HN Theater @HNTheaterMonth

⬐ jonah

Be sure to check out the helicopter they're using, a Kaman M-MAX. It had dual counter-rotating rotors and not tailrotor. It's also basically designed specifically for this kind of lifting/hauling job with a very narrow cockpit allowing the pilot to easily see what he's doing below.

http://www.kaman.com/aerosystems/solutions/air-vehicles-mro/...

https://www.youtube.com/watch?v=iEx3dJTIjww

They've also developed an unmanned version for military resupply missions:

https://www.youtube.com/watch?v=jQ4X7Y2ydS0

http://jalopnik.com/this-is-the-weirdest-dang-helicopter-i-h...

⬐ Gravityloss

The synchropter is originally a German design. It's a fascinating way of solving the torque problem.

⬐ robryk

Usually tying an in-flight helicopter to the ground is a huge no-no. E.g. there's a subtle sequence of steps for airlifting a casualty from a steep hillside that prevents the helicopter from ever being connected by a rope to the ground (the reasoning, AFAIK, is that the helocpter migth need to depart or move at a very short notice and the line may hinder it and injure people if it breaks).

It seems that there are reasonably long period of time here when the helicopter is still connected to a tower segment when the workers are in the process of screwing bolts in. Why isn't this problematic?

⬐ sandworm101

Google how the canadian navy lands helos on ships in heavy seas. They drop a line, tie the helo to the boat, and literally winch it down onto the deck. The helo pulls against the line so as the deck rises so does the aircraft. Joined by the line, boat and helo move up and down as one. It sounds crazy but really works.

⬐ user2283

I googled it, but didn't find anything involving a rope. Can you post a link?

⬐ sandworm101

https://www.youtube.com/watch?v=tAbm2XDpx9w

You need to see it in HD to see the rope. It's called "recovery assisted landing" or sometimes "hauldown".

⬐ Animats

The high-tension power-line tower people have a better approach.[1] They have a way to make the tower segments self-align, using a square of cables that fits around angled guides atop the section already in place. So the helicopter puts a section on without help from the ground, and with no workers near the tower. Once the helicopter has cast off, workers climb up and bolt the sections together, and remove the alignment guides.

Ski lift installations are rare, but power line towers go up by the tens of thousands. So the power line people need a way to do this routinely and safely.

[1] https://www.youtube.com/watch?v=YdynKxCloUQ

⬐ cperciva

I'd assume the sequence of states is:

1. Tower segment is hanging from helicopter.

2. Tower segment is in place with pins preventing it from falling over, but can be lifted away by the helicopter.

3. Tower segment is in place with pins preventing it from falling over, and will be released if the helicopter needs to fly away.

4. Tower segment is in place, fully secured by bolts.

The key point here is that under good conditions -- and they only ever do this under good conditions! -- a few pins is all it takes to stop the tower segment from falling over, but they won't stop the helicopter from lifting it off again. Securing the tower with two dozen bolts is only necessary when you want it to stay in place during strong winds and with the added load of the lift cable + chairs.

⬐ joering2

Good summary but what is not shown here is that once the lifted element "settles" on element below and all pins are in, the helicopter releases the hold immediately.

This is due to the calculated risk of something going wrong: workers on the pole can quickly move around if the unmounted pole starts falling, similar to lumbar can quickly change position when tree falls. With helicopter however, a violent pull of attached line could probably end up with part of helicopter being chunked out of the hull.

⬐ 6nf

There's no escaping the fact that this is a dangerous operation. The guys bolting the segments together can easily sustain a solid knock to the head, or get a finger squashed, etc. The helicopter pilot has a lot of responsibility hanging from his vehicle!

⬐ dsfyu404ed

There's a difference between "not white collar safe" and "dangerous".

Deck hand on Indian fishing trawler is more toward the dangerous end. This is pretty in the middle. Very few variables are uncontrolled here. Anything involving confined spaces and chemicals is definitely more on the dangerous end.

