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# worm train

You know how a worm moves along? Well...
 (+26, -8) [vote for, against]

A worm moves along the ground by passing longitudinal compression waves through its body so that every part of its body is alternately stretched and compressed - e.g. it stretches out its 'neck' which is stationary while it bunches up the bit of its body just behind, and so on.

So, getting to the point - A train which worked the same way would be miles long. Externally it would be covered in some kind of stretchy fabric. Internally, the walls would be made of grilles such as you see in old lifts (elevators), with seats fixed to the uprights. You'd board a 'compressed' bit of the train, take a seat, and the bit of the train you're on would then stretch out towards the next station (and here, the gap between your seat and your neigbour's seat would increase). A few more compression/extension cyces and you'd be at the next station.
This would work especially well on London's Circle Line (as its name suggests, a loop, 13 miles in circumference) which would be occupied by a circular train.
 — hippo, Jun 12 2001

SRL's Inch-Worm http://www.srl.org/shows/web98/img8.html
Not something you really want to ride... [rmutt, Jun 12 2001, last modified Oct 21 2004]

Robot snake http://robby.caltec...hardware/snakey.gif

 I'm not sure whether it would be very comfortable in practice, but it's a nifty idea. Not sure if I'm misunderstanding this, but ...

 hippo wrote: « and here, the gap between your seat and you neighbour's seat would increase »

 Couldn't this cause practical problems? What would happen if you placed something on the floor while the train was in its expanded state?

Also, why would the train have to be miles long? Surely it would work just as effectively if they were only slightly longer than normal trains, but with a greater number of compression waves to travel a given distance. (The frequency would be correspondingly higher.)
 — cp, Jun 12 2001

impractical + fun = one croissant!
 — mihali, Jun 12 2001

 this would only work if everyone was strapped to the floor/walls etc.

what sort of height would the upward 'lurch' reach? I can just see all these afternoon commuters boarding the worm train, strapping in and going on reading their newspapers, swinging and lurching onto the next station without even looking up. i also think worms are require lubrication/stickyness to do their thing. perhaps a custard worm train?
 — benfrost, Jun 12 2001

//what sort of height would the upward 'lurch' reach?//
That would be an 'inching' worm train. If applied correctly that would reduce stairclimbing.
 — reensure, Jun 12 2001

[waugsqueke] Absolutely right.
[benfrost] There's no upward lurch - the train moves forward through compression waves, not uppy-downy waves (technical term).
[cp] The floor would require some thought. I envisage having it made out of overlapping steel plates.
[Mephista] What's IHS?
 — hippo, Jun 12 2001

I think the key here would be a solid train car with a wormlike exoskeleton. You could take a regular subway car and surround it with some large external rings that move back and forth on pneumatic pistons and voila you're worming your way to work.
 — borivan, Jun 12 2001

[borivan] Good thinking, but I'd prefer the occupants of the train to be able to see the worming motion from inside the train which they wouldn't be able to do if this was an exoskeleton built on top of existing subway cars. Also (in London) there's sometimes only a couple of inches clearance between the subway cars and the tunnel walls so the exoskeleton solution would be difficult to make work on existing subway networks.
 — hippo, Jun 12 2001

OK no exoskeleton. If you want to experience the motion of the worm you could ake individual compartments that hold 2 to 4 people. each compartment could have it's own door and a light on the outside of the worm to indicate weatehr or not it was occupied. it'd be just like private cabins on commercial trains only each cabin would be separate. that way you could avoid joints in the middle of a "train Car" and still experience the worm motion.
 — borivan, Jun 12 2001

...and poop dirt out of the back too?
 — mihali, Jun 12 2001

To control lurching just have the Worm Train do it's compression-expansion in a reasonably smooth, controlled manner--no more lurch than a nice smooth elevator, for instance. Fantastic idea, hippo.
 — Dog Ed, Jun 12 2001

Nobody has asked how the thing is powered. What mechanism causes the lurch, and how? Are we talking about a system of pistons, with a network of synchronized electric motors on each piston, compressing and decompressing according to a programmed pattern? Or what?
 — globaltourniquet, Jun 12 2001

How to power it? Well surely we have to take the 'hovertrain' as our example, and use a magnetic linear motor. All you would need to do is to time the current into the static magnets below the train, as per the hovertrain (originally prototyped in UK, but working in japan) this effectively sends a wave of energy down the track. The current train rides on top of the wave (or in reality just in front - it sort of surfs on the magentic repulsive force, which due to timing is angle forwards instead of straight up (which is why the train moves forward rather than just hovers. speed is obviously controlled by the angle of the force to the track), but see no reason why this wave couldn't be converted to a 'wave' inside the train. Would give exactly the kind of smooth avcceleration and deceleration that you need to stop the jarring.
 — goff, Jun 12 2001

waugsqueke: I imagine the acceleration and deceleration phases of each lurch could be tuned so that {accelerate at .5 g for 1 minute}-{coast for 3 minutes}-{decelerate at .5 g for 1 minute} would result in one speed and {accelerate at .5 g for 2 minutes}-{coast for 10 minutes}-{decelerate at .5 g for 2 minutes} in a faster speed. It would depend on if you were taking the local or the express worm.
 — Dog Ed, Jun 12 2001

 SciFi's Chi-Chan (I think that's the name) has a society where they use actual worms (really big ones, obviously) as a form of transportation. And for the record, the scientific technical term in "transverse."

