THE LEGENDARY SWISS CROCODILE
Second generation SBB Crocodile 13 307, Be 6/8III near Vierwaldstätter See in 1964. Photo by Martin Klinger
When the Swiss Federal Railways or Schweizerischen Bundesbahnen (SBB) initiated electric operations on its rail link between Chiasso and Lucerne via the St. Gotthard Tunnel in 1922, it needed a new, heavy freight locomotive to negotiate very steep grades and countless sharp curves.
The decision to electrify the St. Gotthard route of the SBB was made in 1914. In 1917, the SBB requested that Schweizer Lokomotiven und Maschinenbau Winterthur (SLM) and Brown Boveri Co. (BBC) design a heavy freight locomotive suitable for the St. Gotthard route. Once the four prototype locomotives were built and evaluated, a contract for series production of the winner would be issued. The specifications were very broad and the competitors had a great deal of freedom to arrive at a suitable design.
To meet these requirements, the SBB requested proposals for a locomotive that would be capable developing a tractive effort of 32,400 lb (14,700 kg) at 25 mph (41 km/h) and have a top speed of 40 mph (65 km/h). The new locomotive was also to make use of side rod coupling of its drivers such as was steam locomotive practice. The sharp curves on the Gotthard route imposed a limit of five rigidly mounted driven axles and thus the planned use of six rigidly mounted axles for the new electric locomotive was ruled out. In addition, the planned axle loading had to be considered.
Ce 6/8I or the Köfferli Lok
It took considerably longer to build the four prototype locomotives than originally planned. In addition, the six-axle heavy freight locomotive Fc 6/8 (14 201) (More on the designation Fc will be found at the end of this article) was far too heavy and needed to be fitted with single-axle leading and trailing trucks. When electrification had proceeded to the point where series production locomotive had to be ordered, the four prototypes were not ready yet.
For series production, SLM and Maschinenfabrik Oerlikon (MFO) proposed a 1’C-C1’ locomotive with uniquely long "snouts" and a relatively short center section. None of the prototypes used such a design. The SBB was convinced that the SLM/MFO design was the right one and thus was born the Crocodile, as we know it and the only true Crocodile.
The BBC prototype, Fc 6/8, was redesignated Ce 6/8I in 1919. This engine, the only one of its kind, was nicknamed Köfferli-Lok or "suitcase" locomotive because of its short trunk-like front and rear extensions. Delivered in 1920, the brown locomotive bore the road number 14 201. It was integrated into the SBB inventory and served alongside the Crocodiles – Ce 6/8II and Ce 6/8III. The Köfferli Lok remained in service until 1968 when it was retired but went on serving for many railfan trips. In 1982, the machine was honorably retired to the Transportation Museum in Luzerne.
Ce 6/8II – the first generation
First generation SBB Crocodile 14253. Initially all of these machines were painted brown. Taken from SBB postcard No. 343.
Thus, even before evaluations of this prototype were completed, the successor Ce 6/8II was placed into production. The SBB selected Maschinenfabrik Oerlikon (MFO) to build the electrical systems and the mechanical components were furnished by Schweizerischen Lokomotive und Machinenfabrik (SLM) in Winterthur. Ten engines were ordered.
The road numbers assigned to these ten engines cause some confusion because the first three were numbered 12 251 to 12 253. The other seven were numbered 14 254 to 14 260. To better understand this inconsistency, go the end of this article and refer to "Swiss Locomotive Designation System."
The new locomotive was quickly named "Krokodil", the German word for crocodile. No doubt it earned its new name based on its distinctive long, flat motor housings, double articulation and brown or green livery. The first three Ce 6/8IIs started life not on the steep grades of the Gotthard but rather on the flat stretch between Bern – Thun – Spiez before being delivered to the Erstfeld depot.
The demands placed on the new locomotive were considerable but the distinctive machine was up to the task. The 2.6% grade of the Gotthard had to be done at 22 mph (35 km/h) hauling a 450 ton train (15 to 25 two-axle freight cars). A 300-ton train, up the same grade, had to be at 31 mph (50 km/h). On level track the requirement was for a 1,620 ton train to be moved at 37 mph (60 km/h). But, that wasn’t all. On a 1% grade, 1,200 ton trains had to do 22 mph (35 km/h). There was sufficient power in the Ce 6/8II Crocodile to exceed these required performance levels by 25 percent for 15 minutes. By 1922 the SBB took delivery of 33 of the new locomotives. These were numbered 14 251 to 14 283.
Ce 6/8III – the second generation
Starting in 1925 and continuing into the following year an additional 18 were ordered; their numbers were 14 301 to 14 318 and were considered second generation machines. Their designation was Ce 6/8III. They were also built by MFO and SLM. A side-by-side comparison with the first generation Crocodiles shows the obvious difference in the powering of the drivers.
