Cable car disaster in Italy 3

[LittleInch]

Not a huge amount of detail at the moment but a dreadful tragedy and difficult to understand how this could happen. The factor of safety on a cable car cable must be huge as it is so vital.

https://www.theguardian.com/world/2021/may/23/at-least-eight-dead-in-italian-cable-car-accident

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[waross]

While I have seen some very good safety people on jobsites, too many chose safety as a career because the entry standards are so low, and they couldn't quite make it in a more demanding profession.
Case in point; the Scotia Tower construction hoist accident in Toronto in the early '80s.
The cage ran up and down a tower outside the building.
The counterweight was sized to balance a 50% load.
The drive was a shaft and pinion gear running on a rack gear that extended the height of the tower.
On day with three men in the cage, the pinion shaft broke.
The cage had emergency brakes that were held released by the tension on the counterweight cables.
The brakes applied if and when the cables broke.
Three men was less than half of rated load and so the counterweight accelerated the cage upwards until it struck the top 68 stories up.
Two serious injuries and one fatality.
The following conversation must have taken place.
"Why did the cage go up instead of down?"
"The counterweight was heavier than the cage and the counter weight pulled the cage upwards."
"Why didn't the emergency brakes work?" (Reasonable question.)
"The brakes work going down, not going up." WRONG ANSWER. THE BRAKES DIDN'T WORK BECAUSE THE CABLE DIDN'T BREAK."
"We have to install a second set of brakes that will work when the cage is going up."
That was the fix, a second set of safety brakes installed upside down.
I take this one somewhat personally.
I had occasion to ride that hoist many times after the accident.
The brakes were clearly visible from inside the cage. The normal brake set and a second brake set installed upside down.
There was no other system to stop the car in the event that the pinion shaft broke again.
Every time I rode that cage I had a lot of negative thoughts about "Not ready for prime time" safety weenies.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[1503-44]

You rode it knowing it was messed up?
How do you feel about that today?


If you think I am wrong about anything I say, then please do correct me, but please also refrain from condescending lectures to myself and others here, in the preschool level details of chem, math and physics. Thank you. I will try to do the same.

 

[waross]

Hey. The pinion shaft will never break, did it?
I avoided riding the cage unless it was at about half capacity. Less strain on the pinion shaft and less acceleration if the shaft never broke, again.
Coming down I would use a building elevator to the second floor and walk down the stairs and sneak out.
That's nothing. I worked for over ten years in an industry with a seriously flawed LOTO procedure.
A very good safety man who was the head of the safety department of a company with about 1000 persons on site agreed with me. He tried to have the procedure changed. He was fired for his efforts.
Don't mess with Big Oil. When they're wrong, they're right.
Work it like it's hot and cover your own ASSets, cause the company won't.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[1503-44]

Same here. I used to swing the tarzan ropes on the platforms between the boat and the landing when the wind and waves were too big for the boat to come alongside. When I hit the side of the boat and the deckhand grabbed me and pulled me in, I decided that was the last time. Not to mention free rope swinging off the top of a 20m tall tank to try to reach a valve somebody put in the wrong place and getting detained for 3 days and deported because some AH forgot to pay the bribe to renew my work permit only to have the guerrillas show up and do the same thing again when I got back. Sometimes I wonder how I made it.

I forgot about falling through a rusty platform grating floor 60ft MSL. Fortunately (?) I got stuck halfway through.

 

[epoxybot]

Terrifying video shows the tow cable snap, right at arrive to the gang-port. Link

 

[Tomfh]

Ugh. That’s truly horrific.

 

[dik]

Just so close...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[itsmoked]

Damn straight!

Keith Cress
kcress -

http://www.flaminsystems.com

 

[davidbeach]

That does mean that the passengers on the other car didn’t need much of an effort to rescue. May even have been able to just walk off.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[itsmoked]

May even have been able to just walk off.

That's what I was thinking.

A cable that long must grow and shrink a considerable amount with temperatures. I wonder how they deal with that and if something about the other car docking caused the cable to break. Seem too much a coincidence to break just at the dock.

So sad that the brake was disabled.. They could've just stepped off.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Tomfh]

It's interesting (and scary) how taut the tow cable was. The cable snapped back downhill with a lot of force, it really yanked on the cabin. So there was a lot tension in the tow cable in addition to just the gravity/tow force.

 

[davidbeach]

The tow cable would have been the only thing resisting gravity. The first tower would have been a long ways down. If the prior misapplications of the emergency brake had all occurred when that car was going up hill, and more specifically, if they'd all occurred as that car was reaching the upper station, all of the stress would have been concentrated in a few feet (fewer meters) of cable between the car and the drive wheel. Doesn't seem terribly surprising.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[LionelHutz]

Was that the broken end of the cable that pulled through station and almost hit that observer?

Why is there a tow cable on the downward side? Something to do with the braking system maybe? Pull it into the bottom station? Does the cable change angle enough over a tower it's needed to hold back the car and keep it going a steady speed?

 

[Retiredat46]

The two cars are connected by the tow cable to reduce the load on the drive motor. The motor only needs to overcome some friction and the difference in weight of the passengers between the two cars.

There's not much load on the motor, but the tension on the cable is significant (weight of both cars, passengers, friction, and the cable itself, plus acceleration and deceleration loads).

 

[LionelHutz]

You can't push with a cable, so why is that downward cable there?

 

[Retiredat46]

The lower tow cable reduces the tendency for the upper tow cable to sag or tighten between the support as the load changes, which makes the ride smoother.

 

[IRstuff]

I would think the lower cable keeps tension on the actual tow cable, in case the downward car doesn't have sufficient momentum to make it over a tower. This way, the upward car will drag the lower car over any minor obstacles and keep the tow cable tensioned at all times.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[waross]

You can't push with a cable, so why is that downward cable there?

Gravity?
To keep the other car from running away downhill just as the car at the upper station did when the cable broke.
Also to pull the second car up when the first car is descending.
Think of the second car as a counterweight.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[LionelHutz]

Retiredat46 - that would make sense if the tow cable has enough weight that it could sag between towers and pull the car further up the support cable. At any rate, there certainly was a lot of tension in it pulling downward.


waross - No. That cable goes from the car downhill to the bottom station, then presumably around a big pulley before connecting to the other car. So, that cable is not capable of pulling either car up the hill.

 

[waross]

That cable goes from the car downhill to the bottom station,

That may be true, but that is not where the cable is intended to be. When a cable under tension breaks, it very often ends up lying somewhere that it shouldn't be.
Originally the cable went from one car up and around a drive pulley (or pulleys) at the top and then down to the other car.
The cars counterbalance each other.
I have something else to do. Maybe someone else can find a good drawing of how a counterbalanced cable car system works.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!