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Minimum area for HO return loop

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  • Member since
    March, 2012
  • 7 posts
Minimum area for HO return loop
Posted by RealGomer on Saturday, September 02, 2017 2:43 PM

After sitting in cigar boxes and whatnot for 30+ years, I plan to create (hopefully) an L-shaped layout with return loops at each end. My thought is to make the straight section on an L-girder framework that's two feet deep.  My question is this.

Would using 4'x4' panels at each end and the corner be large enough for a loop return? Hopefully I can use 21" radius track. I hope to run parallel tracks along the straight sections.

Tags: return , size
  • Member since
    January, 2017
  • From: Southern Florida Gulf Coast
  • 729 posts
Posted by SeeYou190 on Saturday, September 02, 2017 2:48 PM

4 foot by 4 foot will only work if you are content with 22 inch radius curves and a nasty "S" curve in the middle. Even then, there will be an additonal "exit" required from the 4 by 4. A nominal total of 4 by 6 is really the effective minimum even with tight radius curves.

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Reverse loops absolutely devour space, and almost always require an access hatch or something in the middle for maintenance/cleaning chores.

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There was an old article by John Armstrong in Model Railroader titled "Doodling by the Squares" that really did a good job of showing how much space is required for a reverse loop using different minimum radius curves. The other frightening fact in that article is how much length is required for a #6 yard throat.

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-Kevin

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Happily modeling the STRATTON & GILLETTE RAILROAD located in a world of plausible nonsense set in August, 1954.

  • Member since
    July, 2009
  • From: somerset, nj
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Posted by gregc on Saturday, September 02, 2017 7:30 PM

a circular loop of radius R require 2R in each direction.  21" radius should fit within a 24" space with appropriate space between the track and layout edge

but a reverse loop requires at least another length of R for the curve joining the loop and mainline (or 2nd mainline track).   in other words, a reverse loop with a nasty s-curve (as seeyou mentioned) requires at least 3R x 3R space, 63" in the long direction.

greg - Philadelphia & Reading / Reading

  • Member since
    March, 2012
  • 7 posts
Posted by RealGomer on Saturday, September 02, 2017 8:27 PM
I'm confused. Where is the S curve coming into play?
  • Member since
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  • From: California
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Posted by DSchmitt on Saturday, September 02, 2017 9:51 PM

 4X4 by Donald Schmitt, on Flickr

 4X4-1 by Donald Schmitt, on Flickr

I tried to sell my two cents worth, but no one would give me a plug nickel for it.

I don't have a leg to stand on.

  • Member since
    March, 2012
  • 7 posts
Posted by RealGomer on Sunday, September 03, 2017 9:32 PM

4x4 is what I was hoping to accomplish. Thanks!

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