I would like to know so as to see what I can carry for my crazy idea.
Thanks
The size is going to depend on the scale of the item and whether or not it is regarded as standard or narrow gauge, and other factors.
A 1:20.3 scale flat built from a Northeast Narrow Gauge kit, for example, measures approximately 4.5 inches wide. A 1:29 scale would probably be narrower. And are you asking about a commercially manufactured model such as AristoCraft or a kit such as those sold by Northeast Narrow Gauge?
As you can see, the closest answer you're going to get will be only an average.
Again, it depends on the scale.
Aristo are mostly 1:29, except for the Classic series that's 1:24.
The 1:29 cars are just under 4 5/8 wide.
The Aristo classic line is 1/24, and the snow plow attachment makes the car very wide. plow blade is 4 5/8 inches wide. LGB mogul with bear trap smoke stack is 8 inches from rail head. Some Bachman 4-6-0's are taller than this.
I allow 5 1/2 inches for my tunnel width and 10 inches for the tunnel portal height to rail head.
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