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85 years of Škoda trolleybus production / Chapter 2

 

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2 Inter-war and wartime trolleybuses

At the turn of the 1920s and 1930s, motoring in Europe faced a lack of imported petroleum products. Countries tried to solve the problem by introducing subsidized fuels with a high share of domestic alcohol. In addition, buses in public transport of that time contended with insufficient dynamics on hilly routes because the development of engines did not proceed as quickly as expected. Thus, attention turned to electricity.

Trolleybus On Stage

A number of cities faced the question of whether it was of any use to renew and expand or newly introduce tram transport. Trolleybuses appeared as a fitting compromise because they meant lower track building costs in comparison with trams and did not suffer from insufficient output in comparison with buses. The vehicle had already won through abroad, especially in Great Britain, and technical experts of Czechoslovak transport companies drew experience from there.

 

(p. 20) The promotional photo of Sunbeam, a British manufacturer, shows trolley double-decker type MS2 operated from 1931 in Wolverhampton. [301]

(p. 21) Pilsen run coal-gas buses even after WWII. However, the photo of Božkov terminal from 1948 already shows overhead wires for trolleybuses which would be introduced in several months. [302]


However, the new means of transport was only slowly gaining ground in the streets of our cities. Prague started its first trial line in 1936 with three prototypes of domestic brands of Škoda, Praga and Tatra. Pilsen began with the preparations shortly after, putting trolleybuses supplied by the Škoda Works into operation in 1941.

World War II – Problems and New Plans

After the war frenzy burst out, the fuel crisis in Europe increased to such an extent that both cars and buses had to be converted to coal gas or wood gas drive. The difficult handling and insufficient efficiency of these solutions made cities’ representatives turn their attention to trolleybuses again. Both dusted-off and completely new plans appeared in a number of cities of the former Czechoslovakia but only Bratislava and Zlín managed to accomplish them by 1945 due to the problems of the wartime economy (in both cases, with trolleybuses made through foreign cooperation, out of the Škoda brand). The Škoda Works was only engaged in small-lot production of vehicles for Pilsen. However, a number of studies and projects emerged that ushered in the post-war technical concept of vehicles.

Prague Prepares Trolleybus Operation

The beginning of the first Czechoslovak modern trolleybus system seen as early as the 1920s, during the period of prosperity and building development of the capital city. The persons who contributed most to the popularization of trolleybus transport were especially Ing. Eustach Mölzer, president of the Board of Directors of the Electricity Enterprises of the Capital of Prague (Elektrické podniky hl. města Prahy), and his colleague Ing. Alois Píbl. director of the Tramway Department of the same Company, who had made a study trip to Ipswich, England. Based on this trip, the British companies of Ransomes, Sims & Jefferies and Richard Garrett & Sons submitted non-binding offers for the supply of trolleybuses in 1929.

 

(p. 22) Richard Garrett & Sons’ trolleybus run by the Ipswich Corporation Transport. [301]


The German concern AEG submitted its offer, too. Nevertheless, the Czech engineering companies of Škoda, Tatra and Praga were given preference one year later, due to the policy of supporting domestic industry during the economic crisis.

UNREALIZED TROLLEYBUS ŠKODA 506 N

At the end of 1930, the offers of Praga (daughter company of ČKD), Tatra, and Škoda (parameters – see Table on p. 23: Manufacturer / Electric outfit / Output (kW) / Capacity (seating / standing)) were gathered in the office of the Electricity Enterprises of the Capital of Prague. Škoda offered a two-axle, two-door trolleybus on Škoda 506 chassis which would have 25 seats and 20 standing places. The engine would have the output of 48 kW, and current would be supplied by a pair of trolley wheels. However, the competitive tendering was cancelled because a unanimous idea of the route of the first line was lacking and there were problems with purchasing land for construction or with the condition of roads in respect of the routes considered. However, the Škoda 506 N was demonstrably the first, though unrealized, design of a Škoda brand trolleybus.

