Sorry its taken me so long to get back to the discussion. I was busy with my son over the holiday.
----- Original Message ----- From: "Erik Reuter" <[EMAIL PROTECTED]> To: "Killer Bs Discussion" <[EMAIL PROTECTED]> Sent: Friday, July 04, 2003 3:04 PM Subject: Re: Spider space elevator? (was: US-based missiles to haveglobalreach) > On Fri, Jul 04, 2003 at 02:42:21PM -0500, Robert Seeberger wrote: > > > > From: "Erik Reuter" <[EMAIL PROTECTED]> > > > > > Can you imagine if steel elevator cables were replaced with > > > bungee cords? If a bunch of really large people got into the elevator, > > > would the elevator still line up with the floors at each level? > > > > Bad example Erik. > > Sounds like you have only a nebulous idea of how elevators actually work. > > <G> > > Bad statement, Rob, as usual. > Sounds like you have only a nebulous idea of the point. There is a > reason elevators aren't built with bungee cables, Rob, but it sounds > like you have no clue about that. > <G> > > > The cables do stretch over time, but they are not used to "level" the > > elevator at each floor. > > Bungees stretch much more than steel and much more quickly, Rob. Quite > different than steel cables. Which was rather the point, Rob. Do you not think that even bungee cables would reach an equilibrium? > > > "Leveling" is done with a system of limit switches and a "flat ribbon" > > cable that locates each floor for the elevator control system. Newer > > elevator systems do almost all of this electronically. (Elevators tend > > to have a very long use cycle. Where I work, the elevators range from > > 20 to 80 years of usage) > > So, you replace the steel cables with bungees. Ignore the fact that > they would be much thicker than steel to support the same weight. When > someone gets onto the elevator, the bungee stretches. Do you think these > feedback systems are built to rapidly reel in and out quickly enough and > long enough lengths of bungee to counteract the bouncing up and down as > people get in and out and keep it perfectly level with the floor? Once loaded, the bungee cables will stretch to a nominal length and remain at that length pretty much the same way steel rope does. (BTW you can't use tables for "steel" to determine elevator cable yields or tensiles because elevator cable has a manila rope core) Elevator cable does stretch quite a bit and elevators do bounce a bit anyway. Elevator cables have a constant amount of tension on them. (Disregarding for just a moment the stresses of stopping and starting that cause steel cable to stretch and bounce) There is no "reeling in and out" of the cable. The cable is attached to the cab on one end and a counterweight on the other with the motor moving the cable whatever direction or distance is required. Regarding the stresses of stopping and starting, if one were to make a serious effort at engineering an elevator using bungee cord, one would "size" the bungee cord with a thought toward minimizing the bouncing effects from acceleration and decelleration. Anything less would be amateurish. >Cause > it sounds like this absurdity is what you are claiming. Either that, or > you just totally missed the point. > I can understand you seeing it that way, but I think the difference is in how we each approach the problem. Each of us is engineering an elevator using bungee cord for cable. You are engineering it with a mind to exaggerate problems because that supports the point you originally wanted to make. I am engineering it with a mind to minimize those same problems because I can see how it could be done. All in all its a ludicrous idea, but it is a fun thought problem. And the elevator techs at work had fun discussing it at break. xponent Is It Friday Yet? Maru rob _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
