HN Theater @HNTheaterMonth

The best talks and videos of Hacker News.

Hacker News Comments on
The IMPOSSIBLE skilift that actually exists

kalsan15 · Youtube · 336 HN points · 0 HN comments
HN Theater has aggregated all Hacker News stories and comments that mention kalsan15's video "The IMPOSSIBLE skilift that actually exists".
Youtube Summary
Traditional skilifts cannot turn in all four directions due to the way they are built. And yet there is one to defeat this limitation with a surprisingly simple invention. Discover the Hohstock skilift, built in 1982 and the very last of its kind located in Switzerland.


Technical data:

Location: Belalp (Naters VS), Switzerland
Length: 1815m
Altitute: 2654-3113m over sea level
Producers: Borer, Küpfer, Kissling


Further links (in German, use a translation service):
- Technical data: https://www.seilbahninventar.ch/objekt.php?objid=42319&lang=de
- History (Belalp): https://www.belalp.ch/belalpbahnen/geschichte.php
- Skilift technologies: https://de.wikipedia.org/wiki/Kurvenschlepplift#Zweiseillift
- Liftworld (overview): https://seilbahntechnik.net/de/lifts/1254/datas.htm
- Gondelbahn Monde (video of full ride): https://www.youtube.com/watch?v=UdQmKq52jB8
HN Theater Rankings

Hacker News Stories and Comments

All the comments and stories posted to Hacker News that reference this video.
Dec 04, 2021 · 336 points, 68 comments · submitted by dan-robertson
the_mitsuhiko
It's BTW also possible to make a left turn on a single rope if you push something against the t-bars. In German it's called "Bachmannkurve" and it uses a giant wheel. You can see it in action here: https://www.youtube.com/watch?v=gfw4em7e2OQ

Video quality is bad, but this is what it looks like on a picture: https://blog.jacomet.ch/wp-content/20170120-schwanden-052.jp...

ethagknight
I’m so glad you posted that, that was the solution I had in my head when the OP narrator asked the viewer to pause and consider a solution. Very interesting.
euske
In Japan, there were a couple of ski lifts that make almost 90-degree turn, called "bending lift (屈曲リフト)". Near the turning point they put up a warning sign like "please hold tight or you might be thrown off". As a kid I always enjoyed the experience though. Sadly all of them have been torn down by about a decade ago, due to its high maintenance cost.

cf. http://cable.cocolog-nifty.com/sakudo/2006/02/post_d5e1.html

moffkalast
You know, it really baffles me how these things can operate safely with the general population. No way for the operator to keep track of the whole thing and thus no way to stop in an emergency, countless ways to injure yourself or others, yet there seems to be hardly any regulation for them (given the laughably sorry state some of them are in) and apparently not that many injuries either.

Compare that to most household products with a thousand warning labels for things that are common sense and/or completely harmless. Like do idiots not go skiing or something?

swader999
You could say the exact same thing about elevators. There's a lot of regulation, inspection and safety features that isn't well known about these lifts. But it does exist and the safety record is impressive. The drive to the hill is a much higher risk.
amluto
> keep track of the whole thing

Do you really expect a human to usefully monitor the whole thing continuously? If you look at a modern lift, there is quite an array of sensors on each tower.

> no way to stop in an emergency

There's an emergency stop button at both ends. They get used on a regular basis due to emergencies. By far the most common emergency is someone falling in the loading or unloading area. (I think a lot of high capacity lifts actually have multiple emergency stop buttons at each end so that any of several operators can stop the lifts.)

Tarq0n
I guess skiing comes with a high acceptance of risk to begin with.
ceejayoz
There’s a reason everyone signs a waiver before they give you the pass.
thecopy
I have never encountered this in Europe. Or i might be misunderstanding what you mean
moffkalast
Never signed anything and have been on some rustbuckets of anchor-style ski lifts. The full seat ones are usually better maintained, but imo an anchor to the face shoulld be pretty nasty.
tjohns
The liability waiver is printed on the back of the lift ticket, and you accept it by virtue of using the ticket.

(I don’t know about the legalities of that as a contract, but it’s how it’s almost always done at ski resorts.)

jdavis703
There’s a lot of ways to die or become severely injured while skiing. I imagine that alone weeds out people who need warning labels on blenders.
Animats
Those are elegant solutions.

The way the San Francisco cable cars work is more brutal. You can look up the details. Some tough spots involve metal sliding on metal. There are soft metal grip guides and "chafe bars" at turns intended to wear out and be replaced frequently. The cable itself has to be replaced every 6 months or so. It's 1870s technology.