⬐ nippoo

In an emergency the helicopter can just drop the load: the pilot can release the hook and fly away. Unlike carrying a casualty, this is unlikely to be anywhere near as dangerous. If the tower is somewhat bolted on, it'll probably stick there long enough for the other bolts to go in. Worst case, it tips over and falls to the ground, but in any case it's unlikely for there to be any injuries.

⬐ Zaheer

Drop the load while there are hardhats waiting on the ground below? Uh ya that's probably not happening here.

⬐ zymhan

Did we watch the same video? There were people below that helicopter quite often. I'm not sure how you'd go about just dropping the pole.

⬐ giarc

They are referring to releasing the load when it's connected to the ground through the tower. Meaning some bolts are in place, therefore is probably unlikely to tip over.

⬐ robryk

As far as I know, one of the reasons why dropping the load is considered dangerous is that the line that was holding the load will be suddenly released from high tension, so it will go flying at fast enough speed to injure someone.

⬐ None

None

⬐ laurencei

Medical helicopters usually have a firing bolt/cuter that the pilot controls.

In the event there is a risk to the helicopter due to the winch operation (such as the line becoming stuck in some tress below) - the pilot has the ability to cut the cable to ensure the helicopter is not compromised.

⬐ robryk

So why does the following manual go to such lengths to prevent the winch line from ever being tied to the ground?

http://www.raf.mod.uk/rafsearchandrescue/rafcms/mediafiles/7...

⬐ ChuckMcM

That is a really good question. Its possible that the helicopter has a quick disconnect on top which simply drops the pole segment although that would seem to endanger the people on the ground.

The use of guide cables/pins was really neat. Assuming the camera is 'real' time (it wasn't sped up for the video) it looks like about 15 seconds between starting to pull the guide cables through to the point where they have two bolts installed. So a pretty narrow window for problems, of course you wouldn't do it when it was windy out either.

⬐ robryk

Such a mechanism might also endanger the helicopter: releasing a line under high tension will cause both ends of the release mechanism to rapidly accelerate away from the connection point.

⬐ dsfyu404ed

And if the connection point being released is on the helicopter... Think about it.

⬐ madengr

Don't some Navy and Coast Guard helicopters land by getting winched down onto a rolling deck?

⬐ nradov

Yes it's called RAST or "beartrap". https://www.curtisswrightds.com/products/naval-systems/helic...

⬐ None

None

⬐ None

None

⬐ brudgers

I suspect it is because the context of construction operations are calendar based. This allows for detailed planning; careful logistics and protocols that suspend flight operations under anything other than 'ideal' conditions. Protocols for rescue operations are designed around an expectation that operations are likely to happen in adverse weather conditions in rough terrain when minutes might be the difference between life and death.

The operations depicted are not uncommon on construction sites (e.g. when mounting rooftop equipment) and there are OSHA regulations for helicopter cranes. https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_id=...

⬐ rhcom2

And how ski lifts are destroyed: https://www.youtube.com/watch?v=u4WPSZojtyE

⬐ james_pm

Footage at 4:55 was terrifying. Incredible forces involved.

⬐ raldi

This could easily be its own front-page submission.

⬐ grecy

I ran ski chairlifts for a few years when I was sick of sitting at a desk.

We were shown this video during our training, and our boss said with a very straight face that if she were ever on a chair that started rolling backwards, she would jump off.

The reason "rollback" can happen is because the weight of all the people is only on one side of the line, and that weight wants to come back downhill. The chair has a couple of different kinds of brakes that are supposed to prevent this, but you can see what happens when it fails / is engaged too late.

Two broken legs are better than that.

NOTE HOWEVER: Newer "Detachable" or "high-speed" chairs and gondolas are often designed to run in reverse, so don't immediately jump off one of those if it goes backwards.

⬐ arethuza

As someone who has spent a lot of time sitting in chairlifts over the years that's a pretty terrifying video - amazing that I'd never even considered what would happen if a lift ran backwards!

