Tunnel Portal

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Anonymous

Member since
April 2003
305,205 posts

Posted by Anonymous on Monday, June 23, 2003 11:26 PM

NMRA Standard S-7 gives lots of dope on "big enough to let the train through." Be careful to note they are for tangent track. If you are on a curve add at least a 1/2" on the outside for more clearance. I suggest you make a cardboard test section and run your equipment past it both ways. Big Boys and other long overhang locos need more space than you would guess.

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Anonymous

Member since
April 2003
305,205 posts

Posted by Anonymous on Monday, June 23, 2003 11:10 AM

A single track portal in HO, for straight track, needs to be a MINIMUM of 2 1/16" wide by 3" high above the railhead. Top corners may be chamfered or radius-filleted.
You might want to consider an NMRA shhet metal track gauge,Mark III, handy for this and many other uses.
regards / Mike