Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:16:p20
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 16 (pt 20/108)
Character Range: 939587–942910

dynamometer shall be equipped with a centring device aligning the vehicle. The restraint system shall maintain the centred drive wheel position within the following recommended limits throughout the coastdown runs of the road load determination:

              6.6.1.2.1. Vehicle position

              The vehicle to be tested shall be installed on the chassis dynamometer roller as defined in paragraph 7.3.3. of this annex.

              6.6.1.2.2. Vertical force

              The restraint system shall fulfil the requirements of paragraph 6.5.1.2.3. of this annex.

              6.6.1.3. Accuracy of measured forces

              The accuracy of measured forces shall be as described in paragraph 6.5.1.3. of this annex apart from the force in the x-direction that shall be measured with an accuracy as described in paragraph 2.4.1. of Annex B5.

              6.6.1.4. Dynamometer speed control

              The roller speeds shall be controlled with an accuracy of ±0.2 km/h.

              6.6.1.5.  Roller surface

              The roller surface shall be clean, dry and free from foreign material that might cause tyre slippage.

              6.6.1.6. Cooling

              The cooling fan shall be as described in paragraph 6.5.1.6. of this annex.

              6.6.2. Dynamometer measurement

              The measurement shall be performed as described in paragraph 6.5.2. of this annex.

              6.6.3. Correcting measured chassis dynamometer forces to those on a flat surface

              The measured forces on the chassis dynamometer shall be corrected to a reference equivalent to the road (flat surface) and the result shall be referred to as fj.

              where:

              c1 is the tyre rolling resistance fraction of fjDyno;
              c2 is a chassis dynamometer-specific radius correction factor;
                  fjDyno is the force calculated in paragraph 6.5.2.3.3. of this annex for each reference speed j, N;
              RWheel is one-half of the nominal design tyre diameter, m;

              RDyno is the radius of the chassis dynamometer roller, m.

              The manufacturer and the responsible authority shall agree on the factors c1 and c2 to be used, based on correlation test evidence provided by the manufacturer for the range of tyre characteristics intended to be tested on the chassis dynamometer.

              As an alternative the following conservative equation may be used:

              C2 shall be 0.2 except that 2.0 shall be used if the road load delta method (see paragraph 6.8. of this annex) is used and the road load delta calculated according to paragraph 6.8.1. of this annex is negative.

              6.7. Calculations

              6.7.1. Correction of the flat belt and chassis dynamometer results

              The measured forces determined in paragraphs 6.5. and 6.6. of this annex shall be corrected to reference conditions using the following equation:

              where:

                  FDj is the corrected resistance measured at the flat belt or chassis dynamometer at reference speed j, N;

              fj is the measured force at reference speed j, N;

                  K0 is the correction factor for rolling resistance as defined in paragraph 4.5.2. of this annex, K-1;

                  K1 is