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Terminology
Crawlers - Tracks - Travel
Fault category
Low crawler power - Steering issue - Crab crawling -
Tracks – Crawlers – Drive system -
Issues – Crab crawling – Low crawler force – Noisy transport -
Knowledge
Crawler systems only differ by detail when you look at the different manufacturers, small machines
can have a combination of motor and transmission [see illustration] where as larger machines migrate to separate drive motors and transmissions.
Often engine power loss is highlighted when transporting the machine since the power demand is at
the greatest.
Compared with trouble shooting a cylinder circuit a extra component needs to be checked out that of
the   – central joint [see illustration] centre passage – rotary joint, the function of this component is to allow flow and pressure to be transmitted to the motors no matter what the position of the superstructure in relation to the undercarriage.
The component contains seals which separate the lines, leakage in most case’s will allow passage to
the leak (Drain) line.
It is common practice that the shock (Port relief valves) are located at the motors as opposed to the
main control valve.
It is not unusual that a manufacture will use different suppliers, it is important to check that
replacement units match that which is fitted to the machine.
The majority motors will be of the variable displacement version, as the drive pressure increase the
displacement will increase slowing the machine. Some manufactures offer an option to lock the
displacement in the slow maximum displacement position.
The crawler negative brake is not dissimilar to that of the slew (swing system) locks on when the
pressure to the motor is at the minimum.