6
7
LIFTING MECHANISMS
The number and lift capacity of chain motors used to lift
the array are dependent on the array’s combined weight,
including the weight of any underhung clusters, and
its orientation and splay. For a smaller array, it may be
sufficient to use 1-ton motors, but for larger arrays, 2-ton
motors may be necessary.
The lift capacity of any single motor or set (in a four-
hoist configuration) of motors must be sized to support
the entire weight of the array, including cable. When you
are assembling the array, as the cabinets are attached,
level the bottom cabinet to allow the next waiting block
to be attached. Because there is often a vertical curve in
the array, the upper cabinets have an increasing uptilt.
At some point, depending on the vertical splay angles
used, the rear motor(s) may not be supporting any weight.
At this point, the front motor(s) must support the entire
weight of the array while it is being assembled.
Conversely, once the array is assembled and flown into its
final position, it is likely that the MTG-3D Top Grid will be
much closer to level. In this configuration, the majority of
the weight then shifts to the rear motor(s). If the array has
downtilt and a curve is being used, the weight may then
shift closer to the rear motor(s).
Furthermore, when you are using three or four motors
and lifting the array during assembly, the array may not
be level in the other plane (onstage vs. offstage). Further
weight will shift onto the highest motor, requiring that
motor to have a larger capacity.
The MTG-3D Top Grid is designed to have the motors
attached to its pickup points at either the center set of the
MTG-3D Top Grid’s main frame, the four corner sets on
the main frame, or the front and rear sets of tabs on the
extension frame in its retracted or extended position.
Refer to the rigging configurations and their associated
tables in “Appendix A — Configurations and Load
Ratings” for details on allowable weights, pickup points,
bridle lengths, and the maximum allowable number of
loudspeakers for the configuration you will be rigging.
USE FRONT AND BACK MOTORS WHENEVER
POSSIBLE
Front-to-back bridle point configurations, illustrated in
Figure 7 and configurations A, E, and F in “Appendix A
— Configurations and Load Ratings,” allow the use of
motors to provide the necessary vertical tilt to the array.
This provides the easiest configuration to use for trimming
vertical tilt for an array.
Figure 7. Bridles may be used in a front-to-back hanging
configuration
If front and back motors cannot be used to provide the
required vertical tilt of an array, such as configurations
B, C, and D in “Appendix A — Configurations and Load
Ratings,” the technician can use the variable tilt capability
of the MTG-3D Top Grid, to achieve the desired vertical tilt
angle for the array. Refer to the section “MTG-3D Top Grid
to First M3D Angle Adjustment.”
