Minimum table witdth for different curves.

Add about 6" (Minimum) to the Curve.  O54, 60"  3" on either side.  Keep in mind some track is dimensioned, inside rail to inside rail.  Other track outside rail to outside rail.  IMO.    

My table measures 7'x16'. IMO, for a 72" curve, the minimum table width is 7'. 

If you do not use a constricting table, but instead use 30" wide shelving around the room you will be able to use almost any width curve.

The template in place is 0144".

You gotta' watch Tom Dave, he's a lot better at this than most of us, so what he makes look easy is not always so easy.

Mike CT posted:

Add about 6" (Minimum) to the Curve.  O54, 60"  3" on either side.  Keep in mind some track is dimensioned, inside rail to inside rail.  Other track outside rail to outside rail.  IMO.    

and some track is measured from outside tie to outside tie...

aside from key bows, the trains i run hardly leave the outside track diameter.

I place my track, 2 rail on 2 inch centers.     On the edge of the layout that means the center of the track is 2 inches from the edge.

There's also the equipment factor. A Big Boy has pretty large boiler swing out on sharp (36" Radius/O-72) curves. That decreases as curves get larger. Anything next to the bench work on the outside of the curve could get clipped when a Big Boy comes around. I usually design for 4" between the center of a larger curve and the edge of the bench work. If I was building a simple 16' x 8' oval, I'd use nothing larger than 44" radius/O-88.

Citing Tom Tee's post above, if you build "around the walls" you can use narrower bench work and use curves limited only by the size of the room. You might have to put in gussets for some curves depending on size and placement relative to the depth of the bench work.

Matt, you are so right....I learned the hard  way. 

ToledoEd posted:

Matt, you are so right....I learned the hard  way. 

 

So did we. We had a tunnel portal near a turnout. Over the years, the building/bench work shifted due to weather/temperature variations over the past several years and the portal (mounted against a building wall) shifted and we have to use 0-5-0 helper service to move Challenger and Big Boy boilers in about 1/8" when the go into that portal from the through yard. We're going to pull it out and shave it, then re-mount it with a Big Boy in place to verify the clearance.

We also have an issue in the staging yard where we keep the curve on track #3 clear if a Big Boy is running on the mainline (track #4) because at the time we built the staging yard, no one owned a scale Big Boy. It was easier to enact a procedural change than re-track the entire staging yard.

As they say, "Wisdom prevents you from making dumb mistakes, but wisdom comes from learning from your dumb mistakes,"

Articulateds (like Big Boys) always cause trouble.  I agree with Matt's guideline of 4" from the center rail for wide-radius curves.  If you're operating large equipment (like a 773) on small-radius curves, you might need to go 5" from the center rail.  In other words, at least 40" wide platform if you are using postwar Lionel "O31" (which actually has a CENTER RAIL diameter of about 30"!)

Another important question: Is the benchwork free-standing in the middle of the room, or against the wall?  If you don't mind the corners of your $1500 loco hanging out into the aisles, you can set the ties right to the edge of the platform.  But if the layout is going against a wall, you need to be sure of the clearances before you lay your track.  Measure with your largest equipment!

You also need to consider whether your layout will have a fascia board installed along the edges and, if so, whether it will stick up higher than your installed track height.

Matt,

I am in "S" gauge and run both Big Boys and Challengers, not sure of the difference in the construction of these engines between S and O but we found the Challenger needed more clearance on curves because of the cab overhang more so than the boiler. We had to shave some off of the rock faces on the outside of curves.

Ray

The MTH Challenger doesn't need the same clearance as the Lionel Vision Line Big Boy.  In an interesting twist, the MTH scale Big Boy from the 2017 Catalog needs a bit more clearance than the Vision Line Big Boy, something that surprised me a bit.  We had tested and fixed the club layout mainlines for the VL-BB, and it could make it around successfully,  The MTH BB nails several tunnel portals and a support in one of the tunnels.  I didn't have a Lionel Challenger to test.

By the way, it's not absolute that if your BB or Challenger can pass going forward that it will clear when traveling in reverse...another of life's lessons learned in model railroading.   So if you "just make it"...back it up, before you nail, screw or glue.