The new machines had to haul 2,000-ton trains at 37 mph (60 km/h) on level track and 1,350-tons on a 1% grade at 21.7 mph (35 km/h) and finally 520 tons on 2.6% grade also at 21.7 mph (35 km/h).
Mechanical and Electrical Systems
The SBB Crocodile consists of three major subassemblies – the center section which features two engine driver stations, the massive high voltage transformer, the two pantographs, switchgear and associated electrical equipment and the two "snouts", each of which two substantial electric motors and associated power transmission gear.
All Crocodiles came into this world in brown livery. However, nobody is certain as to why some of them were repainted in green. One thought on the subject is that after World War 2 passenger traffic grew to such an extent that even the Crocodile was pressed into passenger service, certainly in those regions with steep grades. As already noted, 51 Crocodile were built but no two were the same. Modifications were constant and while the differences might have been small, they were there even if not always visible. Still, they all did share much. Here’s what they had in common.
To enable easy negotiating of the Gotthard’s tight radii, the individual "snouts" of the machine are hinged to the center section. Despite their length of 63.8 and 65.8 ft (19.46 and 20.06 m), respectively, the machines easily negotiated the 492 ft (150 m) radii curves. The two motors in each "snout" provide power to a single jackshaft. At this point the first and second generation Crocodiles differ markedly.
In the first generation machine, the jackshaft drives a connecting rod the other end of which is pivoted on a second non-powered auxiliary jackshaft. The first driven axle, the one closest to the powered jackshaft, then transmits power to the other two driven axles by means of a single straight connecting rod.
In the second generation engines, the output of the powered jackshaft is coupled to the third driven axle by a straight connecting rod. That driven axle has a second connecting rod that couples the three driven axles together. This eliminates the second non-powered jackshaft of the first generation Crocodile.
The author of "Märklin Krokodil," H.S. Stammer writes that the Crocodile was rather loose-jointed. The connecting rods could be moved by placing your foot against them. The hinged "snouts" also had considerable play at the pivot points. All of this looseness, which, by the way, required fastidious and frequent lubrication of the plain bearing (no roller bearings here!), contributed markedly to the unique noises Crocodiles of both generations made when underway.
European Train Enthusiasts member Jacque Vuye spent many year in Switzerland and has fond memories of the Crocodile and writes, "Ahh, the Crocodile! So many memories! And to me nothing sounded better than the rhythmic "yuumm-yuumm-yumm" of a Crocodile under load, pounding over the old metal trestle viaduct in Wassen. It filled the whole Reuss valley with its music! And, the noise was very different when coming downhill, under electrical braking! It was more like "whooom-whooom-whoom", briefly interrupt by the "A" tone of the whistle blown by a friendly engineer responding to our hand waving (even though it was not allowed by the SBB rules!) Yes, I can still hear these noises in my head today! Yes, I am still a kid at heart."
The center section accommodated the high voltage transformer, with two tap changers, a rotary converter, switchgear and the ventilation system. Engines 14 251 to 14 273 of the first generation featured two ventilation motors with associated fans. On the other hand, engines 14 274 to 14 283 had only a single motor powering the fan and the oil pump. This combination required ductwork to draw in additional cooling air which some Crocodile enthusiasts liked to an oversized vacuum cleaner.
Eventually, the Crocodiles were fitted with recuperation brakes, which turned the motors into generators when the engine was descending a grade. Rather than wasting the energy thus formed into heat, it was returned into the catenary system.
The two engine driver positions were connected by a narrow passageway. It greatly speeded turning the locomotive around. The driver positions were not marked 1 and 2 or V and H (vorne and hinten; front and rear) as was the practice on such German electric locomotives as the E 18/19 and E 93/94.
The two pantographs picked up 15 kV at 16.67 Hz. In the beginning both pantographs were used and only later when the pantographs with double sliders were fitted, did some of the Crocodiles operate with one pantograph up. The pantographs covered a vertical operating range from 15.7 to 22.9 ft (4.80 to 7 m). They were raised and lowered pneumatically but if that system failed, a hand pump was available for the job. The oil-cooled transformer provided no more than 500 volts to the traction motors. Each motor features two reversing switches and two braking positions. Third generation Ce 6/8s have one reversing switch for two motors. The lighting system of the locomotive was battery powered to avoid the loss of lighting in the event of an electric power failure.
Most of the 51 Crocodiles served the Gotthard line from Immensee (Kilometer post 0) to Chiasso (Kilometer post 206). Formerly this line was called the Gotthard Bahngesellschaft (Gotthard Railway Company).
