Track Centers in HO Scale?

I don't know what the 'North American prototype officially is', but the normal separation for straightaways is 2 inches on center and 2 1/2 inches on curves.

Fred

Thirteen feet, at least for straight yard trackage, which is a smidgen under 1.8 inches in HO scale, but most folks go with 2 inches for the extra

0-5-0 switcher clearance. The 2 / 2.5 is a good general rule, but as always the curve clearance depends on the overhang of the equipment you operate and the curve radius. Running 85 foot passenger cars and large articulateds on curves under, say, 42 inches or so, you might want more.

Protypically, yard tracks can get down to about 13 feet or so on center, which works out to a little over 1 3/4". As Steve pointed out, fingers don't scale down very well (and our curves are sharper than the prototype), so modelers are usually a little more generous than that. I use Walthers Shinohara track, and using #5 turnouts without modifications results in

2 3/8" spacing (17 scale feet), so that's what I used.

See the NMRA recommendations at

Q

Straight tracK Yard tracks: 13ft, 1-3/4" in HO

Double (and passing) tracks on older mainlines: 15-17ft, 2" to 2-1/4" in HO

Double (and passing) tracks on modern high speed lines: 18ft and up,

2-1/2" and up.

NMRA has recommended practoice for curves of different radii and rolling stock of different lengths running on those curves. Sharp curves with longer rolling stock translates into wider track-spacing. Eg, min spacing on 18" radius is 2-1/4", but rolling stock over 50ft (eg, ober about 7") will sideswipe.

Google "NMRA" or "National Model Railraod Association" and explore the site.

HTH&GL

Two inches is the most common value used, but is a little wider than most prototype practice. On th eother hand, a considerably wider separation is needed on HO model curves to avoid sideswipe situations.

2.25" will work for wide radius curves (40" plus), and 2.5" or more may be needed on curves sharper than 30" radius. Note that Atlas used 4" separation between their 18" and 22" radius snap-track curves.

If you're using hand-laid or flex-track, some experimentation is in order with the equipment YOU intend to run.

Generally, long cars swing INWARDS on curves, while (properly) articulated steam locos swing OUTWARDS. Many model artuculateds have BOTH engines pivoted, and these swing both inwards AND outwards, but not by so much.

Dan Mitchell ============

We just reworked our hidden setup yard with ~2.5" track centers. It can still be fairly tight if you have to play with a car that is sandwiched between two other sets of cars. A pair of "near" completion photos:

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It's not very clear in the photo but the curve (~40" radius) separation is closer to 3".

Paul

Good point on the curves! If you use the same radius on every track in a hidden storage yard the centers automatically get wider in the middle of the curve; very handy for rerailing if needed.

ron

True, but 'easements' (or spiral curves) on the ends of the curves will also reduce the effective rolling stock overhang on ANY curve. Overhang is worst as an item enters a curve, and actually is reduced once the car/loco is fully ON the curve. Easements help solve this problem.

A worse case yet occurs in an "S" curve, which includes normal switchwork entering a parallel siding. The direction and extent of rolling stock overhangs can be difficult to predict in such cases. Adjoining coupled cars can change the behavior of any given car as well. Pushing produces a different result than pulling. That's why some experimentations is desirable. Extra clearance space must be allowed in all these cases.

Extra-wide separations remove all these problems, but usually look REALLY bad, and waste (usually) precious space. Still, they are a good solution in hidden areas if you have the room for them.

Normally one wants JUST enough separation, no more.

Dan Mitchell ============

Lucky for us the "left over" space for the hidden yard had plenty of width (at least for the first 6 tracks). The last 3 tracks got shortened into the "fat" space and there wasn't really much we could do about it after laying out the max length of the longest track and the resultant switch ladders. There is an "S" curve on the normal entry side for the short tracks. It's rather shallow (or drawn out) with the use of #8's in the ladders. Trains look pretty cool snaking into the yard on those tracks.

I'm hoping that after a years worth of the complete heating and cooling cycle it stull operates as well as it does now (less than

3 months into it's life cycle).

Paul

It'll likely be fine after a year or so. Layouts tend to 'settle in' to their current location after a while. We find this EVERY time we move the local club's portable layout. WE get everything lined up, and a few days later it's all out of whack again. After about ten days it stabilzes pretty well. You can expect some annual problems changing with humidity level. Some have humidity problems that are worse (by far) than others, but most everyone has such problems to some degree, and just learns to deal with them.

Some woods are more stable for benchwork than others, steel benchwork is more stable still, but even then you have the roadbed, and even the scenery, expanding and contracting to complicate things.

Dan Mitchell ============

Dan,

Exactly what I'm worried aobut. One year is still 9 months away. We have a yearly heat cycle from a low of freezing to 110F or better. We use swamp coolers, and that increases the humidity very dramatically (starting in about a month or so until late August ... usually). We can have a daily variation of 60F ... probably a few days of more than that. The club house as no effective insulation (and a holey metal roof to let the rain in :).

8-10 months from now we will have a verdict on the construction. Poplar 11 ply plywood under Homasote. We will see!!

Paul

I was talking about hidden storage yards where you want as much room between the tracks as humanly possible so you can excavate the derailed car (and possibly rerail it) with out derailing cars on adjacent tracks. I agree that using a larger easement offset on the inside track is the best way of increasing the track centers on curves.

ron

Thanks to all for their helpful responses.

craig

The thing that I'd worry about is the homasote curling and so forth after a few years. That stuff keeps on walking about over time.

-- Why isn't there an Ozone Hole at the NORTH Pole?

Well, we have found that screwing it down seems to work well. After one years heating & cooling cycle it has pretty much done what it is going to do. It's been painted and/or shellac'd so getting wet (unless it's just drenched and submersed) isn't usually a problem. So it's getting through that first 12 month cycle that's the nail biter! *8->

Some of the homasote has been in place 15+ years and hasn't move that anyone can tell. I'll try to remember and post an update in about 10-12 months!!

Paul