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What happens when the Rolling Roads get to the rollers? 
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Heinlein Biographer

Joined: Thu Apr 10, 2008 1:33 pm
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Post Re: What happens when the Rolling Roads get to the rollers?
Baylink wrote:
Is there a mathematician in the house? :-)

I know that the question is "what's the centripetal force generated, measured in G's of lateral acceleration, by an object describing a 1 mi radius curve at 100 mph" (or possibly more; it depends on the design of the plates), but I don't have the math to figure it out off hand; I suspect strongly that it's a pretty substantial fraction of a full G, unbanked; that seems pretty high to me.

Beamjockey: you're a rocket scientist; what's the answer here? :-)

I don't understand why we are talking about a 1 mile turning radius -- no sane engineer would design a turn that sharp for 100 mph belt if not constrained in some other way. For similar reasons, a vertical 180 degree turn is out of the question for a load-bearing structure.

I am also not entirely sure that all the strips made the same turn -- if I were designing something like this I would terminate all the faster strips before the 180 degree horizontal turn, simplifying the problem, (after all, if you're at the terminus, what is the practical need for a 100 mph velocity?)


Wed Mar 04, 2009 8:54 am
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Heinlein Nexus
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Post Re: What happens when the Rolling Roads get to the rollers?
Bill Patterson wrote:
(after all, if you're at the terminus, what is the practical need for a 100 mph velocity?)


What terminus? The roads are continuous loops. I don't see the point in designating any place to be a terminus.

Completely ignored in this discussion of technology is the economic issue, BTW. What's the fare structure? Ticket conductors?

Also, how does freight get on board? I guess you can drive stuff onto the slower heavier belts. Sounds as though the faster ones are only for people who can hop onto them though.


Wed Mar 04, 2009 4:20 pm
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Post Re: What happens when the Rolling Roads get to the rollers?
Bill Patterson wrote:
I don't understand why we are talking about a 1 mile turning radius -- no sane engineer would design a turn that sharp for 100 mph belt if not constrained in some other way.


The number was more or less plucked from the air. It's not orders of magnitude off; it represents a complete turnaround in pi times 60 over 100, um, one minute 53 seconds. I agree that a broader turnaround would probably be saner, but over 10 miles you're starting to fill up a whole county with the turnaround.

Bill Patterson wrote:
I am also not entirely sure that all the strips made the same turn -- if I were designing something like this I would terminate all the faster strips before the 180 degree horizontal turn, simplifying the problem, (after all, if you're at the terminus, what is the practical need for a 100 mph velocity?)


Oh, the turnaround locations for different speed strips could easily be in widely separated locations, especially if you arrange "bridges" for strips of different speeds to cross over one another.

The whole thing is crazy from an energetic point of view (but I think Heinlein had sources of cheap energy up his sleeve).

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Wed Mar 04, 2009 10:10 pm
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Heinlein Biographer

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Post Re: What happens when the Rolling Roads get to the rollers?
Peter Scott wrote:
Bill Patterson wrote:
(after all, if you're at the terminus, what is the practical need for a 100 mph velocity?)


What terminus? The roads are continuous loops. I don't see the point in designating any place to be a terminus.

Completely ignored in this discussion of technology is the economic issue, BTW. What's the fare structure? Ticket conductors?

Also, how does freight get on board? I guess you can drive stuff onto the slower heavier belts. Sounds as though the faster ones are only for people who can hop onto them though.

He spoke in the story about termini -- the Roads went from one place to another place (and back). If we are talking about a 180 degree turnaround, that is ipso facto a terminus of the road, which does not go "ever on and on" but turnsback on itself.

I dont recall a fare being mentioned in the story -- possibly it was by subscription of some kind.


Thu Mar 05, 2009 7:42 am
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Heinlein Biographer

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Post Re: What happens when the Rolling Roads get to the rollers?
beamjockey wrote:
The whole thing is crazy from an energetic point of view (but I think Heinlein had sources of cheap energy up his sleeve).

Yeah -- I believe he said somewhere they were only made possible by the Martin-Douglas Sun Screen


Thu Mar 05, 2009 7:44 am
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Joined: Mon Jan 12, 2009 8:27 pm
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Post Re: What happens when the Rolling Roads get to the rollers?
Bill Patterson wrote:
He spoke in the story about termini -- the Roads went from one place to another place (and back). If we are talking about a 180 degree turnaround, that is ipso facto a terminus of the road, which does not go "ever on and on" but turnsback on itself.

I dont recall a fare being mentioned in the story -- possibly it was by subscription of some kind.


I just reread it, and he doesn't explicitly address the issue of what happens at Okla and Orleans.

As to the fare, I assumed they were just like the Interstates; a public utility. Hence the quasi-military corps and service academy.


Thu Mar 05, 2009 9:40 am
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