This month, engineering manager Peter Huygebaert explains how Sarens developed a special SPMT stability calculation tool to ensure better planning for each project. 

What is an SPMT stability calculation tool, and what does it do?

The purpose of an SPMT stability calculation tool is to evaluate whether a transport is safe. It's designed to evaluate static and dynamic axle loading and tipping angles as well as factors like ground bearing pressures and trailer bending. 

For many years, Sarens had used a calculation tool to evaluate SPMT transport in both static and dynamic conditions. However, the old tool needed updating as it was becoming outdated and unable to work with the larger setups we encounter nowadays, as well as the various ranges of SPMT types. 

Five years ago, we began creating a new calculation tool. After thoroughly testing it, we launched the first complete version two years ago at the Engineering Days in Belgium under the name STCS (Sarens Transport Calculation Sheet). We recently released a further optimised version. 

The STCS is easy to use and is completed for every special transport Sarens executes. Besides the static and dynamic axle loading and tipping angle evaluations that the old tool could perform, the new sheet also allows us to easily pin up axle lines and evaluate ground bearing pressures and trailer bending. 

What are the advantages of the new SPMT stability calculation tool? 

The old tool could be used after a drawing of the transport had already been made, and so was missing a visual interface. The new tool lets us visualise the SPMT configurations and saves considerable time. 

The new STCS allows an engineer to easily position and shift the trailers, with the outcome represented in a clear layout. It can deal with any type of modular trailer regardless of the capacity, brand, axle spacing, etc. Once an appropriate trailer combination is defined, the sheet can easily be read by a CAD designer and translated into a drawing. 

Does the tool take into account the full range of forces affecting an SPMT and its load?

The previous Sarens tool already took dynamic forces such as accelerations and wind into account. Including the dynamic factors into our standard calculations have always lead to be industry leading. The newest version of the STCS does this in an even more detailed manner and evaluates the influences of COG envelopes, wind, accelerations, and more to investigate the worst-case combinations of all of these. 

How did Sarens develop this tool, and how does it train engineers to use it?

For the development and testing of the new STCS tool, we went step by step. We started from a clean sheet in order not to be bound by the restrictions that the old tool had. After the first tryouts proved it was technically correct, we started running it in combination with the old tool and then on specific projects of Sarens Projects before launching it to the entire Sarens Group. 

STCS training is available on our E-learning platform. First, participants are tested to ensure that they have an adequate level of understanding of special trailers. They then get access to the training manual and the sheet itself. A final test confirms that they can properly work with the sheet. If they pass that test, they are granted a 'first degree verification' level. 

If Sarens didn't have an SPMT stability tool, what would the alternatives be?

There are other ways to evaluate whether a transport is safe, but the purpose of the STCS is to do this much faster and more thoroughly than you would be able to do if you worked with just a drawing and an empty excel sheet.