Sisu K-50SS

from Wikipedia, the free encyclopedia
Sisu K-50SS pulls a Bucyrus Erie excavator.
Sisu K-50SS pulls a Bucyrus Erie excavator.
Manufacturer: Oy Suomen Autoteollisuus Ab , Karis , Finland
Production period: 1961
Previous model: none
Successor: none
Technical specifications
Engines: Rolls-Royce C6-TFL
Power: 223 kW

The Sisu K-50SS is a 6 × 6-powered heavy-duty tractor manufactured in 1961 by the Finnish vehicle manufacturer Suomen Autoteollisuus (SAT). The vehicle develops a pulling force of up to 388 kN.

Only one example of this vehicle was made. It is the largest street legal vehicle, calculated without tippers and other superstructures - in other words, the largest single automobile unit - that has ever been built in the Nordic countries .


At the end of 1959, the power plant operator Kemijoki Oy ordered two 6 × 6-powered heavy-duty tractors from SAT in order to be able to transport transformers of over 1000 tons to its construction sites. The original idea was that two K-50SS tractors should be used together with a low loader , one tractor pulling and the other pushing. It was also planned to use the individual vehicles on power plant construction sites across the country.

SAT had previously developed and built six heavy Sisu K-36 dump trucks. The experience from the K-36 project was incorporated into the new type. The main designers entrusted with the new project were Pentti E. Lehtinen, Kalevi Kakko and Olavi Karhu. The first vehicle was delivered after just one and a half years, in spring 1961. Since Kemijoki Oy canceled the order for the second tractor unit, this one built vehicle remained.

Technical specifications

The Sisu K-50SS during construction, still without a cab


The six-cylinder Rolls Royce C6 TFL turbodiesel engine has an output of 223 kW (300 hp) and generates a torque of 1070 Nm. Its power is 43% higher and its torque 56% higher than the standard naturally aspirated engine. The bore is 130.2 mm and the stroke is 152.2 mm. The compression ratio is 14: 1. The diesel engine is started pneumatically.

Transmission and chassis

The Rolls-Royce BF 11500Ms230 hydraulic torque converter has three stages. The three-speed main transmission comes from Foden . A ZF VG-800-4V1 transfer case is installed as a differential between the front and rear axles . The front axle can be switched without drive, then the hydraulic clutch is also switched off, but still mechanically connected.

The axles manufactured by Kirkstall are equipped with a lockable differential. The torque is distributed between the rear axles with a center differential.

The chassis is constructed in the same way as locomotives; the design was taken up again in the 1990s in the earthmoving vehicles Sisu Mammut and Bambino, which were built for the Swedish mining company LKAB .


The large cab is equipped with two beds and a small kitchen.

Use and properties

The K-50SS was used to transport heavy components on hydroelectric power plant construction sites in Northern Finland.

To increase traction, the Sisu K-50SS could be loaded with concrete weights of up to 52,000 kg. The vehicle is 9000 mm long, 3200 mm wide and 3570 mm high. The wheelbase is 4700 mm + 1575 mm.

The torque is transmitted to the wheels via a reduction gear when the vehicle is still stationary. This enables jerk-free start-up. The maximum speed is 10 km / h in the highest ratio and 55 km / h in the lowest ratio. A hydraulic clutch can be used for slowing down.

According to contemporary drivers and other people involved, the vehicle was easy to drive and always lived up to expectations.

The Sisu K-50SS cost 21 million Finnish marks and by 2010 had only driven 43,000 km. It is the largest street legal vehicle without tippers and other superstructures that has been built in the Nordic countries to date. Larger vehicles were built, but they are not street legal.

The original transportation plan: One K-50SS pulls while the other pushes

Current status

In the 21st century, the vehicle was no longer actively used, but was parked in a garage near the Pirttikoski power plant. It has been gradually restored, returned to its original condition and exhibited at various classic car shows. In 2006, Kemijoki Oy handed it over to the Oulu Car Museum.


  • Mäkipirtti, Markku: Sisu . Ed .: Apali Oy (=  Ajoneuvot Suomessa . Volume 4. ). Tampere 2010, ISBN 978-952-5877-05-2 .
  • Blomberg, Olli: Suomalaista Sisua vuodesta 1931 - Monialaosaajasta kuorma-autotehtaaksi . 1st edition. Oy Sisu Auto Ab, Karis 2006, ISBN 952-91-4918-2 .

Individual evidence

  1. a b c d e f g h i j k l Mäkipirtti: Sisu K-50SS 6 × 6 Lavetinvetäjä. Pp. 90-94.
  2. a b c d e f g Blomberg: Sisun tupla-Ässät - Aikojensa suurimmat Pohjoismaissa valmistut autot. Pp. 160-161.
  3. New 300 bhp engine in Foden . In: The Commercial Motor . Temple Press, January 31, 1958 ( [accessed June 12, 2014]).
  4. 180 tonnia kulkee suomalaisella Sisulla . (an old press clipping). Archived from the original on July 25, 2013. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved May 31, 2014. @1@ 2Template: Webachiv / IABot /
  5. Kari Vesala: Hyötyajoneuvot . Oulun Automuseo. Archived from the original on December 24, 2013. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved June 1, 2014. @1@ 2Template: Webachiv / IABot /