Home » Products » Lowbed Semi Trailer » Heavy Duty 3 Axle 4 Axle Lowbed Semi Trailer

Heavy Duty 3 Axle 4 Axle Lowbed Semi Trailer

Production Time: Approximately 30 Working Days 
Packaging: SKD/CKD 
Shipping Method: Sea/Land 
Material: Q345B (Customizable) 
Axles: 1, 2, 3 (Customizable) 
Warranty: 1 Year Warranty for Main Structure 
Brand: Vehicle Master
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Vehicle Master's heavy duty 3 alxe and 4 axle lowbed semi trailer's high quality comes from the high standard production and supervision for every important part on the trailer. Climbing ladder, landing gear, suspension system, and axle system are all the essential parts that make Vehicle Master's semi trailers durable and trustworthy. In this page, we will explain to our customers why that is. Please read alone carefully.


Climbing Ladder of Heavy Duty 3 Axle 4 Axle Lowbed Semi Trailer

  • The climbing ladder is mainly used when the construction machinery is loaded by itself on to the heavy duty 3 axle or 4 axle lowbed semi trailer. When it is necessary to use the climbing ladder to load the construction machinery, first stop and securely park the semi-trailer on a flat surface of an open site or road, and put the ladder down (see the ladder in Figure 1). The ground that the ladder lands on must have sufficient hardness. Otherwise, a suitable board or steel plate should be placed in contact with the ladder and the ground. When the trailer is running or the ladder is not needed, the ladder should be turned up and placed in a safe state (see Figure 1 for the ladder in the trailer running state).

  • The ladder is mainly welded on the tail of the heavy duty 3 axle or 4 axle lowbed semi trailer. It is mainly composed of the main frame of the ladder, the compression spring, the guide post of the compression spring, the compression spring seat, the rotation pin of the main frame of the ladder, the swing adjustment shaft of the compression spring, the rotation pin of the main frame of the ladder, the compression spring, the guide column positioning pins, and other components (see Figure 1). After the ladder has been used for a period of time, check the lubrication of the compression spring swing adjustment shaft, the main frame rotation pin of the ladder, and the compression spring guide column positioning pin, and apply grease in time to ensure the flexible rotation of the ladder.


                                                                            Figure 1 

1- Ladder Main Frame 2 - Compression Spring 3 - Compression Spring Guide Post 4 - Compression Spring Seat 5 - Ladder Main Frame Rotation Pin 6 - Ladder Main Frame Support Plate 7 - Compression Spring Guide Post Positioning Pin 8 - Compression Spring Guide Post Support Plate 9 - Compression Spring Swing Adjustment Shaft


Note: Before the ladder is put down, it is strictly forbidden to stand in front of and behind the ladder. The operator should pay attention and stand beside the ladder so it does not fall down or bounce back before it is placed in position, which may cause injury to people. The hydraulic power ladder is not allowed to be modified by users to other power sources such as the main vehicle power take-off hydraulic pump. Otherwise, it will not work properly or even cause failures such as climbing ladders, deformation of the oil cylinder, etc. After the ladder is returned to its original position after use, pull it forward with a chain or wire rope and lock it to prevent the ladder from accidentally tilting backwards and falling over.


Supporting Device of Heavy Duty 3 Axle 4 Axle Lowbed Semi Trailer


                                                                                Figure 2

1 - Transmission Box 2 - Outer Square Tube 3 - Inner Square Tube 4 - Base 5 - Crank Handle 6 - Grease Nozzle 7 - Transmission Connecting Rod 8 - Self-locking Bolt 9 – Tension Brace 10 - Crank Handle Fixing Hook


  • The supporting device is mainly composed of outriggers, outrigger connecting plates and tension brace. It is used to support the front load of the semi-trailer when the semi-trailer is detached from the tractor. Linkage and single action are the two forms of outriggers. The structure is roughly the same with gearbox, control crank, etc. The linked driven outrigger does not have a gearbox and is connected with the active outrigger by a transmission connecting rod. Rotate the crank handle to lift and lower the bearing device. The outrigger has two speed ratios: fast and slow. When the outrigger rotating shaft is pulled out, it is a high-speed gear. The high-speed gear is used when the trailer is empty, while the low-speed gear is used when the trailer is loaded. 

