Centerlines for large articulated steam

Marc,

In my opinion your question is among the top 3 asked on a regular basis in this forum.  It comes up literally every week, and has done so for at least twenty years.   There is no formula, but there are several good approaches to tackling it.  Unfortunately no one has had the time to compile them into a guide.

Your best bet is to use the forum's Search function and start with the word "clearance".

You will get many, many hits, and you'll have to dig into them, but there will be excellent and detailed suggestions in the posts that come back.

Mike

If you plan on 6" spacing between tracks, you won't have any issues with most locomotives.  I'd say all, but than I don't own "all" of them.  This is sufficient for the Lionel and MTH Big Boy locomotives as well as stuff like the MTH Coal Turbine, Centipedes, and the many other articulated locomotives I have.

The most overhang I've measured is the MTH Premier big boy, 3.25" from the center rail.  That's on the outside of the curve, it doesn't have the same amount of overhang on the inside of the curve.

@gunrunnerjohn posted:

If you plan on 6" spacing between tracks, you won't have any issues with most locomotives.  I'd say all, but than I don't own "all" of them.  This is sufficient for the Lionel and MTH Big Boy locomotives as well as stuff like the MTH Coal Turbine, Centipedes, and the many other articulated locomotives I have.

The most overhang I've measured is the MTH Premier big boy, 3.25" from the center rail.  That's on the outside of the curve, it doesn't have the same amount of overhand on the inside of the curve.

Thanks John, I was thinking 5" but I can certainly go 6" to be safe. Appreciate the heads up.

@gunrunnerjohn posted:

If you plan on 6" spacing between tracks, you won't have any issues with most locomotives.  I'd say all, but than I don't own "all" of them.  This is sufficient for the Lionel and MTH Big Boy locomotives as well as stuff like the MTH Coal Turbine, Centipedes, and the many other articulated locomotives I have.

The most overhang I've measured is the MTH Premier big boy, 3.25" from the center rail.  That's on the outside of the curve, it doesn't have the same amount of overhang on the inside of the curve.

Agreed, I like to leave 3.5 between tracks just for the extra space .

I 'm at 6" on curves and my 2-10-10-2 does well. That's on 0-72 and 0-96 at the tightest point. My straights will have spots where it's 4.5" spacing and traffic travels in both directions.

I'm in a position like you where I don't have the locomotive in hand. I'm getting track a little at a time and the Big Boy will arrive later this year sometime (I hope) so I recognize some spots might need adjusted or special operating conditions will have to be imposed like Big Boy only runs on the outside loop and through the yard.

So far so good though. I have a long boxcar, the 2-10-10-2 and a 4-12-2. I have ran them in every combination I can think of and nobody has collided.

As a little warning, not all track manufacturer's measure their curves (e.g. O31 or O72) by using the centerline of the product.  So, while you might expect O72 and O84 concentric curves to give you a 6" centerline separation, that might not be the case.

Chuck