FS Class E.636
| Company type | Electric locomotive |
|---|---|
| Industry | Railway transport |
| Founded | 1940 |
| Headquarters | Italy |
| Products | Locomotives |
The FS E.636 represents a series of Italian articulated electric locomotives introduced between the 1940s and 1960s and retired by 2006. This class ranks among the most numerous locomotives in Italy's history and was extensively utilized throughout its operational lifespan for a wide range of services, from freight hauling to long-distance passenger transport. Its debut marked the implementation of innovative design elements at the time, notably the articulated body structure coupled with a three-bogie arrangement.
History
The development of the E.636 aimed to address limitations encountered during the 1930s with the FS multi-purpose E.626 and high-speed E.326 locomotives, enhancing capacity to manage Italy’s growing railway traffic.
This model was pioneering in Italy for adopting a Bo-Bo-Bo wheel arrangement with a chassis split into two articulated sections connected via a central bogie. This configuration proved highly effective on Italy’s often winding railways and was later replicated in the FS E.645/646 and E.656 locomotive classes. The increased number of driving wheels improved adhesion on steep gradients prevalent across Italy’s rail network, reducing wheel slip risks. The locomotive’s weight was approximately 101 short tons (90 long tons; 92 t). Initially, it employed the same motors as the E.626; however, early use of the 3 kV catenary system revealed inadequacies, prompting upgrades including a hollow axle transmission system.
Two primary gear ratios were implemented: a shorter 21/65 ratio designed for steep routes or heavy freight trains (with an initial top speed of 95 km/h (59 mph), later increased to 110 km/h), and a longer 28/65 ratio suited for passenger operations reaching speeds up to 120 km/h (75 mph).
Production was divided into three batches:
- First series (units 001–108): built from 1940 to 1942
- Second series (units 109–243): constructed between 1952 and 1956
- Third series (units 244–469): manufactured from 1957 through 1962
The inaugural locomotive entered service in May 1940. Six units were lost during World War II; post-war reconstruction efforts supported by the Marshall Plan expanded the fleet to a total of 469 units, making it one of Italy’s largest locomotive classes. All units originally featured an Auburn color scheme, which was replaced during the 1990s by a white base with green striping—the XMPR livery—used on most trains.
By contemporary standards at the turn of the millennium, E.636 locomotives were considered outdated and lacked modern comfort features. Their cockpit design failed to meet updated safety regulations, as tragically demonstrated in a fatal accident at Sulmona in 1996 where the driver could not evacuate despite low speed impact. Consequently, approximately 200 units underwent rebuilding that included asbestos removal.
From the 1990s onward, these locomotives were predominantly assigned to freight duties except on some congested routes such as those in Sicily. A number of units were also leased to smaller regional rail operators. The entire class was fully retired by May 2006.
Technical specifications
The E.636 locomotives are characterized by their straightforward design. The majority of the primary control circuit's operations are managed by a series of relays and contactors. In the event of a malfunction, the engineer could promptly perform repairs to at least clear the track. Notably, during the final years of their operation, these locomotives were commonly used as training models for novice drivers due to their uncomplicated mechanical systems.
Electrical components and motor configuration
Similar to many older Italian locomotives, the E.636 is equipped with a rheostat consisting of 16 cast iron resistors connected in series, totaling 29 ohms of resistance. This rheostat must be progressively but swiftly bypassed during startup to regulate current flow to the six 32R-200 DC traction motors, arranged as two motors per bogie.
The traction motors can be wired in three distinct arrangements: series, series-parallel, and parallel. Each configuration delivers incrementally higher voltage levels to the motors, thereby increasing current flow.
Their wiring schemes are as follows:
| Configuration | Motor wiring | Voltage per motor |
|---|---|---|
| Series | All six motors connected in series | 500 V |
| Series-Parallel | Two groups of three motors each | 1000 V |
| Parallel | Three groups of two motors each | 1500 V |
The rheostat is connected in series with the traction motors because DC motors inherently draw a current inversely proportional to their rotational speed; at higher speeds, the current demand decreases. At startup, without additional resistance, the current would surge since only the low resistance of the motors and internal wiring would limit it—effectively resembling a short circuit. The rheostat increases total circuit resistance during initial acceleration, reducing current and enabling a smoother launch.
