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|  MIL-C-52437C
4.6.2.3 Road runs. The following road runs shall be performed: Couple the trailer chassis to
the truck and tractor prime movers and tow as specified for a total distance of at least 400 miles
for the trailer chassis at the variable speeds and under the conditions indicated. The load shall be
the payloads necessary to achieve GVWR.
Course
Mileage
Speed (variable)
Loading
Primary highway
250
Up to 55 mph
Loaded
Unpaved roads
100
Up to 30 mph
Loaded
Off-road terrain
50
Up to 20 mph
Loaded
During the road runs and while towing rated payload, perform the following and record actual
results:
a. Tow the trailer chassis on side slopes up to 10 percent, having the curbside downhill
and having the roadside downhill. Make full throttle starts and panic stops on the side
slope.
b. Tow the trailer chassis over obstacles having the height as specified in the
specification sheet such that all combinations of the wheels have passed over the
obstacles. Observe tire-to-surface contact, evidence of binding or interference, and,
after returning the suspension to normal, measure the diagonals and parallels for
evidence of misalinement. Questionable tire-to-surface contact shall be retested with
single sheets of newspaper under the tires. Ability to remove the newspaper without
tearing from under any tire shall be evidence of insufficient tire-to-surface contact.
c. For determining multiple axle equalization, weigh the weight imposed on each trailer
chassis axle (each axle on a seperate scale) simultaneously and record the weight on
each axle. Jack up each axle separately and return it to its scale, again recording the
weight imposed on both the raised axle and those not raised. After each axle has been
raised and all axle weights recorded, compare the suspension equalization differences
between axles.
d. Tow the trailer chassis over a chatter course until at least 2600 either upward or
downward accelerations of magnitudes indicated herein have been applied to a rear
wheel center. The course shall be of such construction that the acceleration
magnitudes indicated below can be obtained by adjusting the vehicle speed without
the frequency of the accelerations exceeding 15 cycles per second (cps) or becoming
less than 3 cps. The maximum acceleration magnitude indicated below shall not be
exceeded, and accelerations having magnitudes less than the minumum shall be
disregarded. The course shall be of such length that a wheel center receives, in one
pass over the course, at least 50 consecutive vertical acceleration cycles of any
magnitude less than the maximum specification herein. The accelerations shall be
measured by a trial test to establish the required vehicle test speed. The recording
instruments shall then be removed or disconnected and the test completed at
established speed. The acceleration values used shall be those of the wheel center
receiving the highest accelerations. Means for assuring that the vehicle test speed is
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