# Minimum radius?



## Jack - Freshwater Models (Feb 17, 2008)

I'm working on a track plan and have limited space. Ideally I'd like to have 12' radius but in our small urban lot that just won't happen. I don't have any interest in running super power but may want to run a light 6 or 8 coupled loco. 

Does anyone know how to correlate rigid wheelbase to minimum radius from a practical standpoint. I don't want to include locos with lots of axle side to side play. Wheels would be G1MRA standard more or less.

Your thoughts and insight would be appreciated.

Jack


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## Pete Thornton (Jan 2, 2008)

Jack, 

When I built my first garden line, the criteria was that I wanted to run an Aster LNER "Mallard" 4-6-2 (at some un specified future date when I won the lottery !) Most larger Aster's have prototypical wheels so no extra blind drivers, and they require 3m radius. I built my track to a 10' radius, although I confess that one end had a tightening curve in a cutting of about 8' radius for a short stretch (see sig photo below.) 
I've not heard of any model that can't get around a 10' radius, 20' diameter curve.

_(P.S. I never did get an Aster. But visitors locos might have needed the wide curves. It looked great - let me know if you want more photos.) _


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## msimpson (Jan 5, 2009)

The rule of thumb is use the biggest radius you can fit in. That said, I spent several years running small 0-4-0's (Ruby, Sammie, Jane) on two foot radius. I had an 8 x 5 table with an oval totaiing about nineteen feet (4 foot diameter circle and two 3 & 1/2 straights). Laugh all you want, but I had a lot of fun and really missed it when the wife took the porch back. Way better than no trains at all. 

An Accucraft Shay needs four foot radius, A Mogul (2-6-0) maybe 30 inches. Roundhouse six-wheeled engines (Lady Anne (0-6-0), Fowler (0-6-2)) have blind center drivers and function as 0-4-0's -- fine on a 4 foot radius. I have a portable layout with 4 1/2 and 5 foot radius that will take most engines, albeit some look better than others. 

But the bigger the radius, the easier it is to pretend you are not running toy trains around a small circle of track I am now plotting a 15 foot radius circle (about 95 feet around), which is huge by comparison to my prior efforts, but only about 2,000 scale feet at 20.3:1 or a quarter mile in 7/8 scale. 

Don't be discouraged -- here is a wonderful example of maximally minimum radius railway. http://www.7-8ths.info/index.php?topic=16680245.0 I think the radius is 13" at the small end of the loop. 

Best regards & happy building, Mike


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## coyote97 (Apr 5, 2009)

there are always some things to consider:

-the sharper the curves, the less safe is operation. Sharp curves and steep grades may leed to derailments.
-the prototypical RR have some rules regarding guidance on track. Therefore the decissions were made if to drive standard or narrow gauge when building the RR.
-->I always would prefer a narrow gauge RR if u just have space for "sharper" curves. 

Maybe this may be an interesting example for you:
In germany, standard gauge railroads have a min. radius of 300m, what would be 14,77m in 1:20,3 or 48 ft.
Sidebranches went down to 180m (8,8m in 1:20,3 or 29 ft.)
The swiss narrow gauge RR have some curves with R35m (1,7m or 5,7 ft.)

The D&RGW 72m (238ft.) what would give 3,56m (11,7 ft.) in 1:20,3 

The Uintah (lol--thatfor my absolute favorite!!!!) they had 7,5 % inclines and curves with 88 ft. rad.. That would give 4,3 ft rad. in 1:20,3.

If u look how absolutely "to-the-edge" the Uintah RR was, i would suggest to run a G scale narrowgauge with a min. rad. of 4 ft. 

All other thing wont run safe or look some kinda...mmmmfffnnn...strange.


Greetings
Frank


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## Jack - Freshwater Models (Feb 17, 2008)

No grades allowed on this track. In the past my interest has been mainly in 1:32 scale but lately I am more and more attracted to small NG locos. Mikes comments are allowing me to further consider 6' radius. 

Jack


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## Tom Bowdler (Jan 3, 2008)

My former garden railway, built in the early '90s, was composed of "large" 4' radius curves (in the days when 2' radius was common) until I discovered live steam when I leveled it and increased the curves to "gigantic" 5' radius. It stayed that way until abandonment in 2006. My largest locos were an Accucraft C-16 and Mogul which traversed the road just fine along with a host of smaller locos. Once a visiting K-27 made some runs. From my experience 5' radius allows lots of possibilities but my new 10' radius track is even better. ;>) 
Have fun, 
Tom


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