42jd
This was a delightful video! as an avid skier I always noticed that chairlifts that turn are pretty uncommon, but I have never thought deeply into why. the final lift shown that can move in all four directions is definitely some ingenious engineering!
eastdakota
Alta Utah's Supreme Lift makes a 10° left turn without detaching from the cable using a traditional angle station: https://www.youtube.com/watch?v=uimHqekX__4
travisgriggs
It is a cool solution. But I’m not sure I agree with the narrator that “any child would figure it out.” They essentially turn the “cable” into a “ribbon” and then can do mobius like things.
teeray
Pretty impressive to see for fixed-grip. The only time I’ve seen a turn is the Blackcomb gondola. That’s detachable though, so it’s basically two lifts together with the mid-station doing the turn as it ferries cabins between them.
gorbypark
Whistler Blackcomb actually has three gondolas that are like that. Excalibur (aka the old Blackcomb gondola), the Village Gondola and the new Blackcomb Gondola are all basically two lifts smushed together so they can make a bend (and also to allow loading people mid-mountain among other reasons).
Sosh101
I love skiing, and I also love contemplating the engineering that's dragging my fat ass to the top.
thrdbndndn
I only skied once in my whole life, but I definitely have been thinking of the mechanism of ski lift a lot since childhood. It's just fascinating.
Sosh101
Can you imagine being the project manger on the construction of one of these on a big mountain?
zuhayeer
Mindblown by the Hohstock skilift with the topmost mast being suspended in midair by the surrounding mountains. Incredible.

Anyone know how this was architected?

_nalply
I think there was a small glacier when the lift was build 1982. So they didn't have a choice and suspended the mast. I suppose when the glacier melt away they lowered the mast. It's not the only skilift with suspended masts. I know of a skilift in Verbier with suspended masts.

And how to architect it: you need steep rock walls not farther than about 300 meters (not sure here, just from what I've seen). Then «just» hang the mast from ropes attached to the rock walls.

I am sure that the word «just» is wrong here as this needs complicated engineering and as in the mountains the weather is harsh you'll need solid and antifragile solutions, as well.

bujak300
In the eastern bloc we have ski lifts where the bars go down vertiacaly from the cable. They are not attached from the side. So they can make left and right turns without any complications.
_nalply
But the rope can't get steeper at a mast. This works well when there are no sharply increasing slopes at the hill.
wbl
How is the rope supported by the mast?
zeckalpha
Related: how can a gondola move slower or stop while it is on/offboarding without stopping the rest of the cars?
teeray
The cabins are detachable from the cable. The two terminals coordinate timing so that you don’t end up with a pile up. Occasionally you can see the lift automatically stop a chair at the base to adjust timing.
amalcon
Detatchable chairlifts have always amazed me. They're definitely one of the bigger quality-of-life improvements that alpine skiing has ever seen. Not only do they let you ski more, but they also help keep you warm (any skier will tell you that the chairlift is always the coldest part) and increase the effective throughput of the lift.

The truly amazing thing, though, is the safety record: they have a mechanism to switch from a fast rope to a separate, slow rope and back. This transition (and, indeed, the grip on the rope) manages to have an excellent safety record despite being relatively complicated and dealing with snow and ice.

Akronymus
Over here, chair lifts often have a cupola you can use to shield you from most of the wind and that keeps you decently warm (After about 2 minutes when your body heat warms it up enough)
ilyagr
Every time a gondola car arrives to the station, it is detached from the main cable and put on a slower cable (or a belt?). I wish I knew the exact mechanism that makes this work reliably.
42jd
while not necessarily on how gondolas work, this is a great documentary on the engineering and design behind the peak2peak gondola at whistler: https://www.youtube.com/watch?v=xEAJmxe27h0
jffry
Maybe there are other mechanisms, but the one shown in [1] seems pretty simple. The top of the gondola arm has a flat spot, and there are both wheels and the cable mechanism on the underside.

In the station it detaches from the cable and just rides on the flat track, and then motor-driven tires push on the gondola to propel it at a controlled speed through the station.