I wonder if the "up and down" lifts that go down and up a valley (e.g. there is one at Alpe d'Huez) or over a ridge (e.g. the one at Val d'Isere) suffer from the same problem - even allowing for the fact that I'm pretty sure that they are modern detachables.

⬐ grecy

> amazing that I'd never even considered what would happen if a lift ran backwards!

Until you work a chairlift they are all fun and games.. after.. well, they are serious pieces of heavy machinery.

On my first day running one I hit the stop button and then watched the chair continue for ~5 feet, which snapped a young ladies Femur clean in two about 3 feet from my face. Safe to say that was not pretty.

I've also seen countless people knocked out by them, seen full derailments (scary) but happily never seen fingers or hands go into places they shouldn't.

Also had guests fall off the chair and die.

so yeah, very serious.

> I wonder if the "up and down" lifts that go down and up a valley suffer from the same problem

My gut says yes, because when all is said and done they are moving a lot of mass from down to up, and all that mass is still only on one side.

⬐ hammock

Femur...What... Can you give note detail on that? Emergency stop?

⬐ grecy

I was at the top station, she was coming up on a chair by herself. She had one arm wound through the slats in the back of the chair, and was using her phone with the other hand so she didn't see the unload coming up.

Her snowboard was dangling and caught on the beginning of the unload ramp. About that time I hit the e-stop, though of course a many-hundred ton machine with a 1200hp drive motor is going to continue for a bit before it actually stops moving. Even with the e-stop a big heavy four-seater fixed grip will go 6-8-10 feet or so. If it wasn't my first day maybe I would have hit that button sooner.

(Side note, they make the chairs heavy on purpose so they are less susceptible to the wind.. Otherwise they blow around and hit towers. I have been sitting on a chair when it slammed sideways into a tower before. Not fun)

Her board caught in the snow and started to pull her forwards off the chair, but her arm through the slats stopped that happening, so the chair started to swing back and load up with all the forces. It got to quite an impressive angle before something gave way, and it was her femur, because it was half off the leading edge of the chair.

Obviously that was a major ski patrol incident, and I had to write witness statements and draw diagrams of the whole thing in case she tried to sue the resort within 7 years (California...)

Another day I watched a liftie raking the top ramp look up just in time for the chair to smash him right on the forehead - he was out cold for 10 minutes.

That same guy was later scooped up by the chair at the top, and the sudden weight in the chair as it went around the bull wheel caused a derailment. The haul rope (cable) came out of the bull wheel (the big wheel at the top). This is a pain in the ass to fix, especially when there is the weight of hundreds of people sitting on the haul rope. That was a full manual evacuation, which takes hours and hours of lowering people down with ropes.

Some of my best days were "saving" people from getting hit. At the bottom once you have worked 100+ days you can see an issue coming three chairs before it happens, so it's like you are Superman. Often kids would be in the worst possible place and were about to get creamed by the big heavy chair. It's not possible to hold the chair back (even if you could , maint. doesn't want us doing that, we can damage stuff) and the e-stop won't stop it in time. I hate seeing kids get hit, so I would run over and tackle them to the ground, holding them down while the chair sails over both of us. Everyone lined up would cheer. It was great fun!

Of course, we screwed around a lot too - holding on the chair and letting it drag us along the snow, sitting on the chair and waiting to be the last to jump off into the powder, trying to "hurdle" the chair as it comes towards you (which was insanely hard because you have to jump the chair, but duck the steel bar at the top)

All in all, really, really good times.

⬐ hammock

What an awful thing to happen on your first day. Thanks for sharing your stories. Another reason added to the list why I'll never try snowboarding (skiier).

I was out in Aspen two weeks ago and we were wondering if the lifties get drug tested (never thought about it before). I said they have to, they are responsible for other people's lives and safety. My friends all said no way.

What's your experience?

⬐ grecy

I have not been a liftie since about 2007, and back then I think drug testing was at bosses discretion.

Where I worked literally every single employee on the mntn smoked, so if you were a pain the neck to your boss they would ask for a drug test and you were basically fired.

