EuroWire March 2015

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The evolution of trolley
wire manufacturing
▲ ▲ Innovation and technology from Cortinovis Sictra
Corporatenews
Among wire and cable machinery
suppliers, Cortinovis and Sictra are
recognised for the advanced technology
of their products and equipment
reliability.
Many users with machinery from decades
ago are still using their equipment,
counting on the continuous supply of
original spare parts from Cortinovis Sictra
when they are needed.
It was at the beginning of the 1980s
when Sictra developed its first integrated
drawing line for shaped trolley wires, and
the development of high-speed railways
was still to come.
At that time, it was common practice to
draw the shaped trolley wires utilising a
single deck bull block, with which the rod
was drawn down with several subsequent
passages until the shaped wire final cross
section was achieved.
The design and construction from Sictra
of an integrated drawing line with
four capstans represented a dramatic
improvement. Productivity increased
by a factor of ten while manpower
requirement reduced. Not only that,
but the scrap rate was also reduced
significantly and the quality of the final
product enhanced.
It soon became evident to the Industry that
competing in the manufacture of trolley
wires was no longer possible unless the
equipment in use was up to date.
The product itself was subject to a
significant evolution. The drives of this
development have been environmental
protection on one side and the increase
of operation speed of the railways on the
other side.
For a long time, copper was utilised for
trolley wire alloyed with cadmium. The
presence of cadmium gives to copper
a much higher resistance to softening
at elevated temperatures and also to
arc erosion, as extremely heat resistant
cadmium oxide forms on the surface of
the wire during arcing and protects it
from eroding.
Cadmium, however, is very toxic, even
more than lead or mercury, therefore it
has been replaced for this application by
other metals to be alloyed with copper.
Nowadays the most utilised copper alloys
for high-speed trains granting operating
speed up to 400km/hour are copper and
magnesium alloys; wear and tear is the
lowest, while breaking load the highest.
Silver copper and tin copper alloys are
also used.
All of this implied a redesign of the Sictra
trolley wire integrated drawing line.
A modern line capable of drawing Cu Mg
0.5 alloy is usually made of four capstans,
the first two with 1,200mm diameter and
the last two with 1,000mm diameter.
The AC motors provide adequate torque
to the capstans to match the higher rod
tensile strength of the new alloys and
the increased breaking load of the final
product.
More often the line is designed with five
capstans (2 x 1,200mm and 3 x 1,000mm)
to be able to draw down copper alloy rod
with inlet diameter up to 30mm.
The process and the increased powers
involved in it require an efficient capstan
cooling system via inside chilled water
circulation and rotating joints. Wire
lubrication and additional cooling is
provided with emulsion spray on the
capstans’ surface and most efficient
lubrication of the round and shaped dies
is achieved with specific oil circulation
and die holders’ chilled water cooling. All
of this requires three separate cooling and
circulating circuits.
Cortinovis Sictra – Italy
Website:
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