The longer the Crocodile served, the greater the demands that were placed on them. The (65 km/h) speed limit was no longer practical. It had to be increased and this proved hard on these machines. To use today’s vernacular, they were maxed out. With that in mind, the SBB decided that 13 of the first generation engines were to be upgraded with more powerful motors and strengthened frames. This work was done at Bellinzola between 1942 to 1947.
This enabled them to haul 520 ton trains at 21.7 mph (35 km/h) up 2.6% grades and 1,350 ton trains at 21.7 mph (35 km/h) up 1% grades. On level track they handled 2,000 ton trains at 37 mph (60 km/h). Top speed of the upgraded engines was 47 mph (75 km/h). The new top speed resulted in the Ce 6/8II being reclassified as Be 6/8II. The road numbers for 14 251 to 14 265, with exception of 14 260 and 265, became 13 251 and 13 265. In 1956, the 18 second generation machines became Be 6/8III and engines 14 301 to 14 318 became 13 301 to 13 318.
Unquestionably, the Crocodile reigned over the Gotthard from its introduction in 1920 to the beginning of its phase out in the 1950s. After being replaced by the Ae6/6 in Gotthard service, the distinctive Crocodile soldiered on hauling heavy freight trains in the central regions of Switzerland. The last of the Crocodiles were mustered out in the early 1980s after having been relegated to yard switching service. The Crocodile switchers operated with a single pantograph.
Two Crocodiles remain in SBB service as active museum engine, these are Ce 6/8II No. 14253 and Ce 6/8III No. 14305. Several are in private hands. One of the most famous of these is No. 13302 in care of the Modell Eisenbahn Club Horgen (Horgen Model Railroad Club).
Swiss Locomotive Designation System
In the Swiss locomotive designation system, the first letter [C] indicates top speed, with [A] being the fastest; the second letter [e] denotes electric propulsion; the numerals are for powered axles/total axles. Hence Ce 6/8II refers to an electric locomotive with a top speed of 65 km/h (40 mph), electrically powered, 6 driven axles, having a total of 8 axles. The Roman letter superscript II indicates the second variant of the basic model.
Road numbers starting with 14 000 are for engines in speed category C, the 12 000 and 13 000 are for speed category B. Thus, the first three Crocodiles were wrongly numbered.
An old Swiss designation system
When I encountered the designation Fc in the article "Die einzig wahren Krokodile" (Eisenbahn Magazin, 2/2002, page 32), my first thought was that he had made a mistake. What to do? I sent an e-mail to the editor of the article. Here is his response.
The designation "F" for electric locomotives was used only until 1920. As with tender locomotives, this letter was followed by a lower case letter that indicated top speed. The system, which was in use from about 1900 to 1920 was as follows:
A = Locomotive with tender and max. speed of about 80 km/h; E.g. A 3/5
B = Locomotive with tender and for passenger use. Max speed 70 km/h; E.g. B 3/4
C = Locomotive with tender for freight with max. speed of 60 km/h; E.g. C 5/6
D = Freight a Freight and locomotive for double-heading with max speed of 60 km/h; E.g. D 4/4
E = Tank engines
E without extra lower case letter = switcher; e.g. E 3/3
Ea = Fast train tank engine; e.g. Ea 3/6 (Gern Neuenberg Bahn)
Eb = Passenger train tank engine; e.g. Eb 3/5
Ec = Freight train tank engine; e.g. Ec 3/5
Ed = Engine for double heading; Ed 2x2/2 (Mallet, mountain engine at Hauenstein
F = Electric freight engine; designation always used with a lower case letter.
Fb = Passenger train engine; eg. Fb 4/6 (became Be 4/6 in 1920)
Fc = Freight engine; e.g. Fc 6/8 (became Ce 6/8 in 1920)
Fd = Slow freight engine; e.g. Fd 4/6 (3-phase engine used on Simplon)
G = Narrow gauge
There is still more and I will post it with the next version of my website. I am very grateful to Mr. Bernhard Studer, the editor of the above mentioned Crocodile article and his patient explanation of this complex designation system.
