In this guide, we will discuss the modular trailer also called as hydraulic axle modular trailers, multi-axles trailer, which is one of the major types of modular transporters as indicated at the last post SPMT ultimate guide. 

Part 1: SPMT Ultimate Guide – Self-propelled modular transporter Design & Specs

This guide outlines the major uses and specs and designs of the hydraulic modular trailer. The chapters in this part also outline the main components of the hydraulic modular trailer and different combination forms of the transporter.

You will also learn the end of the section the forecast of modular transporters in China and the process of selecting a reliable supplier. Let us start with the definition and description of the modular trailer.

Free PDF Download


Chapter One: What Is A Hydraulic Modular Trailer?


A modular trailer is a series of special vehicles that is used to transport large cargos that are difficult to disassemble. The trailer is also used transport over-length goods.

The major applications of modular trailers include power stations, chemical industry, iron and steel industry and the construction industry. Modular trailers are used for mining operations because of their excellent lateral stability.

A self-propelled modular transporter without the power pack unit is similar to the hydraulic modular trailer. The main between the modular trailer and the SPMT without the PPU is that they have a different steering system.

The modular trailer uses a mechanical steering system. Another difference is that the modular trailer can be combined using a gooseneck and a drawbar.

The vehicle loading platform of a modular trailer is kept at balance when transporting goods on bumpy or rough roads in a way that the damping property is excellent.

The brace kit of the vehicle can achieve three or four brace points to ensure that the load of each point is uniform. The four points also ensure that there is no partial set.

The steering system of the modular trailer has a hydraulic planar pitman driver. The vehicle can achieve minimum turning diameter and normal drive by adjusting the hydraulic steering system and using different reasonable pitman layouts.

The supporting assemblies for the trailer part have a solid box beam structure.

High performance welding steel is used to make the main frame longitudinal girder, bogie frame, steering arm, and the platform.

hydraulic axles modular trailer

hydraulic modular trailer

Series modular trailers have two major modes that include full-trailer towing and the semi-trailer towing. The full trailer towing mode can achieve a maximum speed of 40 km/h. This model can achieve the maximum tractive force.

Hence, the full trailer mode is used for heavy duty transportation but at a low speed.

The semi-trailer towing mode can reduce the full length of the vehicle and minimize turning diameter. The semi-trailer mode can also increase the effective load and the speed of the modular trailer.

Hence, the maximum of the semi-trailer towing model is 80 km/h, which is twice the maximum speed of the full-trailer towing mode.

Chapter Two:  The Specs and Dimensions of Modular Trailers


The modular trailers come in different modular units that include 2, 3, 4, 5, 6, and 8 axle models. The maximum load per axle is up to 40 tons. A larger number of axle lines means that the modular trailer has a higher loading capacity.


8 axles modular trailer

8 axles modular trailer

6 axles modular trailer

6 axles modular trailer

5 axles modular trailer

5 axles modular trailer

4 axles modular trailer

4 axles modular trailer

6 axles modular trailer specification

6 axles modular trailer specification


  • Half Modular Unit


The framework of all the axles line of a half modular is combined by the left and right half modular unit. The technical parameter of the half modular unit is the same as that of the modular unit after they have been combined.

The left and right half modular units cannot be used independently. The units can only used when combined or when they are combined with the modular unit.


half modular unit

half modular unit


More specs and dimensions for reference:

Ultimate Modular Trailers Buying Guide


Contact us, get more drawings now!!

Contact us

Chapter Three: Illumination of Main Equipment


This chapter outlines the main components of a modular trailer. The chapter outlines the specifications including the structure and the functions of each component or equipment. At the end of the chapter, you will learn about the additional accessories that come with modular trailers.


3.1 Frame


The main girder of frame has a box-type carrying beam structure. The girder uses high-performance welding steel to ensure stability and reliability. The surface of the frame requires treatment.

The surface of the main structure should be treated with sand blasting. The thickness of the painting used on the surface should meet the national standards.

The brand of the painting used should be among the top brands in the world. All the small-sized parts of the frame should be zinc-plated.


modular trailer frame

modular trailer frame


The box-shaped center beam and the stable crossbeams give the frame a high degree of rigidity. Hence, the frame can achieve its optimal loading level.

The steering system, air tank, and hydraulic oil tank are all integrated into the bogie frame. Thus, the parts are protected against damage and corrosion.

The frame has a reinforced loading deck, which allows extreme point loads. The optimized bolt-plate coupling, on the other hand, eliminates any problems that may arise when assembling the longitudinal combinations.


3.2 Hydraulic wheel bogie


The modular unit uses a hydraulic wheel bogie, which consists of the bogie frame, hydraulic cylinder, axle, tyre, and rocker arm. It has a strong load capacity.

