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Cable car disaster in Italy
3

Cable car disaster in Italy

Cable car disaster in Italy

(OP)
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-l...

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RE: Cable car disaster in Italy

Rode that in June of 2018. Pretty spectacular. It takes two different cable cars to get to the top. Haven’t dug in enough to know which of the two it was.

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

RE: Cable car disaster in Italy

Sounds like it was the upper section.

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

RE: Cable car disaster in Italy

The reporting is strange. In the video the cable appears to be in tact. The cable car either fell off the cable or the mechanism that attached it to the cable failed.

RE: Cable car disaster in Italy

It does look like there is a cable missing.

Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

RE: Cable car disaster in Italy

This image shows the cable-way at the Lower terminal, Google Maps Oct 2017.
Picture of car - 2019

The image at the beginning of the video does seem to indicate a missing cable, if you view further two cables are visible, The smaller safety cable is still attached to the car (at least in one direction). It may have stopped the car from falling all the way down this hill. closer inspection of the video indicates these cables may have been installed by the rescue crew to stabilize the car. There appears to be some cable tangled up in the cable follower, all of the parts of the cable follower that are visible appear to be where they should be, so it is not obvious yet what failed.

RE: Cable car disaster in Italy

(OP)
These photos make it look like the main cables are still there, but the smaller tow cable has fallen.

That indicates that the cable car fell off the cable. So maybe the tow cable snapped and de railed the car?



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RE: Cable car disaster in Italy

Recall that people in the forest "heard a loud hissing sound" which would suggest the cable failed and was rapidly backing out of the ways.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Cable car disaster in Italy

(OP)
Other than self weight there doesn't look to be a whole heap holding the cable car to the wire though?

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RE: Cable car disaster in Italy

(OP)
Some reports now saying the tow cable snapped and the car then didn't apply any brakes (does it have any?) and shot down the hill coming off when it went over the pylon you can see in the photos above.

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RE: Cable car disaster in Italy

I think its the support cable thats gone. Dont the two thin ones make up the towing loop?

Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

RE: Cable car disaster in Italy

(OP)
The big cables are still there and the eye witness reports state the towing cable broke and the cable car started hurtling down hill until it came to the tower when it came off and then rolled a few times. Must have been horrible to be in.

If you look at the top photo I posted it is pretty clear the thicker cables which the cars sit on is still there.

This is what is supposed to be there - one thick cable holding the car, a second thinner one pulling it or lowering it up/down the hill and a third higher cable for comms? or power? from bottom to top.

The top photo I posted shows the thinner lower cable dangling, but the main cable still in place.

You would think there would be some sort of cable brake like you get on lift shafts if the cables break or there is some sort of failure. Clearly didn't work.



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RE: Cable car disaster in Italy

(OP)
Apparently the one going down the hill managed to stop using the said brake, but the one going up didn't.

https://apnews.com/article/world-news-europe-italy...

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RE: Cable car disaster in Italy

Quote:

Apparently the one going down the hill managed to stop using the said brake, but the one going up didn't.
How's that supposed to work? The cars I've been on are driven by the support cable and everything is roughly balanced.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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RE: Cable car disaster in Italy

(OP)
IR stuff - That's because the cable pulling one up whilst the other went down apparently snapped.

When that happens there is nothing to stop the cable car hurtling down the mountain unless it has some sort of mechanical gripper to grip the main support cable. at least that's my supposition.

This though is a classic cable car system where the main support cable is fixed and doesn't move, the cable car has sets of wheels which go over the cable and the two cars are pulled up / lowered down the mountain by a second cable which is then roughly balanced.

Most gondala style ski lifts and indeed some cable cars are nowadays pulled up by a single cable which moves and the wheels are on the support towers.

This one was built in 1970 I think and works the other way around. If you look closely at the photos above you can see the wheels on the cable car arm which run on the main support cable.

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RE: Cable car disaster in Italy

I'm surprised there's not some form of uni-directional (switchable at top/bottom?) wheel or braking system (like in an elevator) that would prevent/reduce backwards movement.

I always thought the main cable moved (never paid close attention), didn't realize it was strictly support.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Cable car disaster in Italy

(OP)
That might work going up but wouldn't work going down....

They usually work on excess speed so I guess the one going down was close to its limit speed whereas the one going up which crashed had a speed reversal and hence possibly wasn't as well adjusted.

I have an idea that they will never know what happened to it now its crashed, but this could have been twice as bad if the other cars system hadn't worked.

I think most cable systems now move and the car is fixed to the cable which eliminates one cable and makes it easier to have more than two cars moving at the same time. I guess there are plusses and minuses to both systems and you make your decision based on which one works for your location, number of people you want to transport etc etc.

