What is the capacity of a modular trailer?

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Tiiger four-axle HMT module at Transporter Industry International headquarters in Haryana, India

A hydraulic modular trailer (HMT) is a special platform trailer unit which feature swing axles, hydraulic suspension, independently steerable axles, two or more axle rows, compatible to join two or more units longitudinally and laterally and uses power pack unit (PPU) to steer and adjust height.[1] These trailer units are used to transport oversized load, which are difficult to disassemble and are overweight. These trailers are manufactured using high tensile steel, which makes it possible to bear the weight of the load with the help of one or more ballast tractors which push and pull these units via drawbar or gooseneck this combination of tractor and trailer is also termed as heavy hauler.

Typical loads include oil rig modules, bridge sections, buildings, ship sections, and industrial machinery such as generators and turbines also many militaries uses HMT for tank transportation. There is a limited number of manufacturers who produce these heavy-duty trailers because the market share of oversized loads is very thin when we talk about the over all transportation industry. There are self powered units of hydraulic modular trailer which are called SPMT which are used when the ballast tractors can not be applied due to space.

History

Goldhofer THPS HMT in two-lane configuration in 1973

The first hydraulic modular trailer modules can be traced back to 1962 when heavy trailer specialist Cranes Trailers limited from Dereham developed two four-axle 32-wheel modules for Pickfords a London based heavy haulage company with combined payload capacity of 160 tons on a total of eight axles and 64 wheels the modules incorporated hydraulic suspensions and each axle interlinked with mechanical steering system at an operational height varied from 2.9 to 3.11ft. The modules had drawbar coupling which could be coupled at any of both ends or even both for push-pull combination.[2]

In 1963 Goldhofer developed modular trailers in Europe for heavy haulers.[3] In the same year, Cometto developed a 300-ton capacity module in 14-axle, seven-row configuration.[4] Scheuerle also demonstrated its modules at events in 19867[5] and later King Truck Equipment Ltd signed an agreement with Scheuerle which gave them exclusive manufacturing rights to produce their trailers in the UK.[6]

In 1971, King Truck Equipment Ltd demonstrated two units that were custom-built for Pickfords. A single unit was able to carry 150 tons on six axle rows and 48 wheels in total. Who would use them mostly with their Scammell ballast tractors via a drawbar coupling. These trailers had independent suspension and steering abilities via the Petter twin-cylinder diesel engine used as a PPU.[7]

A locomotive being hauled to Woodham Brothers yard on an eight-axle HMT coupled via drawbar to a Scammell contractor ballast tractor on A27 highway, England in 1978

The same year, Robert Wynn and Sons Ltd, a Shaftesbury-based Guinness Book of Record-winning heavy haulage company, received two ten-axle row HMT from Nicolas Industrie which had a gross capacity of 600 tons when coupled with a gooseneck coupling. With seven rows, the unit had a total capacity of 350 tons.[8]

In the 1970s, many manufacturers started to developed HMTs as the industry believed that the conventional low loaders had various limitations. To comply with new regulations and keeping safety in mind, the industry knew that they needed more axles to distribute the payload and the ultimate solution for the demand would be HMTs. Manufacturers opted hydraulic suspension instead of mechanical leaf springs and air suspension due to its efficient size and adjustable characteristics. Manufacturers chose high-tensile steel instead of aluminum because when it comes to HMTs and oversize loads, the minimizing the weight of the HMT is not relevant when they have their own payload capacity excluding the ballast tractor. The only weak point that existed on a HMT were the tires,[9] which are still a significant weakness till today, that's the reason why SPMTs have solid tires. HMTs operate at a higher speed then SPMts that's why solid tires are not an option for HMTs.

