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# Stretch travellator

Rubbery
 (+6) [vote for, against]

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.

 — MaxwellBuchanan, Jun 19 2011

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]

 It'll snap and have someone's eye out.

+
 — DenholmRicshaw, Jun 19 2011

 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.

 So the belt starts wide, and slow, accelerates to narrow, fast and highly tensioned, and then decelerates to wide and slow at the end.

 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.

Better to use all that rubber and built a mangonel or an onager to fling the users through the air into a catch net.
 — 8th of 7, Jun 19 2011

 Yes, some sort of studs on the inner surface of the belt would be needed.

 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.

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.
 — MaxwellBuchanan, Jun 19 2011

 Could be made with overlapping metal plates, each joined to the next with a hooky and spring, then there should not be thermal losses?

If only lazy tongs could be incorporated into the mechanism.
 — pocmloc, Jun 19 2011

… with a giant red boxing glove from Acme on the end.
 — 8th of 7, Jun 19 2011

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.
 — MaxwellBuchanan, Jun 20 2011

 [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.

 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.

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.
 — Vernon, Jun 20 2011

 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.

 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.

 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.

Hmm... that's not a very good description. It works better in my head.
 — Alterother, Mar 05 2012

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