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RE: Cable car disaster in Italy

Thanks, I'll have to remember to check any gondolas I get on in the future. The gondolas and ski lifts I usually ride have driven support cables, but the high-speed ones do detach from the support cable during loading/unloading, while convenient, does concern me a bit more, since there's way more wear and tear on the cable clamps.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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RE: Cable car disaster in Italy

Our common language divides us again:
What we have here is

Quote (https://en.wikipedia.org/wiki/Aerial_tramway)

An aerial tramway, sky tram, cable car, ropeway or aerial tram is a type of aerial lift which uses one or two stationary ropes for support while a third moving rope provides propulsion.[1][failed verification] With this form of lift, the grip of an aerial tramway cabin is fixed onto the propulsion rope and cannot be decoupled from it during operations.

This is what most ski lifts are

Quote (https://en.wikipedia.org/wiki/Gondola_lift)

A gondola lift is a means of cable transport and type of aerial lift which is supported and propelled by cables from above. It consists of a loop of steel wire rope that is strung between two stations, sometimes over intermediate supporting towers. The cable is driven by a bullwheel in a terminal, which is typically connected to an engine or electric motor. They are often considered continuous systems since they feature a haul rope which continuously moves and circulates around two terminal stations.

Some useful technical data is found on Lift World 47-AT Stresa - Alpino
Built by Piemonte Funivie, type 47-AT. This business eventually became part of Agudio Leitner S.p.A. which makes material cableways, but does not advertise support for passenger cableways. This adds to the mix of possible contributing causes, aftermarket support available when the OEM no longer exists, or has moved on to other markets.

RE: Cable car disaster in Italy

I hope that the designers had methods in place do safely handle any anticipated failure.
I suspect that this accident was initiated by a failure that the designers did not anticipate.
Here is another cable car disaster.
Cable Car failure

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

RE: Cable car disaster in Italy

Quote (LittleInch)

Other than self weight there doesn't look to be a whole heap holding the cable car to the wire though?

It's always a trade off between passing the towers and keeping the car attached to the wire.

If the car ran away freely after tow line failure it's difficult to imagine a good outcome, regardless of whether it was looped around the main line.

RE: Cable car disaster in Italy

I agree Tom. I'd expect the cable to saw thru the safety loop quickly or for the gondola to hit bottom at slightly subsonic speeds with predictable results.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Cable car disaster in Italy

I'm just glad all worked well one fine day in June of 2018. I was on that car going down; don't have photos to show which car I was in going up, but definitely in the car on the south cable going down. Looking at the photos, it's actually three rides to the top. Starts with FacEngrPE's images from 24 May 21. Then part way up that one ends and you walk, no more than about 50m, to second of that type; the one that failed. That second one gets you nearly to the top and the last bit is on a ski lift type of system. That ski lift system also covers the course of an alpine slide, so it could get a lot more total riders than the two gondola lifts.

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

RE: Cable car disaster in Italy

You have to remember that most of these cable car systems are decades old.

If you look at the modern ones they are completely different beasts.

In fact the old ones are very country dependant on the safety systems if they have any at all. And you really don't want to see the ones in the old Soviet nation's. The cable car in Barcelona looks decidedly dodgy as well.

RE: Cable car disaster in Italy

This one here on Tenerife is looking pretty skinny today. They had to rescue 70 people, 35/gondola in December. The cars stopped 400m from the top and 400m from the bottom.

(Dutch) https://www.tenerifevakantie.com/teleferico-del-te...




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I take no responsibility for any damages or injuries of any kind that may result.

RE: Cable car disaster in Italy

Wonder what's in that white box?

Maybe a drag anchor of some form

RE: Cable car disaster in Italy

(OP)
I was thinking the same thing - if you open the image in a new tab and zoom in it looks like two sets of grippers / brake pads for the cable - I can only presume this is the system that didn't work on one of the cars in Italy.



Now you start to wonder how often they test it....

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RE: Cable car disaster in Italy

test?

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

-Dik

RE: Cable car disaster in Italy

At intermediate supports, are the cables supported from 'little chairs' from the bottom? to allow the 'wheel system' to travel over?

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

-Dik

RE: Cable car disaster in Italy

(OP)
It's not easy to see but I think they get gripped by a number of thin half shell clamps which are only a little bigger diameter than the cable and feathered.

So the car does vibrate a bit as it goes over the cable mounts. Basically the reverse of what happens on a gondola system where the gondola / seat clamp goes over the moving rollers.

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RE: Cable car disaster in Italy

Some news with more technical content. It seems inspections and regular maintenance occur. The technical information is a bit jumbled on translation, perhaps someone fluent in Italian can make sense of the article in it's original language.

Cable car crashed, the spectrum of Morandi: last revision in 2016. VIDEO

From the controls to the cable: the enigmas on the tragedy of Mottarone

Quote (https://www.italy24news.com/local/65055.html)

Meanwhile, the South Tyrolean company Leitner, responsible for the maintenance Stresa-Mottarone cableway plant, after yesterday’s tragedy, declares himself available to the judiciary, specifying that “the daily and weekly checks required by the operating regulations and the use and maintenance manual are the responsibility of the operator“. In a note, the company announces the list of checks and maintenance in recent months, “according to the requirements of current legislation, on the basis of the maintenance contract signed with the management company Ferrovie del Mottarone“.