  • The outriggers should be maintained as well and lithium-based grease should be injected into the gearbox regularly to ensure reliable lubrication of the gears in the gearbox and easy opening and lowering. When the heavy duty 3 axle or 4 axle lowbed semi trailer is unloaded, the semi-trailer must be parked on a flat concrete road or a solid and flat ground. It is not allowed to use outriggers on slopes or soft mud roads. The outriggers are not allowed to exceed the lifting height. When the lifting height is not enough, a regular rectangular pillow block can be put under the base as cushion to reach the appropriate height.

Leaf Spring Bracket and Suspension of Heavy Duty 3 Axle 4 Axle Lowbed Semi Trailer

The suspension of heavy duty 3 axle or 4 axle lowbed semi trailer is mainly composed of front bracket, middle bracket, rear bracket, adjustable tie rod, non-adjustable tie rod, balance shaft, balance beam, "J" type bolt tie rod fixing seat, upper and lower plates of the axle and leaf spring. When the vehicle is in use, The suspension should be regularly maintained, while the lubrication of each tightening bolt and lubricating parts should be checked regularly.


                                                                            Figure 3 

1 -  Front Bracket 2 - Adjustable Tie Rod 3 - Tie Rod Fixing Seat 4 - Axle Upper and Lower Splints 5 - "U" Type Bolt 6 - Balance Beam 7 - Middle Bracket 8 - Leaf Spring 9 - Axle 10 - Balance Shaft and Nut 11 - Leaf Spring Damping Bolt 12 - Rear Bracket 13 - Adjustable Pull Rod Locking Screw


Note: If the trailer has a lifting axle structure, it is not allowed to lift when the vehicle is heavily loaded. The lifting axle can only be lifted when the vehicle is empty. Otherwise, the frame will be deformed or cracked, while axles will be overstressed and break.

Regularly check the U-bolts of the axle and tighten them according to the specified torque. Otherwise, there will be distortion due to looseness, wrong wheelbase, abnormal tire wear, misaligned wear or broken pears of the plate mirror, and left and right deviation of the axle (especially with air suspension axle). It is not allowed to turn on the spot when the vehicle is heavily loaded, which may lead to deformation of leaf spring, tie rod, and steel, or even overturning of vehicle.

Always check the air pressure sealing of the lifting system. There should be no air leakage. It is not allowed to change the airline of the lifting system without permission. Otherwise, it will affect the lifting performance of the axle or the quality of the brakes.


                                                                            Figure 4


Pre-tightening torque of each bolt

  • Balance beam bolt: M30×2 through cotter pin, split

  • Tie rod shaft nut: M14 170-180N.m

  • Adjustable tie rod lock nut: M14 170-180N.m

  • Plate spring stop bolt: M16 through cotter pin, split

  • U-bolt: M24 x 2 600-650N. m

  • Add a little grease to the sliding parts of the suspension parts and the sliding terminals of the leaf springs (see Figure 4)


Axles, Tires, and Rims of Heavy Duty 3 Axle 4 Axle Lowbed Semi Trailer

Axles and wheels play the role of supporting, running and braking for the heavy duty 3 axle or 4 axle lowbed semi trailer. The axle is composed of axle body, axle head, hub, brake, etc. (see Figure 5). The wheel is composed of tire, rim, connecting bolts, etc. The axles are made of high-quality products from well-known factories domestically and abroad such as German BPW, American KIC, FUWA, and L1. These axles are all manufactured on the special production line of reputable factories with advanced technology, excellent quality, high precision, strong power, light weight, and high durability. The wheel specifications adopt 700v×20,7, 50v×20, and 800v×20. Tire specifications adopt 10.00-20 16PR or 18PR, 11.00-20 16PR or 18PR, and 11. 00R20



                                                                            Figure 5

1 - Brake Shoe, 2 – Brake Shoe, 3 – Outer Bearing, 4 – Inner bearing, 5 – Return Spring, 6 – Camshaft, 7 – Brake Rocker Arm


Vehicle Master is China's leading provider of semi trailer solution for transportation and logistic industry. The company has been awarded Provincial Municipal Meritorious Enterprise, Star Enterprise and Advanced Enterprise.




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