For series-parallel and parallel configurations, the rheostat is split into three parallel branches, which lowers the equivalent resistance to approximately 3.5 ohms. In contrast, during series wiring, all resistors remain in series.
Like nearly all Italian locomotives with rheostatic regulation since the E.626 model, traction control is operated via a lever (commonly called the maniglione) mounted on a support known as roncola. This support features multiple notches representing sections of the rheostat, along with three "end combination" notches and two "transition" positions (larger detents between notches).
To accelerate, the driver gradually turns the lever counterclockwise notch by notch. This action closes successive rheostat contactors that bypass resistors, reducing total resistance and increasing motor current. As speed builds and back electromotive force rises, current naturally decreases until the rheostat is fully excluded—typically when in traction and positioned on an "end combination" notch—allowing continuous power delivery within operational limits.
Upon reaching an end combination notch, the operator can engage a single shunt for that configuration or shift to the next motor arrangement. This reintroduces the rheostat, which must again be excluded progressively until reaching the final parallel combination notch.
Shunts increase motor current by bypassing certain motor windings via contactors connected in parallel; this reduces magnetic flux and thus raises current (since these two factors are inversely related). The number of shunt levels varies by locomotive model but generally there is one per configuration. It is critical to remove shunts before transitioning between configurations to prevent electrical arcing caused by excessive currents.
Unlike some E.626 units, E.636 models do not incorporate a "CEM" motor combiner (Combinatore Escluditore Motori), which mechanically adjusts motor connections during transitions through rotating contactors.
Instead, transitions on the E.636 rely on more sensitive windings requiring very slow and careful changes—especially when shifting backward between configurations. The ideal moment to move from one combination's notch to another is when the motor ammeter reads zero amps; this occurs at the transition position on the lever when contactors are optimally aligned. The driver should pause briefly at this point while monitoring the ammeter to avoid damaging electrical arcs caused by premature switching.
Monitoring current within the traction circuit is essential during rheostat exclusion phases. If exclusion occurs too rapidly, wheel slip may happen; applying sanders and reducing throttle can mitigate this risk. Additionally, exceeding maximum allowable current triggers protective relays which open circuits.
Current protection is provided by multiple types of relays:
- A general maximum current relay ("RMx");
- Three relays monitoring individual motor branches ("RMx 1-2," "RMx 3-4," "RMx 5-6");
- A maximum current relay for REC (Riscaldamento Elettrico Carrozze, powering electrical heating in 3000 V passenger cars) labeled "RMx REC".
Activation of any relay results in opening the main circuit breaker, disconnecting power from the overhead line.
Prior to the 1970s, these relays had maximum permissible currents as follows:
| Relay | Maximum Allowed Current |
|---|---|
| RMx | 1050 A |
| RMx 1–2 | 450 A |
| RMx 3–4 | 350 A |
| RMx REC | 500 A |
During the decade spanning 1970 to 1980, these limits were revised:
| Relay | Maximum Allowed Current |
|---|---|
| RMx | 1200 A |
| RMx 1–2 | 450 A |
| RMx 3–4 | 400 A |
| RMx REC | 500 A |
As observed, maximum currents permitted in series remain at 450 A across both periods; for series-parallel and parallel arrangements they increased from 350 A to 400 A and remained at 450 A respectively.
Each configuration allows one level of field shunt (field weakening) corresponding to approximately 31%. However, certain units were fitted with 92-250 type motors (used on FS Class E.424) and later with 32RT-200 motors permitting up to five field shunt levels (field weakening percentages of roughly 65% and 45%, respectively). These specialized units were eventually standardized back to match typical configurations.
Motion transmission
Locomotives numbered from 001 to 243 were equipped with Negri-style transmissions, except for units 195-198 and 176-183. The former group utilized rubber buffers instead of coil springs combined with a double hollow axle transmission, while the latter featured rubber buffers as well.
Subsequent units built after these adopted a transmission similar to that found on units 176-183, albeit with minor variations.
