Z4p / Z4t – Detail (Early Build)

Z4pearlyheadDuring the pre war years high volumes of traffic required SJ to investigate the acquisition of a more efficient narrow gauge loco to replace the ageing steam locomotives in service.

Tests had already demonstrated that the diesel locomotives could replace steam locomotives in shunting and light service duties.  During the summer of 1946 a requirement was identified for the purchase and delivery of twelve Narrow Gauge locomotives – nine Z4t for 1097mm gauge lines and three Z4p for 891mm gauge.

The intention was for eight of the nine Z4t locomotives would be stabled at Sölvesburg, Ronneby, Karlshamn, Kristianstad, Norraryd, Växjö and two locos stabled at Torsås.  The remaining locomotive would be placed in reserve at Karlskrona.

The three Z4p, 891mm gauage locos would be located at Oskarshamn and Knowland and placed into service as a reserve.

Following investigations, the Rail Operations Service Agency identified a need for the new loco fleet narrow gauge locomotives to be increased by a further four.  These were to be initially designed for 1067 mm gauge, but could be converted so that within reasonable cost they could be used on 891 mm gauge lines, to coincide with the the planned widening the Blekinge route. Additional dedicated 891mm gauge locos were not required.

Invitation to Tender

In July 1947 invitations to tender for the four Z4t narrow gauge locomotives along with with a significant number of standard gauge Z4 locomotives were issued.

A number of major Swedish loco manufacturers were invited to submit tenders with only the Märsta loco works submitting a tender for the narrow gauge Z4t locos.  Their offer included conditions to the manufacture of the standard gauge Z4 shunting loco.

Due to the higher than anticipated tender, no orders were made.

The need for new narrow-gauge locomotives was becoming more evident and the situation became precarious as a result of the unordered Z4t locomotives.  The Rail Operations Service Agency directly contacted the Kalmar Workshop to submit quotations for the required narrow gauge locos. Their return quotation included four Z4t for 1067 mm gauge and three Z4p for 891 mm gauge.  As before the 1079mm machines would be built so that it was possible to re gauge them at minimal costs should there be a need to do so.

By October 1947 the ordered locomotives were being constructed at the Kalmar Workshop with SJ provided the primary diesel engines, transmissions and hydraulic braking systems. Delivery would start slowly with the first delivery occurring April 1949. The initial build locos locos were assigned the numbers – Z4t ‘226-229’ and Z4p ‘230-232.

Production of Lot 1 Locomotives

By the summer of 1949 modifications were already being made to the locos which included additional safety gear and the provision of warm air heating in the cab.

Z4p loco ‘230-232’ were delivered between February and April 1950 with loco ‘230’ being stabled at Harmånger for use on the services between Harmånger and Bergsjö. The intention was for Z4p ‘231’ to also be stabled here, however upon its introduction into service, it was immediately placed into service at Stenstorp.

 Z4p ‘232’ was assigned for shunting duties at stations in the Kalmar region. Upon its allocation to service tests were carried out and within weeks of its arrival was operating the Eksjö-Österbymo routes.

 Z4t locos ‘226-229’ were allocated for dutuies in Karlshamn, Kristianstad, Sölvesborg and Ronneby. Sölvesborg and Ronneby.  These allocated locomotives were also assigned for duties on the services between Sölvesborg-Hörviken and Ronneby Kallinge.

By the autumn of 1948  a number of request had been received for further diesel locomotives by the various operating districts. A summary of the responses identified a need for nine Z4p, and was to included 2 spare locomotives. The additional locos were destined for use on the Skara, Lidköping and Mariestad routes, and the recently adopted Gotland island lines replacing the inherited steam locos.

Production of Lot 2 Locomotives

Once again, by August 1949 the Machine Technology Agency issued tender proposals for  eleven Z4p locomotives for 891 mm gauge with design and manufacture similar to the he Kalmar design for the Z4p and Z4t locomotives.

A number of manufacturers were approached – Kalmar, ASJ in Linköping and Kockums in Malmo with the ASJ Falun workshop announcing that the they would not be bidding.  Kalmar proved once again to be the acceptable bidder in both cost and delivery, which would be completed by the summer of  1951.    Unlike the earlier Kalmar built locos, this second batch would be supplied and completed providing DF1.0 hydraulic transmissions from Atlas-Diesel.   By early October 1949 eleven Z4p locomotives from Kalmar has been ordered and would be numbered ‘256-266’.

