Can you use the gooseneck as an aid for securing loads?
Source: Broshuis BV
A semi low loader is a trailer for transporting high inseparable loads. They are used for heavy transport in construction and industry, such as concrete elements, parts of wind turbines and steel structures. Semi low loaders are also perfect for transporting excavators and road construction machinery. The chassis of a semi low loader is fitted with a gooseneck, creating a low loading platform behind the gooseneck and thereby allowing you to transport a higher load. On a semi low loader, the gooseneck acts as a kind of bulkhead. But can you use this gooseneck as an aid when securing loads? And if so, what forces is the gooseneck able to handle? In order to answer this question, our load securing specialist, Niels Bouwmeester, in collaboration with the inventor of the semi low loader, Broshuis BV, made a calculation with the gooseneck. He describes the results in his new blog.
GOOSENECK AS BULKHEAD
A trailer has two types of bulkheads: an EN12642 Code L and an EN12642 Code XL bulkhead. An EN12642 Code L bulkhead has a maximum specified load value of 5000 daN. An EN 12642 Code XL bulkhead must be able to withstand at least 50% of the specified loading capacity.
Of course, a gooseneck is also able to withstand forces. It acts like a kind of bulkhead; only a gooseneck hasn’t been tested, so you don’t know what load it is able to handle. Because no data is available, an inspector will automatically assume a Code L load of 5000 daN. But is this right? A gooseneck forms part of the chassis and, in theory, is able to withstand higher forces than the named 5000 daN.
CALCULATING THE FORCE OF THE GOOSENECK
In order to prove that a gooseneck is able to handle the forces of the load, tests will need to be carried out. In this investigation, we work with computer calculations because practical tests are relatively awkward. Even for an independent test institute, it is difficult to carry this out experimentally (by means of a pressure test, for example). The low loader ‘market’ is also relatively small. However, it is not impossible, because pressure tests were sometimes carried out in the past too.
THE CALCULATION
When making the calculation, we took the following things into account:
What requirements must the part satisfy?
The material stress must not exceed 0.55% of the yield point.
What standards apply?
Steel type S355
What is the maximum permissible material strength?
198 N/mm2
Starting point:
The gooseneck is clamped in the position of the kingpin, so movement remains possible.
To obtain a coupling load of 18,000 kg, we place the load on the trailer.
On the top of the gooseneck (the most unfavourable position), we place a load that presses 18,000 kg (of the weight of the load) against the gooseneck.
RESULT
The forces do not cause the gooseneck to become distorted. Everything remains easily within the applicable margins.
The parameters in the computer model create a red colour due to the clamping. This is not the case in practice, because the gooseneck is able to move freely due to the plate.
The elastic distortion (commonly known as sagging) doesn’t cause any problems either, as it easily remains within the boundaries on all sides.
CONCLUSION: THE GOOSENECK IS STRONG ENOUGH AS AN AID WHEN SECURING LOADS
As you have seen above, the gooseneck contains enough residual capacity. The rule “what a gooseneck is able to/allowed to bear is also what it is able to retain” may therefore be adopted.
In the example, the load has been placed on top of the gooseneck, which can be the most unfavourable point. If you place the load fully against the gooseneck, then the gooseneck is subjected to shearing, making the gooseneck many times stronger!
I believe it is the manufacturer’s responsibility to explain this, to ensure that the product is used correctly.
This can be done by using a document stating the following details:
- The address details (optionally a logo) and the telephone number of the designer/supplier.
- The declaration that the ‘construction’ is resistant to ‘certain’ forces.
- A unique number.
- The VIN number of the vehicle in question.
- A drawing or description with dimensions of the structure and the materials used (including strength calculation).
- The conditions (for example clean/dry, use of anti-slip and position of load)
- This should not be a handwritten document.
- Please note: this document does not meet a standardisation.
I believe that everyone in the chain (the manufacturer, the user and the inspecting authorities) benefits from such a document. It is also useful to issue a BC value (Blocking Capacity, the maximum force to bear a certain direction), as this makes it easy to make load securing calculations.
(No rights may be derived from this example or the calculation).
