What is a hydraulic trailer used for?

History

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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]

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

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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.

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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

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• 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

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Operators

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• 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

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References

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As trailer applications use hydraulics in different ways, we have provided a breakdown of some common types of these below:

Plant trailers

Having to operate in a range of environments, plant trailers are the first choice for transporting construction grade machinery such as diggers and other machinery.

The hydraulic tilt mechanism allows a low approach angle for loading and have advantages over other types of plant loaders as they can cater for plant vehicles with low ground clearance.

Typically available in a range of different styles including all-purpose trailers with a single axis which are suitable for agricultural and building machinery and for vehicles weighing over 3.5 tonnes, twin axle, auto tilt platform trailers are commonly used. Custom made tippers are available that cater for alternate platforms such as scissor lifts.

Regarding the operation of the trailer, the trailer deck typically extends backwards, initiating the lowering of the tailboard which locks on a horizontal plane. This enables the body to balance above the pivot point, which can then be angled allowing the machine to be moved on to the trailer. The pump valve can be closed off to allow the body to remain in a raised position in order to load other items; re-opening of the valve will then lower the body. The body is released when unloading so the tailboard will lower allowing the machine to be loaded up on to the ramp and the body will then tilt, using hydraulic damping, and the machine can be driven back off.

Car transporters

Coming in a variety of sizes and shapes, car transporters are typically enclosed units that protect their contents from the outside environment are and a popular solution for those wanting to transport vehicles around the country or cross continent. They provide a working platform for any owner and the low bed chassis they typically come with provides a stable and safe towing base.

They commonly feature a hydraulic-tilt bed operation, together with a loading ramp/door and popular materials used in their construction include steel and aluminium. Some specifications also include remote control electric winches and various loading and securing equipment as optional extras with the package to aid in getting the vehicle on-board.

Commercial tipper trailers

These units are primarily used to carry commercial and agricultural materials and are found in abundance in the construction industry where they are regularly seen tipping earth, bricks, mortar and other materials.

The trailers are built to have a high clearance for site access but also a low centre of gravity for optimal loading and towing performance. They have a solid and robust build due to the weights of materials they carry on an almost daily basis, and come with a single function high tilt mechanism which allows approximately 60° of tilt to ensure that any materials contained will disperse successfully.

A hydraulic power pack is typically installed in front of the hydraulic arm within a protective case and a pendant hand controller controls the tilt operation of the trailer.

Suppliers of these units comply with health and safety regulations by installing audible warning systems when the trailer bed it raised and lowered to enable operators to work safely and effectively.

Hydraproducts supplies a range of DC power packs complete with 12 or 24VDC Motors containing single and double acting valves primarily for use in tipper applications

As well as manufacturing the power packs themselves, Hydraproducts are also able to tailor their design for a bespoke fit to the majority of applications using state-of-the-art 3D modelling technology.