Various locomotives were fitted with different gear ratios (refer to "Special Units" for further information):
| Gear ratio | Maximum speed | Remarks |
|---|---|---|
| 21/65 | 110 km/h (68 mph) | Initially set at 95 km/h (59 mph), then raised to 105 km/h (65 mph) shortly after, and finally increased to 110 km/h (68 mph) in 1982 |
| 28/65 | 120 km/h (75 mph) | Phased out in 1991 |
| 20/65 | 120 km/h (75 mph) | Exclusive to units 044 and 089 |
| 24/74 | 105 km/h (65 mph) | Applied only on units 271-275 |
Auxiliary and pneumatic services
Up to unit 201, motor cooling fans were powered by two dedicated 4.5 kW, 3,000 V motors; later models switched to 1 kW motors identical to those installed on the FS Class E646. These motors also function as dynamos for recharging the 24 V batteries (activated only if the line voltage exceeds 1,500 V), which supply power to low-voltage equipment such as lighting, heating systems, and contactors.
Air supply on the locomotive was maintained by two C38-type compressors initially; these were later upgraded to the more dependable W242 models. In some cases, only one compressor was replaced, resulting in locomotives with one of each compressor type. The C38 compressors operated until the main reservoir tanks reached approximately 8 bar (800 kPa; 120 psi), while the W242 models functioned between 8 to 9 bar (800 to 900 kPa; 120 to 130 psi). Under normal conditions, only the W242 compressor was in use; the older C38 unit engaged only if pressure dropped below 7 bar (700 kPa; 100 psi).
The main air reservoirs and 24 V battery system provide essential air pressure and electrical current for several components:
- Braking system: utilizes air from the main reservoirs and typically maintains a pressure near 5 bar (500 kPa; 73 psi) when brakes are not applied.
- Main breaker (interruttore rapido, IR): serves as the high-voltage switch connecting the locomotive to the 3 kV overhead line; it can be closed only when air pressure exceeds 5 bar (500 kPa; 73 psi).
- Contactors: extensively used in Italian electro-mechanical locomotives including the E.636, these devices control various functions such as engaging or disengaging rheostat resistors. They operate only under pressures above 5 bar (500 kPa; 73 psi) and require the IR to be closed.
- Horn and whistle (Tromba and Fischio): Each cab is equipped with one horn and one whistle. Horns are activated via a solenoid valve and function only when batteries are connected and pressure is above 5 bar (500 kPa; 73 psi). Whistles can reach their full frequency at approximately 4 bar (400 kPa; 58 psi).
- Sand throwers (Sabbiere): Designed to enhance traction by dispersing sand onto rails, these are manually operated by the driver during wheel slip events and require about 5 bar (500 kPa; 73 psi) pressure.
- Flange oilers (Ungibordo): Introduced in the 1970s to preserve wheel flanges, this DeLimon system sprays oil into the gap between flange and wheel surface of front wheels at regular intervals using compressed air.
- First pantograph-raise compressor (Compressore di primo alzamento): A small compressor powered by the 24 V battery supply used during initial startup when main air tanks are empty; it generates sufficient air pressure to raise the pantograph for the first time.
Originally, locomotives featured a seven-position L-type Westinghouse brake controller paired with a wheel-type brake lever. These were subsequently replaced by more widely adopted Oerlikon FV4 controllers and RA-M2 brake levers respectively.
Braking systems
The locomotive is equipped with three different braking mechanisms:
- Hand brake: operated manually via two wheels located in each cab, one controlling each bogie, which apply the brake shoes onto the wheels; this system brakes four of the six axles in total.
- Locomotive air brakes (Freno Diretto or Moderabile): these brakes draw air directly from the main reservoir tanks, bypassing the brake pipe to pressurize the locomotive’s brake cylinders, thereby slowing only the locomotive itself. This method responds slightly faster than the continuous brake but is not recommended for braking a fully loaded train with wagon brakes, as it can induce a "spring effect".
- Continuous, automatic air brake: designed to slow down the entire train.
This system is classified as a negative-type brake; it is termed continuous because it extends throughout the complete train and automatic since it triggers emergency braking if the continuity of the brake pipe is interrupted (e.g., in case of a general pipe rupture).
On locomotives fitted with Breda-type valves and Oerlikon levers, braking force can be modulated both during application and release. The system operates based on the following components:
- Two reservoirs known as the "auxiliary reservoir" (serbatoio ausiliario) and "command reservoir" (serbatoio di comando).
