Vibrator Frequency Adjustment
Frequency of the vibrator is controlled by the operation of the vibrator control lever which regulates the oil flow
to the hydraulic motor on the vibrator drive. The highest frequency does not necessarily produce the greatest
compaction force. Most efficient compaction occurs when the material being compacted is vibrated at its own
natural frequency; that is, the frequency at which it wants to vibrate. Magnification of the vibrating force by 5 to
50 times can be obtained by vibrating at the natural frequency of the earthroller mass combination.
Resonant frequency of most highway construction materials will fall in the range of 1100 to 1500 vibrations per
minute for this roller. The amplitude of vibration (movement) of the roll will be greatest when it is operating at
the natural frequency of the material being compacted.
The recommended rolling speed is from 1 to 3 mph.
Number of Passes
The number of passes vary, of course, with the amount of lift and the material being compacted. Specified
density may normally be reached after two or three passes. Caution should be used not to make too many
passes and over vibrate the material, because this may tend to pulverize the material, or cause it to loosen
near the surface.
Rolling Heavy Loose Lift
When rolling a heavy loose lift, the first pass should be made with the roll first to improve the footing for the
Construction Engineering Data
For guidance in the optimum use of this equipment under varying soil conditions, operators should refer to TM
5331A, Utilization of Engineer Construction Equipment; Volume A, Earthmoving, Compaction, Grading, and