[1] https://youtu.be/589uRMy4Ty4?t=222

a-dub
they detach and then roll on a series of rubber wheels that decelerate wheel by wheel on the way in and accelerate on the way out.

the grip itself is spring loaded and the spring force is measured every time the grip passes through a terminal. if a grip is weak, the lift stops.

if you look closely at a detachable grip, you'll see two wheels. those go into a funnel that squeeze open the spring loaded grip to release the haul rope. the chair or gondola cabin then is guided with one of those wheels while powered by the 20 or so small rubber wheels mentioned above that move the chair through the terminal. reattachment works the same, the wheels progressively speed up to the haul rope speed (5-6 m/s) as the funnel opens releasing the grip to snap back onto the haul rope.

position sensors throughout the terminal and at the towers stop the lift if anything is out of position. (or a grip is weak, as mentioned above)

and like any safety critical reliable system, a lot of hardworking humans check the system regularly.

bujak300
Either it is detaching from the cable or there is a "conveyor belt" for boarding on some simpler chairlifts
herdrick
https://www.google.com/search?q=detachable+ski+lift+mechanis...
42jd
chairs/gondolas detach from the primary rope that carries them up/down the slope. So while the primary rope is moving the same fast speed, the chair isn't attached to that rope anymore. This is what allows detachable lifts to go so much faster than fixed (non-detachable lifts), the speed of them isn't dependent on people being able to board. If a ski resort wants to speed up their fixed grip chairs without spending the money on a detachable, they will use a loading carpet to move up the max speed of loading people (see: https://liftblog.com/2016/01/02/the-loading-carpet-solution/)
scoot
Despite what the OPs video suggests, there are no ropes used, rather steel cables. A rope's mechanical properties wouldn't be beneficial for a ski lift.
anamexis
No, rope is correct. Wire rope, more precisely.

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

stevenjgarner
The jargon is contextual. In telecommunications the "wire rope" is called "strand".
Waterluvian
So is “rope” just any cord or any material that’s been braided or wound from many smaller cords?
johnwalkr
The terms are largely interchangeable but “wire rope” is the engineering term for cable used to transmit forces. Depending on who you ask it may only strictly refer to wire rope made from multiple bundles of strands.
fnord77
so we should call those things in San Francisco "Rope Cars"?
anamexis
Interestingly, the steel cables used by the cable cars are actually wrapped around a sisal rope.
scoot
You're correct - a wire rope is a cable, but a synthetic rope is not. But "rope" generally refers to synthetic rope, not wire rope, so a rope is not a cable.
johnwalkr
It doesn’t matter much but for a ski lift, the engineering term always used is “wire rope”.
marvin
Might also be a language matter on OP's part? For instance, I know that Europeans often use the term "windmill" for wind turbine, and get corrected that they're using the wrong engineering term.

But for many European languages, the word "wind turbine" would be translated to "windmill", even going as far as labelling parts with the word. Never worked with wind turbines, but been curious about this for years since the language is so systematic. A documentary I recently watched had a Danish wind turbine marked as "Mølle 1" or something like that, translating to "Mill 1".

I'd be surprised if Norwegians didn't use the word "kabel" (cable) to refer to the thing that carries ski lifts.

Akronymus
Wind turbine makes me think of turbines used to generate wind, rather than turbines powered by wind.
anamexis
Unless you’re talking about ski lifts, where rope refers to wire ropes.
scoot
Except that it doesn't, hence "cable car" (in International English).
anamexis
The point is that if you're going to pedantically correct someone, they need to be wrong. No one is wrong when they say rope.
scoot
Nothing pedantic about being correct when someone else is wrong. Nice try though.
anamexis
Someone else wasn't wrong.
Akronymus
"Seilbahn" in german. Literally translated as rope track.

The material that a rope is made out of, doesn't really matter. What matters is it being built up of smaller fibers.

nerdponx
I always knew these as "detachable" chairlifts, and I guess at some point as a kid I figured out that the chair must actually detach from the rope, based on the name.

I probably never would have even thought about it, if it wasn't for the name!

throwaway23490
"Two wrongs don't make right ... but three lefts do!"

Okay, so it was three rights to make a left, but same idea. I shall call this lift "Zoolander" in honor of [0].

[0] https://www.youtube.com/watch?v=uN4kS78vk4E

tgsovlerkhgsel
TL;DW: Most ski lifts use a clamp that attaches to the side of the rope, allowing the rope to have rollers pass on the top, bottom, and other side, but not the side with the clamp. This means you can't make tight turns towards the side with the clamp.

