Trolleybus Škoda 9Tr: a legend of Czech electric transport

Trolleybus Škoda 9Tr is one of the most recognizable models of urban electric transport, produced by a Czech manufacturer in the mid-20th century. This trolleybus became a symbol of the era, serving routes in dozens of cities in the USSR and Eastern Europe. Despite the fact that production ended in 1982, many examples continue to be used today, and some have even become museum exhibits.

In this article we will look at technical specifications, design features and practical aspects of operation Škoda 9Tr. You will learn how the electrical circuit works, which components require special attention during maintenance, and why this trolleybus is still valued by specialists. The material will be useful both to owners of retro equipment and to those interested in the history of public transport.

History of creation and distribution of Škoda 9Tr

Trolleybus development Škoda 9Tr began in the 1950s as a response to the growing need for reliable and cost-effective urban transport. Czech plant Škoda (now part of the concern Volkswagen Group) collaborated with the enterprise Tatrato create a machine that combines simplicity of design and high maintainability. Serial production started in 1961 and continued for more than 20 years.

The main markets were countries Council for Mutual Economic Assistance (CMEA), including the USSR, East Germany, Poland and Hungary. Only in the Soviet Union was it supplied from above 11,000 copies - a record figure for foreign technology of that time. The trolleybus was operated in Moscow, Kyiv, Minsk, Riga and other cities where climatic conditions imposed stringent requirements for reliability.

• 📅 Years of production: 1961–1982
• 🏭 Manufacturer: Škoda Ostrov nad Ohří (Czechoslovakia)
• 🌍 Importing countries: USSR, GDR, Poland, Romania, Yugoslavia
• 🚍 Total circulation: more than 14,000 units

I wonder what Škoda 9Tr became the first trolleybus in the USSR equipped thyristor-pulse control system (TISU) - an innovation for that time. This made it possible to reduce energy consumption and improve ride smoothness, which was critical for congested city routes.

Technical characteristics and device

Construction Škoda 9Tr based on a truck chassis Tatra T3, which ensured high frame strength. The body was made of steel sheets with a wooden frame (in early versions) or completely metal (in later versions). The length of the trolleybus was 11,400 mm, width - 2,500 mm, height - 3 350 mm.

Electrical equipment included:

• ⚡ Traction motor: Škoda ALm 4846e 86 kW (117 hp)
• 🔋 Control system: rheostat-contactor or thyristor-pulse (TISU)
• 🔌 Supply voltage: 550–600 VDC
• 🛠️ Brake system: electrodynamic + pneumatic

Parameter	Meaning
Maximum speed	65 km/h
Capacity (seating/standing)	25 / 75
Weight (empty)	10,300 kg
Turning radius	11.2 m
Service life (according to passport)	15–20 years

A feature of the model was modular layout of electrical equipment, which simplified repairs. For example, resistor blocks and contactors were located in separate compartments under the cabin floor, and access to them was through hatches. This made it possible to quickly replace faulty components without completely disassembling the trolleybus.

⚠️ Attention: In earlier versions Škoda 9Tr were used asbestos brake pads, which are now banned due to carcinogenicity. When restoring retro trolleybuses, they must be replaced with modern analogues.

Operation and typical malfunctions

Despite the simplicity of the design, Škoda 9Tr required regular maintenance, especially in harsh climates. The most vulnerable nodes were:

1. Electrical insulation — over time, wires and cables lost their dielectric properties, which led to short circuits. The TISU control circuits especially suffered.
2. Pneumatic system — Air leaks from brake circuits and compressors were common due to wear of rubber seals.
3. Suspension — leaf springs and shock absorbers required replacement every 3–5 years due to high loads.

One of the most labor-intensive operations was traction motor repair. Due to the lack of spare parts, owners had to rebuild the stator and rotor windings manually or adapt parts from other models. For example, in some depots they used engines from trolleybuses ZiU-5 after modification of the fastenings.

Check the pressure in the pneumatic system (at least 6.5 atm)

Inspect the rods for cracks and corrosion

Test the operation of the TISU (smooth acceleration/braking)

Make sure lighting and alarms are working properly

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Another "disease" Škoda 9Tr was slip ring wear on the traction motor. Signs of a problem included sparking under the hood and loss of power. For prevention, it was recommended to clean the rings from carbon deposits every 10,000 km using special brushes.

How to determine wear of slip rings?

Upon visual inspection, deep grooves or uneven wear (more than 1 mm) are visible on the rings. The problem is also indicated by a characteristic burning smell in the engine compartment and increased noise when the engine is running. In advanced cases, the windings may short-circuit, which leads to complete failure of the traction system.

Modifications and features of different versions

Over the years of production Škoda 9Tr underwent several modernizations, the most significant of which were:

• 🔧 Škoda 9TrHT - version with hydrostatic power steering, which made it easier to control on sharp turns.
• ⚡ Škoda 9TrE — experimental model with electronic control system (prototype for future trolleybuses Škoda 14Tr).
• 🚌 Škoda 9TrH - option for mountain routes with reinforced brakes and lower gears.

The version deserves special attention Škoda 9Tr for USSR, which had a number of adaptations:

• Reinforced thermal insulation of the interior for operation at −40°C.
• Wide doors (1,300 mm instead of standard 1,100 mm) for faster boarding of passengers.
• Additional heaters in the cabin, operating from the on-board 24 V network.

In the 1970s, some trolleybuses were converted into service or cargo options. For example, in Kyiv at the base 9Tr created mobile workshops for repairing contact networks, and in Prague - mobile laboratories for diagnosing electrical equipment.

Current state: where else are Škoda 9Tr driven?