 

(p. 23) Illustration photo of the Škoda 506 N bus, from the chassis of which the first Prague’s trolleybus should have been derived. [301]

ŠKODA 656 / 1 TR

Škoda 656 P Unrealized One-door Variant

Prague did not lose its interest in trolleybuses, and so the Škoda Works presented the first design of a three-axle trolleybus on the chassis of the Škoda 656 P lorry, in the variant with one door for the passengers. It would have had the motor with the output of 103 kW and an AEG collector system. As the route of the first trolleybus line had not been approved yet, it was not produced and was remade one year later. Both Praga and Tatra presented new offers, too. The preparation of the first trolleybus line was underway at that time.

 

(p. 24) Side view of the unrealized variant of the Škoda 656 P trolleybus. [61]

Technical Description and Trials

In its final version, the trolleybus had two doors for passengers and a separate entrance for the driver. The body consisted of a wooden structure reinforced by metal bracing. The mechanical part was made by ASAP – Škoda’s plant at Mladá Boleslav, and the electrical equipment was supplied by the ETD at Pilsen-Doudlevce.

 

(p. 24) Factory photo of the Škoda 656 P / 1 Tr trolleybus in front of the headquarters of the Electrotechnical Factory at Pilsen-Doudlevce at the beginning of 1936. [302]

(p. 25) Driver’s post of the Škoda 656 P / 1 Tr trolleybus [302]

(p. 25) The drawing of the chassis of the vehicle displays basic bearing parts of the chassis, driving system, and steering. [62]

 

It was interesting that even then the traction motor (quadrupole, compound) enabled to return energy to the network when braking. The trolleybus was controlled by two pedals: the power pedal which put the regenerative brake into operation at the same time, and the pneumatic brake pedal. The main part of the electrical equipment was the controller which (to tell it in a simplified way) switched over contacts of control circuits which then connected contactors which switched on/off the branches of the resistors. In that way, the speed of the vehicle was regulated. Trolley booms originally equipped with retrievers served for the supply of current. The method of signalling the drop in tyre pressure (PNEUKA) using switches in rubber cases near each wheel was rather progressive at that time.

 

(p. 26) Except for resistors located on the roof, the whole traction equipment was installed in the contactor box of the vehicle. The controller is in the left lower part, with the three main contactors over it. [302]


Škoda 656 P / 1 Tr

Manufactured in the years

1936

Run in the years

1936 - 1955

Number of units manufactured

1

Countries of operation

CS

Body

wooden, metal-plated

Maximum output

66.2 kW

Transport capacity

72 persons

Maximum speed

46 km/h

Number of seats

28

Service weight

10 365 kg

 

The test line on the premises at Doudlevce did not exist yet in 1936, and that’s why one of Pilsen tramlines served for trial drives. The positive polarity trolley boom was put on the overhead tram wire while the negative polarity consisted of an improvised system for current return by a connecting cable from the negative trolley boom to a single-axle tram truck drawn by the trolleybus. Further testing and driver training took place later in Prague.

 

(p. 28) Škoda 656 P / 1 Tr vehicle on display in May 1936 at the congress of the Czechoslovak Electrotechnical Union (ESČ) at Kopeckého Sady, Pilsen. [357]

Trolleybuses in the Capital Set Out

The Electricity Enterprises of Prague started traffic on the first line from Střešovice to Hanspaulka on 28 August 1936. Three prototypes started operation: Škoda 656 (later 1 Tr), Praga TOT, and Tatra T 86. The inhabitants of Prague especially praised the comfortableness of the new vehicles in comparison with the trams of that time. The first months of operation showed which of the various technical solutions of the vehicles proved to be the best. In the case of the Škoda trolleybus, the trolley wheels were replaced by sliding collectors and automatic retrievers were added.

