How much space is needed for an HO reverse loop to operate?
Gonna need more information than that to answer your question.
Rich
This much (gesturing with arms).
But sometimes can be less.
Thx for the giggle. D.
At 24" radius you’ll need four feet plus four inches for the loop plus another couple of feet for the connecting Wye or turnout. 6’x4’ approximately.
In other words you need a lot of space.
Its not the reversing loop part that takes the space, it’s the return loop dogbone shape. The reversing connection doesn’t add any space requirement by itself, the dogbone end loop is the space hog.
3x the radius in length and 2x in width
Welcome to the forums. [#welcome]
The basic reverse loop is just that, a loop of track coming back on itself. If you’re happy with 18 inches radius curves, then it’s a circle of track about 36 inches in diameter. If you prefer larger curves, then you need a larger loop.
A second possibility is a wye, not really a loop. A wye is good for turning an engine or a short train, but it involves a backing maneuver which can be awkward.
If you already have, or plan to have, a regular loop just for running trains around, sometimes you can cross from one side of, say, an oval, to the other side and do the reversal that way.
Simple geometry. A radius is half a diameter and the diameter is the width of the loop. However you aren’t going to want to run your track to the very edge of the layout so you have to decide how much space your want between the track and the edge of the layout. 2 inches on either side would be the bare minimum. On my layout, 4 inches is the minimum. So multiply your track radius by 2 and do the same for the minimum distance you want between track and layout edge and add those two together. If your track radius is 24" and the minimum distance between track and edge is 3", the total width needed is:
(2 x 24) + (2 x 3) = 54 inches or 4 feet, 6 inches.
22 inch sectional track allows for a semicircle of track on a 4 x 8 sheet of plywood with 2 inches to spare on either side.
A wye is a reversing section, but not a loop. Not sure if that suits your needs, but here is a discussion about a scissors wye
One way to visualize the required space for a reversing loop is to add two legs of a Wye to the outside of a circle.
A reversing loop just lacks the connecting arc of track completing the circle. Put another way, a Wye reversing track is missing the connecting circle in model railroading terms. The circle allows reversing of much longer trains then does a more compact Wye. To reverse a long train requires far more space when using a Wye than a loop. Depending on the shape of your space a Wye might work better though.
So the required space for a reversing loop is the same as for a circle plus the added track length on one side required to include the two reverse curves that meet at the Wye turnout. Most reverse loops don’t use a Wye turnout and so take up a bit more space than the minimum required.
This formula was very helpful to me yesterday as I was trying to lay out a problematic reverse curve on our reconstructed layout. A similar space problem presented itself and I was having a hard time visualizing the construction. The drawing seemed fine but reproducing that in track was not as easy as it should have been.
In my case I was trying to connect one half of a loop to a second half loop turning the opposite way, a long S curve. The problem needing a solution was the two halves were interlocked I.e. I lacked the necessary total width (48" for 24" radius) so needed to figure out how much added length I needed to turn back the ends of each half circle into a narrower space (about 44" rather than the simplest 48"). It’s the same concept as connecting up the ends of a reversing loop but requires less additional length because I’m not trying to connect the track into a complete loop. I’m accommodating an overlap between the ends of the half circles.
A wye requires a tail track or legs at each end in addition to the curves. While two of those legs can run parallel to or be incorporated into the mainline, that third leg is going to require some length. How much depends on whether you just want to turn a loco or an entire train.
I am currently very unsatisfied with the performance of my stacked reversing loops. It’s very difficult to get at the lower level if there is a problem. If I had it to do over again I would not stack the loops even though it would mean a shorter mainline. I am trying to figure out a solution t
another approach that requires a little less space and avoids the S-curves (rad=1)
My first layout, built by my father, had two reversing loops on a 4’x8’. The inner one was likely an 18" radius, while the outer up-and-over one was around 24"…
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It worked well enough with the locos and cars that I had at that time.
My current layout, an around-the-room type, has no return loops, but has turntables near both ends of the mainline tracks, and a wye for turning locos (with a couple of cars, when necessary).
Lower level…
…upper level…
…and main level…
…the tail track is about 23" long.
Wayne
Depends. Street car in a small urban setting? Small layout, HO, 2X6? If that’s what we’re dealing with, you would need about 4 square feet, and all you’d have room for is the one ‘teardrop’ loop wnding with the turnout, and maybe another foot of tail track to reverse. Not much.
Are you intending to build a dog bone setup? How long between the end loops? If we intend to build an 18" radius at the extreme of the loops, you’re going to need at least six square feet for each loop, closer to seven. That’s just for the loop part, not the turnout closing it up for you.
The radius you use for the loops must work with the rolling stock and their couplers. Do you know what you’re dealing with here?
A dogbone layout presents the possibility of creating a crossover track in the center that can also be the key element in a reverse loop. It’s actually the same idea that I suggested earlier about crossing diagonally from one side of an oval to the other.
The OP never mentioned whether he was planning to run DC or DCC. That would have a few repercussions with placement of rail gaps and wiring.
Hello All,
Actually, sometimes it’s more!
Depending on how long your arms are…[;)]
Know this won’t help!
I’m going to guess the outer loop on that 4x8 track plane was 22" radius track because 24" would take the track right to the edge of a 4x8 sheet.
On my layout, my lower level of the stacked loops are a major problem area. Because of the limited access, the track needed to be bullet proof and it is anything but. It was one of the first sections of the layout I built and I didn’t do a very good job of it. I’m thinking of blowing it up and starting over. It will be quite a task but it needs to be done. I just have to come up with the right design for the redo and haven’t figured it out yet.