"0" gauge clearance standards

Since three-rail trains are not entirely scale and the curves are disproportionately sharp, and there is a huge assortment of different equipment by different manufacturers, you just have to figure out for yourself how much clearance your largest equipment needs on your tightest curves.

It's fairly easy to do. For example: set square blocks of wood (or whatever) on either side of your O72 curve, run your Big Boy around the curve and experiment with how close you can place the blocks to the track without hitting. Measure the distance from the center of track for inside and outside clearance. Add a quarter inch or so for a safety margin.

The NMRA has standards for scale trains:

http://www.nmra.org/index-nmra...ecommended-practices

Those numbers are a good starting point for determining vertical and horizontal clearances for scale equipment on straight track.

ACE is right....O3R clearances are a function of your track and specific motive power/rolling stock.

My add to this is be sure you well understand your items of widest swing, maximum height,  longest wheelbase, etc..  I thought I had that fully considered when I designed and began construction of my layout. 

However, as Murphy's and other 'rules' dictate.....I found myself receiving an early diploma from the School of Hard Knocks!  I had accumulated a fair collection of the MTH RailKing autorack cars, having four nifty diecast cars aboard.  Why I never considered that they were of atypical height, I'll never know.  But not only were my over/under clearances inadequate for them, but many of the commercial bridges....bascule, lift, etc....requiring the train to pass through them, were never designed to accept those exceptionally tall cars (when fully loaded, of course).  And, so, they were sadly sold......much easier to do than correct all the other limitations on the layout!!

FWIW, of course...

KD

The only standard for O gauge is the track width (hence the gauge part).  Anything else goes in relation to size (though it should be 1/48 based on track width).  I'd think you could make a 1/32 scale locomotive and as long as it's wheels fit the O Gauge track it is considered O Gauge.  It like in the real world you have different gauges of track still in use in Europe.  A train cannot go from England to Russia without changing track gauge (does this still apply today or did they switch?).  Track gauge has nothing to do with the equipment running across it other than the wheel spacing.  

If you remember, or even heard, I think it was Paris that ordered new interurban trains that were the correct gauge for their existing track.  But when the first units were delivered they didn't fit the stations as they were just a bit wider than the existing cars used when the stations were built!  Talk about embarrassing!  

"(though it should be 1/48 based on track width)."

You'd think so, wouldn't you? But, no. Based on prototypical track gauge of 4' 8.5" ("width"), the proper "O" scale is actually 1:43 (or 1:43.5, I suppose). But, N.American O-scale and gauge went with the 1:48 (so easy - every ruler...) without changing the gauge. Leaving us with a scale 5-foot "O" gauge. Wrong.

Before WWII, there were various O-scale/gauge companies (including Lionel) offering O-gauge models built to 17/64" scale (1:48 is 16/64") - they ran on O-gauge track, but were slightly (and properly) larger. Didn't survive; too bad.

The Lionel 17/64" (but O gauge) loco was the Prewar scale Hiawatha 4-4-2, as I understand.

Ditto Ace's reply above. Additionally, as the locomotive and rolling stock roster of my railroad grew, clearance problems arose that I had no clue to when I built the layout. For examples:

• I bought an AC12 Cab Forward, and it has an overhang on curves that knocked out two loading docks, one trestle and a lot of shrubbery;
• New car carriers and a Coca Cola bottle car would not clear bridges on the railroad.

Lesson learned! When building a layout, plan for future locomotives and rolling stock that will require more clearance than your current roster necessitates. You can obtain a lot of info about locomotive overhangs by asking questions on this forum.

For most dual curves I use at least 4.5 inch center to center. However with longer engines or passenger cars you may need up to 6 inches center to center on dual curves.

You might be able to run 21 inch passenger cars on curves below 72 inch but the overhang may be a really bad issue.

Lee Fritz

D500 posted:

 

The Lionel 17/64" (but O gauge) loco was the Prewar scale Hiawatha 4-4-2, as I understand.

The Hiawatha 4-4-2 was actually 1/48 scale, as it is the same size as the scale Lionel loco that came out in '06 or '07. The oversized loco of that time (36-37) was the M 10,000.