In Canada, as far as I know, it never happened (I worked there a few seasons, everyone smoked)

I would say on the majority of days that other people lives and safety were in our hands, the vast majority of lifties were severely hungover and/or stoned.

⬐ None

None

⬐ arethuza

Not good - only bad skiing lift accident I have seen was over 30 years ago when I saw someone hit in the head by a flying T-bar - lots of blood but I think (hope) that it looked worse than it was.

Did see 2 guys jump from a chair from about 10m up onto a pretty horizontal surface - no idea what they were thinking fortunately the snow was quite deep so they just looked dazed rather than badly injured.

⬐ poirier

Here's a smaller clip: https://www.youtube.com/watch?v=FwPP4i7ENvQ

⬐ caconym_

Cool video of a K-MAX in action. That's a really unique aircraft: https://en.wikipedia.org/wiki/Kaman_K-MAX

⬐ pxeboot

Watching the cable get run would be much more interesting.

⬐ monk_e_boy

PEAK 2 PEAK Gondola - Cable Installation

2:12 https://www.youtube.com/watch?v=IHsF1kRKEV0

TLDR; Spool out cable (rope), lift the end up with helicopter drape it over the sheave train (the wheels on the cross arm) pull out more rope, etc

⬐ techman9

Oh my god, there's a guy riding on the outside at the end of the video. I've been on this lift several times and it's scary enough in the cabins, I couldn't imagine doing that in a million years.

⬐ stinos

You should try a different angle of imagination: the guy is tied to the cabin (or maybe even the part that is directly tied to the ropes) with a safety harness. You on the other hand, are just standing/sitting in the cabin, not tied to it. Should the doors open, should the attachment somehow fail, ... you would actually be in a less safe situation than the guy. Yeah I know the chances of any of these are minimal, but the chance of anything going very wrong with lifts is on average minimal. Trying to think in another way about it sometimes does wonders for deaing with fears, at least for me.

⬐ salimmadjd

How do they tie the cables together? To get 9KM of cable they must use multiple spools and somehow tie them together. I'm curious how they're joined so they do not become the "weakest link in the chain" and are not too bulky for the wheels.

⬐ teh_klev

There's another video here that covers the splicing aspect:

https://www.youtube.com/watch?v=5itSfxJoXY4

⬐ lflux

It's spliced like any other rope, you can see this in action here: https://youtu.be/5itSfxJoXY4?t=183

The splice for the Vail lift is about 300 feet long apparently.

⬐ tschellenbach

Ski-resort tycoon, now that would be an awesome game :)

⬐ mstade

I'd pay money for this!

⬐ clarkm

You're in luck: https://en.wikipedia.org/wiki/Ski_Resort_Tycoon

I used to play it quite a bit when it first came out.

⬐ mstade

You Sir will be the end of me, or at least my productivity. Thanks for the tip! :o)

⬐ apk17

In this day and age it's not that fun anymore. You need to prepare what to do when there is a lot less snow around.

⬐ tenaciousJk

I never knew I always wanted to know. Neat.

⬐ BenjaminDyer

Thats quite fascinating to watch, however I'm not sure if I missed it but I didn't see the tower being earthed. Those installers must have some impressive protection in place.

I used to be a volunteer on an emergency lifeboat crew, we would do a lot of drills with a man on a winch and the first rule is, don't touch until he's earthed. Helicopters pick up a hell of a lot of static electricity so you normally see a small earthing line hanging below the man on the end of the line.

One time we were practicing fast recovery, the boat and the helicopter doing crew exchange at high speed. We screwed it up and the static charge blew a hole in the side of the boat!

⬐ sidegrid

Where are you from? Never heard anyone use earthed instead of grounded.

⬐ BenjaminDyer

UK, Electronic Engineer originally. We tend to use both terms I think.

TIL: Not everyone uses the term earthed!

⬐ None

None

⬐ pcarolan

Compare this to the cost of installing light/medium rail in your city. Why we dont install these in every city baffles me. You could run them right alongside buildings.

