conagher wrote:Another thing...if you change the portal opening to accommodate the Big Boy's overhang, remember the portal at the other end of the tunnel and also remember to measure for running the loco in the reverse direction.
Count on one inch from the outside edges of the rails, both inside and outside the curve. I just measured my Lionel Challenger's overhang on a true 22" curve, and it is very nearly one inch at the rear corner of the firebox on the outside of the curve, and is just over 5/8" on the inside. The Big Boy will probably be somewhere around that figure, too, but err on the side of caution and make your clearances 1.6".
I do agree with Chuck, though, there is no real substitute for an actual measurement.
The absolutely best way to find out is to put it on a track with equal curvature and measure the overhang - ideally with the exact loco you intend to run.
A true Mallet-type semi-articulated is the worst-case scenario, since the rigid rear engine shoves the smokebox WAY out there. Big Boy, with its long (for an articulated) rigid wheelbase, might be the worst performer in this respect.
In my case, the worst overhang on the roster belongs to a GG-1, so that's what I use to make sure that relay boxes, fenceposts and so on are sufficiently clear of the curve. If that monster can get by, anything I own will be happy. (For the inside of the curve it's a tossup between an auto rack, a container car and a DD51 class diesel-hydraulic.)
Chuck
TomDiehl wrote:Depends on who made the model.