Which is a helical moving staircase, within a tube rather than the conventional inclined plane.
Yes. Already been done.
Here’s a picture of one: Spiral Escalator | There are very few of these in the world … | Flickr
I was going to post to say I know they can, because there’s one in the Shops at Caesar’s Forum in Las Vegas, and that’s the one Whack-a-Mole has linked to. 
I’m assuming the escalator steps essentially go up a giant screw. But how do they come back down? I suppose they can enter some kind of side chamber and just be directed downwards. But then you have to have steps that’ll work with the screw support, and then also work with some linear mechanism for returning them to the ground.
The engineering of these escalators must be amazing.
I’ve been on a curved escalator at Nordstrom’s in San Francisco. The steps appear to be horizontally wedge-shaped. This is fine as they go up, but if they come down underneath, in the same way as straight escalators, their narrow sides are probably separated or spread apart at some point.
I don’t think so. I’ve seen the ones in San Francisco (and Whack-a-Mole’s link confirms); they don’t describe a full circle (as seen from above) and there’s empty space in the center of the arc where the screw would have to be. Or did you mean a flexible shaft (like a speedometer cable) acting as a worm gear under the steps?
I think it probably works just like a regular escalator (diagrams here and here) but with the steps and tracks custom made for the particular amount of curvature. It seems to me it’s just a matter of getting the drive chain, the steps and the hand rails to run on curved guide tracks without binding up.
Why couldn’t the steps just fold over and go back down the underside of the track (like I assume normal escalators do)? It’ just be a big conveyor belt that’s been twisted.
I was going to say that, from the viewpoint of the steps, they are now curving in the opposite direction and their wedge shape would be opposite to what is needed. But then I realised that the returning steps would also be upside-down, and their wedge shape would still be appropriate.
At the ends of the escalator, though, special arrangements would need to be made. The “combs” or whatever they are called, on the top of the steps and at the edge of the landing platforms, are curved, IIRC, and this curve would have to be maintained until the steps are completely underneath the landing platforms and can be redirected.
I suspect that all the curving escalators made have a single constant curvature, and all the steps and such are custom-made to suit that curvature. Builsding an escalator to do a reverse curve would be a lot harder.
I think that the curved escalator was developed by Mitsubishi. Here is a story on it.
Mitsubishi makes all of the spiral escalators out there. They’ve got some PDF scans of brochures and installation specs, but nothing really giving details.
The patent text is here. To see the images, you’ll need the free “AlternaTIFF” plugin. (Click the red “help” in the yellow titlebar for more info) Unfortunately, the images aren’t all that useful for visualizing the mechanism.
The Mitsubishi web page gives no detail unfortunately. I see the Forum Shops at Caesars Palace escalators ‘only’ twist 180°. That’s very impressive, but I was really thinking about the general solution where any number of twists can be employed, up the tube all the way to the top. If that can be built that would be extremely impressive. Probably, if it’s not in Dubai already then it can’t be built.
Well, the slope of an escalator is already determined (by expectations and probably building codes), the floors of the Forum Shops are a certain distance apart, and I would imagine there’s some minimum radius of curvature for the escalator. I can’t see any reason why a spiral escalator couldn’t make a full circle, but there just aren’t many places that need one with enough altitude change.
I still read and hear about plans for a subway/light rail system in Seattle. One of the snags is that the obvious route from downtown is to go east under Capital Hill, then northbound under broadway to the U District. But subways and trolleys are very limited in the grades they can climb, and even at their best the first Capital Hill stop would be more than a hundred feet underground. That usually means long runs of stairs and escalators. I wonder if they’ve thought of a round shaft with spiral escalators and stairs.
Firstly, light rail can cope with surprising slopes and curves. Secondly, I doubt there’s much difference in a cut-and-cover construction of a large escalator compared to a spiral one.
Has anyone ever built an escalator that levels off and then resumes climbing? It would have a ‘landing’, where people could exit and enter sideways.
That seems like a solution in need of a problem. It’s much cheaper and easier to build an escalator, a flat stretch of floor, and then another escalator. No new design required. Not as “gee whiz” but more economical. Plus, stepping onto a surface moving sideways relative you to would be problematic for many people.
Alright, here’s the problem: build an escalator which allows young healthy people to travel from the first to the second or third floors but prohibits those frail elderly people on the second floor from getting on and visiting your 4//3Z()|V|@ icecream parlor on the third floor. Now all we need is someone to build us this kick-ass escalating wonder and we can enjoy our icecream in peace without having to look at all that wrinkly old people skin.
sinjin
Why would that be a significant problem? The Bank platforms on the Docklands Light Railway are something like 130 feet underground, and it’s a relatively minor inconvenience. There is a station more than 190 feet down, but it uses a lift (elevator) if I recall correctly.
It would be expensive to dig so deep, but providing there’s a bit of elbow room to put the shafts in, normal escalators would be A-OK.
I think for very deep or narrow shafts, spiral stairs/escalators are a bad idea. If they are too narrow, the treads get extremely shallow (barely a toehold) towards the centre, and if they are too deep, you get dizzy by the time you reach the bottom. This may be why they were abandoned as soon as technology advanced beyond the 'sink a well and put a staircase in it" level.
Yep, that’s Hampstead station. And Angel’s escalators have a vertical rise of 90ft.
They were? Many tube stations were originally served by lifts, with escalators being fitted later on because they have a far greater capacity. The original street-level entrances were no longer in the correct place, and so new ones were built in different locations. (And in the case of the British Museum station on the Central line, it would have ended up so close to Holborn station that it was simpler to put in new platforms and tunnels connecting to there, closing the old station - hence the long walk when you change lines at Holborn) Plus, new stations such as Southwark and Canary Wharf have been built using escalators.
My bad, I wasn’t clear enough. Spiral stairs were very widely used as standbys for those old lift stations. If you’ve ever used the stairs at somewhere like covent garden or at the Greenwich Foot Tunnel you should hopefully take my drift - they are really bloody awkward. I assume spiral escalators would suffer from the same problem, but to a lesser extent if they all have as wide a central gap as the one pictured.
Straight escalators are easier to engineer and when not running turn into plain, if slightly awkward, stairs. Given the well-known “can’t walk down a stationary escalatory” syndrome, I imagine a stationary spiral escalator might be a bit of a challenge, especially after chucking-out time.
It’s not an insurmountable problem, but it’s not ideal, either. I can think of a station on the Boston subway, and a couple on the D.C. metro that have very deep escalators. They’re all in slightly less built-up areas than Capital Hill, so there would have been more room for the necessary digging. Soil conditions probably play a role, too; when the Interstate 90 tunnel under Beacon Hill was built nearby it was the largest soft-earth tunnel in the world. One idea I’ve heard was for when the rail tunnel changes from east to north, instead of a 90-degree left turn, build it as a 270-degree, climbing right turn.