
Sisu K-50SS is a
six-wheel-driven
ballast tractor
A ballast tractor is a specially weighted tractor unit of a heavy hauler combination. It is designed to utilize a drawbar to pull or push heavy or exceptionally large trailer loads which are loaded in a hydraulic modular trailer. When feasi ...
made by the
Finnish heavy vehicle producer
Suomen Autoteollisuus (SAT). The vehicle can generate a 388 kN drawing force and it was used for pulling
flatbed trailers
Trailer may refer to:
Transportation
* Trailer (vehicle), an unpowered vehicle pulled by a powered vehicle
** Baggage trailer, a large flatbed baggage trolley
** Bicycle trailer, a wheeled frame for hitching to a bicycle to tow cargo or passen ...
.
Only one unit was produced in 1961 and it is the largest roadworthy motor vehicle ever built in the
Nordic countries
The Nordic countries (also known as the Nordics or ''Norden''; ) are a geographical and cultural region in Northern Europe, as well as the Arctic Ocean, Arctic and Atlantic Ocean, North Atlantic oceans. It includes the sovereign states of Denm ...
.
Development
K-50SS was developed under assignment of
Kemijoki Oy, which ordered at the end of 1959 two 6×6-driven heavy haulers for moving over 1 000 tonnes weighing transformers and other heavy components on flatbed trailers. The initial idea was having two units, of which one would have been used for trailer pulling meanwhile the other one would have pushed the trailer from behind. The vehicles were also planned to be used separately serving on power plant construction sites all over Finland.
SAT had previously produced six heavy Sisu K-36 earthmovers and the know-how was utilised in the engineering work. The first unit was ready in spring 1961, just 1.5 year after the assignment. However, Kemijoki cancelled the order of the other K-50SS and the produced vehicle remained unique.
Technical data
Engine
The vehicle is powered by
Rolls-Royce C6TFL turbocharged
In an internal combustion engine, a turbocharger (also known as a turbo or a turbosupercharger) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake air, forcing more air into the ...
6-cylinder in-line,
four-stroke
A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either directio ...
diesel engine
The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which Combustion, ignition of diesel fuel is caused by the elevated temperature of the air in the cylinder due to Mechanics, mechanical Compr ...
. Its 223-
kW (300
hp) output is 43% and 1 070
Nm torque
In physics and mechanics, torque is the rotational analogue of linear force. It is also referred to as the moment of force (also abbreviated to moment). The symbol for torque is typically \boldsymbol\tau, the lowercase Greek letter ''tau''. Wh ...
56% higher compared to the standard
naturally aspirated
A naturally aspirated engine, also known as a normally aspirated engine, and abbreviated to N/A or NA, is an internal combustion engine in which air intake depends solely on atmospheric pressure and does not have forced induction through a turboc ...
type. The
cylinder bore
In a piston engine, the bore (or cylinder bore) is the diameter of each cylinder.
Engine displacement is calculated based on bore, stroke length and the number of cylinders:
displacement =
The stroke ratio, determined by dividing the bore b ...
is 130.2 mm and
stroke
Stroke is a medical condition in which poor cerebral circulation, blood flow to a part of the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemor ...
152.2 mm. The
compression ratio
The compression ratio is the ratio between the maximum and minimum volume during the compression stage of the power cycle in a piston or Wankel engine.
A fundamental specification for such engines, it can be measured in two different ways. Th ...
is 14:1. The engine is fitted with an
air-start system.
Transmission and chassis
The
hydraulic
Hydraulics () is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counterpart of pneumatics, which concer ...
Rolls-Royce BF 11500Ms230
torque multiplier has three steps. The three-step main gearbox is made by
Foden. The power is divided between the front axle and two rear axles by a
differential inside the
ZF VG-800-4V1
transfer case
A transfer case is an intermediate gearbox that transfers power from the transmission of a motor vehicle to the driven axles of four-wheel-drive, all-wheel-drive, and other multi-axled on- and off-road machines. A part of the vehicle's drivetr ...
. The mechanism includes disengaging possibility of the front-wheel-drive for transition drive; then also the hydraulic clutch can be passed by a mechanical connection.
The maximum ratio passes nearly 65 000 Newton circumferential force on each wheel.
The
Kirkstall
Kirkstall is a north-western suburb of Leeds, West Yorkshire, England, on the eastern side of the River Aire. The area sits in the Kirkstall (ward), Kirkstall electoral ward, ward of Leeds City Council and Leeds Central and Headingley (UK Parl ...
-made driven axles are equipped with
interlockable differentials. The torque between the rear axles is divided by a longitudinal differential.
The chassis is constructed in a similar manner as in locomotives; the solution was re-used in 1990s when the company produced Sisu Mammut and Bambino earthmovers for the Swedish mining company
LKAB
Luossavaara-Kiirunavaara Aktiebolag (LKAB) is a state-owned Swedish mining company. The company mines iron ore at Kiruna and at Malmberget in northern Sweden. The company was established in 1890, and has been 100% state-owned since the 1950s. Th ...
.
Cabin
The large cabin is fitted with two beds and a small kitchen.
Usage and characteristics
The K-50SS was used for heavy hauling in
North Finnish hydroelectric
Hydroelectricity, or hydroelectric power, is Electricity generation, electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other Renewable energ ...
power plant construction sites.
The 19 300 kg weighing vehicle could be further loaded by extra
concrete
Concrete is a composite material composed of aggregate bound together with a fluid cement that cures to a solid over time. It is the second-most-used substance (after water), the most–widely used building material, and the most-manufactur ...
weights up to 52 000 kg total weight in order to improve the tyre grip.
The hydraulic torque multiplier enables passing torque to the wheels when the vehicle is standing still, enabling a smooth start. The maximum speed with the highest ratio is 10 km/h; the maximum speed during transition drive is 55 km/h. The hydraulic clutch can be used for decelerating.
According to the contemporary drivers and other people who were involved, the vehicle is easy to drive and it has always fulfilled the expectations given to it.
The vehicle cost 21 million
marks
Marks may refer to:
Business
* Mark's, a Canadian retail chain
* Marks & Spencer, a British retail chain
* Collective trade marks
A collective trademark, collective trade mark, or collective mark is a trademark owned by an organization (such ...
in the early 1960s and it has only run 43 000 km till 2010.
The K-50SS is the all-time largest individual roadworthy automobile unit produced in the Nordic countries, without a tipper or other superstructures. Larger vehicles have been built but not homologated to be used on public roads.
Current status
When coming to 21st century, the K-50SS was not in active use any more but stored in a garage at Pirttikoski power plant. It was restored to its original outfit little by little and presented in various vintage vehicle meetings,
until Kemijoki Oy gave the Sisu to Oulu Automobile Museum in 2006.
Sources
*
References
External links
Side view on Sisu K-50SS
{{Authority control
K50ss
Vehicles introduced in 1961
Heavy haulage