(a) The dynamometer shall have a single roll with a diameter of at least 0.400 metre.
(b) The dynamometer shall be equipped with a roll revolution counter for measuring actual distance traveled.
(c) Flywheels or other means shall be used to stimulate the inertia specified in Sec. 86.529.
(d) A variable speed cooling blower shall direct air to the vehicle. The blower outlet shall be at least 0.40 m \2\ (4.31 ft \2\) and shall be squarely positioned between 0.3 m (0.98 ft) and 0.45 m (1.48 ft) in front of the vehicle's front wheel. The velocity of the air at the blower outlet shall be within the following limits (as a function of roll speed): ------------------------------------------------------------------------
Actual roll speed Allowable cooling air speed------------------------------------------------------------------------0 km/h to 5 km/h......................... 0 km/h to 10 km/h.5 km/h to 10 km/h........................ 0 km/h to roll speed + 5 km/
h.10 km/h to 50 km/h....................... Roll speed [5 km/h.50 km/h to 70 km/h....................... Roll speed [10 pct.Above 70 km/h............................ At least 63 km/h.------------------------------------------------------------------------
(e) The dynamometer shall comply with the tolerances in Sec. 86.529. [42 FR 1137, Jan. 5, 1977, as amended at 42 FR 56738, Oct. 28, 1977]