This new drive unit is specifically designed for driving road
roller wheels.
It is specially shaped and sized for installation
on roller-compactors which generally feature rear
axles with four drive wheels and steering front axles
with idle wheels.
Only two units are needed to drive all four wheels
on the rear axle, each unit powering two wheels.
Drive is delivered through a hydrostatic transmission
system with two variable displacement axial piston motors
installed horizontally along the machine's lengthwise
axis at 90° to the wheel axis, in a position where they are
well protected but still easily accessible.
In design terms, the drive unit comprises 2 hubs,
on which the two driven wheels are mounted.
Each hub contains a double stage planetary gearbox.
Inside a central connecting housing a bevel gear
pair provides initial reduction and receives drive
from a hydraulic motor through a mechanical drive shaft.
The central casing also provides the fixing points for
securing the unit to the machine.
The load bearing hubs are designed to withstand
the particularly high loads that road rollers apply to
their wheels.
A multi-plate hydraulic brake is mounted at the input
to the drive unit to provide dynamic braking to
stop the machine (assisted by the braking effect
of the hydrostatic transmission and diesel engine),
and static braking for parking.
Hydraulic fluid passes through the braking system
and is cooled by the machine’s on-board
cooling system. Heat generated by braking,
and especially that generated by speed control
and braking on long downhill slopes, is thus removed
and dissipated.
A pipe passes through the rotational axis of the
wheel hubs. This is connected to the machine’s
compressed air system via a rotary joint and feeds
two compressed air drop lines to the two tyres.
Tyre pressure can thus be controlled and adjusted
as required.