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Switch backs

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  • Member since
    February 2005
  • From: Vancouver Island, BC
  • 23,330 posts
Posted by selector on Monday, April 3, 2017 6:26 PM

cuyama

 

 
carl425
I don't have any experience that would contradict this advice, but I'm curious why you wouldn't start the vertical curve as soon as you're off the turnout.

 

It's easy for the grade to slide into subroadbed under the turnout during construction unless great care is taken. In addition, there's always a track joint at that point -- and a grade transition exactly at a track joint is usually trouble. 

As I said, it’s possibly a bit conservative. I design for others to build, so I want to maximize reliability. On the flip side, I can’t count how many times I’ve seen reliability problems result from a grade starting right at or within the turnout – and it’s an error found in many published plans.

 

Yes, precisely, Byron.  Those of us very patient and highly skilled at laying bullet-proof track could get away with a change of grade near a frog and its guards, but like any change of grade on rails, scale or not, it must be a vertical curve starting with the grade of the frog rails.  For the rest of us mere mortals, giving our rolling stock and long-wheelbased engines about a boxcar length from the frog before starting the grade is cheap insurance and will keep us from developing anxiety every time we go over that place with a train.

  • Member since
    December 2001
  • From: Northern CA Bay Area
  • 4,387 posts
Posted by cuyama on Monday, April 3, 2017 5:20 PM

carl425
I don't have any experience that would contradict this advice, but I'm curious why you wouldn't start the vertical curve as soon as you're off the turnout.

It's easy for the grade to slide into subroadbed under the turnout during construction unless great care is taken. In addition, there's always a track joint at that point -- and a grade transition exactly at a track joint is usually trouble. 

As I said, it’s possibly a bit conservative. I design for others to build, so I want to maximize reliability. On the flip side, I can’t count how many times I’ve seen reliability problems result from a grade starting right at or within the turnout – and it’s an error found in many published plans.

  • Member since
    August 2013
  • From: Richmond, VA
  • 1,890 posts
Posted by carl425 on Monday, April 3, 2017 4:00 PM

BRAKIE
You can but,it would have to be gradual like a industrial siding that is lower then the main

Yes, I get that.  It always has to be gradual - that's track laying 101, but why the 1-car length of level track between the turnout and the start of the grade?

I have the right to remain silent.  By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.

  • Member since
    October 2001
  • From: OH
  • 17,574 posts
Posted by BRAKIE on Monday, April 3, 2017 3:56 PM

carl425
I don't have any experience that would contradict this advice, but I'm curious why you wouldn't start the vertical curve as soon as you're off the turnout.

You can but,it would have to be gradual like a industrial siding that is lower then the main.

A sudden raise or drop in the track can cause issues like a pilot or snow plow striking the rail to cars uncoupling if the couplers are not perfectly in gauge.

Larry

Conductor.

Summerset Ry.


"Stay Alert, Don't get hurt  Safety First!"

  • Member since
    August 2013
  • From: Richmond, VA
  • 1,890 posts
Posted by carl425 on Monday, April 3, 2017 3:18 PM

cuyama
I allow a distance equal to the longest car length on either side of any turnout before changing grade

I don't have any experience that would contradict this advice, but I'm curious why you wouldn't start the vertical curve as soon as you're off the turnout.

I have the right to remain silent.  By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.

  • Member since
    February 2002
  • From: Reading, PA
  • 30,002 posts
Posted by rrinker on Monday, April 3, 2017 12:24 PM

 That would make the most sense. I'm not sure why you couldn't have a turnout on a grade, as long as you do not CHANGE grade. Side to side could be problematic, helping wheels pick the points or the frog to the downhill side. But along the length of the track, so long as it was all even on both sides and through the turnout, should be no less reliable than a level turnout.

                --Randy


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    December 2001
  • From: Northern CA Bay Area
  • 4,387 posts
Posted by cuyama on Monday, April 3, 2017 11:23 AM

UNCLEBUTCH
My question is how mutch level track? Is it dependent on the equipement used, or is there a rule of thumb?

I allow a distance equal to the longest car length on either side of any turnout before changing grade (not just in switchbacks). Turnouts can be on a grade, I just don't change the grade within or near the turnout. Other designers may be less conservative.

  • Member since
    November 2015
  • 723 posts
Switch backs
Posted by UNCLEBUTCH on Monday, April 3, 2017 11:14 AM

In another thread the guys were talking about turnouts for switch backs,and the need for level track on both ends of the turn out.

My question is how mutch level track? Is it dependent on the equipement used, or is there a rule of thumb?

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