# Limitations of 18" Radius Track



## gordonzo (May 13, 2010)

What is the maximum steam loco axle configuration that will run smoothly on an 18" radius track? I have been searching the forums here but have not found a definitive answer.

Background: I had a really nice old Mantua 0-4-0 which obviously is compatible with the track but it had some issues I was unable to resolve so I returned it. Other than slow, jerky, laboured forward movement it was a really nice little engine and I will probably regret that decision but am ready to move on and maybe move up to something larger.

I am considering something like an 0-8-0, 2-8-0 or 2-8-2. Based on recommendations from this forum I am looking at Mehano, IHC, or Rivarossi. From what I read, Tyco, Bachman and Model Power are lower end? I want to pull 6 small (40' to 50') cars and have a 16-1/2 foot oval layout of Lifelike power-loc track. Keep in mind that I am not a collector (at least not yet!) but have setup the ho track around a slot car track for myself and my young grandkids to play with. By the way, my grandaughters (4 & 6 yrs) enjoy the track as much as my grandsons (2,6 & 8 yrs).


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## dozer (Jan 2, 2010)

I'm not master of steam, but I think if you get an articulated engine, you can run a bigger engine. As I said, just a thought that I don't even know if it's correct, lol..


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## tjcruiser (Jan 10, 2010)

This doesn't answer your specific question (I think it depends a bit on each individual loco), however ...

Sometimes when navigating into a tight turn (say 18" radius), it's beneficial to make the first track into the curve a softer (larger) radius ... i.e., straight, 22" track, 18" track, 18" track, etc. Same thing exiting a turn ... 18, 18, 22, straight.

As Anton here on the forum will tout, always try to avoid immediate left-to-right turns ... i.e., always put a straight section inbetween transitions of left to right turns and/or switches.

TJ


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## shaygetz (Sep 23, 2007)

Older Rivarossi 4-8-8-4 Big Boys were actually designed to go around 18" radius. If you run older equipment chances are good that it can handle 18" curves. I run Blue Box Athearn diesels on 14" radius curves with no problems at all.


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## tkruger (Jan 18, 2009)

Not only do you need to look at the configuration of the wheels (2-6-2) look at the wheel base and the diameter of the wheels. I have an 2-6-2 Prairie that can make 15" radius. It has the smaller diameter wheels. The same loco from the same company but with larger diameter pre war wheels binds on an 18" turn. The wheel base (spacing between axles) makes a big difference also. I have an 4-4-0 American that has issues due to the long wheelbase. Some of the configurations with 3 or more drive axils may not place flanges on the inside wheels. This can allow them to handle tighter radiuses than other locos of the same configuration.


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## tjcruiser (Jan 10, 2010)

Also, I think many mfrs will list in each loco's specifications what minimum track radius it's designed to navigate.


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## tooter (Feb 26, 2010)

tkruger said:


> Not only do you need to look at the configuration of the wheels (2-6-2) look at the wheel base and the diameter of the wheels. I have an 2-6-2 Prairie that can make 15" radius. It has the smaller diameter wheels. The same loco from the same company but with larger diameter pre war wheels binds on an 18" turn. The wheel base (spacing between axles) makes a big difference also. I have an 4-4-0 American that has issues due to the long wheelbase. Some of the configurations with 3 or more drive axils may not place flanges on the inside wheels. This can allow them to handle tighter radiuses than other locos of the same configuration.


You're right. The middle wheels on my 0-6-0 center cab switcher have no flanges. I'm planning a small layout with lots of very tight radius turns, and set up some flex track for testing. It easily chuggs around 10" turns pulling short wheelbase rolling stock.


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