The second batch of locos were delivered with detail differences from the Series 1 locomotives.  The oil cooler for the hydraulic gearbox was positioned in a different location on the long bonnet of the locomotive, and maximum speed had increased by 5km/h to 45km/h.  Hydraulic gearboxes were supplied by the Märsta-works in Eksjö, initially intended for use on YCo4p/YCo4t  railcars ‘672-681’.  One loco was fitted with a modified Diesel DF 1.0 hydraulic gearbox, acquired from the SJ spares reserve.

During manufacture of Z4p locomotives ‘256-266’ were fitted with a direct injection version of the Scania Vabis D812 8-cylinder diesel engine.  This engine later became the standard engine in use throughout Lot 1 and 2 Z4p/Z4t ‘226-232’ fleet replacing the Scania Vabis D802 engine.

By 1950 a review indicated a need for a further 25 Z4p locos for 891 mm gauge and 4 Z4t for 1067 mm gauges. Eleven Z4p locos were already on order, and hence funding was amended to  cover the cost of the additional locos.

During April 1951, tenders were invited for the required additional locomotives.  ASJ in Linköping, Kalmar Workshop, Kockums in Malmo, Märsta works in Eksjö, Power and Machinery in Stockholm, Plåtindistri in Limhamn, Hammarby works in Stockholm, with Diesel Power in Stockholm were all invited.  The design would be similar to those being built at Kalmar, with the drawings being provided by SJ.  During manufacture, SJ would provide the hydraulic gearboxes, roller chains and brake system components.

By June 1951,tenders had been received from the ASJ in Falun, SWE Engineering and Kockums in Malmo. Kockums tender although cheaper, could not guarantee delivery until the beginning of November 1953, at 4 locos per month.

ASJ were significantly more expensive with delivery commencing during the summer of 1953 at a delivery rate of 2 locos per month.

The most expensive option came from the Kalmar workshop who were already in build of the Lot 2 locomotives, however delivery would commence earlier during quarter 2 1952 with the final loco delivered by Quarter 1 1953.

SJ selected the Kalmar workshop as the supplier for the additional locomotives.  SJ had managed to negotiate the cost per loco down and by June 1951 the order was completed.

The additional batch of locos will receive once commission into service Z4t ‘307-310’ and Z4p locos ‘311-324’.

Additional Orders

An inventory review during the Summer of 1951, resulted in the funding for an additional 5 Z4p locomotives.

During November 1951, a verbal agreement was reached between SJ Director General and the head of the Kalmar Workshop for the production and delivery of 5 locos were required in addition to those previously ordered.  Kalmar were to construct these locomotives “at risk” and SJ would purchase them when the funds become available.  Delivery for the additional 5 locos was excepted between January and March 1953 and be allocated the numbers ‘327-331’

Production of Lot 3 Locomotives

During November 1952 an agreement was reached that a number of additions be made to the locos cuurently in build.  Locos ‘327-331’ would be equipped with chain lubrication, and ceiling and cab walls would become insulated.

Z4t locos ‘307-310’ were delivered during Q2 1952 intended to be used on the Karlskrona Torsås-Bergkvara routes and switching in Vislanda. Z4p ‘311-324’ were delivered between July 1952 and April 1953.  As in previous deliveries their intended duties changed due to the weakening freight operations and employed on services such as Visby – Burgsvik, Böda-Ottenby, Eksjö-Österbymo and Kalmar

Stations that received locomotive allocations were East Gothenburg, Uddevalla Port, Norsholm and Åtvidaberg.

Hultsfred was due to receive Z4p 328 for switching and shunting duties but this changedafter the successful test at Falkenberg Limmared and employed on train services. Hultsfred also received Z4p ‘248’ from Gotland as this was an older style locomotive with shorter wheelbase and employed on shunting duties. Upon delivery Z4p ‘322’ was immediately employed on the service Uddevalla-Bengtsfors

Multiple Driving on Gotland

A study conducted during 1949 identified that there was an increase in traffic operation costs on the island of Gotland due to high cost of maintenance of steam loco boilers and damaged caused by inadequate water supplies.  As a result it was decided that a complete ‘dieselisation’ of traffic would be required to try and reduce the operation costs.  It was decided that the Z4p locomotive would be ideal for this role.