On May 3, 2021, maintenance and control of vehicle hydraulic braking units; the non-destructive tests on all the mechanical safety components of the plant envisaged by the five-year review, expiring in August 2021, were brought forward from March 29 to April 1 2021; on 18 March 2021 operational tests of the entire drive system; on 4 and 5 March lubrication and checks of the rollers and pulleys of the stations; on 1 December 2020 ‘fake cuts’ (test which involves a simulation of the breaking of the hauling cable and consequent activation of the emergency brake); on November 5, 2020 periodic magnetic inductive check of the hauling ropes and all the ropes of the plant with positive results.

RE: Cable car disaster in Italy

Thanks...

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

-Dik

RE: Cable car disaster in Italy

I've seen this in german media: https://www.sueddeutsche.de/panorama/seilbahn-lago...

To paraphrase:
three arrested for manupilating the brake system
There where issues with the brake system that would have to be repaired with a lengthy procedure,
instead they deactivted the brake by installing a fork like thing ("Vorlegegabel" would be a serving fork), to avoid downtime and loss of income
Still unclear why the cable broke

RE: Cable car disaster in Italy

(OP)
That link by MartinLe is pretty damning.

I didn't know it had nearly reached the top before the pull cable snapped, but, from the reports, jamming open the brake pads so that the cable car would work is most definitely criminal behavior.

Being in something out of control and hurtling down the mountain must have been truly terrifying. Really doesn't bear thinking about.

Similar report here. https://clippers.com.pl/gondola-accident-in-italy-...

Key phrase - they made the decision on the basis that "the cable will never break".

There be a lesson to us all on low probability high consequence events. Nothing is perfect and failures do happen. This system had been there 50 years so possibly approaching a million operations. Then the one in a million event happens. And you've disabled your safety system.

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RE: Cable car disaster in Italy

There is that fallacy in the low probability - high consequence events mathametics. Right now nobody can say for sure if its a 1 in a MM or 1 in 50yr event. There is so little data on low probability events, all we can do many times is to make a WAG that the sum of all the probabilities involved will be inconsequential. Then there are those times that we do the math right, but somebody forgot there is a >0 probability of defeating some protection system that is many orders of magnitude higher than the sum of all the other numbers on the spreadsheet. The probability of defeating the safety system now looks like it is 1:50yrs, but someone will also come along and take that one occurrence as over the total time of all cable car oprations in the whole world and find, no it really is 1:100 MM. Here its 1:50, but everywhere its 1:100 MM. Its the one I'm riding that's worrying. Would you not have to ride every cable car in the world for the statistics to directly apply to you? smile

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RE: Cable car disaster in Italy

Now I'm speculating but: The problem with the brake turns up shortly after the cable car was closed due to Covid. Did they do the normal maintenance on the braking sytem during that time?
Is there a specific maintenance schedule forthe calbes? Quality check, lubrication - and was that followed?

My thinking with redundancies is - what could be a common cause for two, in themselves unlikely, failures. The one thing I come up with is maintenance.

Other possibility: Did the cable break near the faulty car? Could the repair attempts or the problem have damaged the cable?

According to the link I posted there's a legal fight over ownership of the cable car - communal or regional? Noone wants it. Did this legal bullshit (onoing since 1997) in any way affect maintenance and operation?

RE: Cable car disaster in Italy

(OP)
From the reports it looks like they discovered the fault which sounds like it was clamping on when it shouldn't as they were dusting the cars off and doing some trial runs after the long covid hiatus.

https://www.theguardian.com/world/2021/may/26/ital...

This is equally bad as if the car stops whilst you're dangling in mid air you need helicopters and people need to climb onto the roof to escape etc etc. Not as bad as failing to work when its needed but you can see how the pressure of needing to get the cars working so that they can get revenue after xx months of no operation can cloud the mind.

I wasn't trying to say with the statistics that if this was a one in a million event then it happens after the millionth time, but give some context to those numbers.

Failure rates on equipment I design is in this order of magnitude but incidents still happen.

And that's the point I'm trying to make. just because something is a very low probability doesn't mean it can't happen and you rarely get any idea of when it could happen. So maintain all the safety devices you have and don't rely on the "it won't break / fail / leak / explode" thoughts to justify operating without them.

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RE: Cable car disaster in Italy

Most companies that I have been dealing with used Covid shutdown time to perform maintenance and upgrades. Airlines have many passenger jets that have been sitting around unused for months. I'd expect a robust checkout on all systems before they're returned to service. Disabling a safety system is never an acceptable practice.

Brad Waybright

The more you know, the more you know you don't know.

