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Re: 1969 Cuesta grade derailment-Yes U-33 problem....
Author: Max Wyss
Date: 02-03-2017 - 17:53
This description strongly reminded me of an accident happening in Switzerland, some twenty years earlier (February 22, 1948).
It happened on the Südostbahn (SOB), on the line between Einsiedeln and Wädenswil (where it connects to the main line between Zürich and Chur). The line joins the main line with a high valley, and has very steep grades (5%).
The train was a skier's special, consisting of a Ce6/8" (aka "Crocodile"), and 9 2- or 3-axle passenger cars (pretty much the common consist of such a train at that time. Because of the steep grades, they were using a locomotive which was then more or less exclusively assigned to freight service. Not very fast, but with high pulling power.
What happened is that after a station stop halfway down the slope, the train accelerated normally, and then the driver wanted to activate the regenerative braking. On this locomotive, this is one by switching the operation switch from "traction" to "(regenerative) braking", and then crank up the tap changer, just as if one would speed up. For reasons unknown, the driver die not realize that this switch was still in "traction" position. One feature with the start of the regenerative braking, is that the ampere meter shows a specific peak. So, the driver assumed that he had activated the regenerative braking an accelerated even more. He applied the air brakes, but the locomotive was too powerful, and continued pulling. The chief of operation who acted as pilot (SBB drivers were not familiar with the SOB), stepped back to tighten hand brakes, but without success.
The train passed a red signal at the intermediate station, whose station master notified Wädenswil about the runaway. Unfortunately, both mainline tracks to which it was possible to get to from Wädenswil were occupied, an it was not possible to clear one of those tracks in time (the station master in Wädenswil had about 2 minutes time). So, the only option was to let the train run into a siding which also works as protection towards the main line.
The train overran the buffer, and crashed into a warehouse. The consequence… 22 dead and more than 150 injured to a higher or lesser degree.
So the cause was that the behavior of the instruments was the same whether the switch was in "traction" or in "braking" position. After that, they did install an indication lamp showing that "braking" is active. Considering the age of the locomotives of that series (almost 30 years), this was the only modification. Such a set up (separate switch for "traction" and "braking"), was, however abandoned very soon after the last Ce6/8 got delivered. With electro-pneumatic switches (instead of a direct controller on the transformer), operation changed to a hand wheel, where turning in one sense meant switching to higher voltage for traction, and turning in the other sense meant lowering the voltage, and beyond "neutral/zero" the regenerative brakes were activated.
It happened on the Südostbahn (SOB), on the line between Einsiedeln and Wädenswil (where it connects to the main line between Zürich and Chur). The line joins the main line with a high valley, and has very steep grades (5%).
The train was a skier's special, consisting of a Ce6/8" (aka "Crocodile"), and 9 2- or 3-axle passenger cars (pretty much the common consist of such a train at that time. Because of the steep grades, they were using a locomotive which was then more or less exclusively assigned to freight service. Not very fast, but with high pulling power.
What happened is that after a station stop halfway down the slope, the train accelerated normally, and then the driver wanted to activate the regenerative braking. On this locomotive, this is one by switching the operation switch from "traction" to "(regenerative) braking", and then crank up the tap changer, just as if one would speed up. For reasons unknown, the driver die not realize that this switch was still in "traction" position. One feature with the start of the regenerative braking, is that the ampere meter shows a specific peak. So, the driver assumed that he had activated the regenerative braking an accelerated even more. He applied the air brakes, but the locomotive was too powerful, and continued pulling. The chief of operation who acted as pilot (SBB drivers were not familiar with the SOB), stepped back to tighten hand brakes, but without success.
The train passed a red signal at the intermediate station, whose station master notified Wädenswil about the runaway. Unfortunately, both mainline tracks to which it was possible to get to from Wädenswil were occupied, an it was not possible to clear one of those tracks in time (the station master in Wädenswil had about 2 minutes time). So, the only option was to let the train run into a siding which also works as protection towards the main line.
The train overran the buffer, and crashed into a warehouse. The consequence… 22 dead and more than 150 injured to a higher or lesser degree.
So the cause was that the behavior of the instruments was the same whether the switch was in "traction" or in "braking" position. After that, they did install an indication lamp showing that "braking" is active. Considering the age of the locomotives of that series (almost 30 years), this was the only modification. Such a set up (separate switch for "traction" and "braking"), was, however abandoned very soon after the last Ce6/8 got delivered. With electro-pneumatic switches (instead of a direct controller on the transformer), operation changed to a hand wheel, where turning in one sense meant switching to higher voltage for traction, and turning in the other sense meant lowering the voltage, and beyond "neutral/zero" the regenerative brakes were activated.
