[robocat]

Key lines:

> the air brake and the manual brake were quickly applied by the brakeman of cab #1, but that in the current configuration, the brakes do not have sufficient capacity to stop the cabins in motion without their empty masses being mutually balanced by the connecting cable. Therefore, the existing brakes does not constitute a redundant system in case of a failure in the connecting cable.

[DetroitThrow]

So, the brakes would have never worked if connecting cables broke? And this specific failure has just never happened before? Jesus.

[mastazi]

No that's not what it's saying. I've read the whole report. The hydraulic brakes are designed to be applied automatically and stop the car in case of cable failure. By mentioning "current configuration" the report is implying that the brakes were not applied fully, and the reason for this is still being investigated

[ncruces]

> The evidence confirms that the emergency system installed in the flywheel located at the top of Calçada da Glória, tripping the power switch to the cabins in the event of a loss of cable tension, worked as intended, which would result in the immediate and automatic application of the pneumatic brake in each cabin.

> At this time, it has not yet been possible to conduct verification checks to confirm whether the system for automatically applying the pneumatic brake to the cabins following a loss of cable tension in the trambolho worked.

The cable breaking (or in this case, going loose at its attachment point) should be the detected at the flywheel area at the top, and result in power being cut to both cabins — this happened. This should result in pneumatic brakes being applied at the maximum force — it's unknown whether this worked.

> However, regardless of this, the evidence indicates that the air brake and the manual brake were quickly applied by the brakeman of cab #1, but that in the current configuration, the brakes do not have sufficient capacity to stop the cabins in motion without their empty masses being mutually balanced by the connecting cable. Therefore, the existing brakes does not constitute a redundant system in case of a failure in the connecting cable.

Irrespective of the automatic system, the brakeman immediately applied the air brake and manual brake. Then: in this configuration the brakes are not sufficient and are not a redundant system.

One possible interpretation is that the brakes when manually applied are insufficient to stop the vehicle when the counterweight provided by the cable is absent.

Another is that the manual brake is insufficient, but the pneumatic/air (assuming those are the same) brake should be at maximum force, but for some reason, it wasn't applied at maximum force by either the brakeman or the automatic system.

[vascocosta]

> One possible interpretation is that the brakes when manually applied are insufficient to stop the vehicle when the counterweight provided by the cable is absent.

> Another is that the manual brake is insufficient, but the pneumatic/air (assuming those are the same) brake should be at maximum force, but for some reason, it wasn't applied at maximum force by either the brakeman or the automatic system.

Agree and I would add a third possibility:

The delay between detection and automatic full brake application, or by the cabin driver was long enough to allow enough speed/inertia to build, beyond the threshold until which the brakes would actually make it stop.

[robocat]

I disagree. The last sentence kinda strongly implies that there was no redundancy:

"the existing brakes does not constitute a redundant system"

Or from the Portuguese report:

  Desta forma, não constitui um sistema redundante à falha dessa ligação

Google translate:

  Therefore, it does not constitute a redundant system in the event of this connection failing.

Of course it could just be saying that the brakes were critical (not redundant?). Summary reports often have spin rather than facts.

It turns out that the brakes were critical and they didn't work for whatever reason (design or maintenance or operation or unforseen failure)

[DetroitThrow]

>By mentioning "current configuration" the report is implying that the brakes were not applied fully, and the reason for this is still being investigated

Thank you for clarifying since the brakes never being able to stop a high up car is an alarming design. It does make me imagine the reason for this failure will be some horrificly implemented operational process.

[phire]

The report only states the conclusion that the breaks did not work for the current configuration.

Which is a slightly awkwardly worded way of saying, “well obviously they didn’t work because we know they were applied and look at the result“

This is only an initial report. They still have no idea why the breaks didn’t work, and for how long they haven’t been working. Could have been a recent malfunction, something that happened during redesign, or a an inherent flaw going back to the original design.

[vlfig]

Although it isn't yet clear how much the brakes did actually brake, it is known they would never be enough.

So the cable was a critical component and initial findings suggest it wasn't being verified as rigourously, thoroughly and often as it perhaps should have.