RE: Cable car disaster in Italy

If the cable could never break, there wouldn't have been a need to design a braking system. These guys are screwed; their only saving grace is that the EU doesn't have a death penalty.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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RE: Cable car disaster in Italy

"Leitner di Vipiteno said on Monday that a series of checks had been carried out over the past seven months, starting with the yearly magnetic inspections on the primary cables of the lift in November 2020 and followed by further checks on safety components and braking systems between late March and early May."

You never cease to learn. This is the first I've heard of magnetic steel cable inspections: https://www.ndt.net/article/v04n08/zawada/zawada.h...

I still want to know how exactly they jammend the brakes open.

RE: Cable car disaster in Italy

(OP)
A "fork like device" which may actually be a fork...

Although one report said it was a device they used to hold the brake pads apart during a service so maybe some sort of U bolt like device, which normally would have a red tell tale string so you don't leave it in place. A bit like the "doors to manual" operation you used to see on planes when we used to travel by plane.

This is a bit of a wild leap here but you wonder if the cars were kept one at each end for months on end, did the pull wire end up at a strange angle or bent over a pulley for a long time, not moving and stretched a bit or somehow work hardened? The report said the cable sheared just as the top car was about to enter the top station.

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RE: Cable car disaster in Italy

News...

"Police arrested three people Wednesday in the cable car disaster that killed 14 people in northern Italy, saying workers placed a clamp on the emergency brake to deactivate it as a patchwork repair - one that prevented the brake from engaging when the lead cable snapped."

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

-Dik

RE: Cable car disaster in Italy

LI, yeah I know. Its just a statistics thing with me. All we can do is follow the science. Sometimes it works and sometimes it doesn't. I try to remember the reason we try to make it practially impossible to happen is because it does, seemingly one way or another, as we tell ourselves its a low P event, it should never. Then on the other hand, each one that happens lowers the P of the next. Is it asymptotopic to something? I wonder what? It all reinforces an idea that at least low P events are way more common than we can possibly calculate, that's all. Maybe just calculating such things lowers the P, like measuring the position of a photon or something. Just another intriguing question in a list of many.

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RE: Cable car disaster in Italy

Could the tow cable have been damaged by an excessive load caused by the emergency brake malfunction?

RE: Cable car disaster in Italy

It appears the brake was disabled...

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

-Dik

RE: Cable car disaster in Italy

From an article in ABC News May 26:
https://abcnews.go.com/International/wireStory/arr...

"Carabinieri Lt. Col. Alberto Cicognani said at least one of the three people questioned overnight admitted to what happened. He said the fork-shaped clamp had been placed on the emergency brake to deactivate it because the brake was engaging spontaneously and preventing the funicular from working."

Seems like the brake would engage all at once with enough force to hold several times the weight of a fully loaded car in the event the tow cable broke. Likewise, the tow cable would be sized to pull several times the weight of a fully loaded car. There would be a short time between brake engagement and shutdown of the tow motor (because of the overload) when the forces would be very high.

It's possible the shock loading of a spontaneous brake engagement was about the same as the strength of the tow cable, damaging the cable. We don't know the safety factors used in the design or how many times the brakes malfunctioned before they were disabled, but it could have been a contributing factor.

RE: Cable car disaster in Italy

But the emergency brake doesn't act on the tow cable (that broke) but on the other (carrying?) cable.

RE: Cable car disaster in Italy

I imagine once the brake did not engage, 5-6G dynamics did the rest.

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RE: Cable car disaster in Italy

(OP)
Retiredat46, (did you?, really??, how???) You might be onto something there.

Safety devices need to work when they're needed and not work when they're not. Spurious operation can often be only slightly worse than the event they are meant to avoid.

Yes the brake is on the main cable but the tow cable is fixed solid to the car so suffers shock loading. Probably worse if the stop is very close to the main winch wheel.

I would imagine the brake is quite powerful as the down car would be moving quite fast before the activation so needs to allow the car full of 30 people to a halt within a reasonably short distance/ time.

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RE: Cable car disaster in Italy

What is supposed to trigger the brake's engagement? 1.1 x Normal Velocity? 1.5G aceleration?
It would seem to be a poor design if the brakes engaged late enough to break the cable. After "V2" speed, they should only deploy a drag chute or something. No point deploying only to snap the cable.

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I take no responsibility for any damages or injuries of any kind that may result.

RE: Cable car disaster in Italy

I was think about that as well..

Maybe tension on the pulling cable?

RE: Cable car disaster in Italy

(OP)
No idea, but probably a mixture of the two.

So max velocity x 1.2 sounds about right given that the speed is fixed by the cable. A bit of stretch or sag every now and then, but within small limits and then lose the cable / lose tension it triggers activation also.

Given that this was designed 50 years ago and the brakes are never supposed to activate, maybe the impact on the tow cable wasn't fully thought through or calculated in the event of spurious operation - who knows? I don't know what the equivalent would be on a plane to test a safety device but in pipeline terms I guess this is like test triggering an ESD whilst at full flow in a pump station / compressor station - could get a bit hairy...

