TM 5-3895-374-24-2
3-8-8 Screen Adjustment
A. DETERMINING THE STOKE OR AMPLITUDE
To determine the stroke or amplitude of the screen the following procedure is recommended:
1.
While the unit is stopped, firmly affix a piece of tape or paper to the unit
housing side plates.
2.
Draw a horizontal line on the paper.
3.
Start the machine. After the unit has attained full speed, lightly touch the paper with a sharp pencil or ball point
pen.
4.
Remove the paper and check the marks.
5.
Measure the full length of the mark imposed on the paper. The total length of that mark is considered to be the
stroke for the vibrating surface.
B. ADJUSTING THE STROKE OR AMPLITUDE
The stroke or amplitude of the screen can be adjusted on the job site by altering the amount of counter weights to increase
or decrease the throw of the unit.
To increase the stroke, add counter weights equally to both flywheels. To decrease the stroke, remove counter weights.
However, we must caution individuals who do want to alter the stroke, that it is of vital importance to ensure that the proper
balance of the unit is maintained. Each flywheel should normally contain the same amount of counter weights.
C. SCREEN SPEED
The operating speed of the vibrator unit may vary from 775 RPM to 875 RPM depending on the condition and nature of the
material being processed. Primarily the screen should operate only fast enough to prevent blinding of the screen openings
and not so fast that the material may carry over without being screened. Unnecessarily high speed tends to create a
higher degree of inefficiency than a slow speed but the speed must be sufficient to keep the decks clear.
The speed of the shaft may have to be increased up to 1200 - 1400 RPM when using a sand screen. This high frequency,
coupled with short stroke or amplitude will move fine material effectively across the screen cloth.
page 3 - 1286