Have the trains accordion-folded, and use pistons attached at every other fold to drive it.
 — nick_n_uit, Jun 13 2001

 No matter what you made the floor out of, you would have problems with one of two things:

 (a) people could lose their stuff between the plates; or (b) things could be crushed at the plates compress.

 I think that the best way around this would be to do what Borivan suggested.

benfrost: You're right, you would need to have some form of stickyness on the front bit when it was in a compression cycle and the at the back during an expansion cycle. You might be able to do this using magnets like goff suggested.
 — cp, Jun 13 2001

 There are articulated buses with a big rotating join in the middle. In theory people and objects can get crushed by this joint when the bus turns a corner, but in practice the bus is designed so that's unlikely. (There's still a sign saying "don't put stuff here! or stand here!" in the corner though.)

There should also be an indication on the train's door that that segment is about to start its lurch, so that you know not to get on right then.
 — wiml, Jun 13 2001

[borivan] I'm still not convinced by the compartment idea. I was thinking that if the whole train was one big space than (on straight bits of track) you'd be able to look far down the train and see the compression wave heading towards you. Also the element of danger as the floor rearranged itself would be nice.
[Rods Tiger] Good idea - although probably impractical :-)
The burrowing idea though does highlight why this method of locomotion is so appropriate to subway (rather than surface) trains.
[Mephista] Thanks for the lucky charm. Alas, some swine has fishboned the worm train...
 — hippo, Jun 13 2001

Thank you, UnaBubba.
 — hippo, Jun 13 2001

Oh yes - something else I forgot about: The possibility of making new friends during the compression part of the cycle...
 — hippo, Jun 14 2001

I'll try and get into the garden this weekend and watch some worms - The 'compressed' bits of worms may just be fatter than the 'stretched' bits which would make sense in soil as they would then grip the soil better which would enable the worm to stretch forward.
Variable-diameter worm-action subway trains would be a nice variation on this idea.
 — hippo, Jun 15 2001

 Worms do, in fact, compress and decompress their internal structures as they move. You can see them doing this with the naked eye if you have a well-constructed worm box. The movement is integrated with their digestive process, I believe, which is of course fore-to-aft.

 The "stickiness" everyone keeps referring to is primarily provided by very stiff hairs set at an angle. They are a bit hard to see in most worms.

If you live in an area that has nightcrawlers (good fishing bait!) you can go outside in early summer late at night with a flashlight and very soft-soled shoes... the worms will come to the surface to (hermaphroditically) copulate, but they are very sensitive to ground vibrations so you have to sneak up on 'em. Grab one, and you will be astonished at how hard it pulls back towards its hole. Capture one, and let it move through your hands, and you can feel the hairs pricking your skin as it drags itself about.
 — Medievalist, Jun 28 2001

 The digger that created the Channel tunnel worked on this principal. The forward portion would extend arms to provide gription while it pulled the rear portion forward. The rear portion would then press against the sides of the tunnel to provide leverage to push the rock crunching forward portion forward.

Of course it was quite slow, but then it could only go as fast as it could clear its own path. Given an existing tunnel, I believe this is bakable!
 — phoenix, Jun 28 2001

'Gription'! Yeah!
 — angel, Jun 29 2001

Baked by Frank Herbert.
 — zaphod12, Nov 29 2001

the game
 — missingdonuts, Feb 16 2005

I like it! It would have its own track I assume. And it would just extend 'till it reached the next station, then contract? It would, of course, probably never work, but it would be cool! [+]
 — TahuNuva, Nov 20 2007

Hang on! Has anyone seen "Core"? Put a laser-dirt-annihilator-beam on the train and you could tunnel like a freaky mechanical worm in the dirt! Also, the cartoon show "Avatar: The Last Airbender" has a machine like this. It's massive and it has little legs on the sides that retract and extend toward the ground. The thing has wheels on the bottom and when it extends, the legs go to the ground. The legs move in ripples, so the back legs stay down to hold the back of the machine while the front of the machine goes forward. Aaaaaaaa-nyway, I give this a [+].
 — TahuNuva, Nov 20 2007

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