PR-750B PAVEMENT PROFILER Major Machine Components Caterpillar

Major Machine Components
1.1. Mainframe
2.2. Water Tank
3.2. Fuel Tank And Hydraulic Oil Tanks
4.1. Legs
5.1. Tracks
6.1. Reclaiming System (Conveyors)
7.1. Powerpack Assembly
8.1. Cutter

1. Mainframe

a. Fuel Tank
b. Hydraulic Oil Tanks
c. Water Tank

2. Legs

3. Tracks

4. Conveyors

5. Powerpack

6. Cutter

7. Consoles and Controls

8. Elevation Sensors

9. Cross Slope Sensor


The mainframe is an all-welded, heavy plate assembly with box-type structural support beams. Decking is grid plate with grated inspection panels. The mainframe rides on three hydraulic cylinders which fit inside the legs and are used to adjust the elevation of the mainframe and the attached cutter.

Water Tank

The water tank has a capacity of about 1500 gallons (5676 L). Water is drawn from the tank by the water spray system pump or by the optional high pressure pump that supplies the water for the machine cleanup. An external 3-inch (7.62 cm) male, automatic check type, quick connect coupling provides the capability of filling the tank from ground level. The tank can also be filled through an uncapped top fill opening.

Fuel Tank And Hydraulic Oil Tanks

The 325-gallon (1233-liter) fuel tank supplies fuel to the engine from its location just in front of the engine. The fuel fill pipe has a cap and an internal strainer to strain fuel being added. Two manual shut-off valves are located at the bottom of the tank, one valve in the supply line to the engine and one valve is used to drain water and sediment from the tank. A sight gauge on the side of the tank provides a continuous indication of the fuel supply.

There are two tanks that hold hydraulic oil, a 46-gallon (174.1 L) main tank and a 12-gallon (45-L) replenishing tank. Oil for the hydraulic pumps is drawn from the main tank. If the main tank oil level gets low, oil is transferred to the main tank from the replenishing tank by using the hand operated pump mounted on the main tank. The oil passes through the 10-micron system filter before it enters the main tank.

The main hydraulic oil tank has a sight gauge so that the oil level can easily be checked. A 10-micron breather filter mounted on the tank filters any air drawn into the tank as the tank "breathes" because of atmospheric and/or system temperature changes. The breather filter has a valve in it that will allow the tank pressure to build up to a maximum of 5 psi (34.5 kPa). This pressure should be relieved by opening the needle valve before breaking any connection on the tank or in the systems.

------ WARNING! ------



The replenishing tank has a screen in the fill pipe that should always be in place when adding hydraulic oil. Only ATF Type F hydraulic oil should be used. A breather in the top of the replenishing tank will prevent dust and other large particles from entering the tank as it "breathes".


The legs each consist of a leg yoke, a leg barrel, a leg cap and a hydraulic cylinder. The front leg assembly also has a steering plate and a drive sleeve to provide for steering of the front track. The upper portion of each leg barrel is an integral part of the mainframe.

On the rear legs, the leg yoke fits into the lower portion of the leg barrel and the elevation cylinder is installed inside the leg yoke and leg barrel. The cylinder is connected to the bottom of the leg yoke and to the leg cap. When the cylinder extends or retracts, it moves the leg barrel up or down the leg yoke, thus raising or lowering the mainframe.

The front leg yoke fits into the drive sleeve which rides in the lower portion of the leg barrel, and the steering plate bolts to the drive sleeve. When the steering cylinders move the steering plate, the plate turns the leg yoke and drive sleeve inside the lower leg barrel. When the elevation cylinder extends or retracts, it moves the leg barrel steering plate, and drive sleeve up or down the leg yoke, thus raising or lowering the mainframe.


Each track has a variable positive displacement hydraulic motor that drives a 98:1 planetary gear reducer on which the motor is mounted. A drive sprocket bolted to the reducer turns with the reducer and meshes with the track chain on which the track pads (shoes) are mounted. The drive sprocket pulls the machine forward over the portion of the track chain on the ground. The weight of the machine is distributed over the portion of the track chain on the ground by the lower (track) rollers. The upper (carrier) rollers support the upper portion of the track.

The slack in the track chain is controlled by an adjustable tensioner that presses the idler sprocket forward against the track chain. The tensioner also acts as a relief to prevent damage whenever foreign material is caught between the track chain and a sprocket or roller.

The front track has a parking brake between the motor and the planetary gear reducer. The brake is engaged by springs inside the brake case and disengaged by control system (auxiliary) hydraulic pressure. The brake will automatically engage anytime the control system pressure falls below 180 psi (1241 kPa).

Reclaiming System (Conveyors)

The reclaiming system consists of two separate belt conveyors; a lower or collecting conveyor and an upper or loading conveyor. Material loosened from the roadway by the cutter is funneled onto the lower conveyor which carries the material back under the machine and empties it onto the upper conveyor. The upper conveyor then carries the material up and dumps it. The discharge end of the upper conveyor can be positioned anywhere within an arc of 90°, 45° each side of center. The discharge height of the upper conveyor is 14 feet (4.3 m) at a 30 degree angle of incline. This provides a clearance under the head pulley of approximately 12 1/2 feet (3.8 m).

The conveyors are powered by the dual-section conveyor pump that is driven by the engine through the pump drive gearbox. The inboard section of the pump powers the two hydraulic motors that turn the upper conveyor head pulley. The other pump section powers a single hydraulic motor that turns the lower conveyor head pulley.