 

(p. 28) The trial drive of the three prototypes that began the trolleybus transport in Prague: from the left Škoda 656 P / 1 Tr, Praga TOT, and Tatra T 86. [301]

(p. 29) Škoda 656 P / 1 Tr passes under the railway arches of the Buštěhrad Railway from Starodejvická street to Na Ořechovce street during testing in summer 1936. [302]

(p. 29) In August 1936, the inhabitants of Prague familiarized themselves with the most modern means of transport on the territory of the capital city. [303]

Further History of the Prototype by Škoda

The vehicle passed through two main changes during its running in the streets of Prague. The first was the conversion to right-hand operation in 1939. The other one came even later – the big traction motor was replaced by two smaller ones. The oldest trolleybus of the Škoda brand served the inhabitants of Prague until 1955. Unfortunately, the intent to preserve it as a museum exhibit failed, and so this technically unique object was scrapped in 1961.

ŠKODA 539 / 2 TR

Based on their experience with the 1 Tr prototype, the representatives of Prague ordered five more Škoda trolleybuses which they received in 1938. The vehicles were made by the plant at Mladá Boleslav again, and the electrical equipment by the factory at Doudlevce where the final assembly took place.

 

(p. 31) The Electricity Enterprises of the Capital of Prague ordered five more three-axle trolleybuses from the Škoda Works less than a year after this means of transport set out on the streets for the first time. [61]

(p. 32) Factory photo of the Škoda 539 / 2 Tr trolleybus taken at Pilsen-Doudlevce in 1938. [302]

Brno Showed Interest Too

The Škoda Works entered this type for the tender issued by the Transport Company of Brno in 1938. The order was finally not realized because the Company’s new management changed its mind and a tram line was constructed to the quarter of Černá Pole in 1942.

Technical Description and Trials

Though the vehicles had a similar chassis conception, the construction of the bodywork was different (it was all-metal already), as well as the drive. The vehicles were equipped with two smaller compound motors instead of a large one, by which the height of the floor could be considerably lowered. At the beginning, two doors on the left side served the passengers while the driver had his separate entrance on the right. After the conversion of 1939, the doors for passengers were transferred to the right side too. The vehicle was controlled by two pedals. In principle, the electrical control was similar to the previous type. Starting and braking resistors were located both under the floor and on the roof of the vehicle. The vehicles made were tested first at the newly finished, short test line in Pilsen and then in Prague using the tram infrastructure (described under 1 Tr type).

 

(p. 32) Driver’s post of Škoda 539 / 2 Tr [302]

 

Škoda 539 P / 2 Tr

Manufactured in the years

1938

Run in the years

1938 - 1960

Number of units manufactured

5

Countries of operation

CS

Body

steel

Maximum output

90 (2x 45) kW

Transport capacity

74 persons

Maximum speed

50 km/h

Number of seats

30

Service weight

10 900 kg

 

(p. 34) The complete delivery of 2 Tr vehicles captured before dispatch in 1938 at the new test line between the buildings of the ETD plant at Pilsen-Doudlevce. [302]

Operation in Prague and End of Life in Pilsen

During the war, the vehicles were employed mainly for the heavily utilized line to the Walter factory at Jinonice, which manufactured arms for the German Wehrmacht. After the war, Tatra T 400 trolleybuses were used more often, and that’s why the public transport company of Prague sold the used Škoda trolleybuses, after repair, to Pilsen in 1953, where they helped to cope with rush hour traffic for four more years. None of these vehicles is preserved up to the present.

 

(p. 34) Škoda 539 / 2 Tr vehicle with Prague reg. no. 316 still in the left-sided version captured in the depot at Střešovice in winter 1938 / 1939. The photo was taken by trolleybus driver Milan Horký. [304]

(p. 34) Another photo of vehicle reg. no. (number missing) in the Střešovice depot, this time during WWII. The vehicle had already been converted to right-hand drive operation. [304]

UNREALIZED TROLLEYBUS ŠKODA 538 A

Together with the three-axle 2 Tr type, Škoda was developing a vehicle with smaller transport capacity for the needs of smaller cities. The first variant was supposed to be 7.8 m long and 2.3 m wide, with a single door for passengers on the left side and a capacity of 50 passengers, of whom 26 seated. The vehicle was intended for Bratislava but another supplier was selected.

 

(p. 35) Side view of the first variant of the type Škoda 538 A considered in 1938–1940. [62]

 

At the end of 1940, another vehicle variant 9.1 m long and 2.5 m wide, with two doors on the right side and a total capacity of 69 passengers, of whom 23 seated, was designed. The trolleybus was intended for Zlín.

