The Semi Low Loader is the "workhorse" of the oversize cargo market. Combining the maximum possible deck length (within the regulations), with a low deck height, this style of special trailer is suited to both over height and over width cargo. Normally configured with three, four or five axles, these trailers generally offer 3.25/3.50m on the upper deck (A), between 8.75 and 9.50m on the main deck (B), with the deck height varying between 0.75 and 0.95m (H).

Extendible, Semi Low Loaders

The vast majority of Semi Low Loaders also offer extendibility on the main deck. Dependent on whether the trailer in question is a single, double or triple extendible version, deck lengths in excess 35m (B) are achievable (for indivisible cargo). However, in order to manoeuvre and, at one and the same time, satisfy international regulations, extendible trailers have to be fitted with sophisticated steering mechanisms. Equally, many semi low loaders are equipped with ramps, making it possible to load/discharge self propelled cargo, thereby avoiding crane expenses.

In the previous section, we describe conventional, three, four and five axle, Semi Low Loaders. However, more sophisticated Semi Low Loaders are available, with axle combinations ranging from five to ten (eight axle illustrated). Obviously, these offer far greater payloads, normally ranging up to 100 tons (regulations permitting). The greater the number of axles, the more complex the suspension and steering mechanism becomes, not only to negotiate corners but also guarantee equal axle loadings.

It is self evident that the main deck length (B) is largely influenced by the number of axles. One compromise on this type of trailer is that the deck height (H) is generally greater, being in the region of 0.90/1.00m. This is primarily to provide for additional axle deflection, over the length of the trailer, when operating in extreme road/ferry conditions i.e. acute ferry link span angles, hump back bridges etc.

This type of trailer also comes available with a wide range of ancillary equipment i.e. support cradles, turntables with girder sets (for split axle combinations), remote steering using an auxiliary power pack etc.

If the deck height of a Semi Low Loader is too great, it may be necessary to utilise a conventional Low Loader. In this instance, the deck height is generally between 0.40 and 0.65m (H). It follows that the lowest versions, sometimes also known as slim or wafer decks, have a much reduced payload, due to the profile of the deck. Main decks generally have a length of 8.00/9.00 (B), with the rear deck length being dependent on the number of axles - two, three or four. The majority of low loaders have a removable neck (A), for ease of loading self propelled cargo i.e. construction equipment etc.

Extendible Low Loaders

A limited number of Low Loaders offer extendible main decks. Generally, these are intended for light weight, volume cargo i.e. silos, yachts etc. In most cases, the level of extendibility is limited, taking the main deck from around 9.00m to possibly 14.00m (B). However, stg can offer modular, extendible low loaders capable of accommodating cargo up to 20m length (B). As with extendible, semi low loaders, these are equipped with remote steering, enabling the trailer to manoeuvre in restricted spaces.

With conventional Low Loaders, in order to satisfy axle load restrictions, there is limit to the payload achievable. Generally, this is a consequence of the maximum weight that can be imposed on the tractor unit. As a result, it is necessary to move up a category, into Heavy Duty, Low Loaders. In the majority of cases, these are made up of a forward bogie, followed by a centre deck, followed by a rear bogie. In the illustration shown, this is referred to as a 2 + 5. Numerous combinations are available, normally only restricted by the ability of the particular configuration to negotiate the route.

Needless to say, the deck length of B and D are determined by the number of axles on the forward and rear bogies. In both cases, the deck height is generally in the order of 1.00/1.15m. As far as the centre deck is concerned, the length can vary enormously, from a modest 6.00m to a gargantuan 20.00m (and beyond), with a running height of between 0.55 to 0.75m (H).

Centre decks come in numerous shapes and sizes. Some have a narrow profile, others a wide profile, mainly intended for larger construction equipment i.e. excavators, dump trucks etc. Others have a removable floor, enabling transformers (or similar) to be carried "in suspension". The combinations are endless, with the choice being influenced not only by the cargo characteristics but also national & international regulations, combined with bridge and road restrictions.

The ultimate piece of armoury in the oversize market is Hydraulic Modular equipment. As the name suggests, these are axle modules which can be combined to give virtually any length and, placed side by side, to create virtually any width. Once assembled to meet a particular requirement, the steering geometry needs to be set up especially, bearing in mind the intended route. For on site work (i.e. off highway), axle combinations in excess of one hundred are not uncommon.