When the road is uneven on the transverse direction, the axle swings to compensate. If the road is uneven in the driving direction, the hydraulic lifting system adjusts the modular supporting system.

The modular unit can assume 3-point or 4-point supporting system to ensure that each supporting point carries an even load.


3.3 The Mechanism of Steering


The steering mechanism consists of the steering central panel, steering orifice plate, steering cylinders, and steering rods. The steering orifice plate is welded together with the bogie frame.

The plate has specific quantities of assembling holes that are used to install steering rods. The positions where steering rods are installed on the steering orifice plate can be changed to suit different combination modes of the modular unit.

The unit can meet the minimum steering radius and the maximum turning angle of 55 degrees.

The modular unit uses three major steering modes that include the all wheel steering along (over five axle lines), diagonal steering along, and the front-wheel steering mode.

The steering rods can be adjusted quickly and easily to suit the desired steering angle.


steering rods

steering rods


The modular has a hydro-mechanical all-wheel system with a two-circuit system, which ensures that the steering system maintains its functionality even when one or more steering circuit fails.

The hydraulic modular trailers have two types wheel bogie steering system. The two system include ball bearing race ring and pivot bearing.


modular unit wheel bogie steering

modular unit wheel bogie steering


  1. Ball bearing race ring

The steering system used in a modular transporter determines the types the operation and terrain that the transporter can handle. The modular transponsters with ball bearing race ring steering systmes are designed for off-road operations.

The transporters can bear heavy loads within a site. Their structure are well-engineered for safe and top performance in heavy-duty operations.

  1. Pivot bearing

Hydraulic modular transporters with pivot bearings are designed for heavy-duty on-road transport operations. The transporters have reinforced frames that enable them to handle axle loads. These transporters are ideal for in-plant operations.

The mechanism of steering uses two ways to steer the axles. The two ways include:

  1. Self-steering: When the tractor or truck is steering, its drawbar or gooseneck delivers a signal that makes the axles to start steering at the same time.
  2. A remote control or valve switch is used as a manual control for axle steering.


3.4 Hydraulic system


The pump in a modular transporter uses the hydraulic technique, which is effective in controlling the driving speed.

The steering and suspension pumps use the constant pressure controller to realize a quick response whenever they need steering power.

The driving motor switches between driving and follows uses a large torque radial motor. All the hydraulic cylinders in the transporter have anti-block valves, which are important when the pipe line is broken.


3.5 Brake system


The modular unit is equipped with a compressed air brake system. The system consists of double brake chambers, single brake chambers, relay valves, brake drums, and reservoirs.

The brake system consists of tow brake lines that function as the service brake and the parking brake.


3.6 Hydraulic suspension


The individual swing axles in a hydraulic modular trailer consist of the hydraulic suspension, which can be connected to different support circuits.

The purpose of connecting the suspension to different circuits is to ensure that the axles have equal loads.

When the axles have equal loads, you are guaranteed of the optimal lengthwise and crosswise leveling even if you are driving on uneven terrain. The equal loads also regulate extreme cross falls.


3.7 Lifting system


The total lifting length of modular unit’s platform is modular trailer lifting600mm. The platform gives a compensation of ±300mm, which is enough compensation for the axial load.

The suspension cylinder is installed as the steer wheel bogie.

The two ends of the suspensions have joint bearings, which protect the cylinder from damages.

The hydraulic accumulator provides good cushioning when the modular transporter is unloaded.

3.8 Combination system


All modular units can be combined side-by-side or from end-by-end.  A hydraulic link-pin is used to combine modular units end-by-end.

Combining hydraulic and brake pipeline requires fast coupling connectors, which have a high performance level. The electric interfaces use a heavy connector, which is reliable.


3.9 Power pack


The hydraulic power pack and the controlling devices of the hydraulic modular transports can perform various functions include steering, adjusting, and maintaining the vehicle combination. 

power pack

power pack




The power pack is different from the PPU in its function and performance.

The power pack cannot provide the same high power like the PPU.  It can only power to steer the modular trailer but the power cannot drive the axles.


3.10 STZ-V Gooseneck


When the tractor truck is steering, the STZ-V gooseneck will deliver signals that makes the axles steer at the same time. Hydraulic gooseneck also has a lifting function that can adapt to the height of the cargo platform.

Sometimes the fifth wheel and gooseneck bear part of the cargo weight. The gooseneck is considered the best alternative to the drawbar equipment.

STZ V gooseneck

STZ V gooseneck


Connecting the front axle line cylinders with the gooseneck cylinders guarantees the load transfer from the axle lines to the gooseneck.

This connection eliminates the need to add more weight to the truck tractor to generate enough traction force. The ratio between the axle load and the fifth wheel load can be adjustable both hydraulically and mechanically to a wide range.

Goosenecks in modular trailers have two pairs of steering cylinders that supply the front and rear steering systems of the trailer. The coupling height and clearance of the rear gooseneck can be adapted to fit most of the truck tractors in the market.


