How high are your highest HO scale car? Please give me the answer in mm if possible, from the rails to the highest point of the car. Are there cars that are higher then the NMRA gauge?
My 250 ton crane car, 3 1/2 inches tall (boom height), about 86 mm’s.
Electro;
I model the 1940’s so I don’t have any excess height cars. My nominal car would be a box car, with an average height of 48mm.
The stove chimney on my Walthers UP yellow caboose is 58 mm above the rail tops.
I run under (virtual) catenary which is (nominally) 70mm above the rails, about 6mm lower than the maximum height allowed by the NMRA gauge.
None of my rolling stock comes anywhere being that tall, except for pantographs which can extend to (and are secured at) that 70mm height. HOWEVER, I do have one 16-axle well flat, designed for oversize, overweight loads. The removable loads for that car are restricted to a maximum height (rails to top of load) of 68mm, 2mm below the standard catenary height.
Even though I model in 1:80 scale, I use the NMRA HO scale gauge to set clearances.
Chuck (modeling Central Japan in September, 1964)
EL, are you concerned about tunnel portal heights, or maybe cross members on a bridge? I cut down my Woodland Scenics “stone” portals, made of plaster or hydrocal, by nearly 15 mm, and still have lots of clearance with all my engines and cabooses. No crane, mind you.