TM 5-3810-307-10
in a small enclosure.
in place. hardware fasteners and slide-in locking pins
are used to secure the sections into one rigid
The anti-two block weight is placed around the
structure.
main cable on the side where the main cable return is
fastened at the boom.
When a catwalk is used with the ATEC Crane,
interference exists with the spare tire mounting
When the hook block moves close to the block
bracket when swinging the boom to the left. To
in the boom end it encounters and lifts the weight.
eliminate this interference, brackets need to be
As the weight is lifted it releases a spring held
locally fabricated, and installed on the cab catwalk
switch that stops the cable movement thus
mount brackets. These brackets raise the catwalk
preventing further movement of the hook block.
over the top of the spare tire mount bracket.(See
(See Figure 6).
Fabrication Drawing at the end of this Appendix and
The hook block is used to lift and place the pile
driving components in the staging area. After that it
is not needed. The operator swings it out of the way
and lowers it to the ground on cribbing. Personnel
unhook the main cable and remove the hook block
from the boom nose.
In crane operations, as well as in pile driving
operations, the anti-two block assembly is used.
ANTI-TWO BLOCK ASSEMBLY
A PAT LMI (Load Moment Indicator) System
is used on the ATEC crane to guide the operator to
stay within the crane design parameters. Part of the
LMI system is a safety device that prevents the
Hook Block from running into the Boom Nose
Block.
The ATEC uses an anti-two block assembly as
the safety device. It automatically stops any
When the hook block moves close to the
impending collision of the Hook Block with the
block in the boom end it encounters and lifts the
Boom Nose Block when the operator is paying-in
weight. As the weight is lifted it releases a spring
cable to lift a load or otherwise raise the hook block.
held switch that stops the cable movement thus
preventing further movement of the hook block.
An anti-two block assembly has a chain,
weight, switch, relay, buzzer, warning light, and
wiring. The chain, relay, and switch are located at
the end of the boom. The light and buzzer are
located inside the cab and on top of the dash panel
L-3 C-1
