OECD Code Research Articles

Verifying Power Claims of High-Power Agricultural Tractors Without a PTO to Sell in Nebraska

Nebraska law requires the Nebraska Tractor Test Board of Engineers to compare results of the tests of an agricultural tractor model with the manufacturer's claims regarding power, fuel use, and other performance ratings in order to recommend a permit to sell that tractor model in the state. PTO tests are conducted to verify the manufacturer's PTO power and fuel claims for tractor models. In recent years, several tractor manufacturers have been producing models of large tractors either without a PTO or with a PTO not capable of transmitting the full engine power and, therefore, have chosen to advertise engine power. The objective of this project was to determine a reasonable alternative to removing engines from these tractors for tests to determine whether these tractors met their power claims. Linear regression analyses of advertised engine power claims and OECD Code 2 drawbar power test results from 48 tracked (R2 = 0.98) and 43 4WD tractors (R2 = 0.99) were used to establish two linear relationships to verify the engine power claims for these tractors. These relationships provide a reasonable means of verifying engine power claims for large agricultural tractors without a PTO, or without a PTO capable of transmitting full engine power.

Assessing Rollover Safety Provided by ROPS Tests Following SAE Standard J1194 versus OECD Code 4

OECD test codes were developed on the basis that the energy to be absorbed by the ROPS during an overturn is proportional to the tractor mass. The selection of the tractor mass used as a reference for the calculation of this energy determines the result of the tests. SAE Standard J2194 and the OECD codes/ISO standards/EU directives generally use the unballasted mass of tractors, but SAE Standard J1194 uses the maximum gross machine mass. We used 300 tractor models to compare the safety provided by the two different methodologies for testing ROPS: OECD Code 4 and SAE J1194. It was possible to establish that SAE J1194 provides a higher level of safety than Code 4 for tractors having ballast greater than 35% of their unballasted mass. SAE J1194 is more demanding with light tractors than with heavy tractors and, as the tractor mass in the moment of overturning can be very different from its unladen mass, it is more in line with the current situation of modern tractors. OECD Code 4 provides the same safety level for light and heavy tractors, but the level of real safety depends on the quotient between the maximum admissible and unballasted masses. Because of that, OECD Code 4 is valid for tractors having moderate ballast, but for highly ballasted tractors its validity is very doubtful.

Development and Validation of a Computer Program to Design and Calculate ROPS

In Spain, there are more than 250,000 tractors built before 1980, when it became mandatory for all new tractors to be equipped with a rollover protective structure (ROPS). A similar situation is found in the European Union, but the situation is worse in the U.S. and in developing countries. Directive 2003/37/EEC establishes that tractors over 800 kg weight can be homologated by using the OECD standard code for the official testing of protective structures on agricultural and forestry tractors (static test), called Code 4. A ROPS attachable to the rear axle of different tractor models has been designed, and a computer program for the calculation of the ROPS design has been developed. The program, named ESTREMA, is available at: www.cfnavarra.es/insl. Using this program, it has been possible to design a ROPS for the Massey Ferguson model 178 tractor, one of the most common tractor models without a ROPS in Spain. After the tractor was equipped with the designed ROPS, it was tested at the Spanish Authorized Station for testing ROPS and passed the homologation test (OECD Code 4), the main results being a maximum distortion of 21.3 cm when the absorbed energy was 5437 N and the maximum force applied was 34 kN during loading from the side. The ROPS was improved, redesigned, and remounted on the tractor, the tractor was tested in a real overturn, and no part of the structure intruded on the driver's clearance zone during the test. In conclusion, the ESTREMA program worked correctly, and the designed ROPS was able to pass the authorized test and provide adequate protection to the operator during a real overturn.

PM—Power and Machinery: The Effect of Tyre Size on the Non-continuous Rolling Test for Narrow Tractors

In both the OECD Code and the EC Directive for testing dual-pillar front-mounted roll-over protection structures for narrow track width tractors, a non-continuous rolling preliminary test in case of lateral overturning is provided. This test can be simulated with a computer programme.The role of the tyres (and also of the rims) in the lateral overturning of narrow tractors is very important. Frequently the same tractor can be alternatively equipped with four, five, or more different tyre combinations, which can vary its total mass, width, centre of gravity position and moment of inertia about its longitudinal axis. According to the Standards the preliminary test must be carried out with the tractor fitted with tyres having the greatest diameter.Tests carried out on 17 tractors and 50 tyre combinations show that in eight of the 17 cases examined, the tyres providing the most restrictive conditions were not the highest ones. Therefore, the Standards do not provide the most restrictive conditions for the preliminary test of non-continuous rolling.This paper supports the selection of the tyres giving the highest moment of inertia of the left (or right) wheels about the tractor longitudinal axis for the non-continuous rolling test. Using this parameter in 14 of the 17 cases, the most restrictive conditions are met.