⬐ daviding

DisneyWorld seem to be planning a gondola-based system for between two parks and two hotels. It is cheaper than extending the mono-rail and probably nicer for all than the usual buses they have.

http://wdwnt.com/blog/2017/04/depth-speculation-disney-world...

⬐ gregcrv

Some cities already have them and a lot of new projects are being built too.

http://www.curbed.com/2016/7/25/12248896/urban-gondolas-cabl... http://www.curbed.com/2016/5/19/11714678/urban-cable-austin-...

⬐ degenerate

They are great for getting up a mountainside, but horizontally... they might be too slow. What if we simply speed them up? Maybe too dangerous... but I'd love to see a proof of concept, maybe on a tech campus, and see how it does. I don't see any downside because ski lifts are so damn fun.

⬐ None

None

⬐ pcarolan

Fun is a great reason to do this. Id love to see the Chicago loop from the sky for example.

⬐ pjc50

La Paz actually has a gondola-based commuter system: https://en.wikipedia.org/wiki/Mi_Telef%C3%A9rico

Unique geography there; the city is in a bowl, but El Alto, its main commuter suburb, is on the high plain above the rim of the bowl. There is a single road linking them, which in rush hour is jammed with minibuses.

London also has its "Emirates Air Line", which is a pointless gimmick that doesn't serve a useful route.

⬐ volkl47

They're not really comparable, rail offers far higher passenger capacities and multiple stops are much more practical.

While you can make a multiple stage detachable gondola, every detach point/stage is adding significantly more points of failure and complexity. There is a reason you don't see more than ~3-4 stages and that's it.

They are also very maintenance intensive and not all that reliable.

⬐ gehsty

Rio de Janeiro has these to help people travel around favelas. Really great as they can be installed nearly anywhere and they allow people to travel from point to point without navigating the potentially dangerous streets.

⬐ Cthulhu_

Those have a lot more requirements; capacity and such was already mentioned by others, but things like e.g. wheelchair accessibility is also important.

⬐ None

None

⬐ ethagknight

Because they can only haul 2,000 people per hour, with limited travel lengths and single point termini

⬐ pcarolan

Detachable gondolas exist which means you can travel any length you want if you switch cables and have as many terminals as you want.

https://en.wikipedia.org/wiki/Detachable_chairlift

⬐ Retric

2000 people per hour per direction is a person every 2 seconds per direction which is not that far from a highway with single occupant cars. 1900 per lane is peak, but congestion is much slower. Speed is an issue, but larger gondolas can move more people fairly quickly.

⬐ Fezzik

A slight modification: though slow, they can have multiple un/loading points. The main gondola at Whistler has a mid-mountain loading point along with a top and bottom un/loading point. The Peak to Peak Gondola only has a loading point at each end because it's crossing a giant chasm.

Your point stands though: gondolas are probably not a great form of transport. That said, I have no idea what the speed limits would be for a gondola that was designed for speed.

⬐ pcarolan

They have those unloading points because they are able to take them off of the cable while loading and unloading. We don't design these for cities, but we could. This means loading/unloading could be coordinated across multiple nodes and you could even switch tracks which takes care of the fixed distance problem. Detachable chairlifts can do 12mph which is faster than many city buses. https://en.wikipedia.org/wiki/Detachable_chairlift

⬐ jacquesm

Judging by the curve of the cable the load is suspended from they're not exactly slacking either while moving it to the drop site.

⬐ zyztem

TL;DR: with helicopter, one section at a time

⬐ rattray

Mods: should perhaps be labeled with (2011)

Fun video

⬐ mmmpop

All that work and still 25 minute lines on a powder day...

⬐ AlphaWeaver

[video] (2011)

⬐ jonknee

Because ski lift installation has changed since 2011?

⬐ grzm

It's common on HN to include the year if it's not from the current year. It's not a reflection on the submission's appropriateness: it's just additional information many find useful, just as the [video] tag is.

