What is Hydraulic Modular Trailer and Why Do We Use Them?

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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

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Goldhofer THPS HMT in two-lane configuration in

In the first every hydraulic modular trailers were made by Willy Scheuerle a Germany based trailer specialist which were four axles 32 wheeled modules for Robert Wynn and Sons Ltd, a Shaftesbury-based Guinness Book of Record-winning heavy haulage company.[2] Wynns were also the first to use pneumatic tires for loads weighing more than 100 tons and also to use hydraulic suspension trailers which were manufactured by Cranes Trailers limited from Dereham.[3]

In Cranes Trailers limited 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.[4]

In Goldhofer developed modular trailers in Europe for heavy haulers.[5] In the same year, Cometto developed a 300-ton capacity module in 14-axle, seven-row configuration.[6] Scheuerle also demonstrated its modules at events in [7] and later King Truck Equipment Ltd signed an agreement with Scheuerle which gave them exclusive manufacturing rights to produce their trailers in the UK.[8]

In , 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.[9]

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

In the s, 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,[10] 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

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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,[11] 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[12] 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.[13] Draw bars and tow hitches are manufacture red by companies like jost and Ringfeder.[citation needed]

Since 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.[14]

Accessories

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

• Gooseneck
• Draw bar
• Drop Deck
• Vessel Bridge[15]
• Intermediate spacer
• Excavator deck
• Extendable spacer
• Turntables (bolster)
• Blade Lifter[16]
• Tower adapter[17]
• Girder frame[18]
• Trailer power assist[19]

Manufacturers

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

Operators

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

Gallery

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With competitive price and timely delivery, Haiheyuan sincerely hope to be your supplier and partner.

• 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 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

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References

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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.

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.

This is useful 16 panel Hydraulic Platform Transporter Reference Card is developed by me, Marco J. van Daal, and is applicable for every type of hydraulic platform transporter on the market today, both pull type as well as self propelled modular transporters (SPMT).

overview of the standard 3-point and 4-point suspension settings. It identifies every hydraulic suspension valve and hydraulic line on the transporter and an easy to understand diagram visualizes the oil flow and the effect on the operation. Furthermore, this panel offers definitions and principle working and highlights terminology. All other panels refer back to this panel 1 for terminology and abbreviations. explains the difference between an axle and an axle line. It illustrates the possible movements of such axles with their respective minimum and maximum height to negotiate uneven terrain. A picture clarifies the various components of a pendulum axle assembly. This panel offers a sample calculation of the so-called &#;equalizing effect&#; that takes the guessing out of a transport operation. highlights the difference between pull type and self propelled transporters, in terms of steering capabilities, steering angles, tires per axle, payload per axle line, self weight and dimensions. This panel also offers a sample calculation of how to determine the minimum required number of axle lines to carry a certain load. This calculation can be easily applied to your situation. an overview of rolling resistance of vehicles and how you can quickly determine the required truck capacity to pull a certain load. Similarly it shows how to figure out how many drive axles an SPMT would need to transport the same load and what the capacity (kW or hp) of the power pack (PPU) needs to be to handle the demand. In case the transport is climbing a gradient it is obvious that the required power increases, the panel provides this as well. a quick and easy calculation on how to determine the hydraulic stability angle of a transport, in a 3-point as well as in a 4-point suspension configuration, with a single formula. The hydraulic stability angle is a measure of how close the combined center of gravity (CoG) is to the tipping lines of the stability area. This gives the crew a better level of comfort when changes in the field take place. calculating the structural stability angle of a transport, in a 3-point as well as in a 4-point suspension configuration, with a single formula. The structural stability angle is a measure of how close the transporter is to being structurally overloaded. In addition, this panel provides information on the limiting factors on 3-point and 4-point suspension and on the recommended Safe Stability Angles. a complete hydraulic and structural stability sample calculation based on the information and formulas from the preceding panels. It also calculates the minimum number of requires axle lines given a certain load and the required pull force while going up hill. This panel gives an outline that can be easily adopted to your load. The spine beam offers resistance against torsion, bending and shear forces. It is important not to exceed the maximum values of these forces. Specifically with concentrated loads there is a significant risk of spine beam overload if not correctly analyzed. This panel shows how to determine the spine beam bending moment and how many axles may extend beyond the load given the type and approximate age of the transporter model. deals with ground pressure, arguably the most controversial topic in the Heavy Transport industry. This panel offers two easy methods of calculating ground pressure underneath a transporter. Both methods are an approach with acceptable outcomes and avoid that a full soil analysis by geophysicists has to be carried out. One method is a bit more conservative than the other, they both use the transporter &#;shadow area&#; as the base for the calculation. handles the first of 3 types of external forces, the curve or centripetal forces. The centripetal forces cause the transporter and load to have the tendency to move away from the center of the curve. The faster the transporter moves (higher speed), the higher these centripetal forces become. Centripetal forces can get out of control rather rapidly as they quadruple when the velocity doubles. handles the second type of external forces, the wind and acceleration/deceleration forces. These forces are determined in a similar way although they act differently on the load. The deceleration forces, when applying the brakes or when making an emergency stop, are the most significant and therefore have the largest impact on transport stability. Still, the other forces cannot be neglected. handles the gradient forces that act on a load when traveling on an incline/decline or when negotiating a road camber without the transporter being compensated for the angle. These uncompensated situations result in a longitudinal force (in case of an incline/decline) and a transverse force (in case of a road camber) that have an influence on the axle loads and ultimately on the stability of the transport. about lashing and securing. It shows how each lashing contributes in each direction given the angle it is applied at. This panel shows how much lashing is required to secure against the external forces from the preceding panels. The dunnage placed between the load and the transporter deck increases the friction which is taken into account as well. An added benefit is that correctly and sufficiently applied lashing reduces the combined Center of Gravity. a complete lashing calculation using the information from the preceding panels. The external forces, wind, centripetal and acceleration/deceleration forces are all taken into account as well as the friction that is provided by the plywood placed between the load and the transporter deck. An easy to understand matrix indicates how much lashing is required in each direction under the given conditions. about the application of a goose neck. Used by many, understood by few. This panel explains the difference between the two types of goose necks in existence. The goose neck transfers part of the load weight to the 5th wheel of the truck via a hydraulic hinge system, herewith eliminating the need for counterweight and resulting in a lower gross vehicle weight (GVW). This transfer of load results in a reduced axle load. a Beaufort wind scale and a number of recommendation when deciding on a suspension configuration. It highlights the pros and cons of both the 3-point as well as the 4-point suspension configuration and recommends when to use which one. These recommendations are determined by the center of gravity (CoG) and the potential to overload the transporter.

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