how many inches do you need for an steam engine to to go under a bridge in ho scale
Ken,
The NMRA (National Model Railroad Association) minimum standard for clearances is 3" for HO. This link will also provide you with similar answers along those lines:
NMRA Standard and Recommended Practices
Hope that helps…
Tom
While I agree with the above, the prototype you follow and other factors may well influence your choices. Crandell (Selector) once showed us a photo of a NYC Niagara coming out of a tunnel portal with less than NMRA standard clearance - quite prototypical, since the NYC had some restricted-clearance tunnels that, among other things, kept dome cars from running into Grand Central Station.
Best bet is to measure the actual height of your locomotive and add 3 millimeters - and then check to make sure that the cupolas and stovepipes of your caboose(s) will also clear. (If you’re running steam, double stacks and hi-cubes shouldn’t be a problem.)
I have one route where I could go down to 80mm or even less - operated with small, low-roofed cars and teakettle tank locomotives that could run under a duck…
Chuck (Modeling Central Japan in September, 1964)
Don’t make the classic mistake of measuring from the top of the rail on the bottom track to the top of the rail on the top track. The proper measur ent is from the top of the rail on the bottom track to the lowest support member over the track. Those sudden stops tend to be a little annoying after once or twice.
Well I put an addition on my layout and have a removable/ duck under bridge, my layout it’s U shaped and my controls are there. I’ve taken an interest in the double stack rail cars so when I built my tressels, I put 3 in, the bridge is 42" long, and made them 4" high (clearance). I think if you are to use those cars you need more than that 3 1/2 inches. Haven’t got the double stack cars yet, but I was told I need 4 inches for them to clear.
Soooooo truuuuue… [:-^] But it wasn’t the portal, it was the clearance between the rails and the tunnel roof, well behind. [:I]
The Pennsylvania Railroad also had tunnels with limited clearance. In the early twentieth century, it complained to the Southern Pacific that its then-new furniture/automobile box cars were too high for some PRR tunnels.
Mark