I am putting together a layout and I am pretty unfamiliar with the difference between 15, 18, 22, etc. radius curves. I remember as a child my father’s diesel locomotives had a hard time navigating the 18 radius. Just curious if I could find out how compatible the 18" radius is to modern locomotives.
Thanks [:D]
I assume you are in talking about HO scale.
While a long time standard,due in part to fiting on a 4 x 8 sheet of plywood, 18" radius is pretty tight. Small steam locos and 1st generation diesels (for example F7 and GP7) will operate on it OK. Some modern power will negotiate 18" radius, but it will look and operate better on broader curves. Even 22" radius is tight for most modern power. In general it is best to use the broadest radius you can on your main lines and sidings. Some yard tracks and Industrial tracks only used by switchers can have smaller radii.
Some small 6 axle diesels will navigate 18" radius curves and up to 72" cars, but will look unnatural.
This page on the NMRA’s site http://www.nmra.org/standards/rp-11.html has their recommended minimum radius / turnout for different classes of equipment.
Enjoy
Paul
Double the radius to get the curve’s (or circle’s) width; i.e., an 18" radius would result in a half circle measuring 36" across. Atlas snap track is 18" radius. With the newer locomotives and rolling stock, 18" radius is not going to be adequate. Most items today, such as the newer diesel locomotives and passenger cars, require a 22 or 24 inch minimum radius, and recommend that it be even larger if possible.
At the Cochise & Western Model Railroad Club’s HO-scale layout, our minimum radius is 22" and even that is not good for something like an SD-70 because of the amount of overhang on these curves. We have encountered some cases where a particular locomotive has so much overhang on the ends that it can’t be coupled to a shorty car, such as an ore car, because the overhang drags the cars off of the track.
Bear;
Some additional information; track radius is measured centered between the rails. Thus 18" radius track, 36" diameter as measured at the center, take 38" or so diameter on the table.
The rule of thumb is to go as large as you can, there some locomotives out there that need more than 30" radius. All of our model radii are ridiculously underscale. An incredibly tight prototypically scale curve would be on the order of 100" radius in HO scalee the curve in Rochester MN new 2nd st and 2nd ave NW (use mapquest) is about that size. It is very tight for a real train.
I was also wondering how my equipment will run on 18" curves since the plan I currently have will require them in one section due to space constraints. Since I already have my primary locomotive purchased I decided to simply buy some snap track, make a short oval and see how things go. I am using a Bachman Spectrum 4-6-0 with 36’ and 40’ freight cars along with a 25’ caboose. As soon as the track arrives and I test, I will repost here.
Jay
The 4-6-0 would be pretty good. I own one of those. I also have a few 40 footers or less cars for it to pull that will fit on the future branch and not look too bad.
Now I love big steam the radius for those is 24" minimum I may suck in the asile widths and make it 26" radius minimum.
But on my 2x8 shelf the 4-6-0, 2-10-0 and P2k 0-6-0 will be the ones making and breaking trains.
I consider 18" industrial and branch line (Logging, mining and quarrying)
Tested my ten wheeler on 18" radius circle of track this evening, everything operated and looked good. Well except for the masking tape ballast and the dining table woodgrain ground cover!
Jay
You have a 10 wheeler now, but what happens when you have to have that 2-6-6-2? Trust me, I’ve been here. I started out with 18" because my F units and GP-35 fit fine. Then I had to have an SD-50, not fine.
I’ve since rebuilt my layout and 22" are the minimum, 24" everywhere else. We all have a weakness, so I say, plan for it at the beginning.
I started off with 18" curves on my layout on the mainline. I removed all of them for 22"
curves.
Do as most of the guys have suggested, go as high a radius as your space will allow now before you build anything.
You can get 22" curved track from Atlas as that’s what i used on some of my curves, flextrack on most though.
Gordon
I have a Penn Line 4-6-2 K4 Pacific, (now produced by Bowser). when I put it on the cycle of 18’ that is around my Christmas tree it ran good, but was very noticable that the cab swung way out away from the front of the tender. also the cow catcher was hangin over the edge of the track . This was a good test for me because I plan to build a 2x8 shelf layout myself.
My 4’ x 10’ BRVRR has some 18" track in it. The mains are 23 1/2" and 21" radius. I use snap-switches to save space. I have a Bachmann ‘Niagara’ 4-8-4, a BLI 2-8-2, three SD40-2s, a flock of F7s, a GP30, 40, 50, a couple of PAs and an FP45 loco running on it, together with various 2-6-2s, 0-6-0 and even a couple of 0-4-0s. Admittedly, some of the larger locos overhang too much. The radius doesn’t seem to cause derailments nor do the snap switches. My Athearn, Walthers and ‘unknown maker’ passenger cars track well and even back through the reverse loop.
Bigger is better! Use the largest radius that your space will allow!