So what was apparently repeated spurious activation before they locked it open won't have done it any good for sure.

The excess speed of the car that crashed caused it to hit the pylon then jump off the cable by all accounts. Truly terrifying and it could have held 30 people. You would have needed a massive drag chute to stop it doing that.

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RE: Cable car disaster in Italy

I'd bet on the tow cable pulling on a mechanism that holds the brake off. Release the tension on the tow cable and the brake engages.

The brake coming on during towing certainly could have been shock loading the tow cable and caused some damage to it.

RE: Cable car disaster in Italy

In normal operation there would always be a substantial load on the tow cable, so my guess is that the brake is triggered if the load falls below a specified level. It's probably something like the slack line detector/alarm/shutoff systems on cranes, which stop the hoist before the wire rope can wander out of the grooves in the drum. I could tell an interesting story about my experience with one of those, but this is probably not the place.

LittleInch, yes, I did retire in 1992 at age 46. I had several years warning that my job would go away if I didn't want to relocate, so I started saving and investing everything I could. I got a substantial bonus payment for volunteering to leave a little before I'd expected to. My mother, who grew up during the Great Depression, broke down in tears when I told her I no longer had a job.

My plan (if you can call it a plan) was to start looking for a job if my nest egg ever fell below half of what I started with. That never happened, so I spent my time sailing, building and flying model planes, learning how to operate machine tools, getting my private pilot's license, owning my own plane, and doing welding, machining, and fabrication at the local tech college. I started my latest hobby of tree climbing a couple years ago. I'm a huge fan of early retirement, and I marvel at the fact that I was able to pull it off.

RE: Cable car disaster in Italy

I agree with Lionel.
If the tow cable breaks,the brake grabs the stationary support cable.
I wonder if, for some reason, the car ran up against the stops at the terminal with the tow cable still pulling.
That may break the cable.
I know that that is not supposed to happen, but the brake was not supposed to be disabled either.

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

RE: Cable car disaster in Italy

"I wonder if, for some reason, the car ran up against the stops at the terminal with the tow cable still pulling."

The load on the cable in that (very unlikely) scenario would be higher than having the brake engage spontaneously while the car was being towed, but the load from a spontaneous brake engagement is going to be much higher that the normal load of towing the car up the incline. Either may be enough to damage the tow cable. It just depends on what safety factor was applied in the design.

RE: Cable car disaster in Italy

I'm not convinced the emergency break engaging would seriously stress the tow cable - here's why:

* the cable is long, this means there's (small) 'springiness' in the calbe itself
* more importantly: the cable sags. more tension=less sag=lifting the cable. This is another mechanisms that can absorb some energy and reduce the acceleration

That said it's still suspicious that the tow cable broke near (or at?) the car with the damaged brake.

RE: Cable car disaster in Italy

I think there is a horrible failure mode here.

If a single car's brake spontaneously applies it's going to have a huge load on it since it's going to have to stop both cars at the same time. That's also going to put a huge load on the the tow cable connecting the two cars together.

I can see that all overlaid on the assumption that if the cable breaks each car is instantly isolated and each car's brake is sized to stop it's own/only car.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Cable car disaster in Italy

(OP)
Depends where the car was when the brake was applied. If within say 50 m of the end point then there isn't much line stretch available.

If, as we suspect, one activation of the emergency brake is no force on the pull wire then as it approaches the end, you would expect the force in the car to reduce so more likely to activate.

That's also the worst location for high load on the pull wire.

But we really are working on very little information.

All we really know is that to get the service running they knowingly deactivated the safety system. And have no info on the cable.

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RE: Cable car disaster in Italy

Would not the force in the support wire be more or less equal (before braking) no matter where the gondola is, given only small changes of cable's angle between gondola and support towers?

After applying brake, the braking force must increase tension on one side of the gondola and reduce it on the other. Then the impulse travels towards the towers in both directions at the speed of sound in the cables? I'm guessing.

Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

RE: Cable car disaster in Italy

Was it a jump on while its moving or it gets taken off the running wire type?

I

RE: Cable car disaster in Italy

(OP)
It's a two car old fashioned cable car system so each car ends up at the top and bottom at the same time and just stops next to the ramp where you get off. Then the cable direction reverses and the top car goes back down the same wire to the bottom whilst the one at the bottom goes up.

Whenever I've been on ones whilst skiing, the heavy car transporting people up the mountain slowly moves as the weight is released which can be a bit hairy.

I don't know what the angle of the main support wire is at the top and bottom. Sometimes the cars go almost horizontal over the last few metres to allow people to get on and off easily sometimes they stay at an angle.

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

RE: Cable car disaster in Italy

It certainly would stress the tow cable if the emergency brake engaged and it held until the tow cable drive tripped on overload. It wouldn't matter how long the cable is, the same stress level would still need to be reached before the cable drive would trip on overload.

