9 ms·

How can a ski lift allow turns to the left and the right on its route? [video]

336 points by dan-robertson 5y ago

42jd 5y ago
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!
DaveExeter 5y ago
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 5y ago
  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 5y ago
  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.
throwaway23490 5y ago
"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 https://www.youtube.com/watch?v=uN4kS78vk4E
Sosh101 5y ago
I love skiing, and I also love contemplating the engineering that's dragging my fat ass to the top.
- thrdbndndn 5y ago
  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.
  - deleted 5y ago
    [deleted]
dan-robertson 5y ago
Apologies for the editorialised title. It felt better to me to be descriptive than to take the click-bait title from the video.
- dTal 5y ago
  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 5y ago
    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 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 5y ago
      My mistake, dang! I should probably find the time to reread those guidelines, eh?
      - dang 5y ago
        I just changed them so now would be a good time :) https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
teeray 5y ago
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 5y ago
  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).
zeckalpha 5y ago
Related: how can a gondola move slower or stop while it is on/offboarding without stopping the rest of the cars?
- ilyagr 5y ago
  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.
  - a-dub 5y ago
    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.
  - snowytrees 5y ago
    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 https://www.youtube.com/watch?v=xEAJmxe27h0
  - jffry 5y ago
    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 https://youtu.be/589uRMy4Ty4?t=222
the_mitsuhiko 5y ago
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 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.jpg https://blog.jacomet.ch/wp-content/20170120-schwanden-052.jp...
- ethagknight 5y ago
  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.
zuhayeer 5y ago
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 5y ago
  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.
avianlyric 5y ago
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 https://youtu.be/M7ghP4YTk3M?t=204
eastdakota 5y ago
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 https://www.youtube.com/watch?v=uimHqekX__4
euske 5y ago
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 http://cable.cocolog-nifty.com/sakudo/2006/02/post_d5e1.html
- moffkalast 5y ago
  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?
  - Tarq0n 5y ago
    I guess skiing comes with a high acceptance of risk to begin with.
  - ceejayoz 5y ago
    There’s a reason everyone signs a waiver before they give you the pass.
    - thecopy 5y ago
      I have never encountered this in Europe. Or i might be misunderstanding what you mean
    - moffkalast 5y ago
      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.
Animats 5y ago
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.
travisgriggs 5y ago
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.
deleted 5y ago
[deleted]
bujak300 5y ago
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 5y ago
  But the rope can't get steeper at a mast. This works well when there are no sharply increasing slopes at the hill.
- wbl 5y ago
  How is the rope supported by the mast?
faebi 5y ago
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.
deleted 5y ago
[deleted]
isoblvck 5y ago
it's a chair on a string why is it surprising that the line can turn?
tgsovlerkhgsel 5y ago
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.
swader999 5y ago
Still waiting for a drone powered personal poma tow. Maybe this will do for the time being: https://www.zoaeng.com/ https://www.zoaeng.com/
- lambdatronics 5y ago
  It's been done, although I doubt it's cost-effective. :D https://youtu.be/At3xcj-pTjg?t=87 https://youtu.be/At3xcj-pTjg?t=87
immmmmm 5y ago
"Pas de Boeuf" in St Luc does 4 direction with a single cable. different system tho. https://youtu.be/8a4cvYpKGxg https://youtu.be/8a4cvYpKGxg

336 points by dan-robertson 5y ago

42jd 5y ago

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!

DaveExeter 5y ago

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 5y ago
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 5y ago
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.

throwaway23490 5y ago

"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 https://www.youtube.com/watch?v=uN4kS78vk4E

Sosh101 5y ago

I love skiing, and I also love contemplating the engineering that's dragging my fat ass to the top.

thrdbndndn 5y ago
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.
- deleted 5y ago
  [deleted]

dan-robertson 5y ago

Apologies for the editorialised title. It felt better to me to be descriptive than to take the click-bait title from the video.

dTal 5y ago
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 5y ago
  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 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 5y ago
    My mistake, dang! I should probably find the time to reread those guidelines, eh?
    - dang 5y ago
      I just changed them so now would be a good time :) https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html

teeray 5y ago

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 5y ago
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).

zeckalpha 5y ago

Related: how can a gondola move slower or stop while it is on/offboarding without stopping the rest of the cars?

ilyagr 5y ago
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.
- a-dub 5y ago
  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.
- snowytrees 5y ago
  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 https://www.youtube.com/watch?v=xEAJmxe27h0
- jffry 5y ago
  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 https://youtu.be/589uRMy4Ty4?t=222

the_mitsuhiko 5y ago

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 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.jpg https://blog.jacomet.ch/wp-content/20170120-schwanden-052.jp...

ethagknight 5y ago
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.

zuhayeer 5y ago

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 5y ago
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.

avianlyric 5y ago

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 https://youtu.be/M7ghP4YTk3M?t=204

eastdakota 5y ago

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 https://www.youtube.com/watch?v=uimHqekX__4

euske 5y ago

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

moffkalast 5y ago
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?
- Tarq0n 5y ago
  I guess skiing comes with a high acceptance of risk to begin with.
- ceejayoz 5y ago
  There’s a reason everyone signs a waiver before they give you the pass.
  - thecopy 5y ago
    I have never encountered this in Europe. Or i might be misunderstanding what you mean
  - moffkalast 5y ago
    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.

Animats 5y ago

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.

travisgriggs 5y ago

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.

deleted 5y ago

[deleted]

bujak300 5y ago

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 5y ago
But the rope can't get steeper at a mast. This works well when there are no sharply increasing slopes at the hill.
wbl 5y ago
How is the rope supported by the mast?

faebi 5y ago

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.

deleted 5y ago

[deleted]

isoblvck 5y ago

it's a chair on a string why is it surprising that the line can turn?

tgsovlerkhgsel 5y ago

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.

swader999 5y ago

Still waiting for a drone powered personal poma tow. Maybe this will do for the time being: https://www.zoaeng.com/ https://www.zoaeng.com/

lambdatronics 5y ago
It's been done, although I doubt it's cost-effective. :D https://youtu.be/At3xcj-pTjg?t=87 https://youtu.be/At3xcj-pTjg?t=87

immmmmm 5y ago

"Pas de Boeuf" in St Luc does 4 direction with a single cable. different system tho. https://youtu.be/8a4cvYpKGxg https://youtu.be/8a4cvYpKGxg