Track spacing on curves

[7Dave7]

Hello to the group ! I'm quite new to the hobby and studying designs for my first layout. I wanted to enquire about track spacing around curves.

First off, as I understand it, for HO scale, 2 inches, center to center, is adequate track spacing on straight sections. It has been suggested that 2 1/2 inch spacing is great, if one has room. I'd like to go with 2 1/2 for straight sections, so long as it looks OK ( as compared with prototype).

I'd like to know minimum suggested spacing for parallel tracks on 180 degree curves for 36 inch radius and 22 inch radius. I feel this will give me a general guide-line.

 Thank you in advance to anyone who replies.

Dave J. 

 

 

[rrinker]

 The best answer is to try your equipment and see what works. If you run 85' passenger cars you might need more space than you think.

                             --Randy

 

[Last Chance]

I run 31" Kato with a train length run around of 28 inches inside that. The spacing is enough to clear foot long high cube auto boxcars which are worst case scenarios as far as really long/large cars.

If I find a bigger car like a autorack (RTR version that is like really high and long) Im not sure if I can clear it but would issue track order to restrict that train to the outside line.

[selector]

I would have to echo what Randy said.  I did very well with my various clearances around the layout until I got a new Rivarossi H-8 Allegheny with an injector overflow pipe on the engineer's side that noisly scraped things, even to the extent of stopping the engine in reverse.

On your 22" curves, you would need very close to 3" between centers for insurance and future acquisitions.  But do try a mock-up of temporary track and run your items with the greatest overhang around curves and see how close they come when running around parallel tracks of close radii.

[twhite]

You mention a 36" radius, does that mean that your inside parallel curve would be a 34"?  If so, I'd recommend a 3" minimum separation center to center, especially if you plan on running 85' cars, either freight or passenger because of overhang.  The minimum radius on my layout is 34", the maximum is 36", and even on radii as generous as these, overhang from long cars or long wheel-based locomotives (I run almost exculsively big steam) can be considerable.

Tom  

[7Dave7]

Hello Tom,

To answer your question - yes 36 in radius and so 34 or 38 inch parallel is what I was wondering about. I figured for longer cars and engines, I'd need 3" on the curves, even if 2" is sufficient on the straigh-a-ways. Like i said, I'm new to this and designing mostly on computer, or drafting paper, so I don't yet have the luxury of trains and track to test clearances. I was pretty sure I could get the answers I need for the good folks here and I was right. Thanks again to you and the others who posted replies.

Dave J. 

 

[twhite]

Dave--

You're very welcome.  Another thing to think about--I don't know how large your locomotives are, but I run a lot of brass articulateds, which are prototypically articulated--only the front set of drivers 'swing' with the rear set fixed under the cab--and even on 36" radius, there is a considerable overhang, so my suggestion of a 3" center between curves is an absolute MINIMUM.  3-1/2 or even 4" will work very well also, and the distance between the parallel curves can be 'hidden' with ballast. 

Here's a shot of one of my big articulateds on an inside 34" radius curve (the outside is 36") as you can see, there is enough 'overhang' from the boiler that if the trackage was not separated a little wider than 'prototype'  I'd be running into some pretty severe clearance problems. 

Tom

[tomikawaTT]

  Welcome aboard.

As has been suggested, the best way to be absolutely, positively safe is to lay concentric test curves and see if your longest, widest equipment will clear.  Worst case is probably an auto rack on the outside and a brass Big Boy (fixed rear engine) on the inside.  The 24" curve will require more clearance than the 36" curve. but it would simplify your life to use the same center-to-center distance on both.

As for parallel straight tracks, while the NMRA says a little over 14 scale feet is adequate, present-day railroads have widened out to 20 feet and more on new construction and realignments.  2.5 inches between centerlines in HO would have been good 1960s practice.  (The NMRA recommended practices were originally based on midwest prototype standards in the late 1930s.)

A good way to widen the spacing on curves is with the spiral easements entering them.  The outside track should have a normal easement.  Giving the inside track a longer easement with greater offset will gently spread the two tracks to the desired relationship, while the easements themselves will smooth the change from tangent to curve.

Chuck (modeling Central Japan in September, 1964 - with spiral easements)

[cuyama]

The NMRA's recommended practices on track centers are also a good place to start, although at the tighter radii, you may need more distance for very long modern or particularly "stiff" equipment.

Byron
Model RR Blog

[Medina1128]

cuyama

The NMRA's recommended practices on track centers are also a good place to start, although at the tighter radii, you may need more distance for very long modern or particularly "stiff" equipment.

Byron
Model RR Blog

Click on this link for the specfic NMRA RP National Model Railroading Association - Recommended Practices for Track Spacing.