Sisu Nemo

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Sisu Nemo is a hydraulic radial piston motor type developed and initially produced by Suomen Autoteollisuus (SAT). The system was patented in 1961.

The motor produces a high torque at low speed and it has been primarily used to power both civil and military lorry trailers. A number of other applications have been designated for various industrial applications.

Development

The idea of the motor came from DI Ilmari Louhio who worked in SAT as design engineer. The operating principle was so simple, that when Louhio presented his invention to the technical department and company management, he was not taken seriously; the answer was "if that would work, someone would have invented it for long ago". However, Louhio didn't give up and soon there was set up a team for developing of the concept. The members were Louhio, Pentti Tarvainen, Antti Saarialho and Lasse Airola; in addition, dozens of people from different departments took part in the development work. A number of prototypes were built and they went through intense testing before the construction was ready for production. The first field test took place in autumn 1960; a Fordson Major tractor was pulling a hydraulically driven trailer. The invention was granted with a patent in January 1961 and it was named Nemo, which comes from nestemoottori ("fluid motor").[1]

Operating principle

The motor contains five radially positioned hydraulic cylinders. The pistons, of which top are with rollers, press against an outer ring of which inner profile consists of eight cams, forcing it to rotate. The hub consists a distribution valve that adjust the flow in and out in each cylinder. A drum brake could be integrated together with the system and the whole application could be fit into a 20-inch rim.[2]

Despite of its small size, the system can deliver a torque of 8 000–10 000 newton metres. A planetary gear set is not needed, as the motor provides an internal ratio of 8. Each round contains 40 strokes which provides a smooth torque. In freewheeling mode the pistons go into the hub so that the rolls are not in contact with the cam ring.[2]

The system contains also a twin pump unit attached to the free end of the towing vehicle engine. One of the elements can be bypassed, which halves the transmission ratio.[3]

Applications

Logging trucks

The first Nemo applications for vehicles to be used on roads came in 1963–1964.[1] Nemo was successfully tested in logging vehicle trailers. In addition to improved off-road performance the system had other benefits; a trailer with a driven front axle could be driven on the lorry platform for transition and set down when the place of loading was reached. When full laden, the Nemo could be used to assist on steep uphills: in case the driver had to gear down, he could switch on the hydraulic drive that was powered directly by the engine, and use clutch and change the gear without risk that the vehicle would stop going. Nemo systems were available for example for Sisu KB-117, M-162 and K-142 logging trucks.[3]

Military vehicles

In 1960s the Finnish Defence Forces had 1 800 field cannons. The number of suitable haulers was so small that in case of mobilisation moving of the cannons would have relied on deployed civil lorries. The Nemo system was seen as a solution to improve the mobility.[2]

In 1965 one of new Tampella 122 K 60 cannons was equipped with a tandem axle driven by Nemo transmission system. The system was tested with single wheels at first but later double wheels were applied. The hauler was Sisu KB-45 off-road lorry with an integrated hydraulic system. The pump was mounted on the front end and the oil container was placed between the cabin and platform. The field test were continued in Santahamina during summer 1967; the KB-45 hauled an SAT-produced trailer. The total weight of the vehicle was 6 490 kg and the trailer weighed 5 220 kg. The vehicle traction was measured 48 000 Nm and the trailer delivered 30 000 Nm; the combination produced 72 000 Nm. The effect of the tyre size was not considered. Later the system was tested with Sisu K-141 4×2 together with field cannon 130 K 54 and Vanaja KK-69 ET 6×6 coupled with a three-axle carriage powered by a separate aggregate-run pump. The test proved that with the help of Nemo system even such trucks, which were not intended for off-road use, could haul heavy cannons in terrain. During the trials it was observed that the trailers even pushed their haulers forward.[2]

Equipping the cannons with Nemo was conceivable on all cannons and most of the haulers. In 1968 the price of Nemo was 30 000 Finnish marks so that it was divided in half between the hauler and carriage. The price was high compared to a normal truck that cost 50 000–60 000 marks; on the other hand, the tracked cannon hauler AT-S cost 130 000 marks. Nevertheless only few vehicles and cannons were ordered with the Nemo system. In 1970 the Defence Forces procured a batch of 13 Nemo-compatible Sisu AH-45 lorries. At the same time the Nemo transmission was mounted on howitzer 152 H 38, field cannon 130 K 54 and 122 K 60; the latter one was with a tandem axle. One artillery battalion was armed with Nemo-driven 130 K 54 cannons. In 1976 the Defence Forces took a delivery of 14 more Sisu AH-45's and next year followed a batch of 13 vehicles more. Eventually, the Defence Forces had three artillery battalions motorised by Nemo-compatible Sisu's.[2]

The Nemo was further tested in an ammunition trailer prototype equipped with Nemo driven posterior axle; the brakes were built into the fore axle. The motors were built in a such manner that the trailer had an extra high ground clearance. The prototype did not lead to serial orders.[2]

Industrial applications

A number of applications were designed for machinery and industrial use; these include rear-wheel drive of an articulated dumper truck, excavator transmission, mining train transmission, telescopic crane extractor motor, mobile portal crane transmission and a ferry wire winding motor.[1]

Production

The first motors were produced in the Sisu axle factory that was located then in Helsinki. In 1973 the company made a decision to transfer the Nemo production to another organisation. SAT founded a separate company Nesco Oy jointly with Multilift (40%) and investment fund Sponsor (20%). The production was moved to Iisalmi where it shared the premises with Multilift demountable skip factory. Later the Nemo's were produced in Valmet gear works from which it was moved on to Valmet Hydraulics Oy in Jyskä. Valmet became later a part of Metso Corporation, which sold the hydraulic motor factory to international investors in December 1999.[1]

American Kelsey-Hayes Company produced Nemo's under licence.[3]

References

  1. ↑ 1.0 1.1 1.2 1.3 Blomberg, Olli (2006). "Vuosisadan keksintö...". Suomalaista Sisua vuodesta 1931 – Monialaosaajasta kuorma-autotehtaaksi [Finnish Sisu since 1931 – From multi-industrial expert to lorry factory] (in Finnish). Karis: Oy Sisu Auto Ab. pp. 319–324. ISBN 952-91-4918-2. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Mäkipirtti, Markku (2006). Puolustusvoimien moottoriajoneuvot 1960–2000 [Motor Vehicles of the Defence Forces 1960–2000] (in Finnish). Tampere: Apali Oy. ISBN 978-952-5026-50-4. 
  3. ↑ 3.0 3.1 3.2 Mäkipirtti, Markku (2011). "Sisu nestemoottori (Nemo)". Sisu. Ajoneuvot Suomessa (in Finnish) 4 (2. ed.). Tampere: Apali Oy. pp. 178–181. ISBN 978-952-5877-05-2. 

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