ER2 electric trainset is a DC electric multiple unit which was in production by the Railroad Machinery Plants of Riga (in consortium with the Electrical Machinery Plants of Riga and the Railroad Machinery Plants of Kalinin) from June 1962 to mid-1984. It was essentially an improvement of the ER1 design, featuring footboards for low platforms, and aprons for high platforms, as well as improved electrical equipment and minor changes to the bodywork (specifically, the engineer's cab, side walls, headstocks, and door mountings). Since the mid-1960s, the ER2 has been the most widely used type of suburban train in the Soviet Union and its successor states.
Previous Soviet electric multiple units Electric multiple units were first used in the Soviet Union in 1926 on the Baku-Sabuncu segment of the Baku mainline. These consisted of 2-car or 3-car sections, each of which had 1 power car and 1 or 2 trailer cars (a similar consist to that still used today). The motor cars used 1200 V DC current and had 4 75-kW motors for a total power output of 300 kW. These trainsets were retired in the 1940s.
In August 1929, a second electrified suburban line was opened, from Moscow to the northern suburb of Mytischi. This line operated the S-series electric multiple units (S standing for "Severnye Zheleznye Dorogi", or "Northern Railroad"). These consisted of standard 3-car sections, each section having 1 power car and 2 trailers. The power cars used 1500 V DC current and had a total power of 600 kW (up to 720 kW on later versions). The electrical equipment for these trains was manufactured by Metropolitan Vickers (later license-built by the Dynamo factory in Moscow), and the mechanical equipment was made by the Mytischi Railroad Machinery Plant. After World War II, the entire production was transferred to the Riga Railroad Machinery Plant, which continued producing these trainsets until 1958. The many versions of the S-series trains produced included 1500-V and 3000-V versions, dual-current versions and some versions fitted with dynamic brakes. All of these had one common design flaw: the traction motors were mounted directly on the axles to simplify manufacture, which in turn limited maximum speed to 85 km/h.
In 1954, the Riga Railroad Machinery Plant built several prototype 3-car electric multiple units designated SN ("Severnaya Novaya", or "Northern New"). These had their traction motors mounted on the truck frames, which allowed them to reach speeds of up to 130 km/h. The traction motors had a 1-hour rating of 200 kW. At that time, commuter railroads were expanding and widespread electrification was being implemented; the resulting increase in commuter traffic required much higher average speeds between stations. This, in turn, required greatly increased acceleration, which the underpowered S and SN multiple units could not provide. With this in mind, in 1957 the Riga Railroad Machinery Plant and the Dynamo Plant made a drastic redesign of the SN multiple units, producing 5 service prototypes of what would ultimately be known as the ER1 trainset. These were 10-car trains consisting of 5 2-car sections (each comprising 1 power car and 1 trailer), which were permanently coupled together. This greatly improved the power-to-weight ratio (hence improving acceleration) and simplified production; the disadvantage was that train length could no longer be adjusted for traffic conditions. These trains also had automatic sliding doors (as opposed to the manually operated doors on the S-series trains), lightweight car bodies (10% lighter than the S units), and coil-spring rather than leaf-spring suspension. They were used extensively on the suburban lines out of Moscow and St. Petersburg, where they significantly reduced travel times; however, their biggest shortcoming was that their entrance/exit doors were only designed to be compatible with high platforms, which precluded their use on other lines (most of which had stations with low platforms).
Development and production history As stated in the previous section, there were many busy suburban railroads in the Soviet Union which required a faster and more powerful replacement for the obsolete S units, but also one which was compatible with the low passenger platforms used on these lines (which the ER1 could not accommodate). Accordingly, it was decided to update the ER1 trainsets with exits which were compatible with both high and low platforms; the updated design was to be known as the ER2. The new exits required changes to the underframe, which could have had deleterious consequences for the cars' structural integrity; to avoid this, the cars' side walls, headstocks, door frames, and head-end bulkheads (on cars with engineers' cabs) had to be reinforced. Also, to maximize commonality of parts with the ER9 AC electric trainsets (which were to be produced concurrently with the ER2 on the same assembly lines), the brakes were redesigned—instead of 1 master cylinder actuating all of a given car's brake shoes, 4 brake cylinders were installed (2 per truck). The designers also took the opportunity to improve the electrical equipment: lead-acid storage batteries were replaced with safer alkaline storage batteries, and the motor-generator windings were redesigned. (Both of these improvements were already tested on selected ER1 trainsets.) The new trainset was given the factory designation 62–61.
