What is the absolute minimum radius that say, a 4 axle GP-9 or GP-38 would run on in N-Scale? What about HO? FOr some reason I’m thinking the minimums fall somewhere around 9" and 18" respectively, but I’m not entirely sure.
What would be a decent “recommended” radius for either of those? I’m thinking that if 9" in N-Scale is the absolute minimum, then 18" would be like a broad sweeping curve, or atleast have the appearance of one on a shelf type layout. The same could be said about a 36" radius in HO, no?
And just in case, I’m more so referencing a 90* turn.
Thats the problem, you cant talk for all or average them out. All you can do is consider what the MFG recommends for a minimum radaii.
For example, a 10 coupled locomotive in plastic could possibly run on 20-24 inch radius, while it’s Brass counter part will need between 28-32 inch (depending on the prototype and MFG).
Now, if you asked “what radius do I need to run my Atlas GP7 in N scale?”, then I (or others) would be better prepared to offer up a target radius.
That being said, if you run 18-20" in N scale, you are pretty much set. If you run 9", then you have many, many limitations.
I don’t have any motive power right now. I’m looking to the (near) future now that I’ve obtained the RoW located in the spare bedroom as long as I keep space for her sewing space. Design is going to be around the walls with a “shelf” type apperance.
I’m trying to decide between HO and N, and the 9" (N scale “minimum” as advertised) and the 18" (HO scale, respectively) don’t look “good”. 12" starts to appear “okay”, but I wasn’t really pleased until I hit right around 16" in N-Scale. For 4-axle GP’s and similar engines, 16" should be sufficient, I think. 16" radius in N is roughly 32" in HO. I’d say that’s a pretty fair compromise.
My dilemma is that if I increase my radius to anything greater then say 18" I risk having the curve dominate the scene and greatly diminishing the other scenery or space for buildings. The more I look at it, 16" keeps looking like a pretty safe bet for small “run of the mill” 4 axle locos.
Don’t forget to build the shelving high enough, so the wife’s sewing stuff can fit under the layout and neither will interfere with the other and will peacefully share the space. The closer you get to eye level the better the viewing.
BTW the corners don’t have to be right angles, making them 45’s will allow for broader curves.
Well the rule of thumb for HO curves has long been:
18"R = “Sharp”
24"R = “Conventional”
30"R = “Broad”
36"+ = “Super Broad”
For N scale you could cut those to about 60% - 18" for 30" “Broad” track for example. I think the Atlas 9-3/4"R track is about as sharp as anybody goes in N.
David Popp recently wrote about how he thought about backdating his layout to the 40’s, but decided he couldn’t because his 15" radius curves (that worked well with four-axle diesels and 40’-50’ freight cars) didn’t look so good with 80’ passenger cars and larger steam power. I guess the lesson there is to go for the largest radius curve you can, rather than just basing it on what you think you’re going to use in the near future.
From my aged perspective it seems that the definition of minimum radius has changed over the years. Way back when, before there were 85’ cars and Athearn 60 foot cars were perceived as the ultimate in realism, model railroaders were using 18" radius on sidings and 20-24 was considered mainline Radii. About 1963-65 when AHM started making full length scale cars it was accepted that 30" radius was what one should design to in order to run them realistically. Personally, as an empty nester (finally!) I am building with 48" radius curves. I have never regretted making my radii bigger throughout the years and have always done so since I built my first cookie cutter layout after experimenting with one 4 x8 . Now we are paying a fortune for detail that most of us can’t even see and asking questions about how do I get this around minimum radius curves. This seems regressive to me. It seems we need a calming voice who can explain in a constructive and helpful manner that if you want minimum radius curves you have restrictions and here is a list of what you should do and expect if you want to use X radius curves. We seem to be trying to make the scale hobby portion into tiny tinplate layouts. One of the main reasons I went to HO was to make the switch from tinplate style layouts. Minimum radius has gone from a definition of “caution don’t go below this and use it sparingly” to “I can design an entire scale model railroad using this as my standard radius”. It ain’t gonna’ work folks. I know some people don’t have a lot of room. If you want a scale model railroad then design within the parameters of spce you have. You just can’t put a coal mine, steel mill, auto plant, major station, engine terminal and six loops in a 4 x 8 railroad. You have to accept the limitations and then you can build a railroad that makes people scratch their heads in disbelief over the realism.&n
Thanks for the link. Looking at what is suggested in RP-11, and without looking at the radius chart, I can see that what I want to run would fall between M and N for motive power. Cars would fall into the realm of N to O.
6 Axle power is not an option, period. Not going to happen. So if parts N and O are designed to allow 60 foot 6-axles, then the 4-axles shouldn’t have a problem. (Again, generalization. each manufacturer is different, but I’d rather test run it be
Probably one of the all-around best guides I’ve seen online to minimum radius in any scale is the Layout Design Special Interest Group’s Curve Radius Rule-of-Thumb.
For example, a GP9 is about 57 feet long, which is about 7.7" in HO.
The curve radius rule of thumb says you can get away with about 3 times the length of the equipment for good tracking, 4 times will look better, but 5x is best if you want reliable coupling. For a GP9, this means:
3x = 24" good tracking
4x = 30" will look better
5x = 38" will give reliable coupling
Now you can often cheat and push to perhaps 2.5x with model loco tracking reliability, which would be just over 18" in HO. But don’t expect to go much less.
You can also cheat with the 4x “looks better” number, and drop to 3.5x if you are looking at the curve from the inside instead of from the outside. Curves viewed from the inside don’t look as sharp, and the equipment looks a little better.
As to reliable coupling, anything under about 5x means you can’t expect the couplers to align themselves all the time – you may have to manually push the couplers into alignment to couple. Not the end of the world, but it’s nice to be aware of this limitation when designing a layout. In the case of the 38" for a GP9, I think cheating just a little and dropping to 36" minimum radius would probably be okay.
The point is, these rule-of-thumb guidelines get you pretty close for layout designing. If you want to “cheat” on these figures, you should do some additional testing yourself with the specific equipment you have in mind to see what really will work for you.
To convert these numbers to N scale, just multiply by 0.54 (54%).
I’m planning a similar N scale layout to fit in corner of my basement. I’ve been asking myself the same question and have decided that my mainline will be 18" where allowed. I plan on having two reverse loops at each end, to save on space, these will most like be 12" but will not be visible to the viewing public. My GP7’s and RS2’s should negotiate these OK. My concern will be with Kato RDC’s on the 12" curves as I plan on picking up a few and running them as well.