Document ID: chunk:federal_register_of_legislation:F2024C00356:reg:21:p3
Version: federal_register_of_legislation:F2024C00356
Segment Type: reg
Provision Reference: reg 21 (pt 3/35)
Character Range: 295669–298491

the load absorbed by a dynamometer brake. The load absorbed comprises the load absorbed by frictional effects and the load absorbed by the power-absorption device.

                The dynamometer is brought into operation beyond the range of test speeds. The device used for starting up the dynamometer is then disconnected: the rotational speed of the driven roller decreases.

                The kinetic energy of the rollers is dissipated by the power-absorption unit and by the frictional effects. This method disregards variations in the roller's internal frictional effects caused by rollers with or without the vehicle. The frictional effects of the rear roller shall be disregarded when the roller is free.

              2.2.  Calibration of the load indicator at 80 km/h

                The following procedure shall be used for calibration of the load indicator to 80 km/h as a function of the load absorbed (see also Figure 4):

              2.2.1.  Measure the rotational speed of the roller if this has not already been done. A fifth wheel, a revolution counter or some other method may be used.

              2.2.2.  Place the vehicle on the dynamometer or devise some other method of starting-up the dynamometer.

              2.2.3.  Use the flywheel or any other system of inertia simulation for the particular inertia class to be used.

                Figure 4

  Diagram illustrating the power absorbed by the chassis dynamometer
         □ = F = a + b · V2          ● = (a + b · V2) - 0.1 · F80            = (a + b · V2) + 0.1 · F80

       2.2.4.  Bring the dynamometer to a speed of 80 km/h.

       2.2.5.  Note the load indicated Fi (N).

       2.2.6.  Bring the dynamometer to a speed of 90 km/h.

       2.2.7.  Disconnect the device used to start-up the dynamometer.

       2.2.8.  Note the time taken by the dynamometer to pass from a speed of 85 km/h to a speed of 75 km/h.

       2.2.9.  Set the power-absorption device at a different level.

       2.2.10.  The requirements of paragraphs 2.2.4. to 2.2.9. shall be repeated sufficiently often to cover the range of loads used.

       2.2.11.  Calculate the load absorbed using the formula:

 Where:
 F       =  load absorbed (N),
 Mi      =  equivalent inertia in kg (excluding the inertial effects of the free rear roller),
 Δ V     =  speed deviation in m/s (10 km/h = 2.775 m/s),
 t       =  time taken by the roller to pass from 85 km/h to 75 km/h.

       2.2.12.  Figure 5 shows the load indicated at 80 km/h in terms of load absorbed at 80 km/h.

Figure 5
Load indicated at 80 km/h in terms of load absorbed at 80 km/h

       2.2.13.  The requirements of paragraphs 2.2.3. to 2.2.12. above shall be repeated for all inertia classes to be used.

2.3.  Calibration of the load indicator at other speeds