Hacker News Reader

Comment by mindvirus | Hacker News Reader

This was a really neat read, thanks for sharing. The thought of a 2 mile high skyscraper is pretty neat. I'm curious if sway is really so easily solved as the article suggests.

If elevators are the limiting factor, I wonder how much of an engineering challenge it would be to have multiple elevator cars in a shift. I'm picturing a system where each floor has some number of elevator car parking spots off of the main shafts, and elevator cars move backward then horizontally first to get to the main shaft to travel vertically.

The other limiting factor I could see though is limits on parking, public transportation and utilities.

View on HN

The problem with making elevator shafts longer is the tensile strength of steel cables; a thicker cable weights more and so for a longer and longer cable more and more of the cable is only around to carry the cable itself, much the same way as increasing payload on a rocket. Thicker cables require bigger sheaves to avoid fatigue, but the sheave can't be larger than about half the shaft width. Just gets impractical.

The solution is cable-less elevators. Rack and pinion elevators seem to be used only for construction elevators, guessing NVH is not up to snuff. Thyssen Krupp has maglev elevators though (experimental): https://engineered.thyssenkrupp.com/en/multi-our-sideways-mo...

edit: Also if you go too fast it'd be really uncomfortable due to the air pressure changing too quickly. Vertical acceleration is also really unpleasant, personally I find the quickly accelerating elevators I've used to be very nauseating.

>Thyssen Krupp has maglev elevators though

Yes they do! I'm glad you mentioned them cause it isbpretty legit. I know one of their graphic designers (for brochures and stuff), and he was proud of their experimental elevator in Atlanta, Ga

Other option is to use something other than steel cable. Like carbon fiber, which at least marketing can get realistic use to 1000m...

Why not synthetic line? I think high-end winch cables are made out of poly propylene now and exceed the strength of steel for a given diameter

> Why not synthetic line?

Fire.

Elevator problems can be worked around with "sky lobbies" where an elevator only covers a portion of the available floors, then you have a lobby at points in the building where you can stack another elevator on top of the last one. So if you are on the bottom section you can get to any floor in one trip, otherwise its a maximum of two trips.

This image shows it off pretty well https://en.wikipedia.org/wiki/Sky_lobby#/media/File:World_Tr...

That diagram really highlights one of the points of the article -- the taller you go the more space you have to dedicate to elevators. Looking at that plan, nearly 1/3 of the floor space is taken up with elevators.

Multi-elevator systems have been talked about for a very long time, similar to trains. The problem is still that these layover spots or crossover points take up floor space. And one bad elevator has the potential to jam up the whole system, compared to today where one bad elevator only impacts its shaft.

Manhattan actually has a parking cap; with Manhattan today, the view is that building more parking mostly just encourages people to use it, and to accommodate Manhattan's existing land use would probably require paving over Manhattan, the rivers surrounding it, and a whole lot more.

With remote work, why are we still all trying to cram ourselves so close together?

Also, why isn't building down economical?

> With remote work, why are we still all trying to cram ourselves so close together?

For one thing, many jobs can't be done remotely.

But it's not just about work. People want to go to restaurants, community centers, live entertainment. The more sprawl there is, the fewer people can live within reasonable distance of it.

Even if you want to live in a single family home, tall buildings are good. Instead of having to drive an hour through a landscape of other single family homes, you can live in one closer to the city while some of the people who used to live there can live in the city because they prefer being within walking distance to having a half acre of grass. Currently there are more people who want that than most cities have housing units and many of them get priced out, which in turn makes it more expensive to live in the suburbs.

> Also, why isn't building down economical?

Several issues:

* Digging is expensive. There's several factors for this, but some unavoidable stuff include things like "you need to put the stuff you took out of the ground somewhere."

* The deeper you go, the hotter it gets. Although it's probably not that bad if you're only digging a mile or so.

* Natural light is hard to come by underground.

* Groundwater intrusion becomes a much more significant concern.

* Having to pump all of the sump water and sewage up to the sewer lines is not going to be fun.

The idea is thrown around enough that it has been named depthscrapers or earthscrapers. There are many articles on it, if you're curious: https://duckduckgo.com/?q=depthscrapers+OR+earthscrapers&ia=...

A simpler system might be to have dedicated upward and downward shafts, with change over points in the roof and basement. The cars all queue up to go up or down depending on which shaft they’re in.

The elevator cars couldn’t have cables of course, but they could be driven by electric motors on the cars themselves (powered by induction), driving a gear wheel that runs on a fixed track on the side of the shaft.

> A simpler system might be to have dedicated upward and downward shafts, with change over points in the roof and basement.

You mean a paternoster (https://en.wikipedia.org/wiki/Paternoster_lift)?

I think a Paternoster wouldn't be viable for a number of reasons (mainly ADA/accessibility). Instead you'd need to have each car independently powered and allow them to communicate back to a central planning server to allow cars to stop without stopping all other cars in the lane (and to prevent other cars from bunching up).

Reply on news.ycombinator.com