DezignGuy Wrote:
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> Thanks Chris. Wow that is tight.
>
> Also, out of curiousity, how does the minimum
> curvature compare with a small rod engine, say
> something like a 4-4-0 like the "Eureka" or an NG
> 2-6-0? What were their minimums?
>
> Thanks!
With the 4-4-0's it depends on the locomotive's arrangement: Does it have four flanged drive wheels with a pilot truck that has a swinging/sliding bolster, or a rigid front truck with blind lead drivers? Does the lead truck have a radius bar? That'll stiffen it up a bit too. "Eureka" itself is not built with maximum possible flexibility because its home railroad did not have such tight curvature. The 4-4-0's used by the 3 foot gauge Camden, Glousecter & Mt. Ephraim could manage a 120 foot radius curve on that railroad. These engines were built with the rigid lead truck and rear driver-only flange layout. Crowns could probably handle even tighter curves than 1870's designs but they're not built as road engines (Crowns have tiny truck wheels and low boiler capacity) so in my mind they don't count.
What a mogul could do depends heavily on the pattern. Long-wheelbase moguls were limited to not much tighter than ~30 degrees. Short-wheelbase moguls derived from switcher designs (basically switchers with a lead truck) could manage sharper curves, limited mainly by available play of the lead truck. 120 foot radius was certainly doable, and 100 might not have been outside the realm of reason. The small 0-6-0's such engines were derived from could in some cases manage curves down to 75 or 80 feet radius.
Very small 0-4-0's could frequently take curves less than 50 feet radius, in some cases down to less than 20 feet radius. Such designs frequently appear for purposes such as mill service or public street tramways.