3.11 Beams


The concave beam, flat beam and the frame beam are engineered for the tanks and over height and over length goods.

The flat beam comes in different dimensions including 4.5 m and 6 m while the concave beam is normally 10 m in length.

flat beam

flat beam

3.12 200 Ton turntable


The 200 ton turntable is used to transport over length goods that cannot be transported with other structures of modular transporters.

As the name suggested, the turntable has a weight limit of 200 ton, which means that is cannot transport over length goods that are above 200 tons. The turntable should be used in pairs and on a modular combination trailer.

turntable for modular trailer

turntable for modular trailer


Many modular transporters have a front and rear turntables that enable them to transport long and heavy loads. The front turntable in most cases uses a purely mechanical system while the rear turntable uses a hydraulic self tracking device.

The front turntable can have 1-point or 2-point bearing depending on the requirements. The bearing is adjusted by the removable sliding shoes.

The device in the rear turntable operates the rear dolly automatically. The turntable bearings are not limited to 1-point and 2-point bearings.

You can order a customized turntable for a 3-file combination or 4-file combination trailers. The customized turntables may come with load repartition frames depending on your preference.


3.13 Drawbar Equipment


The drawbar is the main accessory in a modular transporter. The drawbar can have different dimensions including 2.5 m, 3 m, and 5 m. A drawbar is sometimes used to pull or push a modular platform.

Transportation companies prefer modular trailers with drawbar equipment because they offer high maneuverability even in the most difficult situations. The easiest way to operate a modular trailer is using the drawbar equipment.

A modular transporter that has a drawbar on each edge can easily change the driving direction where necessary.

Drawbar Equipment

Drawbar Equipment


Some manufacturers use a common rule of thumb that all trailers with more than 18 axle lines should use a drawbar system instead of the common gooseneck system.

Drawbar trailers are often assembled or combined in 3-file or 4-file side by side combinations. The purpose of these combinations is to reduce axle loads, increase the payload or to improve the bending moment usage.


3.14 Electric system


The modular trailer has a power pack with a rated voltage of 24 V. The equipment in the trailer that use electronic monitoring and control have an LCD color monitor.

The micro control system has a special controller whose function makes the control system of the module unit more stable and reliable.

The system also has a CAN bus that enables data transmission from one controller to another and from the controller to the displayer.

The displayer has several functions including the normal monitoring and operation. It also has settings for the meter display, lighting alarm, and lighting.

The meter display shows the speed, water temperature, pressure of the braking system, oil pressure, and engine speed.

The lighting alarm shows the hydraulic filter alarm, fuel oil lower alarm light, air pressure brake warning light and engine oil pressure alarm light.

It also consists of the parking brake indicator, accumulator charging indicator, cooling indicator temperature alarm and engine filter alarm.

The third function of the displayer is the lighting, which consists of the blinker, warning light, side light, and reversing light.


3.15 Additional accessories


Hydraulic modular transporters come with different accessories depending on their configuration and combination form. The different combination forms are discussed in detail in chapter nine.

Manufacturers give a wide range of accessories to enable users to customize their modular transporters to suit different operations.

Some of the accessories that come with these transporters include goosenecks, radio controls, and hydraulic bolt couplings.

Other accessories include hydraulic power packs, steering heads, load spreaders, long-load turntables, side-by-side devices, and pulling devices among others.

Sometimes the accessories are already installed in the modular trailer depending on the manufacturer’s preference.


Chapter Four: Combination Forms of a Modular Trailer


The modular combination hydraulic trailer has the capacity to achieve 3 towing forms. The forms are possible when the entities in the vehicle are connected with different combination accessories and auxiliary equipment.The three forms include a semi-trailer, trailer, and self-trailer. The modular hydraulic trailer can realize three major combinations including:

Combination with drawbar: The combination includes the drawbar, vehicle entity, and side steering frame

Combination with STZ-V gooseneck: It involves the STZ-V gooseneck and vehicle entity

Combination form or self-towing: The modular trailer can achieve self-towing through a combination of several components that include the PPU device, module unit, and self-propelled module unit.The power device supports multiple functions that include hydraulic driving, air brake system, hydraulic lifting system, and hydraulic steering.

The modular trailer with this combination form can replace the traditional vehicle completely in a specific transportation environment, that is, transporting overweight goods at speed below 5km/h. Let us now look at the combination forms in details.


4.1 Combination with drawbar


This form of combination is in different series include the 2-file, 3-file, and 4- file combination with drawbar. The main difference on these combinations is the type of accessories used. Each of these combinations is outlined below.

2-file combination with drawbar

This combination consists of the drawbar, power pack, modular unit, side steering frame and the combination accessories. You choose the modular unit based on the type of goods you want to transport.