It's interesting theory, but I'm not sure if it would apply or not. Possibly, the issue was occurring as the car was being parked into the stations. If the cable is supported horizontally at the stations then there could be some mechanisms to ensure the brake doesn't lock when it's moved horizontally and even if not, there could be some kind of mechanism to lock the car into place when parked that was causing the brake to act up.

RE: Cable car disaster in Italy

Good point Lionel.
If the reduction in tension as the cars entered the terminal was causing a faulty brake to engage, then the cable would be under less tension and less liable to break as the car entered the terminal.
Hence my suggestion that for some reason the car was driven up against an end stop.

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

RE: Cable car disaster in Italy

I thought the brake were supposedly rendered more or less inoperable by the cable guys?
If they had some excuse like it was a bad docking manouver, they probably wouldn't be in jail.


Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

RE: Cable car disaster in Italy

(OP)
Do keep up.

The cars had been out of action for months due to COVID.

When they started them up again and were seemingly running test operations, the brakes on the blue car that crashed apparently started activating spuriously.

They couldn't fix it and with opening day upon them decided that they could jam open the brakes with some sort of mysterious "fork like" device because "the cable will never break".

We are speculating and I emphasis speculating here, that these apparently numerous activations of the emergency brake on only one of the cars may have been the reason why the pull cable then did break, apparently only a few metres up from the car which crashed. Maybe coincidence, maybe not. The brakes on the other car are reported to have worked, though no one said anything about how the occupants, if there were any, were later rescued, but I guess that wasn't newsworthy compared to the 14 who died.

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

RE: Cable car disaster in Italy

The brake were supposedly rendered more or less inoperable by the thing they used to purposely lock the brake open which over-rode that safety feature. Hence why they are in jail.

What I wrote was that the tow cable might lose tension when the car is parking and that might then need a mechanism in the station to solve the brake applying problem and that mechanism could be what was acting up. Something like that being the brake issue could mean the cable braking was not the brake locking up and stressing the tow cable.

RE: Cable car disaster in Italy

It would be fairly easy to have an arrangement that would keep the emergency brake from activating when it was docked in the terminal. A pawl like this could engage a fixed pin in the dock to lock the brake out before the cable went slack. The brake would be armed as the car left the dock.

(image snipped from the post by LittleInch 25 May 21 16:48)

RE: Cable car disaster in Italy

OK we know what happend with the safety grab - perhaps not the contributing factors why the grab was not working correctly.

Things we do not know about the pulling cable -
  • Did the cable part?
  • Did the cable pull out of a anchor socket? (like the spelter socket failure at the Arecibo Observatory
  • Did the attachment anchor in the car fail
  • Something else?
Does the tow cable have the strength to handle a safety grab stop? or did the design assume a safety stop could only happen when the tow cable parts? Perhaps the designer intended for the tow cable to be replaced after a safety stop? Is the original design intent still available?

RE: Cable car disaster in Italy

...and

" The three suspects in Italy’s cable car disaster that killed 14 people were allowed to leave prison Sunday after a judge indicated that most of the blame fell on just one of them: a service technician who intentionally disabled the car’s emergency brake because it kept locking spontaneously.

Judge Donatella Banci Buonamici said there wasn’t sufficient evidence suggesting the owner of the Mottarone cable car company, Luigi Nerini, or the maintenance chief, Enrico Perocchio, knew that the technician had deactivated the brake on several occasions even before the May 23 disaster.

After evaluating prosecutors’ request for continued detention of the three, Buonamici ordered the managers freed while allowing the technician, Gabriele Tadini, to leave under house arrest. The three men, who remain under investigation, left Verbania prison early Sunday, accompanied by their lawyers."

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

-Dik

RE: Cable car disaster in Italy

That just proves that shit does flow downhill.

RE: Cable car disaster in Italy

Perhaps the technician was afraid to admit he couldn't figure out why the brake wasn't working properly. That brings me to my one and only crane story, which involves people not being able to figure out the solution to a problem.

About thirty-five years ago I got the chance to climb to the machinery platform of a 50T bridge crane in a building that handled solid propellant rocket motors. The building was only a year old, and the electrical engineer I was with said they had been constantly getting calls to adjust the electronic slack-line detector that was shutting down the crane. Several other engineers and some manufacturer reps had been called in to analyze the situation, but the problems persisted.

He had attached a large-face analog meter to a circuit that monitored current to the crane motor, and I could see the needle from almost anywhere on the platform. It was moving back and forth as the crane hook was run up and down with no load. I asked about that, and he said the reps had told him it was a tight bearing somewhere in the drive train, and not related to the problem.

