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My layout has 0-72 curves so I enjoy running the big scale locomotives. However the overhang is so extreme on the Big Boy I usually keep it on the shelf. I just think it looks goofy with such a big swing out on the curves. Was the real Big Boy ever taking such short curves for a huge swing out? I am curious if anyone else feels the same as I do. I love the Big Boy but I guess my layout is just not able to handle it. I guess that's why they call it the Big Boy!

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@Dwayne B posted:

Was the real Big Boy ever taking such short curves for a huge swing out?

Dwayne,

If you scale up an O-72 to real life you end up with a 144' radius if I've calculated correctly (3' x 48 feet/foot).  Small switchers can probably take take this tight of a curve in real life, but certainly not a Big Boy.

The Big Boy is 132' long.  A half circle of real track at 144' radius is 452' long.  You'd have to bend the Big Boy somehow in order to wrap it around such a tight circle.

Mike

Last edited by Mellow Hudson Mike
@bluelinec4 posted:

What we found out at the club this week is that the mth big boy has significantly larger overhang than the Lionel big boy. Keep finding more spots that the mth can’t handle after guys have been running the Lionel all over.  Doesn’t matter to me though I think they are all junk. P-u

I found the same thing Ben, we adjusted the clearances for the VL-BB, and the MTH one smacked into several tunnel portals!

@Jim R. posted:

There is absolutely no sectional track curve made in O scale that would be prototypically correct for the Big Boy, or for that matter most of your long scale trains.

So unless you have space for a 25-foot diameter curve and you’re laying flex track to fit your space, I’d say stop worrying about the “look” of the overhang and enjoy your trains.

This is an issue with the semi scale versions too such as the LC+ 2.0.  Several pictures in this thread with smaller radius track.

LC+ 2.0 big boy overhang o31 | O Gauge Railroading On Line Forum (ogaugerr.com)

Here are a few conversions from degrees of curvature to the more familiar O scale diameters.

  • 5 degree curve = O-575
  • 10 degree curve = O-287
    This is considered a SHARP curve on a railroad main line.
    A 10 degree curve would have a 10 mph speed restriction.
  • 15 degree curve = O-192 (rarely used on a main line)
  • 20 degree curve = O-144 (NEVER used on a main line)
  • 25 degree curve = O-115 (NEVER used on a main line)

The sharpest curve I have run around in real railroading was a 26 degree curve, which would be about O-110. The speed restriction on that curve was walking speed, less than 5 mph.

As you can see, an O-72 curve is extremely sharp in real-world comparisons.

The limiting factor with a Big Boy is not the locomotive. It is that long, rigid wheelbase on the TENDER that is the limiting factor. Up front, the boiler overhang on a 20-degree curve would likely not clear the next track.

Here's a PDF reprint of a one-pager from Run 245 that will help put things in perspective.

Attachments

Images (1)
  • OGR 245_Sharp Curve
Last edited by Rich Melvin
@Rich Melvin posted:
The limiting factor with a Big Boy is not the locomotive. It is that long, rigid wheelbase on the TENDER that is the limiting factor. Up front, the boiler overhang on a 20-degree curve would likely not clear the next track.

Correct, the VL-BB will do an O60 curve on Fastrack, but the tender jumps the track.  I spaced the tracks as 5.5", and no issue with collisions between tracks.  Obviously, 5.5" in the prototype world would be 22 feet between tracks, not exactly prototypical for real RR tracks!

@bluelinec4 posted:

What we found out at the club this week is that the mth big boy has significantly larger overhang than the Lionel big boy. Keep finding more spots that the mth can’t handle after guys have been running the Lionel all over.  Doesn’t matter to me though I think they are all junk. P-u

The MTH Big Boy is about 3/4" or so longer than the Lionel JLC/Vision (same tooling) model. I think the Lionel model is correctly scaled, with the MTH model being slightly too long.

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