In 1962, the Riga and Kalinin Railroad Machinery Plants finished the production run of the ER1 and immediately switched over to production of the ER2, producing 48 of them straight off the drawing board by the end of the year. As with the ER1, the ER2s were produced by a consortium of several different factories: the Riga Electric Machinery Plant manufactured the traction motors and other electrical equipment, the Kalinin Railroad Machinery plant built the car bodies and trucks for the trailer cars (including the driving trailers), and the Riga Railroad Machinery Plant built the car bodies and trucks for the power cars and performed the final assembly. From 1968 onward all car body manufacturing was transferred to the Riga Railroad Machinery Plant, the Kalinin plant only producing the trucks for the trailer cars.
In 1974, the engineer's cab was redesigned, its shape changing from round to rectangular. (This was done to increase commonality with later ER22 trainsets.)
The total production run for the ER2 numbered 850 complete trainsets; of these, 629 were built with 10 cars each, 134 with 12 cars, 75 with 8 cars, 7 with 6 cars and 5 with 4 cars each. Unlike the ER1, the cars in the ER2 trainsets were not permanently coupled, which allowed their length to be adjusted according to traffic levels. To facilitate this, from 1964 to 1970 and from 1981 to 1984 the Kalinin and Riga plants produced 133 separate driving trailers (to allow the splitting of trainsets into shorter sections); in 1967–68, the Riga plant produced 52 separate power cars to go with the driving trailers; from 1967 onward, 173 intermediate 2-car sections were produced (to lengthen trainsets as needed); from 1973 onward, 58 head-end 2-car sections (with an engineer's cab) were produced; and in 1980, 4 intermediate trailers were built. Production of the ER2 trainsets was ended in September 1984, the Riga Railroad Machinery Plant switching to production of the improved ER2R and ER2T trainsets (basically ER2s, but fitted with rheostatic braking).
Design
The ER2 is mostly similar to the earlier ER1; the most significant design changes were made to the passenger doors (which were now compatible with both high and low passenger platforms, unlike those of the ER1 which were only compatible with high platforms) and the electrical equipment (improved storage batteries and motor-generators). Also, braking equipment was redesigned: the number of braking cylinders was increased, the connecting levers simplified, and automatic adjusters which adjusted the travel of the brake piston rods were deleted.
General specifications The ER2 trainset consists of 2-car sections, each of which includes a power car and a trailer (either a driving trailer with an engineer's cab on one end, or an intermediate trailer without an engineer's cab). Sections with a driving trailer are called head sections; those with an intermediate trailer are called intermediate sections. The sections cannot operate independently; the minimum train length is 2 head sections, and the maximum is 6 sections (2 head sections and 4 intermediate sections), with a train 5 sections long (2 head and 3 intermediate) considered standard. Coupling more than 6 sections is unsafe due to overloading of motor-generators which power the engineer's controls. The cars are coupled together with the SA3 coupler, which is standard on Soviet rolling stock and allows vertical movement of up to 100 mm.
To maximize passenger accommodation, almost all electrical equipment is mounted either on the roof (pantograph) or under the car floors (starting resistors, compressors, etc.) All underfloor equipment is enclosed in cabinets with removable spring-latched access panels to protect it from blowing dust and snow. Some of the auxiliary equipment (including some high-voltage equipment such as the electric meter) is placed in cabinets inside car vestibules. Control equipment is concentrated in the engineer's cab. Numerous changes were made during the production run (see below), which caused variations in equipment layout.
Specifications (for a standard 10-car train): Overall length: 201.81 m Empty weight: 470-484 t Number of seats: up to 1050 Traction motor 1-hour rating: 4000 kW Tractive effort: up to 26,350 kilograms-force Maximum speed: 130 km/h () Acceleration up to : 0.6-0.7 m/s2 ()
Interior layout Most of the cars' interior space is taken up by the passenger salon. The majority of the floor space is occupied by bench seats, above which are mounted luggage shelves and coat hooks. The bench seats usually seat 6 passengers (3 facing front, 3 facing rear) and are placed on either side of a central aisle. The total number of seats was often varied during the production run; also, during overhauls some of the seats were often removed to increase the amount of standing room and thereby the total passenger capacity. Intermediate trailer and power cars typically have 107-110 seats, and driving trailers 77-88 seats; a 10-car train has up to 1050 seats in all and a total passenger capacity of up to 1600 people. The passenger salon is separated by sliding double doors from vestibules on either end of the car, which have pneumatically operated sliding double doors for entry and exit of passengers.
Lighting is provided by ceiling lamps with incandescent bulbs (nowadays usually replaced by fluorescent lighting or LEDs); the passenger salons of intermediate trailers and power cars normally have 20 ceiling lamps, those of driving trailers 16, and vestibules 2 each. These lamps are powered by the motor-generators (see below), so if this fails, all lights in the 2-car section go out; to prevent the section from being completely darkened, some of the ceiling lamps include an emergency light which consists of a low-powered incandescent bulb next to the main light, and draws its power from the storage battery.