The upper conveyor is mounted on a pivot frame that rides in two self aligning bearings on the mainframe. One hydraulic cylinder rotates the pivot frame and the attached conveyor in the bearings to swing the discharge end of the conveyor. A second hydraulic cylinder is mounted between the pivot frame and a spreader frame connected to the conveyor. This cylinder raises or lowers the discharge end of the conveyor.

The lower conveyor is suspended from two turnbuckles at the rear, and from a support assembly at the front. A hydraulic cylinder mounted between the support assembly and mainframe will raise the front of the conveyor to disengage the mounting hooks on the conveyor from the moldboard. This makes removal of the cutter easier.

Powerpack Assembly

The AVSpare 3412 diesel engine supplies the power for machine propulsion (track drive), to drive the conveyors (reclaiming system) and for the machine controls. A pump drive gearbox transmits the power from the engine to three hydraulic pumps tandem mounted on the gearbox:

1. A track drive pump which supplies the pressurized hydraulic oil to drive the three track drive motors.
2. A control system (auxiliary) pump mounted on the rear of the track drive pump.
3. A dual-section conveyor pump that provides the hydraulic oil to drive the conveyor motors.

The 54-inch fan that provides the flow of cooling air through the hydraulic oil cooler and engine radiator is belt driven from the front (left side) of the engine.

The engine also drives an air compressor that provides the compressed air for operation of the air hammer used to change cutter bits, and for operation of the cutter clutch in the power take-off (see page 2-38).

The cutter is belt driven by a power take-off mounted on the rear (right side) of the engine (see page 2-14).

The engine is protected against dust and other foreign material by a dry type induction air cleaner that has a centrifugal pre-cleaner, a main filter element and a safety filter element. As the induction air passes through the pre-cleaner fins, it is given a cyclonic twist that separates most of the dust from the air and sends it into the dust cup where it is collected. Any particles not removed by the pre-cleaner are trapped by the main filter element. The safety filter element protects the engine if the main element is damaged, and a service indicator shows when the main element requires service.




The cutter assembly includes the cutter, the housing and the moldboard.

The cutter is a cylinder (drum) with 216 replaceable tungsten carbide bits (teeth) mounted in holders welded to the cutter flighting. The auger-type cutter flighting is welded to the drum. The bits break the material loose and the flighting channels the loose material onto the lower conveyor. The cutter drum is filled 3/4 full with a 50% solution of water and ethylene glycol antifreeze that cools the planetary gear reducer.

Power from the engine is transferred to the cutter by means of a drive shaft and a belt drive (see page 2-14) that turns the input shaft of a 24.96 to 1 planetary gear reducer. The planetary gear reducer fits inside the right end of the cutter drum and bolts to the cutter drum. When the planetary gear reducer rotates, the cutter rotates.

The cutter housing, which is pin-connected to the mainframe, supports and encloses the cutter. Nozzles, in the top of the door, spray water into the housing to control the dust created by the cutting operation. A moldboard at the rear of the housing prevents material loosened by the cutter from moving back under the machine. Two hydraulic cylinders connect the moldboard to the housing and provide the moldboard with 6 inches (15 cm) of vertical "float". Hydraulic pressure in both sides of the cylinders is vented to the hydraulic oil tank when the moldboard control is at "Float", so the weight of the moldboard keeps the moldboard in contact with the freshly cut surface at all times. As the replaceable moldboard blade wears, mechanical stops must be adjusted to allow the moldboard to move further downward.

A hydraulically operated full width door on the front of the cutter housing provides easy access to the cutter for inspection and/or replacement of cutter bits. A hydraulic motor that uses control system pressure can be used to slowly turn the cutter so that the bits can be reached. A block-out feature in the cutter clutch actuation circuit prevents the cutter from being engaged if the door is open.

An air operated hammer and a punch are supplied with each machine to facilitate changing the bits when they are worn or broken. The bits should be replaced as a group so that all bits are approximately the same length. A single bit longer than the surrounding bits may break the bit holder when the bit hits the concrete. Uneven bits may also cause a surging in the machine travel.

A manually operated bit puller is also suppled with each machine so the bits can be changed without air pressure if necessary.

The cutter is powered by the AVSpare 3412 diesel engine acting through a power take-off unit mounted on the rear (right side) of the engine. The power take-off turns a U-joint drive shaft which drives an air operated clutch. The output shaft of the clutch turns a cutter drive shaft through a belt drive arrangement and the cutter drive shaft turns a planetary gear reducer inside the right end of the cutter drum.

When the cutter control valve on the front control panel is moved to "On", air from the compressed air system is sent to a hose connected to the end of the clutch output shaft. The compressed air travels through an axial chamber in the output shaft to three radial chambers, through the radial chambers and three short connected hoses to an actuating member in the clutch. The air pressure inside the actuating member, which is a full-circle neoprene tube, causes the actuating member to expand and apply pressure to the friction faces of the clutch. This engages the clutch.


When the cutter control valve is moved to "Off", it stops the air flow from the compressed air system and vents the clutch actuating member to the atmosphere. This relieves the pressure applied to the clutch friction faces by the actuating member and allows releasing springs to disengage the clutch. The releasing springs will disengage the clutch anytime air pressure is lost in the actuating member.

The flow of compressed air to the clutch is stopped and the actuating member is vented to the atmosphere by one of two valves when:

1. The cutter door is opened. This prevents the cutter from turning when someone might come into contact with the cutter and be injured.
2. The machine starts to travel rearward while the cutter is engaged. This prevents the machine from riding up onto the cutter and suddenly moving rearward when the cutter hits an uncuttable object such as a manhole.