(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 §86.529.

(d) A variable speed cooling blower shall direct air to the vehicle. The blower outlet shall be at least 0.40 m2 (4.31 ft2) 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):

Open Table
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 §86.529.

[42 FR 1137, Jan. 5, 1977, as amended at 42 FR 56738, Oct. 28, 1977]


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