The Lucas starting system fitted to the Ford Falcon XK is designed to crank the engine at sufficient speed to allow it to start. The system includes the starter motor and drive mechanism, battery, remote starter switch and heavy circuit wiring.
When the ignition switch is turned to the start position, electrical current flows from the battery through the starter control circuit to energise the starter solenoid. The solenoid then engages the starter motor drive with the engine flywheel and closes the high-current circuit supplying power to the starter motor.
This arrangement allows the starter motor to rotate the engine until combustion begins and the engine becomes self-sustaining.
Starting System Components
The Lucas starting system consists of several major components:
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Starter motor
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Starter drive and pinion assembly
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Solenoid unit
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Battery
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Starter control switch
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Heavy electrical wiring
Vehicles equipped with automatic transmission also incorporate a starter neutral safety switch in the starter control circuit. This switch prevents starter operation unless the selector lever is in the Neutral (N) or Park (P) position.
Lucas Starter Motor Construction
The Lucas starter motor is a series-parallel wound four-pole, four-brush machine using a solenoid pre-engaged operating system.
Under normal operating conditions, the starter motor produces torque only when the starter pinion is fully engaged with the flywheel ring gear.
If the starter pinion meets the flywheel teeth in a tooth-to-tooth position, special provisions allow the motor to overcome this condition and achieve proper engagement without damage.
Armature and Drive Assembly
The armature shaft is mounted within the starter housing and connected to a splined drive sleeve carrying the clutch and pinion assembly.
The bore of the drive sleeve contains helical splines that mate with corresponding splines on the armature shaft.
These splines allow the pinion assembly to move forward and rotate slightly to ensure proper engagement with the flywheel ring gear.
Roller Clutch Mechanism
A roller clutch assembly is incorporated within the pinion drive.
This clutch allows torque to be transmitted from the starter motor to the engine but prevents reverse torque from the engine driving the starter motor.
This protection ensures that once the engine starts, the armature cannot be driven at excessive speed by the engine.
The clutch assembly contains three rollers which move within cam tracks and are held under spring pressure against the clutch outer member.
The unit is sealed within a rolled steel cover and cannot be dismantled for reassembly.
Solenoid Unit Operation
The solenoid assembly contains a soft iron plunger, which operates the starter engagement mechanism and electrical contacts.
The solenoid includes:
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A main closing (series) winding
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A hold-on (shunt) winding
When the starter control circuit is energised, both windings operate together to pull the plunger inward.
Movement of the plunger operates the forked engaging lever, forcing the pinion gear into mesh with the flywheel ring gear.
At the same time, the starter switch contacts within the solenoid close, allowing heavy current to flow from the battery to the starter motor.
Once the pinion is fully engaged, the closing winding is automatically shorted out by the starter contacts and only the hold-on winding remains energised to keep the pinion engaged while the starter motor operates.
Starter Disengagement
When the starter switch is released, the solenoid windings are de-energised and the engaging lever retracts the pinion from the flywheel.
A lost-motion spring mechanism ensures that the electrical contacts open before the pinion disengages from the flywheel, preventing damage to the starter drive.
Armature Brake Assembly
The Lucas starter includes a moulded brake shoe assembly which presses against a steel brake ring attached to the armature shaft.
This braking system rapidly stops the armature once the starter motor is disengaged, reducing the possibility of the pinion re-engaging the flywheel while still rotating.
Starter Motor Protection
The starter drive clutch and braking system ensure the starter motor is protected against:
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Reverse torque from the engine
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Excessive armature speed
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Accidental re-engagement while rotating
These protective mechanisms contribute to reliable starter operation and long service life.
Safety, Copyright and Source Notice
Safety Disclaimer
Working on motor vehicles involves mechanical, electrical and chemical hazards. Always ensure the vehicle is safely supported, the engine is switched off when appropriate, and suitable safety equipment such as gloves and eye protection are used. If you are unsure about any repair or maintenance procedure, consult a qualified mechanic before attempting the work.
Source
Information compiled from period factory service literature.
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