The
UNIMOG Principle
Unimog
stands for “Universal-Motorgerät” which roughly
translated means “universal motorized implement machine”.
Unimogs are multipurpose,
all-terrain, utility vehicles built by Mercedes-Benz. In addition
to extreme off-road capabilities, they are designed to be operated
in some of the harshest conditions in the world. Unimogs are widely
recognized as the most capable off-road vehicles in the world.
The term "Unimog" is a general term that applies to many
different vehicles in the same way that "Jeep" or "Land-Rover
" refers to a wide range of vehicles. A 1950's CJ is a very
different vehicle than a 1990's Grand Cherokee but the are both
“Jeeps.”
Although Unimog models differ greatly in many respects, all Unimogs
incorporate the same design principle that make them such extraordinary
vehicles. This principle is the combination of low gearing, torque
tube suspension with coil springs, and portal axles with differential
locks combined with a very strong chassis that allows for a high
degree of flex. The result is an extremely versatile and capable
vehicle which can be used in a wide variety of roles, from a tractor
to an expedition vehicle.
Below is a list of the primary design concepts that make the Unimog
such an extraordinary vehicle.
Portal
Axles
The portal
axle design is a solid beam axle that incorporates
a hub reduction. The result is a very strong axle with the axle
tube and differential located above the center axis of the wheel.
This means that the Unimog has greater ground clearance than a normal
solid axle vehicle using the same tire size. The portal axles, combined
with large diameter tires, means the Unimog has unrivaled ground
clearance that is not even matched by most monster trucks! The hub
reduction gears allow for extreme ratios while at the same time
reducing stress to the rest of the drivetrain and allowing for even
more gear reduction in the gearbox or transfer box.
Torque
Tube Suspension
Torque tubes
are an element of the Unimog suspension that many people are unaware
of. The torque tube suspension dates back to the model T Ford which
used this design for its rugged simplicity. Instead of having trailing
arms, multi-link suspensions or leaf springs which limit travel
and cause the axle to get awkwardly contorted at extreme angles,
the Unimog incorporates front and rear torque tubes. The torque
tube extends from the transmission to the axle and encases the driveshaft.
The axles and gearbox are essentially connected and as a result,
no trailing arms or multi link suspensions are necessary. This system
allows for extreme axle articulation but prevents the axle from
being contorted when it is at extreme compression or droop. It also
prevents axle wind-up and axle hop, and encloses the driveshafts
and protects them from obstacles and the elements.
Coil
Springs
Since 1948, Unimogs have
always had coil springs front and rear
and they were always designed to provide maximum articulation. Combined
with the solid axles, torque tube suspension and the flexible frame,
the Unimog has unrivaled articulation which allows for excellent
traction even over extremely uneven surfaces. The coil springs also
allow for a comfortable on-road ride.
4x4
with All Wheel Differential Locks
All Unimogs have 4x4
with locking front and rear differentials that can
be engaged “on the fly” anytime by the driver. Conventional
four wheel drive systems only provide power to the wheel with less
traction on each axle. In these vehicles, engaging four wheel drive
doesn’t actually engage four wheels but rather engages both
axles. If one wheel on each axle has little or no traction, the
vehicle gets stuck even if the other wheels have excellent traction.
Automatic traction control devices such as limited slips, auto locking
diffs or electronic traction control, help overcome this situation
to varying degrees. However, only manually locking differentials,
such as in the Unimog, provide on demand, 100% drive to all wheels
Low Gearing
All Unimogs have very
numerically high gear ratios which allow
for crawl ratios that exceed the 100:1 ratio. The higher the ratio,
the lower the gearing and slower the speed. With optional gearboxes,
many Unimogs can exceed 3000:1 while still maintaining high ratio
gears for driving on-road. On other vehicles, aftermarket ratios
are sometimes available that exceed 100:1. However, few 4x4 drivetrains,
including “heavy duty” ones, were designed to take the
extra torque produced by these ratios. The result is other vehicles
with extreme crawl ratios have unreliable and weak drivetrains that
often lead to catastrophic failures. Unimog drivetrains are truly
heavy duty and designed to handle the high torque of these extreme
gear ratios. While other vehicles often fail at ratios of 150:1,
Unimogs are designed to take ratios of 4000:1!
Approach
and Departure Angles
Virtually all Unimogs
have at least 45 degrees approach and departure angles
as well as phenomenal ramp angles. As a result, the Unimog is able
to clear very large and steep obstacles without the body or chassis
interfering. This also allows them to climb inclines up to 110 percent,
giving the Unimog a higher climbing ability than any Land Rover,
Jeep or Hummer.
Implements
and PTO's
The Unimog was primarily
designed as a road going tractor intended to take a
wide variety of implements - hence the name “Universal-Motorgerät”.
To this day, Unimogs are primarily built as tractors and implement
carriers. As a result, all Unimogs (except the 404) are designed
to take a wide range of implements; from snow blowers to cranes,
and from dump beds to backhoes. Most Unimogs can take more implements
then multipurpose tractors! Many Unimogs come with front and/or
rear PTO's and hydraulics as well as three point hitch systems.
In addition these features can usually be retrofitted by simply
bolting on the various optional equipment. One Unimog can be used
as a snowblower, backhoe, dumper, grader, brushhog, etc. The combinations
are endless. As a result, Unimogs make an ideal tractor for small
scale farming, land management and logging.
No
other vehicle combines all the elements of the Unimog Principle
Some vehicles
use elements of the Unimog design. For example, Humvees and Pinzgauers
use portal axles while Land Rover Defenders use an excellent solid
axle/coil spring suspension system. Furthermore, many vehicles can
be retrofitted with locking differentials, larger tires or better
suspensions. However, the Unimog is the only vehicle in the world
that incorporates torque tubes, hub reduction, solid axles and coils
springs and it is this combination that makes it one of the best
off-road vehicles in the world and fundamentally different than
other 4x4s. No other vehicle combines all the elements of the Unimog
and, as a result, no other vehicle has the capability of a Unimog. |
