DLG e.V. - Cabin tests for tractors, construction machines and commercial vehicles

Cabin tests for tractors, construction machines and commercial vehicles

Certified safety cabins preserve the driver’s residual space

The difficulty in designing tractor cabins or rollover protection lies in finding the correct balance between energy absorbing capability and rigidity. If a vehicle tips or rolls over, rollover protection must be capable of absorbing and withstanding both lateral stress in a longitudinal and horizontal direction and vertical pressure.

The DLG Test Center Technology and Farm Inputs conducts about 200 cabin safety tests every year to ensure that drivers of tractors, construction machines and commercial vehicles are optimally protected in case of accidents. Legislation requires the stability of the so-called safety cell of tractors, construction machines and commercial vehicles to be tested, that is the structure that provides a residual space for drivers in case of an accident. These tests always comprise tests for rollover safety (ROPS – rollover protective structure) and to some extent also tests for protection against falling objects (FOPS – falling object protective structure) as well as additional criteria.

In contrast to tractor and construction machinery cabins, which are tested “statically”, commercial vehicle cabins such as truck cabins are tested “dynamically”, that is energy is introduced suddenly into the system by means of pendulum impact. In static testing, the necessary energy is introduced gradually into the safety structure by means of a hydraulic cylinder.

The DLG Test Center is one of the test laboratories designated for conducting safety cell tests by the Federal Motor Transport Authority in Flensburg (Germany).

Testing of tractor and construction machine cabins

ROPS testing of construction machine cabins – longitudinal tension

FOPS testing

Testing of cabin windows

Testing of seatbelts including anchor points

There are specific regulations for testing rollover protection structures for virtually every machine type. Within the EU, agricultural tractors are subject to Regulation (EU) No. 1322/2014 and similar regulations, while construction machines are subject to the machinery directive (Directive 2006/42/EC) and European standards such as EN 474. In terms of practical testing procedures for minimum requirements for rollover protective structures and falling object protective structures, these standards refer to the ISO standards 3471 and 3449, among others. Once cabins have passed the official tests, they are certified as “safety cabins”.
Ultimately, however, any successfully tested cabin can only perform the functions of a safety cabin in relation to a specific type of use, regardless of which regulations it was tested under.

Rollover protective structures for tractors must therefore be designed to ensure that the residual space of a driver restrained on the seat by a seatbelt is not restricted in case of a single rollover. For agricultural tractors, the energy to be absorbed is calculated on the basis of their unladen weight plus a safety margin based on the ratio between the tractor’s unladen weight and total permissible weight.

As a rule, heavy construction machines, in contrast to agricultural tractors, are fully equipped and do not tow additional implements. This is precisely the main advantage of agricultural tractors, which can be used as universal engines for any agricultural works on farms as well as related works beyond. These machines are appropriately subject to different regulations, and it is their total permissible weight that forms the basis for calculating the minimum required forces and energy to be absorbed by the protective structure in case of a rollover accident.

Once all parts of a test have been completed, the protective structure, that is the cabin, may only have suffered deformation within certain limits if the residual space is to be preserved. This always constitutes a challenge, as all aspects of testing need to be performed using a single cabin and no repairs are permitted throughout the course of the test.

The DLG Test Center operates two test benches, which allow it to carry out compliance testing on safety cabins of tractors and construction machines up to a total permissible weight or unladen weight of about 100 tons. Put in terms of force, these values correspond to 1500 kN of horizontal and 2000 kN of vertical forces that the Test Center can apply to structures.

Testing of truck cabins

Simulation of front impact with a flat impact pendulum (test A)

Test of A-pillar strength with a tubular impact pendulum (test B)

A new test bench now also allows truck cabins to be tested dynamically, that is using pendulum impact, according to the test standard, Regulation ECE-R29/03. This new regulation, which will become effective from 30/01/2017, applies to commercial vehicles, that is trucks and vans of categories N1, N2 and N3.

As European trucks no not normally have long bonnets, manufacturers of cabins for commercial vehicles need to meet particular, additional challenges. Commercial vehicle cabins must, by design, be able to withstand most impact deformation, and impacts must not result in penetration into their structure. The high energy that acts on cabins in case of impact must be converted into deformation energy as immediately as possible. Accidents cause very high forces to act on safety structures and cabin supports, which are designed to give towards the rear and therefore also contribute to preserving the driver’s residual space.

According to the new regulations of the ECE-R29/03 test standard, which simulate a rollover accident, the structural stability of truck cabins will need to be tested by means of four tests carried out with impact pendulums of various designs from January 2017 onwards:

  1. Test A:
    Simulation of front impact with a flat impact pendulum
  2. Test B:
    Test of A-pillar strength with a tubular impact pendulum
  3. Test C:
    Simulation of roof strength by lateral impact with a flat impact pendulum and subsequent application of a roof load of no more than 10 t

Once all tests have been completed, the cabin may only have suffered deformation within certain limits if the residual space is to be preserved.


DLG Test Center Technology and Farm Inputs
Max-Eyth-Weg 1
64823 Gross-Umstadt
Tel: +49(0)69/24 788-611
Fax: +49(0)69/24 788-690
E-Mail: tech(at)DLG.org

Thilo Keunecke

Tel.: +49(0)69/24 788-644

working areas:
cabines (ROPS/FOPS), components, construction machinery

Maik Dubielski

Tel.: +49(0)69/24 788-645

working areas:
cabines (ROPS/FOPS), components, construction machinery

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