Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:16:p4
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 16 (pt 4/108)
Character Range: 894203–897457

10 km/h overlap, or by comparing the average force in the specific speed range.
              4.3.2.4.4. It is recommended that coastdown runs should be conducted successively without undue delay between runs. If there is a delay between runs (e.g. for a driver break, checking vehicle integrity, etc.), the vehicle shall be warmed up again as described in paragraph 4.2.4. and the coastdown runs shall be re-commenced from this point.
              4.3.2.5. Determination of the equation of motion
              Symbols used in the on-board anemometer equations of motion are listed in Table A4/5.
Table A4/5
Symbols used in the on-board anemometer equations of motion
Symbol   Units      Description
Af       m2          frontal area of the vehicle
a0 … an  degrees-1   aerodynamic drag coefficients as a function of yaw angle
Am       N           mechanical drag coefficient
Bm       N/(km/h)    mechanical drag coefficient
Cm       N/(km/h)2   mechanical drag coefficient
CD(Y)                aerodynamic drag coefficient at yaw angle Y
D        N           drag
         N           aerodynamic drag
Df       N           front axle drag (including driveline)
Dgrav    N           gravitational drag
Dmech    N           mechanical drag
Dr       N           rear axle drag (including driveline)
Dtyre    N           tyre rolling resistance
(dh/ds)  -           sine of the slope of the track in the direction of travel (+ indicates ascending)
(dv/dt)  m/s2        acceleration
g        m/s2        gravitational constant
mav      kg          arithmetic average mass of the test vehicle before and after road load determination
me       kg          effective vehicle mass including rotating components
ρ        kg/m3       air density
t        s           time
T        K           temperature
v        km/h        vehicle speed
vr       km/h        relative wind speed
Y        degrees     yaw angle of apparent wind relative to direction of vehicle travel

              4.3.2.5.1. General form
              The general form of the equation of motion is as follows:
               where:
              ;
              ;
              In the case that the slope of the test track is equal to or less than 0.1 per cent over its length, Dgrav may be set to zero.
4.3.2.5.2. Mechanical drag modelling
              Mechanical drag consisting of separate components representing tyre  and front and rear axle frictional losses  and  (including transmission losses) shall be modelled as a three-term polynomial as a function of vehicle speed v as in the equation below:
              Where Am, Bm and Cm are determined in the data analysis using the least squares method. These constants reflect the combined driveline and tyre drag.
              In the case that the tested vehicle is the representative vehicle of a road load matrix family, the coefficient Bm shall be set to zero and the coefficients Am and Cm shall be recalculated with a least squares regression analysis.
4.3.2.5.3. Aerodynamic drag modelling
              The aerodynamic drag coefficient CD(Y) shall be modelled as a five-term polynomial as a function of yaw angle Y as in the equation below:
              a0 to a4 are constant coefficients whose values are determined in the