Having said that, the illustration shows a twelve axle combination, made up of 3 + 4 + 3 + 2 axle modules. In this particular case, it results in a main deck length of 18.00m (A). Likewise, this example is shown in drawbar form, ready to be coupled to a heavy duty, ballasted, tractor unit (or several). An added feature is that, unlike conventional axles (with four wheels per axle line), most Hydraulic Modular trailers have eight wheels per axle line, effectively "doubling" capacity (subject to road/bridge/ground limitations).

It goes without saying that Hydraulic Modular trailers come with a vast range of ancillary equipment, much of which is engineered with a particular project in mind.

Sometimes, mainly where the cargo is only marginally oversize, an Open Flat Trailer is the best solution. Above all else, it provides for ease of loading, particularly where the aim is to load as many trailers as possible, over the shortest possible time (keeping crane and labour expenses to the absolute minimum). In this category, there are two points that need to be made. Firstly, we presume that the cargo has already been prepared for shipment. If it does need to be protected on route, using tarpaulin sheeting (limited protection only), we need to be told. Secondly, whereas Standard Trailers are generally available at 24/48 hours notice, Open Flat Trailers are not commonly available and may take several days to arrange.

Extendible, Open Flat Trailers

Where the cargo length exceeds 13.60m (A), possibly with an over width but not an over height element, an Extendible, Open Flat Trailer may be the best solution. These come in varying forms "single, double and triple extendibility" up to 40m length and beyond. Here again, availability may be limited, further influenced by the time required by the authorities to process abnormal load permits and, if necessary, organise escorts.

We open this description by pointing out that Standard Trailers are not our main activity. As our name suggests - The Specialist Transport Group we concentrate on solving transport problems which, by definition, involves the use of specialist trailer equipment (see other categories). Having said that, over the years, we have established a good, working relationship with many of the best Standard Trailer operators in Europe.

In many ways, the expression Standard Trailer is itself a misnomer. Standard Trailers come in a variety of styles, each with subtle variations. Some are described as 13.60m Tilts, Curtain Siders, Euroliners or whatever. To a large extent, the final choice is dependent on the nature of the cargo and the method of loading. On both these aspects, we would be pleased to give advice.

In elementary terms, most Standard Trailers offer a loading length of between 12.00 and 13.60m (A), with internal heights varying from 2.40m to 2.90M (H). The point perhaps worth emphasising is that, because they are intended purely for general cargo, most Standard Trailers are not suitable for machinery i.e. where there is a concentrated load, a high centre of gravity or difficulty in securing the cargo safely.

The trailer types described are only intended to give a general outline of the resources available from STG. Under the Standard Trailer banner, no mention is made of Roads Trains. Where a loading length in excess of 13.60m is required, and the cargo does not qualify as indivisible, a Road Train may offer the best solution. If the cargo is temperature sensitive, Refrigerated equipment may provide the answer, maintaining the temperature within a specific tolerance, throughout the journey.

For fragile and delicate cargo (i.e. scientific instruments), modified Air Suspension may go a long way towards providing the solution. Combined with an air frame, speed restrictions and shock meters, G forces can be kept to the absolute minimum.

For cargo that needs to arrive in pristine condition, a Covered Semi Low Loader may be the answer, particularly if the cargo is for an exhibition. Likewise, these are ideal for cargo which needs to be kept away from the public gaze (i.e. prototype vehicles). If you want us to go to the far north, many times in the past we have prepared vehicles for Arctic Conditions. Likewise, we have worked close to the Equator, where the opposite applies.

In some of the earlier descriptions, you may have noticed that we can provide trailers with ramps. Sometimes, this is not the answer. It may be that a Truck Mounted Crane is the best solution. This particularly applies in the case of multiple collections and deliveries.

Finally, in the Hydraulic Modular section, no mention is made of Self Propelled, Hydraulic Modular units not only capable of carrying pieces of several thousand tons but also of turning and manoeuvring in the tightest possible space.

The options are endless. Remember that, whatever the problem, stg will provide the solution.