Instead of making a thinner clamp that can go through the rollers as I would have expected, they used two ropes with a hinge from which the "seat" (t-bar) hangs. That way, they can put either the left or the right rope on top, causing the "clamp" part to be on the left/right accordingly, allowing turns in both directions.

faebi
I grew up in the area of Chäserrugg. As a kid it took me really a lot of thinking to understand what's going on there while driving through. Sometimes it would be nice if more of the engineering thoughts could be exposed to the users.
wcoenen
Halfway the video, I realized I didn't quite catch what problem was being discussed exactly.

After rewatching, it's narrated around 2:55 but the video is not illustrating it at that point. This part would have benefited from a sketch showing how horizontal wheels would be required, and the resulting issue with the clamp.

immmmmm
"Pas de Boeuf" in St Luc does 4 direction with a single cable. different system tho. https://youtu.be/8a4cvYpKGxg
swader999
Still waiting for a drone powered personal poma tow. Maybe this will do for the time being: https://www.zoaeng.com/
lambdatronics
It's been done, although I doubt it's cost-effective. :D

https://youtu.be/At3xcj-pTjg?t=87

kazinator
Note that every ski lift has a sharp U-turn at either end, so ...
isoblvck
it's a chair on a string why is it surprising that the line can turn?
dan-robertson
Apologies for the editorialised title. It felt better to me to be descriptive than to take the click-bait title from the video.
dTal
Your title absolutely is better. I think HN's policy can be quite damaging.

Thanks for link to the amazing video, it's truly in the spirit of gratifying intellectual curiosity!

dang
Since the original title was clickbait, it was quite within HN's policy for dan-robertson to rewrite it:

"Please use the original title, unless it is misleading or linkbait; don't editorialize."

https://news.ycombinator.com/newsguidelines.html

When rewriting a title for correct (by the guidelines) reasons, the main thing is to use representative language that accurately and neutrally says what the article is about. Preferably the language should come from the article itself, though that's harder to check with a video. In any case, the rewrite here wasn't editorialized.

dTal
My mistake, dang! I should probably find the time to reread those guidelines, eh?
dang
I just changed them so now would be a good time :)

https://news.ycombinator.com/newsguidelines.html

DaveExeter
As an engineer, I say, yeah, fine.

But now you've got twice as much cable and twice as many rollers needed.

Not impressed. Do it without doubling all the equipment, that would impress me.

dan-robertson
The cables are twice as long but must there be twice as much? Surely the cables can be weaker and a cable break would be less catastrophic (though I’d assume the safety margins are high).

Ultimately the thing to achieve is an economical solution and this scheme (admittedly the last machine of its type) might be a lot cheaper than more earthworks or changing ski runs or building two lifts.

SkyPuncher
I'd argue you're optimizing for the wrong thing. Maintenance (ease and cost), reliability, and safety are extremely important. You could engineer a more complex solution, but why would you?

Everything in this is extremely simple and easy to maintain. You basically have 3 unique components:

* Dual left and right hangers for guides

* The mounting for the t-bar

* Dual line bullwheel

Of those, the t-bar grip is the only unique thing.

avianlyric
Not the only approach that's possible. There's quite a few lifts in France that pull a similar trick, but with only one cable.

They solve the problem by having the bar below the clamp be a flexible section, as the bar approaches the turn, a section a static rails forces the bar to rotate 30-40 deg around the cable, moving the protruding part of the clamp out of the horizontal plane. Then the cable passes around a large diameter wheel, also 30-40 from vertical, to create the turn.

Because both the bar and the wheel are both 30-40 degrees from vertical, the wheel meets the top of clamp, rather than the side, but cable can still make a turn in the horizontal plane. They're a little uncomfortable for the rider, because the bar you holding onto gets jerked left and right, but you make around the bend just fine, and without an elaborate 2 wire system.

I think the Chardonnet ski lift at Val d'Isère is an example of this type of lift, but I can't find any photos of the corner unfortunately.

For chair lifts, the lift at Ski Dubai has turn half way up, and their chairs are permanently clamped to the cable. For going up the chair just goes around the outside of normal wheel. For going down, to passes around an elaborate wheel with cutouts to make space for the chair clamp and bar. The running surface of this wheel is made up of smaller rollers, and there's a big friction break on hub. So a computer watches for incoming chairs, then slows the big wheel down as needed to align the chair with a cut out. You can catch a glimpse of this here (best video I could find)[2].

[2] https://youtu.be/M7ghP4YTk3M?t=204

HN Theater is an independent project and is not operated by Y Combinator or any of the video hosting platforms linked to on this site.
~ [email protected]
;laksdfhjdhksalkfj more things
yahnd.com ~ Privacy Policy ~
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.