[mastazi]

> it is known they would never be enough.

No that's not what it says. Brakes were not enough "in the current configuration" in other words they were not applied fully. The investigation will focus on why brakes were not applying full breaking force.

In railway jargon "brake configuration" refers to "how much are you braking" but you seem to have interpreted "braking configuration" as "the number and type of brakes that are currently installed in the vehicle"

[Animats]

The evidence indicates that the air brake and the manual brake were quickly applied by the brakeman of cab #1, but that in the current configuration, the brakes do not have sufficient capacity to stop the cabins in motion without their empty masses being mutually balanced by the connecting cable. There- fore, the existing brakes does not constitute a redundant system in case of a failure in the connecting cable.

So the braking system is insufficient to stop after a broken cable.

There's more than a wheel brake system. There's a mechanism to clamp against the track slot from both top and bottom. See Fig. 2, right. Apparently it wasn't enough.

Funiculars are a problem because they're too steep for railroad wheel brakes, too heavy for elevator braking systems, and rare enough that there are not good standards for them. Angels Flight in LA has had two major accidents, one in 2001 and one in 2013.[1][2] Different causes. The 2001 accident was due to bad design - only one cable, no track brakes, and a system where each car had its own winding drum. The spline connecting the drums failed. The 2013 accident, after a total redesign and replacement of the hauling system, was due to bad maintenance. So bad that it involved a stick being used to hold down an override switch.

Elevator rail brakes are often jam brakes - once they're triggered, a wedge is jammed between brake and rail such that motion forces it into tighter contact. Stops with jam brakes are rather drastic. San Francisco cable cars have a jam brake for emergencies. That's the red lever, which drives a wedge into the slot. When used, there are usually passenger injuries and the wedge will be welded to the track by frictional heating.[3] So that's for serious emergencies only.

[1] https://www.ntsb.gov/investigations/AccidentReports/Reports/...

[2] https://www.ntsb.gov/investigations/AccidentReports/Reports/...

[3] https://www.cbsnews.com/sanfrancisco/news/cable-car-6-riders...

[vascocosta]

It's my understanding that this particular funicular system uses eight shoe brakes, where rubber pads basically clamp a metal track (from above and below) causing friction.

Hearing some local experts, they often mention that this is physically not enough to stop a 14 ton vehicle (plus passengers) going downhill when the slope is as high as 18%. So basically even if in perfectly working condition, the bake pads or wheels would just slide down the tracks as there's not enough friction for the resulting force.

Maybe something like a rack and pinion railway or some other kind of drastic metal locking mechanism are the only realistic way to prevent catastrophic events when the cable breaks/detaches, considering the masses and slopes involved here?

[lstodd]

rack and pinion will just strip the teeth and/or disengage.

one needs just more pad area and more clamp force

[sho]

While I personally lean towards your interpretation, the language is ambiguous - perhaps intentionally so - and it is premature to read too much into it in either direction. We’ll just have to wait.

[dingaling]

> In railway jargon "brake configuration" refers to "how much are you braking"

I've never heard that terminology in a European rail context, you'll need to provide a citation.

In EU regs, "braking configuration" literally means the mechanical configuration of braking; how much braking force the inertial, hydraulic or pneumatic braking circuits can apply in total.

[robocat]

> In railway jargon "brake configuration" refers to "how much are you braking"

I presume the quote in English is translated from the original Portuguese. I would hope it was carefully translated but I wouldn't personally bet on that.

A Portuguese source document might be clearer.

[edit]

Document in Portuguese: https://www.gpiaaf.gov.pt/upload/processos/d054238.pdf

  No entanto, e independentemente disso, as evidências indicam que o freio pneumático e também o freio manual foram rapidamente aplicados pelo guarda-freio da cabina n.® 1, mas que na configuração existente os freios não têm a capacidade suficiente para imobilizar as cabinas em movimento sem estas terem as suas massas em vazio mutuamente equilibradas através do cabo de ligação. Desta forma, não constitui um sistema redundante à falha dessa ligação.