MANITOWOC ENGINEERING CO.
Division of The Manitowoc Company, Inc. Manitowoc, Wisconsin 54220
GANTRY ASSEMBLY
3900
PURPOSE
This folio contains gantry raising and lowering instructions
for the folding gantry.
GENERAL
The crane can raise and lower its own gantry when fully
rigged with 60 feet or more boom (see Boom Rigging
Drawing).
The folding backhitch assembly provides the following gan-
try positions (see Figure 3):
LOW CLEARANCE POSITION for traveling and for handling
some boom lengths.
OPERATING POSITION for handling loads.
NOTE
Refer to the Boom Rigging Drawing (in Service
Manual) for boom handling instructions.
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Avoid an accident.
--Do not lift loads when gantry is in low clearance posi-
tion; gantry and boom may collapse.
--Stay off crane roof and counterweights while gantry is
being raised and lowered.
NOTE
For 60 foot boom length the equalizer comes to rest
on the boom top. For this boom length, equalizer
rails are not provided; therefore, equalizer should be
blocked on boom top to prevent the wire rope from
rubbing against the lacings.
RAISING GANTRY (Figures 1 and 3)
1. Unpin the gantry from the rear of the crane (see Gantry
Assernbly Drawing in Service Manual for tie-down arrange-
ments).
2. BOOM UP slowly to raise the gantry until the backhitch
straps are fully extended.
Raise the boom slightly off the blocking or the ground to
make sure the backhitch straps are fully extended.
3. Install two backhitch pins; the pins should go in freely by
hand.
Install and spread cotter pins.
LOWERING GANTRY
(Figures 1 and 3)
1. BOOM UP to tension the backhitch straps. When the
backhitch straps are properly tensioned, the backhitch pins
will be loose in the holes.
Raise the boom slightly off the blocking or the ground to
make sure the backhitch straps are tensioned.
Tension backh.ch strapswith boom
~i~ii~;:~::~:~:::~i~::~i~i~:~:~:i~i~:::~:i~:~:i~:::~:::~:~:`~:~:: hoist rigging before removing back-
hitch pins. Gantry will fall violently if backhitch pins
are removed before straps are tensioned.
2. Attach a tagline to each eyelet on the backhitch straps.
The taglines must be long enough to be held by ground
personnel.
3. Remove both backhitch pins;
pins should come out
freely by hand.
4. Get off
crane roof and counterweights.
5. BOOM DOWN slowly. At the same time, pull on the
taglines to assist the straps in folding to the rear.
6. Stop booming down when the gantry comes to rest on
the roof.
7. Pin the tie-down links to the rear of the crane as shown in
the Gantry Assembly Drawing.
Eyelets
\
R~r,k hifr, h d
Gantry
Figure 1 Operating Position
©Manitowoc 1990
(continued)
11-22-66 (Rev. 3-5-90) GANTRY ASSEMBLY FOLIO 442-1
395143
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