BASE (DRIVE) UNIT TUNING CONTENTS PAGE 1 3 4 LASTPAGE
Tuning a bowl to proper frequency involves the proper
proportions between the mass and the springs
The natural frequency of the bowl should be as close
as possible to the 60 cycle (rectified) or 120 cycle running frequency of the
coil.
Sixty cycle base units normally use thinner springs
than 120 cycle base units. You can sometimes tell if a bowl is rectified (60
cycle) by finding an extraneous bolt head on a controller indicating the
addition of a diode.
Generally a 3/8 thick spring=2 1/2-1/4 springs
1/4 thick spring 2 1/2 = 1/8 springs.
When springing a base unit, you should attempt to
maintain equal springing in all spring packs. If this is impractical, the
spring packs that have striker plates bolted to them should be spring heaviest,
still attempting to hold as even and symmetrical springing as possible. If you
add a spring to one side, the next spring should be placed exactly opposite.
Also, keep the thickest springs nearest the cross arm.
Base units have fairly wide range between the lowest
and highest points of the tuning and should be finally tuned with the bowl
carrying a normal load of parts and running at the slowest possible control
setting, while maintaining the specific rate.
Extremely heavy parts require a few more degrees of
overtuning than normal.
TO CHECK TUNING, LOOSEN TOP SPRING BOLTS ON ONE
SPRING PACK WHILE THE BOWL IS RUNNING:
A.
Undertuned - bolt loosened - parts slow down.
If a slow down of parts travel is noted, the unit is undertuned. If more
speed is needed,
adding one or more springs, with proper spacers, or substituting another
spring with greater
thickness is required. Always recheck tuning after each change. If
springs are added, be
certain you have ample threads to withstand the torque necessary for
tuning.
All bolts should be tight when the tuning is
complete.
1/2 bolts min 90
ft/lbs. torque
3/8 bolts min. 110
ft/lbs. torque
3/4 bolts min. 130 ft/lbs.
torque
B.
Overtuned- bolt loosened- parts speed up.
If a bolt is loosened slightly and parts speed up,
the unit is overtuned. The degree of
overtuning must now be established. When this bolt
(at the top of the spring pack) is
loosened just slightly more and the parts slow down,
the unit is not excessively overtuned
and can be correctly tuned by removing one or more
springs.
Slight overtuning is better
than slight undertuning.
a. 60 cycle
units-.045 to .090 gap
120 cycle units- .025 to .040 gap
b.
to adjust air gap,
loosen set screws in the back part of the coil stand. Loosen the
two bolts
holding the coil stand to the unit. Slide the coil assembly forward or back
to
obtain the proper air gap. The gap must be sufficient to prevent armature plate
from
striking the coil assembly.
c, Tighten
the coil stand and tighten screws.
d. Recheck gap alter tightening
cover.
Note:
A bowl that is sprung properly will run rate at about 60% to 80% of full power,
will not
be weight sensitive and will pull anywhere from 2-6 amps.
The above would apply not only to new
equipment, but older units as well. Most problems
are
caused by improper use, improper installation, or damage from handling in
transit between
the
factory and the customer.