- One or two pipes running along the train: the "main pipe" (condotta principale, typically present only on passenger stock and absent on some E636 units; freight cars generally lack this) and the "general pipe" (condotta generale, which serves as the actual brake pipe).
- A control valve (the brake controller used to adjust braking intensity).
- A specialized component called "distributore", consisting of two chambers separated by a movable piston—one chamber maintains pressure from the general pipe (variable), while the other holds pressure from the command reservoir (fixed at approximately 5 bar (500 kPa; 73 psi), though this may vary if brakes are overloaded).
- Brake cylinders.
- Brake rigging.
When brakes are disengaged, pressure in the brake pipe is around 5 bar (500 kPa; 73 psi), while pressure in the brake cylinders is near zero.
To apply brakes, the driver manipulates the controller to create a vacuum in a specific reservoir called "bariletto". This vacuum, transmitted through a series of coils, causes a gradual reduction in pressure within the general pipe to match that of the bariletto. The time required for this pressure drop depends on train length—the longer the train, the slower this process occurs. Within the distributore, because command reservoir pressure exceeds the lowered pipe pressure, its piston shifts, establishing a connection between auxiliary reservoirs (supplied by main tanks) and brake cylinders. This action allows air to flow into the cylinders proportional to how much pressure has decreased. On E636 locomotives, maximum cylinder pressure reaches about 3.8 bar (380 kPa; 55 psi), corresponding to a general pipe pressure near 3.5 bar (350 kPa; 51 psi).
During emergency braking, the brake pipe is vented directly to atmosphere, causing a rapid pressure drop that results in swift braking application. Note that this procedure affects only braking speed, not braking force magnitude.
To release brakes, raising pressure in the bariletto via controller action causes air from main reservoirs—and from main pipe if available—to restore general pipe pressure to that level. Inside the distributore, when pipe pressure surpasses command reservoir pressure, it alters or disconnects linkage between auxiliary reservoirs and brake cylinders. Consequently, cylinders expel air until their internal pressure aligns proportionally with any remaining depression. When general pipe pressure returns to approximately 5 bar (500 kPa; 73 psi), cylinder pressure falls to zero.
For quicker brake release, an "overload" function temporarily increases system pressure beyond normal levels proportional to previous depression—up to a maximum of 7.2 bar (720 kPa; 104 psi)—before gradually reducing back to about 5.5 bar (550 kPa; 80 psi) and finally stabilizing at 5 bar (500 kPa; 73 psi) over roughly 240 seconds.
Locomotives equipped with Triple Valves (Distributore tipo Westinghouse) and 7-position levers employ a slightly different braking circuit. Although their distributore also has two chambers as described earlier, they lack a command reservoir tank; instead, when brake pipe pressure decreases, it is directly balanced against auxiliary reservoir pressure that moves the central piston. In this setup, releasing brakes is not gradual: switching controller to "release" fully disengages brakes immediately. However, if reapplication occurs too soon afterward, there is risk of reduced braking capacity due to insufficient air availability for effective re-braking—since no fixed command reservoir pressure ensures adequate air supply for safe release and reapplication. Excessive depletion of auxiliary reservoirs can even prevent stopping altogether. This risk is mitigated on units with Breda or similar valves by preventing full release unless sufficient air remains in main reservoirs for subsequent braking.
The "overload" function carries inherent risks as well. Within the distributore, pressures in both chambers balance each other; during overload both command reservoir and brake pipe pressures rise proportionally. Although these pressures normally return gradually to 5 bar (500 kPa; 73 psi), occasionally command reservoir pressure may become stuck at elevated levels while pipe pressure drops lower. This imbalance maintains connection between auxiliary reservoirs and brake cylinders, keeping brakes engaged unintentionally. To resolve this condition, operators may perform another overload cycle to rebalance pressures or manually reset command reservoir by emptying it via an external lever.
This issue is more pronounced in units with seven-position levers, where direct connection between main tanks and brake pipe during overload can cause pressures to rise significantly—potentially reaching up to 9 bar (900 kPa; 130 psi) if controller remains too long in overload position. Under such circumstances brakes often remain applied until manual emptying of command reservoirs is performed as described above.
