From: ahk@chinet.com   
      
   Stephen Sprunk  wrote:   
   >On 05-Oct-14 14:47, Adam H. Kerman wrote:   
   >>Stephen Sprunk  wrote:   
   >>>On 05-Oct-14 12:51, Overmod (Robert M. Ellsworth) wrote:   
      
   >>>>https://www.scribd.com/doc/241718975/NYC-Tunnels-Assessment-Report   
      
   >>>Not interested in giving them a bunch of personal information just   
   >>>to read what _should_ be a public document.   
      
   >>User: buggsme1; password bugmenot   
      
   >Thanks.   
      
   >>>What does "top-down track system" mean?   
      
   >>In direct fixation, it means top of rail and gauge are established to   
   >>the specification, then the fasteners are attached, then the concrete   
   >>is placed last. That really makes a lot of sense, because there's   
   >>just the one step at which things are calibrated. Bottom up requires   
   >>a lot more calibration.   
      
   >Ah, okay; I hadn't seen the term before, but that makes sense.   
      
   I'm not claiming expertise; I looked it up.   
      
   >>Doesn't explain how they get the concrete underneath it all (very   
   >>carefully).   
      
   >Pour it between the rails and smooth it out?   
      
   I don't know. There are concrete pads and a trough and fasterners, and it's   
   all installed in a seemingly illogical order. It also means the equipment   
   suspending the rail and maintaining top of rail and gauge to spec is supported   
   well outside the area the concrete is being installed.   
      
   With bottom up, how do you make adjustments where gauge and top of rail   
   problems are found without chopping out some concrete? I suppose there's   
   limited play in the fasteners to adjust.   
      
   >>>I'm a bit surprised they're still using ties on ballast inside   
   >>>such important and high-volume tunnels; direct fixation has been   
   >>>the norm for decades, and from the sound of it, they wouldn't have   
   >>>had these problems.   
      
   >>Uh, whatever, Stephen. Of course you know for a fact that the timber   
   >>amd ballast work was botched and failed to maintain gauge and desired   
   >>top of rail when installed. Your 20-20 second guessing is always   
   >>superior knowledge to anyone's first-hand experience of the quality   
   >>of the original work.   
      
   >WTF are you going on about?  I said nothing about any of that.   
      
   Your criticism of what's done in the field always inspires sarcasm. If   
   you've made a proper business case, it's not for "best" and it's not for   
   "cheapest" and it's not for "most expedient", but it takes into   
   consideration capital and maintenance and operating costs throughout   
   the life of the installed system.   
      
   >>If you read the report, it doesn't say there's anything wrong with   
   >>ballast, but it's not done that way today.   
      
   >Ballast and ties are not inherently bad, but the cost of maintenance   
   >(including the cost of service outages, not just materials and labor)   
   >must be balanced against the cost of installation.   
      
   Ballast and ties are inexpensive to maintain and don't really take your   
   track out of service for terribly long. Nothing lasts forever, and   
   the ballast must be removed completely, so there's an opportunity to   
   consider other methods.   
      
   You're acting like direct fixation requires no routing maintainance.   
      
   >Tunnels and bridges are also special because you _already_ have a solid   
   >floor to build up from,   
      
   Sigh. On a bridge deck, ballasted deck is the superior method, and railroads   
   have replaced bridges in other styles. You've read what I've written about   
   Shermer Road in Glenview, Illinois, over the last two years, yes?   
      
   >plus you can't use concrete ties because they quickly grind the ballast   
   >to dust; you have to use wooden ties, which have a higher maintenance   
   >cost--and that is apparently what tips the scale to direct fixation in   
   >those areas, whereas ties and ballast are still (for now?) the norm in   
   >other areas.   
      
   Oh my gawd. Would you knock it the fuck off? In the terminal area of each   
   railroad station in downtown Chicago, some of the world's heaviest   
   railroad traffic, concrete ties are used in tight radius curves WITH BALLAST.   
   No, the ballast wasn't quickly ground to dust; I would have noticed. I'm   
   sure they used ballast with the correct characteristics to hold concrete   
   ties in place. You can see 'em on the north approach to Chicago Union Station   
   and the approach to North Western Station.   
      
   You don't know what the hell you are talking about.   
      
   >>The ballast must be removed because it's coated with chloride,   
   >>which sure as hell sounds like water infiltration and drainage   
   >>which, last I looked, are problems that direct fixation of rail   
   >>has fuck all to do with correcting.   
      
   >Direct fixation means no ballast, so there would be no opportunity for   
   >such a problem to exist in the first place.   
      
   Really? It's highly desireable to have saltwater sitting on concrete work   
   due to uncorrected drainage and water ingress in your world, is it?   
      
   >That was my point, which (as usual) you deliberately ignored so you'd   
   >have an excuse to argue with me.   
      
   I can't prevent you from making absurd points, Steven.   
      
   >I assume they'd still want to clean the tunnel walls/floor to prevent   
   >other problems, but washing smooth surfaces is a lot easier than washing   
   >ballast.   
      
   How the fuck does washing correct water infiltration and drainage problems?   
   It's the Hudson River, one of the most expensive and inconvenient places to   
   tunnel beneath on the whole planet. There's sandy soil, sea water, and   
   high water table beneath the river bottom.   
      
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