INTERNATIONAL ANDSPECIALIZED TRANSPORT
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APRIL 2015
26
TOWER CRANES
onagrowingnumberofChinese luffers.
Examples includeZoomlion, SCJCand
Useter. In this case a central triangular
connection frameworkabove the slewing
ring joins the foldableA-frame,machinery
deckand jib foot. Special benefits are the
lightweight layout of themachinery
deckand the forces generatedby the jib
entering the slewing ring ina central
line. Terex, Jaso, YongmaoandSYMuse
a similardesign.
Designpreference
Most luffing jib cranemanufacturers
prefer a folding two legA-frame
structurebut someopt for amassive
lattice towerhead section toweringover
the centreof the cranewhile at theback
themachineryplatform is connected
bypendants. In thiswayWilbert found
thenecessary flexibility to enhance the
A-frameheight tobe able to raise the
crane’smaximum capacity just by inserting
anadditional section into the towerhead.
Inmost cases suchamassive towerhead
generates a lager transport volume in
contrast toa foldingA-frame arrangement.
Witha short tail radius itmust be
considered that the assist cranehook finds
aplacebehind the towerheadwhenadding
themachinerydeck.When competing
against fast rigginghammerhead cranes
the luffing rope installationmust
be considered.Missingpre-reeving
arrangements and the longwaybetween
theA-frame topand the sheaveblockbeing
parkedon the jib, cause erectiondelays.
Rigging time is extendedbyat least half
adayover saddle jibversions in the same
capacity class.Deviceshavebeendeveloped
tokeep the luffing rope
in reevedpositionduring
transport.Comansaand
Wilbert followedmodern truck
cranedesignby storing the luffing
rope inpre-reevedpositionon
thehoistingwinch.Wolff avoids
reeving the luffing ropeduring
crane installationby integrating
the luffingwinch into theA-frame
or towerheadup to the350 tonne-
metre class.
Liebherr reduces the time
for luffing rope reevingby
minimising thenumberof sheaves
and raising the linepull.
FavelleFavcoandManitowoc
Potainopt for a small auxiliary
assistwinchwhich could speedup reeving
byhavinga lightweight erection rope
pulling the luffing rope.
In2014 the Japanese cranemanufacturer
Ogawadevelopedapatentedmethodof
avoiding reevingof the luffing rope, for
itsOTS-140ES. Pre-reevingat thebackof
theA-frame andonly two ropependants
holding the jibare connectedduring crane
riggingat the front.Whenboomingup the
pendant lines aremovedover theA-frame
head sheaves and thesependant ropes are
storedbya traversemovingupanddown
at thebackof theA-frameoperatedby the
luffing rope.
The trend for reducing tail radius
ismoreobviouson Japanese luffers. In
Europewhere tail radius is 7 to8m,
Japanesemanufacturers reduce it to5or
6m, in the same capacity class. For this
purposewidemachineryplatforms are
acceptedwhere sometimes even luffingand
hoistingwinches forma line and theback
of theplatform,withhandrails, follows the
rear slewing circle.
Jost,Useter, SCJC,Krøll andFavelle
Favcouse an enclosed electrical cabinet
behind thedriver’s cabin.Other
manufacturers, includingPotain, Yongmao,
ZS,XCMGandLiebherr still use separate
cabinets close to thedriveunits.On
Liebherr’s latestmodel, however, the
710HC-L centralises the cabinet in the
lattice framework forming thebaseof
themachinerydeck.Wilbert uses a
suspendedair-conditioned container
unit underneath themachinerydeck to
centralise electronic controls.While space
For its all-newFHTD
seriesFinehope
designedamachinery
platform that canbe
disconnected from the
slewingunit (coloured
in red) by four bolts
The luffingwinchplatformwith
pre-reeved luffing ropeandpulley
block in transport condition froma
WilbertWT2405Le.tronic
ZoomlionDR1250-63witha63 tonne capacity
follows theoriginalWolffmachinery deck
designbut has adiesel hydraulic drive
On theWolff
355B is
a central
triangular
framewhere
machinery deck,
jib foot and
A-frameare
connected
Witha central tower head sectionatwhich the
A-frame, boom foot andmachinery deckare
connected, Jaso foundanotherway to reduce
componentweights of its J380PA
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