box-section weldments built from S355 plate. The front frame carries the front drum yoke and a polyethylene Water Tank; the rear frame carries the engine deck, the second water tank and a cast iron Counterweight that balances the engine mass over the rear drum. The Articulation Joint uses two hardened Pivot Pin elements, self-aligning Spherical Plain Bearing units and tapered Ball Bearing sets running on grease retained by Oil Seal rings. Two opposed Steering Cylinder units swing the halves through about 34 degrees each way. Each cylinder is a Cylinder Barrel and Cylinder Rod pair sealed by an O-Ring Set and rod seals.

Drum units

The Front Drum Unit and Rear Drum Unit are identical in construction, which is what makes the machine a true tandem. Each Drum Shell is a rolled and welded Drum Shell Cylinder closed by two Drum End Plate castings. Inside the drum, an Eccentric Weight Shaft carries two cast Eccentric Weight masses on a forged Eccentric Shaft Core, supported on heavy Ball Bearing units. A Vibrator Motor spins this shaft at 40 to 67 Hz. The rotating offset mass produces a centrifugal force of 60 to 120 kN per drum; moving the weights changes the amplitude between about 0.40 mm for thin asphalt lifts and 0.80 mm for thick base layers.

Propulsion comes from a Drum Drive Reduction built into each drum hub. A hydraulic Servo Motor feeds a two-stage Planetary Gear Set inside a Gearbox Housing, with the output Helical Gear Pair turning the drum at travel speed. Eight bonded rubber Isolation Mount elements sit between each drum and its yoke so vibration enters the ground rather than the frame and the operator. Two spring-loaded Drum Scraper bars, each with a replaceable Scraper Blade held by a Coil Spring, keep asphalt from building up on the drum face.

Hydrostatic propel and hydraulics

The Hydrostatic Propel Drive is a closed-loop hydrostatic transmission. A variable-displacement Propel Pump with a tilting Swashplate and a Pump Rotor Group sends oil to the two drum motors; a Charge Pump keeps the loop topped up and a Propel Flow Divider flow divider holds both drums at equal speed so the machine does not crab. Loop Pressure Sensor readings feed traction control.

The Hydraulic System supplies steering, vibration and cooling. A Hydraulic Tank feeds a Vibration Pump for the vibrator motors, and a Valve Block of cartridge valves and solenoid Relay coils routes flow on a drilled Manifold Body. A Hydraulic Oil Cooler and two Hydraulic Filter elements protect the oil, carried by the Hydraulic Hose Set.

Engine and cooling

A turbocharged four-cylinder Diesel Engine of 74 to 100 kW drives the pumps through a Pump Drive Flange flange. The Engine Block Assembly carries a forged Crankshaft and four Piston and Rod units on Ball Bearing shells, sealed by an O-Ring Set. A Turbocharger and common-rail Fuel Injection System meet Stage V limits. The Engine Cooling Package package uses a Radiator and a Cooling Fan driven by its own Servo Motor, regulated by a Thermostat.

Water spray, cab and electrics

Hot asphalt sticks to bare steel, so the Water Spray System keeps both drums wet. Two Water Spray Pump diaphragm pumps draw from the tanks through a Water Filter and feed a Spray Bar over each drum, where brass Spray Nozzle tips lay an even film across the Spray Manifold.

The operator sits in the Operator Cab and ROPS on a ROPS Frame certified to ISO 3471. The Operator Seat slides sideways for edge visibility. A Control Console holds the Travel Lever and a Display Unit built around an LCD Panel, a Bare PCB board, an Microcontroller and SMD Passive (R/C/L). The Electrical System runs from a Battery charged by an Alternator with its Stator Assembly, Rotor Assembly and Drive Belt. A Machine Controller on a Power Supply and Connector set manages propel and vibration over CAN.

Variants and use

Most models in the 8 to 12 tonne class share this layout. Combination variants replace the rear steel drum with pneumatic tyres for kneading action on softer mixes, and oscillatory variants tilt the eccentric phasing to shear the mat horizontally near bridges. Operators run two to four passes per lift, starting with high amplitude on the base course and finishing with low amplitude or static rolling to seal the surface without crushing aggregate.