Specifications of 1st and 2nd Generation Crocodiles
|Be 6/8II (13 251)||Be 6/8III (13 302)|
|Years built||1920 - 1921||1926 - 1927|
|Builder(s)||SLM and MFO||SLM and MFO|
|Power supply||15 kV @ 16.67 Hz||15 kV @ 16.67|
|Overall length||63.8 ft (19,460 mm)||65.8 ft (20,060 mm)|
|Wheelbase||54.1 ft (16,500 mm)||55.78 ft (17,000 mm)|
|Wheelbase of power units||21.9 ft (6,700 mm)||21.8 ft (6,650 mm)|
|Ctr. to ctr. distance of pantographs||17.9 ft (5,450 mm)||18 ft (5,500 mm)|
|Wheel dia., driven||53.1 in. (1,350 mm)||53.1 in. (1,350 mm)|
|Wheel dia., pilot||37.4 in. (950 mm)||37.4 in. (950 mm)|
|Axle loading||17 - 17.6 tons||16.4 to 18.8 tons|
|Number of motors||4 single-phase commutator type||4 single-phase commutator type|
|Weight||126 tons||130.9 tons|
|Weight, tractive||103 tons||108.4 tons|
|Max. starting force||30,000 kg||30,000 kg|
|Continuous tractive effort||48,148 lb (21,840 kg) at 28 mph (45 km/h)||41,890 lb (19,000 kg) at 21.7 mph (35 km/h)|
|Hourly rating||3,650 hp (2,721 kW) at 28 mph (45 km/h)||2,460 hp (1,834 kW) at 21.7 mph (35 km/h)|
|Hourly rating at the jackshaft||4 x 705 kW at 28 mph (45 km/h)||4 x 490 kW at 21.7 mph (35 km/h)|
|Hourly rating at the wheels||3,320 hp (2,475 kW) at 29 mph (46.5 km/h)||2,200 hp (1,640 kW) at 23.6 mph (38 km/h)|
|Continuous rating at the jackshaft||4 x 645 kW at 29 mph (46.5 km/h)||4 x 440 kW at 23.6 mph (38 km/h)|
|Top speed||46.6 mph (75 km/h)||46.6 mph (75 km/h)|
SLM = Schweizerische Lokomotiv- und Maschinenfabrik (Winterthur)
MFO = Maschinenfabrik Oerlikon
First Generation Crocodiles
|Number||Factory No.||Year||Conversion||New number||Out of service|
|14 2511||2671||1919||1943||13 251||12/'74|
|14 2521||2672||1919||1942||13 252||12/'68|
|14 253||2673||1919||1947||13 253||2|
|14 254||2674||1919||1944||13 254||3|
|14 255||2675||1919||1946||12 255||12/78|
|14 256||2676||1919||1943||13 256||11/80|
|14 257||2677||1919||1947||13 257||7/784|
|14 258||2678||1919||1944||13 258||9/75|
|14 259||2679||1919||1944||13 259||12/74|
|14 260||2680||1919||---||14 284 since 1949||2/65|
|14 261||2697||1920||1944||13 261||8/68|
|14 262||2698||1920||---||14 285 since 1948||6/68|
|14 263||2699||1920||1945||13 263||2/73|
|14 264||2700||1920||1944||13 264||11/73|
|14 265||2701||1920||1942||13 265||2/74|
1 - Delivered as 12 251 - 53; after 1920 14 251 - 53
2 - Since 4/74 14 253 designated historic locomotive
3 - 1982 VHS
4 - To Austria (Attnach - Puchheim)
5 - 1982 Erstfeld
6 - With Historische Eisenbahn Frankfurt e.V.
Second Generation Crocodiles
|Road Number||SLM No.||Year built||End of service|
|14 301||3072||1925||March 1976|
|14 302||3073||1925||Dec. 19761|
|14 303||3074||1925||April 19772|
|14 304||3075||1925||Dec. 1974|
|14 306||3077||1925||Jan. 1968|
|14 307||3078||1925||Oct. 1973|
|14 308||3079||1925||April 1972|
|14 309||3080||1925||May 1967|
|14 310||3111||1926||August 1973|
|14 311||3112||1926||May 1968|
|14 312||3113||1926||March 1970|
|14 313||3114||1926||Nov. 1972|
|14 314||3115||1926||August 1970|
|14 315||3116||1926||March 1968|
|14 316||3117||1926||Dec. 1971|
|14 317||3118||1926||October 1973|
|14 318||3119||1926||January 1967|
1 - Be 6/8III 13 302 owned by Modelleisenbahn-Club Horgen
2 - Individual parts for maintenance of 14 302
3 - Since July 1979 historic engine Ce 6/8III 14 305
"Die einzig wahren Krokodile," Bernhard Studer, Eisenbahn Magazin, 2/2002, p. 32.
"A Little History of The SBB Crocodiles," Jacques Vuye, ETE EXPRESS, Issue 64, 1994, p.7.
Märklin Krokodil, H.S. Stammer, Gebr. Märklin & Cie, Göppingen, Germany, 1984. Catalog number 0356.
"Die berühmten Elloks Be/Ce 6/8 der Schweizerischen Bundesbahnen," Märklin Magazin, 2/72, p. 26.