h a l f b a k e r yNot so much a thought experiment as a single neuron misfire.
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The discussion of rubber bands on the linked idea led to
this.
Travellators are limited in speed, largely because you have
to be able to get on and off them at the ends.
However, imagine a travellator whose surface is a
stretchable rubber belt. With a suitable set of rollers
driving it,
it could be arranged so that the band stretches
in the middle and relaxes at each end. (Imagine two
marks drawn on the rubber surface; at each end of the
belt, they are close together; in the middle, they are
farther apart as the rubber has been stretched.)
The result would be a travellator which travels slowly at
the ends, where people get on and off, but faster in the
middle.
Suggestified by:
Toy_20fridge_20that_20actually_20cools
[MaxwellBuchanan, Jun 19 2011]
Not Rubber, but Rigid Parrallelogram Sections
http://books.google...v=onepage&q&f=false
From "Popular Science" magazine, October 1972 [Vernon, Jun 20 2011]
[link]
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It'll snap and have someone's eye out. |
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You can do this with pinch rollers (That is, after all, how a steel rolling mill, or a calendaring mill, work) but they will need to be above and below the belt, unless there are teeth or studs or something on the underside that the rollers can grip. |
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So the belt starts wide, and slow, accelerates to narrow, fast and highly tensioned, and then decelerates to wide and slow at the end. |
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The tension in the fast section is going to be formidable, and it will be a peculiar sensation underfoot. The stretch rollers are going to need to be failry closely spaced, and the system will probably consume quite a lot of energy; when the belt is relaxed again, that energy is going to come back as heat, so cooling will probably be needed. |
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Better to use all that rubber and built a mangonel or an onager to fling the users through the air into a catch net. |
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Yes, some sort of studs on the inner surface of
the belt would be needed. |
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As regards energy, there is always the same
amount of belt stretched and relaxed. There will
be thermal losses (as noted, and as exploited in
the linked idea), but most of the energy should be
recoverable by a clever gearing of the rollers.
You're basically just moving the stretch along,
almost but not entirely unlike a compression wave
in a spring, which propagates almost losslessly. |
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The fact that only a small proportion of the
stretching energy is manifested as heat can be
demonstrated by twanging a rubber band; most of
the energy is handled the same way as in a
Hookean spring. |
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Could be made with overlapping metal plates, each joined to the next with a hooky and spring, then there should not be thermal losses? |
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If only lazy tongs could be incorporated into the mechanism. |
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… with a giant red boxing glove from Acme on the end. |
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Hmm. The ideas in the third and second links are
ingenious, but all seem to involve distinct "on" and
"off" systems which plumb you in to a fast but
otherwise normal centre section. |
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[MaxwellBuchanan], the variant I linked could be used for the whole walkway --it would just have another curved section at the far end, for people getting off-- but probably would cost more than the ordinary sort. That makes it equivalent to your own description. |
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On the other hand, if it was only used as an accellerator/decelerator segment, such segments could be placed anywhere alongside the whole length of a long long LONG moving walkway, for people to board or exit. Your idea could presumably include places in the middle where the rubber, gripped from below, is deliberately allowed to de-stretch, so that people could get off or on at that section --the rubber re-stretches after the slow section. However, I think that's a drawback, since everyone in the walkway would slow down in that section, including those who don't want to get off there. |
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I'm imagining two moving walkways, going opposite directions, separated far enough apart that this speedup/slowdown device could be put in-between them, with 4 curved sections making an overall loop. There would of course need to be a way for people to cross over or under the main moving walkways to reach or leave one end of that looping accelerator/decelerator. |
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I was riding a high-speed chairlift on Friday and
remembered this idea from last summer. It took me a little
while to find it. |
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Several of the high-speed lifts at the major ski resort near
my home use a detatchable system, wherein chairs arriving
at either terminal are detached from the high-speed
continuous cable and 'stacked' onto a low-speed circular
trolley to facilitate loading and unloading. Once the chair
is loaded or unloaded, it is re-attached to the cable and
whisked up (or down) the mountain at about 15 mph. |
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I think a sectional travellator (the kind that looks like an
escalator) could employ a similar system, using a series of
'step-down' gears to remove the segments from the main
drive train and pass them along to slower-moving rollers.
Since the segments on a travellator are linked, not spaced
evenly like the chairs on a chairlift, the 'stacking'
technique could not work. However, if the segments were
very narrow (say 1 cm), some of them could be removed
from the belt by lowering them and having the gap closed
under the passengers' feet smoothly but very quickly. The
removed sections would then transfer to a separate drive
train that would return them to the embarkation terminal
to be replaced in the belt. |
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Hmm... that's not a very good description. It works better
in my head. |
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