Steam engine minimum radius

Ok, I first have to say I've always been a modren era guy, but now I'm working on a old steam layout - early 1900's.

I plan to use smaller steam engines like 0-6-0 s and maybe 2-8-2 at the largest. All rolling stock will be 30 foot of maybe up t o 40 foot.

So here is the question - what minimum radius can I get by with? I'm used to working with 11" with my deisels. Will that work on the smaller steam? can I get by with 9 3/4" in a few places?

 

I use 9 3/4 on my small layout with 2-8-0's and some shay's a lot depends on the loco itself. I've got several Athearn 2-8-0's and they go around pretty good, they sometimes slow down a little but not much issue. The Kato GS4 will also go around with no issues. I also have some video of an Athearn BigBoy going around 9 3/4" radius.

 

Here's my tidbit of experience.

In planning my layout I wanted 14" radius curves to reduce the depth at my blobs where the turn arounds would be, but I wanted my Concor GS4 4-8-4 to run reliably and look good. So I built a reducing radius spiral and came to the conclusion that the GS4 would start to climb the rails at 16" radius thus the 17" minimum on my layout.

I am not saying that it will not run OK on tighter curves but it is what makes me happy.

Consider an experiment to come up with your own conclusions. Keep in mind what angle you will be viewing the layout to. Mine is chest high so the 17" curves look huge. Your shorter cars should look OK on the tighter curves but I would still look into the 2-8-2's.

 

I just tested some of my engines on a 7-5/8" radius and 9-3/4" radius.
The 2-8-2 Model Power runs nicely on the 9 3/4", the Minitrix and Bachmann 0-6-0 as well as the 2-8-0 Bachmann runs good on the 7-5/8".

Fred

 

Fred,

Thanks for the great data. I'll probably stick with 11" radius, but its nice to know I can go to 9 3/4" if need be.

 

I am running 11" radius. My Bman 2-6-6-2 has no trouble negotiating that. Of course all my smaller locomotives 2-8-0, 2-6-0, 0-8-0, 0-6-0 and shays have no trouble either and would probably be fine on 9 3/4.

 

Turning Radii

Over the last 20 something years in N scale, I have learned from batches of error and successes on building several layouts, and running many many different trains. Currently I have over 500 locos from what was available in 1982 to today, including almost every modern model as well.

A few years ago, realizing my age, I wanted my current layout to be as glitch free from my trains or any new trains coming down the pike, so I carefully designed my layout with my physical characteristics considered. Among many rules of the road I adopted in its design, my first primary rule was layout size and turning radius.

I am running Kato UniTrak 100% and am currently trying to paint, ballast and weather it for realism without sacrificing reliability.

My first unbroken rule of thumb is to NEVER NEVER run a radius tighter than 11", and if it is required don't do it, do something else. It took some doing but I am totally satisfied with my layout plan, and have been running trains on it for 5 years, from early Big Boys to the Atlas and Kato modern diesels. I have both the Kato and ConCor GS4's which traverse the curves no problem, as well as a ConCor Challenger, again no problem.

I had an former layout in which I did compromise that rule in a tight place here and there using flextrak, and I did go to 9 3/4" radius, and frequently those became problem areas despite reviewers, magazine and manufacturers' claims their products would go through.

I have helped a few guys around here with getting into the hobby and building a new layout, and they adopted my "rules of thumb" and I am proud to say they are running pretty reliable layouts with only a few glitches, but not attributable to tight radius on turns.

Ken "FloridaBoy" Willaman

 

I agree with FloridaBoy on radius. So does the NMRA.

NMRA - RP-11 Curvature Rolling Stock

The link above is to the standard for radius with all locos and cars based on length and for steamers based on rigid wheel length. Basically take a N scale rule and measure the distance from the bottom center, where it comes in contact with the track, between the first and last drivers. That gives the wheelbase. Then go to the standard and see what is recommended. The small locos such as the low wheeled six drivered, like an 0-6--0 can make it through the 9 and 3/4 fine including a few of the 8 drivered ones. But locos like the Northern and Mountain need the larger radius and that includes some of the 2-8-2s depemding on driver size.

 

Any six-axle anything (steam included) can make it through sharp curves with two different methods - either blind the flanges off the center wheels, or put in enough slop to allow lateral movement.

With side rods, that can be problematic, because then you have to introduce slop in the rod pins, or make wheels narrower than recommended, etc.

If all three drivers have lots of lateral play, then all kinds of mischief can happen.

I generally try to set up my locomotives as 'tight' on the outer drivers, and 'loose' in the middle (run gauge a little narrow) to help.

As a last resort you can always turn flanges off the center drivers, I took a Hallmark brass 4-8-4 and took off the center drivers, took all the lateral play out of the frame, and it works fine now on 11" on hidden track. That's pretty intense and not recommended, but it illustrates the principle.

I get away with 8" radius on my Atlas 2-6-0's. The old Rapido 0-6-0's had a really radical approach - the center driver just coasted around - wasn't attached to anything, and had a ton of lateral play in it. It was really an 0-4-0, and curvature-wise, it was flawless. So individual locomotive design has a lot to do with it, but if you're willing to modify it, you can violate a lot of supposed rules.

 

*kkckck* Barstow Rick! Barstow Rick! We have a S.R.Q.* in progress! *kkckcek* Requesting Backup *Kcckekt*

*(Smallest Radius Question)

I'd like to invite you to rework this question from the inside out. Instead of working from the outside in, by asking what the smallest radius you can run is, ignore the equipment requirements and turn to layout design. Ask, What's the largest radius I can get away with?!

Unless done purpously, like many excellent examples of logging and micro-layouts, I believe a good maybe 80-85% of tight radius curves incorperated in layouts could have been eliminated, all by simply re-working the layout design. Except when space is an extreme limit (probably those remaining 15-20% of layouts), many super tight curves can still be eliminated from small layouts as well.

May I ask if you have a track plan in mind that you would share? If space is not an extreme limit, I bet we could easily find a solution to allow you to keep to at least 11", and possibly 12.5" minimum radius.

 

That's a good track plan.
Yep, no need to go any smaller than 11" on that.