Mechanical alterations
The locomotive consists of two semi-car bodies that pivot atop the central bogie. Positioned between these halves is a bellows, initially crafted from rubber, which was replaced in the 1950s by a waterproof membrane. More recently, this was substituted with a flexible plastic material.
Post-war models incorporated 7 mm reinforcement structures on both the chassis and beneath the cabs, addressing mechanical vulnerabilities identified in the first 108 units. In the mid-1980s, reinforcement efforts were limited to the chassis on pre-war units; however, units 026 and 065 did not undergo these upgrades.
To diminish unwanted oscillations, dampers were installed between the car bodies: glycerine-based dampers were fitted on units 1-276, while special oil-type dampers were introduced starting with unit 277. These dampers were removed altogether in 1977 after being deemed ineffective.
The initial 108 locomotives featured distinct rheostat ventilation shafts on their roofs compared to subsequent units; these were eventually replaced by the more efficient shafts found on later models.
Additionally, early units utilized sliding oil-buckles, whereas later versions were equipped with rolling bearing types.
Units numbered 162 through 171 were outfitted with French-inspired Athermos buckles for experimental purposes, which were subsequently removed.
Sand throwers were originally installed internally within the bogies of units 001 to 108; post-war models and later units came with externally mounted sand throwers as standard.
Safety apparatus
The first 108 locomotives were originally equipped with a vigilance pedal—a type of dead man's switch—developed by FS engineer Minucciani. This device required drivers to periodically acknowledge their presence while the train was in motion; failure to do so would trigger an emergency brake. However, this system was discontinued after World War II due to pressure from labor unions. Beginning in the 1970s, many (though not all) locomotives received upgrades including the "Ripetizione Segnali a 4 codici" system, Hasler speedometers, and an enhanced "speed graph recorder" (Zona tachigrafica) capable of logging signals from the RS system.
Unique and experimental locomotives
- E.636.385 participated in the "PV Train" initiative and was fitted with photovoltaic panels that recharged its 24 V batteries. Due to this feature, it is now part of Italy's collection of historic railway vehicles.
- E.636.082 served as a testbed in 1965 for rheostatic braking technology later adopted on FS Class E.444. It featured an additional smaller lever atop the traction control lever for managing the braking rheostat and was equipped with larger ventilation openings on its sides. Currently, many internal components have been removed, rendering it non-operational.
- Perhaps the most renowned unit is E.636.284. After sustaining damage to its driving cabin in an accident, FS chose to restore it and trial a new type of cab design similar to that used on FS Class E.656. The locomotive acquired the nickname "Camilla," allegedly derived from a worker's girlfriend's name inscribed near one of its couplers during refurbishment. This unit is also recognized as historically significant.
- In 1951, units 044 and 089 were upgraded with type 92-250 motors from FS Class E.424, and their gear ratios were altered to 20/65, allowing a top speed of 120 km/h (75 mph) and a maximum power output of 2,490 kW (3,340 hp) (compared to 2,100 kW (2,800 hp) originally). This modification yielded performance comparable to FS Class E.428 (gear ratio 31/101), but with reduced weight and power consumption; nevertheless, these locomotives were eventually reverted to their initial configuration.
- Units numbered 271 through 275 were constructed with alternative bogies resembling those used on FS Class E.646 prototypes, equipped with 32RT-200 motors, five shunt levels, and a gear ratio of 24/74 permitting a maximum speed of 105 km/h (65 mph). These units were later standardized to match the rest of the fleet.
During the 1960s and 1970s, Ansaldo-Breda developed a locomotive inspired by the E.636 design for Yugoslavian railways, classified as JŽ 362.
See also
References
- Instructions on the Operation of the Automatic Continuous Brake
- Cornolò, Giovanni. Locomotive Elettriche. 1994.
- Portions of this content have been adapted from the corresponding article on the Italian Wikipedia.
- Pages with script errors
- Articles with short description
- Pages with broken file links
- Articles containing Italian-language text
- Commons category link is locally defined
- 3000 V DC locomotives
- Ferrovie dello Stato Italiane electric locomotives
- Bo-Bo-Bo locomotives
- Railway locomotives introduced in 1940
- Gio. Ansaldo & C. locomotives
- Breda locomotives
- Reggiane locomotives
- TIBB locomotives
- Standard-gauge locomotives of Italy