2 file combination modular trailer

2 file combination modular trailer


You can get a modular unit of up to 32 axle lines. You can also choose other equipment that work together with the 2-file combination with drawbar such as a flat beam or a low flat beam

3-file combination with drawbar

The 3-file combination with drawbar comes with the drawbar, power pack, side steering frame, modular unit, combination accessories, half modular unit, central steering frame 1 and central steering frame.

3 file combination modular trailer

3 file combination modular trailer


You can tell from the components that the 3-file combination is better than 2-file combination with drawbar.

4-file combination with drawbar

The combination consists of a drawbar, power pack, central steering frame, modular unit or half modular unit, side steering frame, and the combination accessories.

4 file combination modular trailer

4 file combination modular trailer


For all the file combination with drawbar forms, you can get modular units of up to 32 axle lines.


4.2 Combination form of the turntable


The combination form of the turntable has a drawbar, turntable, modular unit, power pack, side steering frame, and the combination accessories.

turntable combination modular trailer

turntable combination modular trailer


The varying component in this combination is the turntable. The turntable is used in pairs when the modular transporter is carrying over length goods.


4.3 Combination with STZ-V gooseneck


This combination consists of the STZ-V gooseneck, modular unit or half modular unit, power pack, and the combination accessories.

The modular units that have this form of combination have up to 16 axle lines. Hence, you can choose the right modular unit for your type of goods.

gooseneck combination modular trailers

gooseneck combination modular trailers


The only limitation with this combination and its type of modular unit is that it may not transport over length goods. You can also add other auxiliary equipments to the chosen modular unit such as a flat beam.


4.4 Pulling work model


Sometimes the tractor truck does not have enough power to pull the modular trailer from one location to another. In such an instance, a PPU is added to pull the trailer.

pulling modular trailer

pulling modular trailer

Chapter Five: The State Of Modular Trailers In China


The transportation industry in China has been undergoing development as manufacturers adopt the latest technology in their factories.

One reason why modular trailer manufacturers have been adopting new technologies is to keep up with competitors from other countries in the world.

The manufacturers have also been adopting the latest technologies to avert the notion that Chinese products are of low quality. As you shop for a modular transporter from the country, you need to know the real state of the industry as outlined below.

  • The industry is experiencing rapid development

The demand for modular transporters from China has rapidly increased in the recent years. Foreign companies had dominated the market for these transporters for many years. The companies had access to the best technologies to assure their clients of long-lasting and high-performance transporters. As manufacturers in China invest in the same technology, they have been able to guarantee their clients of the same high quality.

Another factor that has contributed to the rapid development in the industry is the high price of modular transporter from other countries. Many business owners are turning to the Chinese market for affordable yet high-quality modular transporters. Chinese suppliers also beat foreign companies in offering timely services to their clients.

  • Many suppliers in the industry

As the demand for affordable module trailer increase, more and more suppliers have been joining the industry. Hence, buyers have many suppliers to choose from when exploring the Chinese market. The entrant of new suppliers is beneficial to buyers because suppliers have to offer fair prices to stay in business. However, many suppliers are still offering the same old models of modular transporter.

ANSTER modular trailer

ANSTER modular trailer

Some suppliers are still using the obsolete models from foreign companies in the manufacturing processes. Such prototypes have restricted growth in the industry. A few suppliers are breaking away from this trending by trying to offer the latest model of transporters. Suppliers like ANSTER have modern designs of modular transporters, which are associated with higher levels of performance and efficiency. Consequently, the brand competes effectively with other brands in the global market.

  • ANSTER can now supply 48 tons per axle load

The latest models of transporter have a high loading capacity. The models are compatible with foreign brands. The high axle load technology should improve the technology used in three major systems. The systems include the structural strength of the vehicle, hydraulic system hoisting capacity, and the capacity of the running gear axle and tire bearing.

The engine and hydraulic system of the ANSTER modular transporter use German parts.

engine and hydraulic system

engine and hydraulic system

The model is compatible with Goldhofer, which one of the top brands in the global market for heavy-duty transporters.

compatible with goldhofer

compatible with goldhofer


Part 1: SPMT Ultimate Guide – Self-propelled modular transporter Design & Specs



The knowledge of the specifications and functionality of modular trailers will help you select the best model for your company. However, you also need to consider the quality standards, prices, factory strength, and technology of different suppliers.

China remains one of the best markets to buy a modular trailer. You can get models of modular transporters that are compatible with other international brands.

If you choose the right manufacturer like ANSTER, you will get a modular transporter with a firm structure and a high loading capacity.

Free PDF Download

  • Thank you for your inquiry
    Our engineer will reply you in 12 hours

  • Thank you for your inquiry
    Our engineer will reply you in 12 hours

  • Thank you for your inquiry
    Our engineer will reply you in 12 hours