Specifications

Steering and suspension controller unit mounted on a Scheuerle HMT

The number of axles on a HMT is not specified; two-, three-, four-, five-, six-, and eight-axle units are manufactured. Multiple units can be coupled longitudinally and laterally to transport a heavier load; each axle has a lifting capacity ranging from 18 tons to 45 tons. With a steering capacity of 50 to 60 degrees. Some combinations require a trailer operator who controls steering and height adjustments of the trailer via a controller which is modular and can be mounted at the frontend or rear end of the trailer. Huge combinations may also have a cabin for the operator, while typical combinations have a seat attached to the controller.[citation needed]

Hydraulic cylinders are used for steering and suspension of the trailer each axle has an individual suspension cylinder, steering rod which is connected to the main steering cylinder which is at the frontend of the trailer which makes all the axles steer at once in the same direction one row of axle consist of two turn tables, two knees, two suspension cylinders and four to eight wheels attached to a high strength metal platform. Steering and suspension cylinders are hydraulically operated using hydraulic fluid through hose pipe from the hydraulic tank, which is located near the PPU. PPU, which powers the steering, suspension to and fro flow of hydraulic fluid from hydraulic tank to suspensions and steering cylinders, puts out about 18 to 25 hp of power and are available in both diesel and petrol variants manufactured by renowned brands like Kohler, Yanmar and Hatz.[citation needed]

Multiple units of HMT can be interconnected longitudinally by pins and interconnecting couplings mounted in the centre of the chassis in the front and rear to interconnect them laterally they are bolted on the side wall of the chassis. HMTs can not move themselves, so There are two ways by which a HMT can be coupled with a tractor unit which can push and pull the trailer, these are gooseneck and drawbar.

Under view of a Tii HMT with visible axle configuration and interconnecting coupling after an accident in Sögel, Germany

[citation needed]

Gooseneck is the most common coupling used in the industry as the name suggest a swan shaped coupling is coupled to the trailer and the tractor via connection of trailer pin and tractor fifth wheel. This coupling can be hydraulically adjusted to suit the tractor's height also the steering controls are connected to the coupling. Goosenecks are easy to use and gives benefit to using conventional tractors,[10] but this coupling has two huge drawbacks this coupling can not be applied in a two file or side by side HMT configuration which limits the payload, and also it can not be applied in push and pull configuration. Goosenecks are manufactured by the trailers manufactures themselves. Drawbar is the most efficient and economical coupling which consists of an A-shaped frame with an I-shaped loop which is coupled to the trailer and connected to a ballast tractor via a towing hitch of the tractor. This coupling is widely used in developing countries because of its economical cost. Unlike gooseneck, this coupling can be applied to side by side and push & pull configuration[11] which, but this coupling can not be connected to a typical tractor, it requires a ballast tractor which has a ballast box instead of a fifth wheel and tow hitches in the rear and front.[12] Draw bars and tow hitches are manufacture red by companies like jost and Ringfeder.[citation needed]

Since 2005 in the United States of America, HMT have extra features and design changes which include widening axles, and half way folding system. Due to different road regulations in different states, almost all manufacturers have adopted the US design and developed a product for the US market. These HMT trailers are named dual lane trailers, which comes from the widening characteristic of the trailer. Dual lane trailers have capability to change its width from 13 feet (4.0 m) to 20 feet (6.1 m) wide to make transport of empty trailers easy and also comply with state regulations when required.[13]

Accessories

Allelys HMT with girder bridge configuration, hauling heavy load with two MAN ballast tractors

• Gooseneck
• Draw bar
• Drop Deck
• Vessel Bridge[14]
• Intermediate spacer
• Excavator deck
• Extendable spacer
• Turntables (bolster)
• Blade Lifter[15]
• Tower adapter[16]
• Girder frame[17]
• Trailer power assist[18]

Manufacturers

Goldhofer THP-SL hydraulic modular trailer with oversize load being pulled by Mercedes-Benz Actros ballast tractor via drawbar

Operators

United States Army five-axle M1000 HMT module by Leonardo DRS coupled with Oshkosh M1070 tractor at Las Vegas

Gallery

• Windmill tower section being transported using tower adapter configuration

• DOLL self steering blade transporter dolly

• Goldhofer FTV blade lifter being pulled by a Mercedes-Benz SK 3553 tractor

• ALE girder bridge with trojan tractors in push and pull configuration

• Volvo tractor with drop deck configuration moving oversize load

• MAN tractors with vessel deck configuration

See also

References

Learn Hydraulic Modular Trailers Specs & Designs

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.

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Chapter One: What Is A Hydraulic Modular Trailer?

A modular trailer is a series of special vehicles 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.

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.

• 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.

More specs and dimensions for reference:

Ultimate Modular Trailers Buying Guide

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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.

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.

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