Asimov's sliding walkway

To get away from boiling water for a bit...
I apologize in advance for the use of imperial units...
Suppose we have uniform slabs of concrete (say 6 feet by 6 feet
by 6 inch thick), that we set moving in a large circle (say a
mile or more diameter). We float them on pumped water "jets"
that splash back down into a sump to get repumped. (Sticking
with water instead of air, for larger pumping efficiency.)
Water source could be reclaimed water. It would require a
constant bleed and makeup.
Flow to each support "jet" could be controlled by a Clack Flo-et.
(Outlet pressure could rise to near inlet pressure before flow
gets significantly reduced. These are not too stable below 15
psid or so.)
The concrete slabs could have an iron base or an epoxy coat to
reduce abrasion from the water.
Once we figure out how to keep from spraying up through the seams
between slabs, could this be more efficient than moving
automobiles over the same route? Perhaps more clearly, what
would be the break-even point in number of cars this would
"match"? (Granted, pedestrians can't carry too many groceries.)
David A. Smith
Reply to
N:dlzc D:aol T:com (dlzc)
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Why bother with that?
When we can eventually make nano-technology mass produced we will be able to electrically move nano-fingers across a surface at varying speeds which will have the effect of moving a mass.
Reply to
Harry Andreas
Dear Harry Andreas:
...
Who polishes the surface to less than a few atoms height variation? What do we use for power, and what makes you think it will be more efficient than a gas-powered car?
David A. Smith
Reply to
N:dlzc D:aol T:com (dlzc)
I was browsing planar hydrostatic bearings and came across an early example used in a hydro electric project as a thrust bearing for the turbine generator. The losses were greatly reduced, and it has stayed in operation since 1917 without maintenance. An engineering evaluation estimated over 1000 years as the time between maintenance calls.
Another hit was about kids shown how to make a slimemobile - which is a hydrostatic platform with low friction while the slime is flowing. I found it in google books. But using slime - or at least a non-Newtonian fluid, maybe a thixotropic goop, might be worth conssidering, to avoid splashes. The fluid pressure needed is well under 1 psi.
Brian Whatcott Altus OK
Reply to
Brian Whatcott
OK, so we place an interlocking joint front and back, something simple to keep steel rods from being jammed down into the works. (The equivalent of derailing trains.)
The flow from each pump is distributed into a few dozen 8-14 inch diameter soft-walled cups (like a hovercraft skirt). The cups are distributed equally on left and right sides, and staggered along the slide path.
A series of panels runs parallel, each at increments of 5 mph (or more), to a top speed of 25 mph (will cut my current commute time on city buses in half).
The circular track is flattened to give two parallel oppositely-directed sets of tracks (lanes). Only the ends open out, close the loop, and slabs get cycled back in (or diverted off for service). Run another track at right angles.
Do we need rotating panels (like bearings) between succesive "speed lanes", not to allow for reduced friction, but to allow someone not athletic to step on and get more gently accelerated to the next lane speed? There would of course be "bearing followers", which would be travelling at half the speed, and would not have you facing the wrong way when you got to the other lane... so may be not necessary.
Brian, I would assume the thixotropic mix would only serve to increase friction, and the "spraying up between slabs" would disappear with the interlocking stuff front and back. The limit of 1 gpm per "cup" would decrease any tendency to spray, but the soft skirt would more than overcome this. So the leading and trailing edges would need to be tapered a bit to vent that off before alignment under a crack.
At night, all but lower speed belts could be shut down.
Linear drives could thrust the slabs above it, and could probably be placed every block or so, depending on how many people get on and off at concentrated locations. Since every installation will be following grade, some of the linear induction motors would actually be removing kinetic energy from the slab above it, and place that power back on the DC bus the other drives draw from.
Handrails? USA-OSHA would say yes...
Is this better than a bus or tram? Could you have such a system, that had beat cops or "transit security personnel" spaced along it? Asimov's future had relatively few people in it...
David A. Smith
Reply to
N:dlzc D:aol T:com (dlzc)
Who says we will need to?
Electricity comes to mind. Most things are more efficient than a gas-powerd car, which is, what, 30% efficient? Last time I worked in a power plant we were getting efficiencies over 90%. Throw in some power line losses and it's still better than 30-something %
Reply to
Harry Andreas
Dear Harry Andreas:
You do, when you specify "nano-fingers". Macroscopic structures lose energy in deforming members, and fatigue under the various loadings. If your "fingers" extend very long, your losses will be similar to those fabricated by other means.
Rolling downhill, with a tail wind, maybe.
Surprising. Power plants that provide electricity are lucky to get 50%.
We'll see.
David A. Smith
Reply to
N:dlzc D:aol T:com (dlzc)
What does that have to do with "polishing the surface to a few atoms height variation?" I just finished a nanotechnology course this spring. AFAIR there was no mention of polishing anything, let alone to a few atoms accuracy. Certainly not after fabrication.
I worked for American Electric Power at one point. I still have the report someplace taht documents the efficiency and losses at the plant wherein I worked.
Yep.
Reply to
Harry Andreas
Dear Harry Andreas:
Nanofingers make nano strokes. Nano strokes have issues with height variations more than a few atoms in height. The difference between a paved road for a car, and Mount Everest.
Not the fingers, the surface you imagine the fingers will be walking over.
You memory recalls (perhaps) a percetnage of Carnot (maximum) efficiency. Which for combustion-fired power plants is between 40 and 50+%
David A. Smith
Reply to
N:dlzc D:aol T:com (dlzc)

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