New, alternative drive concepts
for tow tractors
(10/06/2009, Ostfildern/Gerlingen) The ROFAN brand became
part of the SCHOPF Group in November 2008, and now does business
under the name SCHOPF ROFAN GmbH, thus adding baggage, cargo
and industrial tow tractors to SCHOPF’s very successful
range of aircraft towing tractors.
ROFAN was founded
during the 1950s, and has since sold well in excess of 4,000
specialist vehicles. Innovative product developments, in particular
alternative drive technologies, guaranteed their success. Today,
SCHOPF ROFAN supplies electric, CNG, LPG, biofuel, diesel and
above all hybrid drive technologies. As such, ROFAN is the
only supplier to offer both standard hybrid and “PowerHybrid” technologies.
In a standard hybrid a battery serves as an energy source from
which power is supplied to an electric motor at the rear axle
by way of a regulator. This kind of the hybrid drive technology
is widespread and is also a concept proven by ROFAN. It allows
the diesel engine to charge the drive battery during outdoor
operations, while the drive battery alone is used indoors to
provide emission-free power to the electric drive. One major
disadvantage of this concept is that speed is severely reduced
on inclines and steep slopes e.g. from airport basement baggage
rooms. This is due to the electric drive concept which only
makes high drawbar pull available for very brief periods. The
vehicles are also significantly slower than e.g. diesel driven
vehicles when towing loads on level ground. This disturbs traffic
flow and causes an increase in the number of vehicles and personnel
required.
ROFAN was among the
first to recognize this issue more than fifteen years ago and
thus began development of the patented “PowerHybrid” solution.
In this system the
diesel engine simultaneously drives a hydraulic pump and an
inline generator/motor by means of a specially-designed
clutch; the hydraulic
pump supplies hydraulic motors in the wheels. This type of
arrangement allows high road performance
outdoors with simultaneous
battery recharging for indoor use, and makes continuous
24/7 operations possible.
High performance operations are also possible indoors thanks
to the hydrostatic drive. The greatest
advantage of the “PowerHybrid” system is a doubling
of driving speeds resulting from high drawbar pull always being
available, especially on inclines and steep slopes. And in
contrast to standard hybrid diesel electric drives, this is
also the case in high ambient temperatures. The system has
accumulated more than fifteen years of experience in the toughest
of big-airport environments, where economy of ownership and
low life-cycle costs compared to other drive systems were also
demonstrated.
Gas-fuelled engines
and drives have been successfully developed over the years
to become leading edge technologies. Unfortunately, there is
only a limited selection of engines available, due to specific
component loads. Their advantage lies in substantially reduced
pollution, especially in large cities such as Bangkok, New
Delhi and Mexico City, where thousands of mini-cabs have been
retrofitted with CNG/LPG engines. However, a disadvantage for
daily airport operations resides in a requirement for constructing
the necessary fuelling infrastructure.
In recent years,
diesel engine manufacturers have made significant, successful
efforts toward reducing environmental impact. Regarding COM
1 and COM 2 exhaust emission standards, we are now at Stage
3A (EPA Tier 3). Stage 3B (EPA Tier 4 interim) is in the planning
phase and will be introduced over the coming years according
to performance category. Over the past ten years, and in comparison
to today’s Tier 3 engines in the 120 kW range, pollution
has been reduced by 64% in the case of NOX (oxides of nitrogen),
and by all of 94% for carbon particulates. As a GSE manufacturer,
SCHOPF faithfully follows developments and worldwide trends
in the reduction of environmental pollutants. SCHOPF equips
all of its towing tractors with engines that incorporate the
latest technological standards available.
Alternative electric
drive concepts are
available in SCHOPF
tow tractors such
as the F110, for
towed loads of up
to 150 tons. Depending
on the type of operation and installed battery
capacity, up to eight
operating hours are
possible between
recharges. In higher
weight classes the
relationship between
weight, actual working time, acquisition cost and operating
cost is not yet economically
justifiable,
and performance in
particular leaves
a lot to be desired.
SCHOPF
has previously
delivered three large
electric tow tractors
for towed loads of
400 tons to a customer in South East Asia.
The electrical versions
of the SCHOPF ROFAN 4 ton baggage and industrial tow tractors
are today industry benchmarks and are available as standard
products.
SCHOPF Maschinenbau
GmbH and SCHOPF ROFAN GmbH are pre-eminent tractor technology
manufacturers, and the leaders in a growing market when it
comes to environmental requirements, quality, price/performance
ratio and lifetime costs.
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