Technical Knowledge
Analysis of the electrical and mechanical causes of walking faults such as deviation in the direction of the power trowel machine
Faults such as deviation in direction and poor movement of the power trowel during operation are common but affect the efficiency and quality of construction. This is usually caused by both mechanical and electrical reasons, either jointly or separately.
The following is a detailed analysis of the causes of the walking failure of the power trowel machine:
Ⅰ. Electrical Cause Analysis
The electrical system is mainly responsible for providing power and control to the walking motor. Its faults are usually manifested as one side of the motor not rotating, unstable speed or weak power.
Power supply issue
Internal cable breakage: The outer sheath is intact but the internal core wire (especially the neutral wire or a certain phase wire) is broken, causing single-phase motors or three-phase motors to operate with phase loss, resulting in a significant drop in motor output torque and inability to run normally.
Loose/oxidized terminal blocks: The terminal blocks where the power supply is connected to the machine are loose or oxidized, resulting in excessive contact resistance and insufficient power supply voltage.
Leakage protection device failure: The leakage protection device or circuit breaker of the main power supply itself malfunctions, resulting in unstable output voltage.
Control circuit problem
Poor contact of the walking switch (button) : The switch controlling the walking motor has internal contacts eroded or oxidized due to frequent operation, water ingress or dust, resulting in increased contact resistance and inability to connect the full voltage.
Ac contactor failure: The high-power relay (contactor) responsible for turning on and off the main circuit of the traveling motor has burned contacts and unstable coil engagement, which can cause the motor to rotate intermittently or be powered by a single phase.
Speed regulator failure (frequency conversion/voltage regulation type) : For speed-adjustable polishing machines, if the internal frequency converter or voltage regulation module fails, it will cause unstable output frequency or voltage, directly resulting in abnormal motor speed and deviation.
Problems with the motor itself
Motor winding burnout or local short circuit: The stator winding of the motor is damaged due to overload, water ingress or aging. It is manifested as severe motor heating, a burnt smell, weak operation or no rotation at all.
Water ingress or moisture inside the motor: The insulation performance declines, causing inter-turn short circuits during operation and a reduction in output power.
Severe wear of carbon brushes (series-excited motor) : Many power trowelers use series-excited motors, and carbon brushes are vulnerable parts. Excessive wear of carbon brushes can lead to poor contact with the commutator, increased sparks, decreased motor speed and insufficient torque.
Ⅱ. Mechanical Cause Analysis
Mechanical reasons are the most common causes of deviation, mainly concentrated in the transmission system and the traveling mechanism itself.
Problems with the transmission system
Loose or worn drive belts: This is the most common cause of deviation. The motor output is transmitted to the reducer or traveling wheels through a belt. If one side of the belt is loose, aged, stretched or worn, it will cause insufficient driving force on that side, and the machine will deviate from that side.
Reducer failure
Gear wear or broken teeth: This leads to a decrease in transmission efficiency or jamming.
Lack or deterioration of lubricating oil: It leads to abnormal wear of gears and bearings and increases transmission resistance.
Bearing damage: It causes the output shaft to rotate inflexibly and even get stuck.
Chain drive failure (for a few models) : The chain is loose, worn or the sprocket teeth are sharpened, resulting in tooth skipping and unstable transmission.
Problems with the walking mechanism
Uneven wear of the walking wheels: After long-term use, rubber walking wheels may experience uneven wear and deformation, causing changes in the friction force with the ground and leading to deviation.
Uneven air pressure on the running wheels (pneumatic tires) : If the air pressure on both sides of the tires is inconsistent, it will cause different rolling radii and resistance, similar to a car running off course due to uneven tire pressure.
Axle bearing damage: If the bearings of the traveling wheels are damaged, rusted or lack oil, it will greatly increase the rolling resistance of the wheel, and the machine will deviate severely to the side with greater resistance.
The brake is not fully released (for models with brakes) : If the brake pads on one side do not fully return to their original position, they will always carry a certain braking force, causing difficulty in walking on that side.
Overall structure and adjustment issues of the machine
The installation height of the blades is inconsistent: The four blades (power trowels) of the power trowel machine are not installed parallel. During operation, the pressure and friction on the ground are different, which will generate a turning torque and cause the machine to not move straight. This is a very crucial but easily overlooked mechanical cause.
Deformation of the machine body structure: The machine has been subjected to a violent impact, causing the chassis or bracket to deform, resulting in the two traveling wheels not being parallel and causing the "tire eating" phenomenon.
Ⅲ. Fault Diagnosis Process and Troubleshooting Methods
It is suggested to conduct the investigation in accordance with the principle of "from simple to complex and from outside to inside"
Visual inspection
When the power is off, check whether the walking wheels on both sides rotate flexibly (by hand) and feel if the resistance is consistent.
Check the tightness and wear of the belt/chain.
Check if the heights of the blades are consistent (measure the distance from the blade tip to the ground with a ruler).
Check if there is any obvious damage to the cable.
Side testing (core steps) :
Lift the machine off the ground to lift the traveling wheels.
Start the left and right walking motors respectively and observe whether both wheels can rotate normally, smoothly and powerfully. This is the most effective way to determine whether the problem is electrical or mechanical.
If one side is normal while the other does not rotate or is weak: The problem lies in the electrical system or drive system on that side.
If both sides rotate normally and forcefully: The problem is likely to lie with the traveling wheel itself or the blade adjustment.
In-depth electrical inspection
For the faulty side: Use a multimeter to measure whether the voltage at the motor input terminal is normal.
Measure the voltage section by section along the path from power supply → switch → contactor → motor to find the points where the voltage drops or is missing.
Check the wear of the carbon brushes (if it is a series-excited motor).
In-depth mechanical inspection
For the faulty side: If the motor rotates normally but the wheels do not turn or are weak, the problem lies in the transmission system. Check if the belt is slipping and if there is any abnormal noise from the reducer.
Disassemble and check whether the bearings of the walking wheels are stuck.
Recalibrate the heights of the four blades to ensure they are on the same plane.
Summary
| Fault phenomenon | The electrical cause of priority suspicion | The mechanical cause of priority suspicion |
| Keep running off course to one side | The carbon brushes of the motor on this side are worn out and the wiring is loose | The belt on this side is loose, the bearing of the traveling wheel is damaged, and the height of the blade is uneven |
| I walk with weakness on both sides | Main power phase loss, main switch/contactor failure, motor winding problem | Both sides of the belts are loose and the lubrication of the reducer is poor |
| It starts and stops intermittently, and the operation is unstable | Poor contact of the switch/contactor contacts and intermittent connection inside the cable | The chain teeth are jumping and the bearing is about to get stuck |
For most on-site operators, first adjusting the blade height and checking the tightness of the belt can often solve more than 80% of the deviation problems. If the problem persists, conduct more complex electrical and mechanical disassembly inspections.
Note: The parameters provided in this document are for reference only and are not mandatory. Due to differences in technical characteristics between different brands and models of laser levelers, please consult the manufacturer for a suitable solution before actual operation. This reference document assumes no responsibility for any issues arising from failure to follow the manufacturer's instructions.
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About the Author: Shandong Vanse Machinery Technology Co., Ltd.
Shandong Vanse Machinery Technology Co., Ltd. is a high-tech manufacturer specializing in concrete construction machinery, including laser screeds and related equipment. The company integrates R&D, production, and global sales, with products exported to over 60 countries and widely used in infrastructure projects worldwide.
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