 

(p. 36) The second variant of the type Škoda 538 A model, version for Zlín, prepared at the end of 1940. [62]

UNREALIZED “MIDDLE TYPE TROLLEYBUS”

The direct successor to the second variant of the unrealized type Škoda 538 was a project without type number, designated only as “Middle type”. It was supposed to have the same outer dimensions; it only differed in respect of the internal dimensions of individual components and in the variant of some components. The “Middle type trolleybus” was prepared in two versions. The first one should have had two doors, always located behind the axle, and a capacity of 65 passengers (25 seated). It was expected to serve passengers in Zlín; however, the public transport company chose another manufacturer. The second version differed in that the front door was located in front of the axle and in lower capacity – 60 passengers (23 seated), and it was intended for Prostějov. However, trolleybuses were not introduced there at all.

 

(p. 37) The design of the middle type trolleybus in the first variant from February 1941, i.e. with the door behind the front axle. [62]

ŠKODA 553 / 3 TR

Pilsen Prepares Trolleybus Operation

While other cities in Czechoslovakia were still considering the introduction of trolleybus transport, Pilsen began with the preparations in the second half of the 1930s. The chief representatives of the Electricity Enterprises, Ing. František Mlynařík and Ing. Rudolf Novák, relied on experience not only from Prague but even from abroad, especially from the U.S.A. In 1939, the construction of the infrastructure for two lines began in the city of Pilsen. At the same time, Škoda launched the development of three-axle trolleybuses.

Unrealized Variant of Škoda 553

The first design of the vehicle for Pilsen in October 1939 was based on the previous type Škoda 2 Tr but was intended to have a capacity of 80 passengers (30 seated) and two doors in the right side. It differed in the shape and in some dimensions of the body from the version produced later.

 

(p. 38) Side view of the unrealized version of the Škoda 553 trolleybus. A bigger overhang over the windscreen and a different layout of side window pillars are obvious. [62]

Technical Description

The total number of Škoda 3 Tr trolleybuses manufactured was 34 units in three series. They were the first Škoda trolleybuses originally produced in the right-hand drive version; other novelties were an air servo unit and a coupling for the connection of a trailer. The 3 Tr trolleybus was controlled by three pedals, which was a difference from their forerunners – the newly introduced pedal served as an emergency brake. The electrical equipment was based on the previous 2 Tr type. The trolleybus was driven by a pair of compound traction motors, and its output was regulated by the controller, contactors and resistors. The mechanical part of the 3 Tr1 and 3 Tr2 series was manufactured by the plant at Mladá Boleslav. The fitting of the electrical equipment and finishing took place in Pilsen. These ten vehicles had two doors for passengers.

 

(p. 38) A factory photo of the trolleybus Škoda 553 / 3 Tr1 reg. no. 101 at the test line in the first quarter of 1941. It was this vehicle that opened the operation in Pilsen on 9 April of the same year. [302]


After the war, the substantially enhanced third series that included 24 vehicles was made in 1947 and 1948 where the chassis, the bodywork and the electrical eqjuipment were all manufactured in the Pilsen factory. They differed from their forerunners in an altered shape of the body and in having three doors. At the same time, the 3 Tr3 series was the first model of Škoda’s trolleybus from which the designation according to the chassis of lorries (Škoda 553) was henceforth abandoned, and a new numerical designation of types and series specific to trolleybuses was adopted (which we have been using ever since with slight modifications, while the types previously manufactured for Prague and Pilsen were retrospectively designated according to the new system).