⬐ blhack

Those bolts strapped to the grating as they were putting the top piece on... I love that stuff!

What I mean is: pre-optimizations like that. My current cofounder and I build and run fire effects [flamethrowers] at music festivals, and every load-in/setup is a fun game of seeing what ways we can optimize our setup process. Stuff like figuring out the wrenches and tools we need to assemble a specific component, and then storing those tools with the component.

Seeing those bolts sitting on the grate like that (I think it was 4 on each side) means that somebody had the foresight to realize that it was easier to strap the bolts to the piece like that, than to have the guys assembling it carry them with them up the ladders (imagine if they forgot one, what a pain that would be).

So freaking cool.

⬐ None

None

⬐ tinbad

"means that somebody had the foresight to realize that it was easier to strap the bolts to the piece like that"

Not to curb your enthusiasm or downplay the ingenuity of those builders, but the assembly process seems fairly repetitive and easier to optimize over time. I doubt they had this foresight before doing the first (ever) pole.

⬐ krschultz

Easier to optimize than what? I used to work on manufacturing nuclear submarines. We built exactly 1 of many things. You'd think that would mean there was no repetition, but that's not the case. The processes are repetitive, even if the product is not. Everything can and should be optimized, that's the only pathway to higher productivity.

⬐ tinbad

Easier than doing it the first couple times: whoever came up with the improvement first, before this knowledge was institutionalized within the organization/field.

⬐ None

None

⬐ blhack

That's exactly the type of iterative improvement I'm talking about.

It's like building a really good workshop. Ideally everything is exactly where it needs to be, and in the exact order you might need it.

Another example is: my electronics assembly dreamcart (that I haven't gotten to build yet):

-18-24ga stranded wire in at least 3 different colors on spools above the worktable

-Soldering iron

-Oscilloscope

-Power supply

-Multimeter

-Strippers/side cutters [1]

-Crimpers

-Crimps/ferrules

-Network switch/ethernet cables

All of this stuff on a cart that is on casters, with a UPS that can power it so if I need to move away from an outlet I can.

I didn't figure out exactly the tools I wanted and how I wanted them arranged on my first project, but over time I figured out the exact tools I want, and where in my workspace I want them, so that I have to spend as little time as possible looking for things, or thinking about where they might be.

I think seeing the little improvements people have made is really cool. Like the bolts. It's cool because maybe the didn't figure it out on the first time.

[1]: I particularly like this one because it puts the strippers and the side cutters in the same hand, which is just closer to my optimal dream-shop/workflow: https://www.amazon.com/DA76070-KLENK-Wire-Cutter-Stripper-Sm...

⬐ sandworm101

Be careful about that. In a past life I installed and ran lighting rigs at concerts. One tower contractor thought it wise to ducktape bolts to parts so, rather than pass equipment up and down, the bolts would be exactly where the climbers would need them. But they didn't use/find all the bolts. A week later the tape dried out and a 6" bolt and nut fell onto a mixing board ... which was far easier to replace than the audio tech it missed by inches. He refused to work until I, with climbing helmet, was sent into the rigging to inspect every bit of metal. The stage was closed for nearly a day.

⬐ blhack

Ah, thanks for the heads up. Luckily due to the nature of what we're doing, everything gets inspected and re-inspected a few times when we build it.

Definitely something to keep in mind though.

⬐ sandworm101

I took a very strict approach when it came to things over people's heads. I never allowed anything "extra" up there. There were no spare bulbs tucked away somewhere, no pile of twofers left on a gangway. I even pealed every tiny bit of tape off each truss. If it wasn't needed and secured it stayed on the ground. My worry was always what might happen in an earthquake.

As a lighting guy I saw to much stuff fall from the sky. One concert hall I worked at used a rice-paper snow effect for a Japanese show. Four years later we still had the occasional bit of rice paper glide slowly down from 100' up. It could never hurt anyone, but film/TV clients who used the hall would be screaming mad when they saw it.