I started looking around while not wanting to disturb him. The only thing I could see that revolved in sync with the needle movement was the crane drum, which was about fifteen feet long and four feet in diameter. The end of the outer shell was near a railing, and I noticed the raw edge was wandering about 1/2" as the drum turned, but the machined surface and grooves were running true. I asked him to come over, and got a look that said, "Five minutes on the machinery platform, and suddenly you're a crane expert." But he showed me how to run the block up and down while he looked at the drum. He came back and said, "How the f... did we all miss that? Let's get out of here." He was really pissed, so I didn't ask any questions. Thankfully, I didn't blurt out, "I guess you never looked."

Operations in that building were soon shut down. About two months later, a new drum was delivered and installed, which required removing a section of the roof, and operations resumed. I never spoke with him or anyone else in the company about my trip to the machinery platform or the problems with the crane, so I don't know exactly how what I noticed was related to the replacement of the drum. The out-of-balance condition and the under-spec thickness of the shell under the grooves both seem like good possibilities.

RE: Cable car disaster in Italy

(OP)
The thing being ignored here is why they didn't know or supervise the technician or have some sort of sign off of work on safety critical systems.

It's far too easy to blame an individual rather than the system. I find it very difficult to believe that only one person knew about this.

Fac eng. Good set of questions. I don't have the answers for sure but hope the enquiry will find out. I believe the pull cable parted 20 to 30 m uphill from the cabin but haven't seen any photos.

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

RE: Cable car disaster in Italy

"wasn’t sufficient evidence suggesting [the two guys] knew that the technician had deactivated the brake" Yeah was there sufficent evidence that they knewthe brake worked? The previous problem must have been known to them, burden of proof should be on them that they had good reason to think the problem was fixed in a responsible way.

The technician claimed the other involved new about his tampering (what kind of evidence beyond his testimony would the judge accept?). He also hear d weird noises the morning of the accident, which he discarded. Still no news on why the cable broke.

Given that the cable passed a quality test last november, speculating that the brake problems manifested only since then, your speculation that the brakes stressed the tow cable appears more likely.

The "fork" appears to be, indeed, a fork: the italian word is forchettone. Two where used.

(https://www.sueddeutsche.de/panorama/seilbahnunglu...)

The rescue of the passengers from the other gondola was likely no newsworthy because htey would be close to the lower station, depending on the performance of the brake *in* the station - no fancy helicopter work necessary!

As to the tow cable:
* is the load along it's length is not uniform, but different on both sides of the winch/drum at the top station
* Depending on how much mass is in the tow cable compared to a (full or empty) gondola, the load in the long stretch could be significantly higher, but also the ability to absorb shocks

RE: Cable car disaster in Italy

It might be useful to consider wire rope inspection. I am similar with US practice, and believe EU practice under ISO 4390 is similar. Here is one manufacturers guidance.
Appropriate handling: The correct rope inspection, Verope

Here is one Magnetic wire rope tester Magnetic Rope Testing devices (MRT) Rotec

Magnetic testers can detect broken wires. They could be equipped with devices that measure wear, but there are other failure modes where visual inspection is likely still required.

Hopefully the investigation will produce some more details on this subject.

Nothing is currently published regarding the actual wire rope supplier, or the magnetic testing device used.

This information indicates that magnetic inspection is well enough developed that it is now included in the inspection standard.
ISO 4309:2017(en) Cranes — Wire ropes — Care and maintenance, inspection and discard
This document was prepared by Technical Committee ISO/TC 96, Cranes, Subcommittee SC 3, Ropes.

Quote (https://kebs.isolutions.iso.org/obp/ui#iso:std:iso...)

This fifth edition cancels and replaces the fourth edition (ISO 4309:2010), which has been technically revised and contains the following changes:

— magnetic rope test (MRT) methodology and discard criteria are introduced, as an aid to the internal inspection of wire ropes;
— guidance is given on when to use magnetic rope testing and how to combine its results with other inspection results;
— an example of an MRT report is provided.

I have attached an interesting report "Design of a Ski Lift Inspection & Maintenance System : May 9, 2018" this is a rather extensive report on US maintenance practice of ski lifts (different type from the subject lift).

A comparison of ski lift accidents to elevators both have very low but non zero accident history is telling. Cable failures are rare, but not unknown. Even at this level economics can drive inspections to be more frequent than the minimum required by law.

RE: Cable car disaster in Italy

Quote:

That just proves that sh*t does flow downhill.

The gravity of the situation...

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

-Dik

RE: Cable car disaster in Italy

I knew somebody would have the 100MM miles statistics.

So, ski lifts travel is apparently 2x as dangerous as auto travel and 68.4% of ski lift accidents involve death. Some work needed there.

Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

RE: Cable car disaster in Italy

One obvious safety improvement would be automatic safety bars; I've only had about 1% of my rides where someone actually pulled the safety bar into place. Often, I got up so early to drive to the resort that by midday, I was already bushed and half-asleep during the rides; not a formula for situational awareness and safe riding.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Cable car disaster in Italy

It appears the latest iteration of the ISO for cable cars doesn't require the wire brake (two redundant brakes (motor and mechanical brake) acting on the pull cable wheel are still mandatory). The rationale is that if the emergency brake fails and brakes, someone has to climb onto the car for repair - most gondolas these days don't have a conductor to do this. Also apparently "the cable never breaks"

RE: Cable car disaster in Italy

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!