 

(p. 39) Bodywork mounting on the already finished chassis in the post war 3 Tr3 series. [302]

(p. 39) Driver’s post in the 3 Tr3 series. [302]

(p. 40) The post-war 3 Tr3 series had three doors, and the design of the front already resembled the two-axle types Škoda 6 Tr a 7 Tr manufactured later. [302]

(p. 40) A pair of traction motors driving, with the opposite ends, the auxiliary units: charging generator (left) and compressor (right). [302]

 

Škoda 553 / 3 Tr

Manufactured in the years

1941, 1943, 1947-1948

Run in the years

1941 - 1970

Number of units manufactured

34

Countries of operation

CS

Body

steel

Maximum output

90 (2x 45) kW

Transport capacity

80 persons

Maximum speed

50 km/h

Number of seats

30 (3 Tr1, 3 Tr2)

28 (3 Tr3)

Service weight

10 400 kg (3 Tr1, 3 Tr2)

10 500 kg (3 Tr3)

 

(p. 42) Škoda 553 / 3 Tr1 vehicles reg. no. 106 and 103 at the Městské Lázně (Public Baths) terminal, shortly after the beginning of operation in April 1941. The obligatory blackout of headlights recalls the wartime atmosphere. [358]

(p. 43) The interior of 3 Tr trolleybuses gave the impression of space and comfort. [302]

Service in the Streets of Pilsen

The first series of the two-door Škoda 553 trolleybuses (later 3 Tr1) began running from the Městské Lázně to Doubravka on 9 April 1941, and to the Ústřední Hřbitov (Central Cemetery) one month later. Pilsen thus became the second city in today’s Czech Republic where trolleybuses were in operation. The growth in the numbers of passengers, especially due to the war production in the Škoda Works (then part of the Reichswerke Herman Göring concern), required the delivery of four almost identical vehicles of the 3 Tr2 series in 1943. The third series of 1947 – 1948 served the three newly constructed lines in Pilsen that connected the quarters of Božkov, Skvrňany, Doudlevce, Bolevec, and Košutka. The two-door vehicles of the first two series were given a third door during general overhauls in the 1950s. The 3 Tr trolleybuses remained in operation for a very long time – the last ones of them until 1970.

Second Life of Vehicles nos. 101 and 119

The oldest vehicle no. 101, in pre-renovation condition, is currently preserved in the depository of the Technical Museum in Brno. The 3 Tr3 vehicle no. 119 passed through a well-done reconstruction into condition fit for display, though not for operation, in 2012 and is displayed at the Techmania Science Centre in Pilsen.

 

(p. 43) Vehicle no. 121 of the 3 Tr3 series finished in 1947. [302]

(p. 44) The 3 Tr3 trolleybus no. 121 was the showpiece of the Škoda Works stand at the Prague Motor Show 1947. [302]

(p. 45) The museum 3 Tr3 trolleybus no. 119 at the Techmania in Pilsen, in the company of the Škoda 52Em locomotive (ČSD’s series S699.1, partially visible at the right side of the photo). [308]

UNREALIZED TROLLEYBUS ŠKODA 4 TR

The project of the 4 Tr trolleybus of 1942 was expected to be an enhancement of the 3 Tr1 and 3 Tr2 series. The main change should have been a pair of more powerful traction motors with the output of 2x 60 kW, a compressor with its own motor and an independent dynamo (before, these machines were driven by opposite ends of the traction motor shafts). In the end, the modernization was carried out in another form as the 3 Tr3 series after the war.

 

(p. 45) Size sketch of the unrealized type Škoda 4 Tr. [62]

UNREALIZED TROLLEYBUS ŠKODA 5 TR

The considered type Škoda 5 Tr followed in the development of two-axle vehicles Škoda 538 A and the “middle type trolleybus” and reached the highest level of completion of all unrealized war models. It showed the direction of future development in the form of a unitary body with two axles and one motor. The first variant designed in 1943 should have been 9.1 m long, with two four-leaf doors for the passengers and five windows between them.

 

(p. 46) A model of the 5 Tr trolleybus made according to the first variant considered of 1943. [302]

(p. 46) Unfortunately, the elaborate wooden model has not been preserved. [302]


In 1945, the vehicle was designed in a changed form – the doors should have been two-leaf the 6 Tr type manufactured at the same time.

 

(p. 47) The sketch of the second variant of 5 Tr with longitudinal benches was prepared ainting of the second variant of 5 Tr and the scheme of a possible layout of seats. [62]


 

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