Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:16:p17
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 16 (pt 17/108)
Character Range: 930995–934186

test it shall be checked that at the aerodynamic force measured at a wind speed of 0 km/h yields a result equal to 0 Newtons.

              In the case that the vehicle has movable aerodynamic body parts, paragraph 4.2.1.5. of this annex shall apply. Where movable parts are velocity-dependent, every applicable position shall be measured in the wind tunnel and evidence shall be provided to the responsible authority indicating the relationship between reference speed, movable part position, and the corresponding (CD × Af).

              6.4.3. Wind speeds for wind tunnel measurement

              The aerodynamic force shall be measured at two wind speeds under the following speed conditions:

              (a) Class 1 vehicles
                  Lower wind speed vlow to measure aerodynamic force shall be vlow < 80 km/h;
                  Higher wind speed vhigh shall be (vlow + 40 km/h ≤ vhigh ≤ 150 km/h).

              (b) Class 2 and 3 vehicles
                  Lower wind speed vlow to measure aerodynamic force shall be 80 km/h ≤ vlow ≤ 100 km/h;
                  Higher wind speed shall be (vlow + 40 km/h ≤ vhigh ≤ 150 km).

              6.5. Flat belt applied for the wind tunnel method

              6.5.1. Flat belt criteria

              6.5.1.1. Description of the flat belt test bench

              The wheels shall rotate on flat belts that do not change the rolling characteristics of the wheels compared to those on the road. The measured forces in the x-direction shall include the frictional forces in the drivetrain.

              6.5.1.2. Vehicle restraint system

              The dynamometer shall be equipped with a centring device aligning the vehicle within a tolerance of ±0.5 degrees of rotation around the z-axis. The restraint system shall maintain the centred drive wheel position throughout the coastdown runs of the road load determination within the following limits:

              6.5.1.2.1. Lateral position (y-axis)

              The vehicle shall remain aligned in the y-direction and lateral movement shall be minimised.

              6.5.1.2.2. Front and rear position (x-axis)

              Additional to the requirement of paragraph 6.5.1.2.1. of this annex, both wheel axes shall be within ±10 mm of the belt's lateral centre lines.

              6.5.1.2.3. Vertical force

              The restraint system shall be designed so as to impose no vertical force on the drive wheels.

              6.5.1.3. Accuracy of measured forces

              Only the reaction force for turning the wheels shall be measured. No external forces shall be included in the result (e.g. force of the cooling fan air, vehicle restraints, aerodynamic reaction forces of the flat belt, dynamometer losses, etc.).

              The force in the x-direction shall be measured with an accuracy of ±5 N.

              6.5.1.4. Flat belt speed control

              The belt speed shall be controlled with an accuracy of ±0.1 km/h.

              6.5.1.5. Flat belt surface

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

              6.5.1.6. Cooling

              A