INTERNATIONAL
ANDSPECIALIZED TRANSPORT
■
APRIL 2015
21
TOWER CRANES
custom-built equipment. Their application,
however, is increasing somanufacturers
should reducemanufacturing cost by
streamliningdesign features and, at the
same time,make theirdesignsmore
modular and easier to transport and erect.
Unlike theolddays, rope-activated
counterweight systems arenow rare.
GermanmanufacturerWilbert’s “Heavy-
Lifter”product line isnotable for its crane
size and thepatentedpendulumballast
system.An ideabehind it is touse the same
3.30x3.30metre tower system for 900 to
2,400 tonne-metre class cranes.Most other
movable counterweight systems relyon
designs createdbyFranc Jost. Inone case
the swingingmechanism ison the topof
themachinerydeck, as represented in the
original BKTdesign, theManitowocPotain
MRSeries andEverdigm cranes above
300 tonne-metres.
A secondapproachplaces the swinging
ballast deviceunder themachinerydeck
asdemonstratedbyTerexComedil cranes
above the260 tonne-metre class, andall
D
esign featuresof flat topand saddle
jib craneshavebecome streamlined
all over theworldbut it is a
different story for luffing jib tower cranes.
For this crane typemanufacturers follow
theirowndesign rules.Most opt for a fixed
ballast arrangementwhile someprefer
movingballast systems to compensate
jibmomentwhenboomingupordown.
A classic ropeoperated luffingdevice is
most common,whileothersusehydraulic
cylinders for small andmedium cranesup
to250 tonne-metres.
Even focusingon fixedballast cranes
there is a surprisingvariation indesignof
themachinerydeck,A-frame and luffing
jib reevingmethod. Inaddition, ballast can
be either concreteor steel. Evenwithinone
manufacturer’s luffer rangedifferent design
roots are apparent.A commondesign trend
worldwide remains tobedeveloped. Itmay
be that luffers are still consideredas special
>
Saddle jib tower cranes
follow very similar design
principles. It is adifferent
story, however, for luffing
jib tower cranes.
HEINZ-GERTKESSEL
reports
BridonDyform
langs lay rope
Regional
features
Terexprefersmovable
ballast systems for
itshigher capacity
craneswhilemedium
and small luffers are
operatedwith fixed
concreteballast
TheWilbertWT2405Le.tronic shows its
uniquependulumballast systemand the
distinctive tower headextendedby anadditional
intersection. Amodular designof tower head
andmachinery platformallows adaptation to
different capacity classes in theWilbert “Heavy
Lifter” range
A swingingballast systemmeans the tail radius
of thePotainMR405-24 is9.50m. It is 7.20m
on theFavelleFavcoM390D, a fixedballast
designof similar capacity atmaximumoutreach