By 2026, the majority Škoda 9Tr withdrawn from regular operation, but several dozen copies continue to work in:

• 🇷🇴 Romania: cities of Pitesti and Brasov (modernized versions with new batteries).
• 🇷🇸 Serbia: Belgrade (used as backup transport).
• 🇺🇦 Ukraine: Lviv and Vinnitsa (mainly on tourist routes).
• 🇨🇿 Czech Republic: Prague and Ostrava (museum and retro flights).

In Russia, several trolleybuses are preserved as monuments:

• B Moscow Museum of Urban Transport (1965 copy).
• B St. Petersburg Museum of Electric Transport (restored version with TISU).
• B Yekaterinburg - as an art object on the territory of the depot.

Owners of retro equipment often face a problem search for spare parts. The solution becomes:

• 3D printing of plastic parts (handles, instrument panels).
• Adaptation of units from other Czech trolleybuses (for example, Škoda 14Tr).
• Independent production of metal parts according to drawings.

Repair and modernization: expert advice

If you are the lucky owner Škoda 9Tr, a checklist of key works will help you get it into working order:

Replace all rubber hoses of the pneumatic system (service life - 10 years)

Check the insulation of high-voltage cables with a megohmmeter

Clean the engine slip rings from carbon deposits

Lubricate the wheel bearings (litol or graphite grease)

Adjust gaps in TISU contactors

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One of the most difficult tasks is replacing traction motor windings. In workshops in the Czech Republic, original templates are used for this, but in their absence, you can use universal methods:

1. Remove the old winding without damaging the core.
2. Measure the cross-section and length of the wire (usually copper with a diameter of 1.2–1.5 mm).
3. Wind a new winding on the machine, observing the number of turns (data is in the technical documentation).
4. Impregnate the winding with epoxy varnish to protect it from moisture.

To improve performance, enthusiasts often install:

• 🔋 Lithium-ion batteries instead of lead-acid (increases the power reserve in autonomous mode).
• 💡 LED lighting interior (reduces the load on the on-board network).
• 📱 GPS monitoring systems for retro flights (popular in tourism projects).

⚠️ Attention: When upgrading electrical equipment Škoda 9Tr be sure to coordinate the changes with technical supervision authorities. For example, replacing rheostatic control with transistor control requires re-registration of the vehicle as “modified”.

Where to buy and how much does the Škoda 9Tr cost today?

Price for Škoda 9Tr varies depending on condition and configuration:

• 🚗 Not running (spare parts donor): 50,000–150,000 rubles.
• 🔧 Needs repair: 300,000–800,000 rubles.
• ✅ In working condition: 1,000,000–3,000,000 rubles.
• 🏆 Museum copy (restored): 5,000,000+ rubles.

Where to look:

• 🇷🇺 Russia: Avito, Drom (section "special equipment"), VK groups on retro transport.
• 🇨🇿 Czech Republic: Sbazar.cz, Bazoš.cz.
• 🇺🇦 Ukraine: RIA.com, trolleybus depot forums.

Before purchasing be sure to:

1. Check availability technical passport (registration is impossible without it).
2. Assess the condition frames and bodies - rust on the side members can make restoration unprofitable.
3. Check if it is saved original electrical diagram (many trolleybuses were converted to local standards).

FAQ: Frequently asked questions about the Škoda 9Tr

Is it possible to convert the Škoda 9Tr into an autonomous electric bus?

Technically yes, but it will require serious modifications:

1. Installation of lithium-ion batteries with a capacity of at least 200 kWh (for example, from electric cars Nissan Leaf).
2. Replacing the traction motor with a modern asynchronous one (for example, Siemens 1PB2).
3. Modernization of the control system with the introduction of a controller based Curtis or Zapi.

The cost of such an upgrade will be 3–5 million rubles. Ready-made solutions are offered by Czech companies, for example, Cegelec.

What kind of oil should I put in the Škoda 9Tr gearbox?

For rear axle gearbox Škoda 9Tr recommended gear oil class GL-5 with viscosity SAE 85W-90 or SAE 80W-140 (depending on climate). Popular brands:

• Castrol Syntrax Universal Plus
• Liqui Moly Hochleistungs-Getriebeoil
• Mobil Mobilube HD

Refill volume is 12 liters. Replacement should be carried out every 50,000 km or every 3 years.

How to distinguish an early version of 9Tr from a later one?

Main external and technical differences:

Sign	Early versions (1961–1970)	Later versions (1971–1982)
Headlights	Round, separate (near/far)	Rectangular block headlights
Windshield	Divided into two parts	One-piece, panoramic
Control system	Rheostat-contactor	TISU (thyristor-pulse)
Doors	Narrow (1,100 mm)	Wide (1,300 mm for the USSR)

Can the Škoda 9Tr be used in commercial transport today?

In most countries no, since the trolleybus does not meet modern safety and environmental standards. However there are exceptions:

• 🇷🇴 In Romania 9Tr are still approved for use on secondary routes, subject to annual inspection.
• 🇷🇸 In Serbia, trolleybuses are used as backup transport during rush hours.
• 🇨🇿 Allowed in the Czech Republic tourist flights by special permission.

For legal operation in Russia you will need:

1. Get vehicle type approval at NIIAT.
2. Install GLONASS system and tachograph.
3. Pass electrical equipment certification (according to GOST R 50597).

The cost of legalization may exceed the price of the trolleybus itself.

Which trolleybuses replaced the Škoda 9Tr?

Successors Škoda 9Tr steel:

• Škoda 14Tr (1982–2004) - articulated trolleybus with TISU-2.
• Škoda 15Tr (1988–2004) - single model with improved insulation.
• Škoda 21Tr (1995–2004) - low-floor version for Europe.

In the USSR, trolleybuses became a replacement ZiU-9 (1972–2014), which inherited many technical solutions from the Czech model, including TISU.