During October 1949, the issue of acquisition of addtional locomotives became topical once again.  Rationalisation of the islands freight  operation was being considered by the heads of SJ.  This demonstrated that steam locomotives could be replaced by approximatly 4 diesel locomotieves, and steam only used in the event of failure or operational need.  An estimated saving of 226000SEK was calculated and in light of the savings 4 additional locos were ordered.

Initially requiring a bespoke design for the island, the Machine and Technology Agency responded that delivery would not be able to be completed for another three years at least, and of an untested design.

Prior to delivery of Z4p ‘256’ and ‘258’ in the Autumn of 1950,a number of operating section were asked to carry out tests to determine if any could replace steam locomotives used on freight trains.The tests demonstrated that 2 locomotives could make a gross combination weight of 125-250 tons and to reduce staffing requirements proposed run in multiple saving 20000SEK per locomotive, with an annual staff saving of 13000SEK.

A cost benefit analysis was undertaken and locos ‘311-324’ were chosen to be equipped with multiple operation control.  By May 1952 Z4p ‘315-316’ were delivered from the Kelmar Workshop equipped with multiple running gear.  Simultaneous control of both engines, hydraulic gear and braking system could all be operated from one cab via an electro-pneumatic system.  The braking system differed slightly from production versions, being controlled via the air brake circuit.

By the 1953, Z4p ‘315 ‘ and 316’ had completed their tests.  The results proved a success and by July 1954 a second order had been placed for 2 additional locos to be fitted with the same multiple equipment.

In August 1954 work was underway rebuilding Z4p ‘320’ and ‘323’ at the Kalmar Workshop. They would be equipped to run in multiple as Z4p locos 315 and 316.  By mid-September that year locomotives were operating in revinue earning service. Z4p ‘320’ and ‘323’ were allocated to Småland and Östergötland.

Summary of Build

  Z4t Z4p Original Allocation Comments
Lot 1 226 Karlshamn
227 Kristianstad
228 Sölvesborg
229 Ronneby
230 Harmånger and Bergsjö
231 Stenstorp
232 Eksjö-Österbymo
Lot 2 256 § Multiple Control Test
258 § Multiple Control Test
307 Karlskrona, Torsås-Bergkvara, Vislanda
308 Karlskrona, Torsås-Bergkvara, Vislanda
309 Karlskrona, Torsås-Bergkvara, Vislanda
310 Karlskrona, Torsås-Bergkvara, Vislanda
311 § Visby–Burgsvik, Böda-Ottenby, Eksjö-Österbymo, Kalmar
312 § Visby–Burgsvik, Böda-Ottenby, Eksjö-Österbymo, Kalmar
313 § Visby–Burgsvik, Böda-Ottenby, Eksjö-Österbymo, Kalmar
314 § Visby–Burgsvik, Böda-Ottenby, Eksjö-Österbymo, Kalmar
315 § Visby–Burgsvik, Böda-Ottenby, Eksjö-Österbymo, Kalmar
316 § Visby–Burgsvik, Böda-Ottenby, Eksjö-Österbymo, Kalmar
317 § Visby–Burgsvik, Böda-Ottenby, Eksjö-Österbymo, Kalmar
318 § Visby–Burgsvik, Böda-Ottenby, Eksjö-Österbymo, Kalmar
319 § Visby–Burgsvik, Böda-Ottenby, Eksjö-Österbymo, Kalmar
320 § Visby–Burgsvik, Böda-Ottenby, Eksjö-Österbymo, Kalmar
321 § Visby–Burgsvik, Böda-Ottenby, Eksjö-Österbymo, Kalmar
322 § Uddevalla-Bengtsfors
323 § Visby–Burgsvik, Böda-Ottenby, Eksjö-Österbymo, Kalmar
324 § Visby–Burgsvik, Böda-Ottenby, Eksjö-Österbymo, Kalmar
Lot 3 327 Falkenberg Limmared


Built at Risk by Kalmar, Chain Lubrication system and cab insulation
328 Built at Risk by Kalmar, Chain Lubrication system and cab insulation
329 Built at Risk by Kalmar, Chain Lubrication system and cab insulation
330 Built at Risk by Kalmar, Chain Lubrication system and cab insulation
331 Built at Risk by Kalmar, Chain Lubrication system and cab insulation

§ – Multiple Control Fitted

Drawings and Documents

The above is a direct translation of this document – Z4p Drawing and articleNote the drawing enclosed has dimensional and scale inaccuracies.

Z4p Detailed Drawing and build article – German text.


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