A Picture is Worth a Thousand Words
Just recently I was building a new metal 'bridging deck' that would join my external helix track to my subterranean staging tracks inside the main room of the layout. This bridge supports a 3-way turnout that feeds 3 curved sections of track to the 3 staging areas, and also a rerailer. I had already cut the rectangular hole thru the back wall of the shed. I was replacing my original flat plywood bridge with an alum channel one that would also have 'side fences' on it to protect from derailments falling over the sides of this 'bridge'...
Per my original plans there are to two 24” radii tracks leading off to either side of that 3-way turnout. I had trimmed off a portion of those 2 fences on either side of the alum channel to allow for sideway clearance for cars traveling on those 2 side routes.
BUT as I looked at these clearances (AND those of the cutout in the wall), I began to question if I had provided enough clearance for those very long auto-racks in addition to the long passenger cars?? That's when I decided to come back to this subject thread and look again at my results, and those references supplied by other participants.
I began to look back thru all of discussions, and charts, and other links,...and get more confused by the multiple answers.
I decided to get out the track, and the cars, and the bridge structure and do a full scale mock-up. So here is my bridge with the side fences trimmed in there first configuration
Here are two of the large, long cars I would hope to be able to put down in my staging areas
The question is can they clear the openings I've provided? No questions about height as I've already provided 4"
My first trail was with the AUTO-MAX pair. I figured that this car had its wheel pivot centers at the very ends of the car which would result it it have the greatest overhang to the inside of the curve.
The 24' radius track bending off the 3 way (only tested right hand branch). That little bracket sitting out there will come in handy.
You can see that there is plenty of clearance between the side fences of the deck/bridge and the cars. I forgot to mention that I had already gone ahead and cut an extra 1 inch off of the fences in anticipation of a clearance problem here. It now appears that may not have been necessary, but no matter as I did not require that portion of the fencing.
Moving along down the curve we can now see the that little bracket right up next to the inner side of the Auto-Max.
Looks to be 1 1/8” at the very minimum to the centerline of the track.
So if I gave it 1.5” that should be plenty!