RE: Cable car disaster in Italy

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.

RE: Cable car disaster in Italy

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!

RE: Cable car disaster in Italy

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.

RE: Cable car disaster in Italy

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

RE: Cable car disaster in Italy

Ugh. That’s truly horrific.

RE: Cable car disaster in Italy

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

RE: Cable car disaster in Italy

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

RE: Cable car disaster in Italy

Quote:

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

RE: Cable car disaster in Italy

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.

RE: Cable car disaster in Italy

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

RE: Cable car disaster in Italy

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?

RE: Cable car disaster in Italy

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).

RE: Cable car disaster in Italy

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

RE: Cable car disaster in Italy

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.

RE: Cable car disaster in Italy

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! https://www.youtube.com/watch?v=BKorP55Aqvg
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RE: Cable car disaster in Italy

Quote:

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!

RE: Cable car disaster in Italy

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.

RE: Cable car disaster in Italy

Quote:

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!

RE: Cable car disaster in Italy

(OP)
Well I'm not sure I really wanted to see that and at least glad they fuzzed out the faces.

But there sure was a huge force on the tow cable in the reverse direction such that the cabin was violently flung backwards. I guess several hundred metres of cable might supply that much force as it sags between the towers, but it seemed more than that for some reason.

Horrible horrible incident.

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

RE: Cable car disaster in Italy

Is the towing motor uphill or downhill? I'm thinking uphill, and that the towline snapped because it got jammed on the downhill side and the tow motor kept trying to pull the uphill side upward, but the cable wouldn't move, so it stretched until it snapped. This accounts for the extreme acceleration after the breakage, such that the car was turned 45 degrees, until the tension on the cable reduced enough for the car to catch up and level out. The angle would indicate that the downhill acceleration was on the order of 1g for almost a second and a half.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Cable car disaster in Italy

(OP)
I think for a two car system, the motor is often at the bottom. Hence the car coming down helps pull the car going up if that car is heavier or controls the car coming down if that one is heavier.

This helps in preventing you having to send a big power cable all the way to the top and easier to maintain the motor.

Any big cable car like that that I've been on as you get off at the top it slowly moves up the ramp as the weight in the car reduces and the line stretch is reduced a bit.

Still doesn't explain quite why there appears to be so much force pulling the car backwards, but you have a long weight of cable it is pulling up the hill I suppose which rests on the pulleys. So there would be a significant force, but not one which it hadn't seen for its 50 years of operation.

I've not seen any information on the cable released, but as the main people seemingly responsible are in prison (or at least one is) awaiting trial, this might not be seen until then.

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

RE: Cable car disaster in Italy

Quote:

I think for a two car system, the motor is often at the bottom. Hence the car coming down helps pull the car going up if that car is heavier or controls the car coming down if that one is heavier.

That makes a lot of sense. It appears the uphill cable broke on the way back down the hill, not in the station. Based on when the broken end reached the upper station, the break was maybe somewhere between the station and the first tower down. The upper pulley just being an idler would explain why the cable was able to reverse direction and pass backwards through the upper station easily.


Quote:

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 cable that seemed to cause the initial downwards acceleration was always going down, period. I don't know why you're finding this so hard to understand when it can clearly be seen in the video. I also don't need a grade school education on how the upper cable balances the weight of the cars.

RE: Cable car disaster in Italy

It took 2/3rd of a second for the car to be tilted about 45 degrees; that is not a pure gravity load. The only thing in the system that can apply a load that quickly is an extremely high tension on the tow cable. It takes nearly two seconds before the car is upright again, at which time it should only be under gravitational acceleration.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Cable car disaster in Italy

No, it wasn't just gravity. Isn't the travel distance about 800m and going uphill? The amount of pull from holding up that 800m of tow cable shouldn't be ignored. I'd take a guess that the tow cable length from the bottom to top could easily weight 15,000 to 20,000lbs.

RE: Cable car disaster in Italy

Quote:

A cable that long must grow and shrink a considerable amount with temperatures.
One system that I have seen has a very large diameter drive wheel with two grooves. The cable will go around one groove and then around a similar diameter, sliding idler wheel a few diameters away. The idler is slightly tilted so that one edge lines up with the bottom groove on the drive wheel and the other edge lines up with the second groove.
The serves the dual purpose of increasing the contact area and thus the friction on the drive wheel and the idler wheel maintains a constant tension on the cable.
The idler may be held against the tension of the cable by a weight and multi-part block arrangement.
If the drive is at the bottom, then the upper cable is needed to let one car pull the other car upwards as the first car is pulled downwards.

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

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