30" ain't what it used to be! (in HO scale)

You know, I was so excited for my broad 30" radius curves on the on the Francisquito Valley Railway 2.0 mainline - only to find that it’s actually not that broad or visually pleasing when running an 85’ superliner. The outside rail is just barely hidden and the overhang on the inside is pretty bad.

Well, figures because typical US minimum is 410 feet radius which 717 feet for mainline for long freights. [:'(] My 30" is a tight 217 feet.

This would be the first of many disappointments as the track plan (3rdPlanIt) gets transferred to the real world. Ahem … I mean my little world.

NP

Yes, in HO scale, that 414 ft. minimum translates to 4’ 8-1/2" radius, and that 717 ft. “normal” curve is 8’ 2-3/4" radius. Sobering, isn’t it?

Tom

Keep 30" for inside curves…and more broad for outside curves. It’ll look much better

I have been fortunate, but mostly determined, to have enough room for curves in the 33"+ range for my last two layouts. For my second, a folded loop that I operated from a central pit, the end curves of the overall rectangular shape of the bench were in the 45" and better range, and I got hooked.

However, my equipment was a huge factor. For the third layout, now history, I had a new Sunset Canadian Pacific 2-10-4 that was supposedly good for 30" minimum radius. Were I a Greek God and capable of laying a perfect curve of that radius each time, I might have gone with that as my minimum. Instead, I used 33", a ten percent buffer for the sake of that one locomotive. Walther’s heavyweights do well down to about 27" or so, so I knew they would be fine, even at speed.

Now, with that lovely experience, I will never have less than 33" for track anywhere if I can help it (barring a small industrial complex), but my mains will always be nested 36" and 39" curves, or much wider if I have the room. Things simply work better and look better.

If you look at NMRA Recommended Practice 11 (RP-11), 85’ passenger cars are in category “P” for track curvature which is minimum 40" radius in HO scale.

I just found RP-11 not too long ago, and now that I have seen your post and others, I am convinced that 30" minimum won’t work on my upcoming layout like I thought it would. Fortunately I am still in planning and can change things before finding out the hard way.

I’ve also been doing some reading about adding easements to curves, especially on track that the 85-footers will be operating on.

Jeff L

To look realistic, not necessarily prototypical, the radius of the curve in HO scale should be 3x.

So, an 85’ car needs a 36" radius curve to look realistic.

To calculate, 85’ x12" = 1,020 scale inches, 1020 / 87 = 11.72" (the HO scale length of the car), 11.72" x 3 = 35.2" (the required radius to look realistic).

Rounded, the required radius of the curve must be 36 inches to look realistic.

Rich

Rich, I supect you are right given how the outside rail is barely covered at 30".

David, Umm. Yeah. I wish I knew prior to scratch building a curved trestle at 30" radius. It’s on the main, so without a significant change to my era and theme the superliner and bombardiers will be going over it multiple times a day.

I have a 5’ 6" wide area in the basement and using it gave me about 20’ of main line. A 180 deg turn is 2.5’ radius in that space.

Well I am sure I can live with it.

NP.

Hi Rich,

Assuming you’re refering to the same report I use…

3X is the point where everything should run well.

3.5X looks less toy like when viewed from inside the curve

4X looks less toy like when viewed from outside the curve

5X will allow reliable coupling

You have discovered what many experienced modelers have known for years, that Allen McCelland of V&O model railroad fame discussed this in one of his articles, that long model train cars don’t look very nice on the relatively sharp 30-inch HO curves. Allen was so unsatisfied with how his Walthers 89’ autorack looked, he kit bashed a shorter version by removing one of the panels, after which which he felt the shortened autorack looked better on his 30 inch curves.

I built my first sizable layout in a garage in Indiana, which was 16x19 feet and had minimum 30 inch curves, but I also put in a 36-inch curve in a central point and was running my Walthers autoracks around it, and did notice even the 36-inch curve looked quite sharp under them and the middles of the long cars really overhang on that 36 inch curve!

While I was still living in Indiana, I had attended the GATS train show in Louisville KY and watched a train full of Walthers autoracks on a modular layout and noticed how nice they looked on the corner modules curves. I asked one of the club members what the curve radii were and he answered something like 56-inches.

The lesson I have learned since then is 30, 32 even 36 or a bit more, it doesn’t make that much difference for the really long cars like the 89’ autoracks or 89’ TOFC flat cars, the curves have to be much larger to get a significant visual benefit - like well north of 40-inch radii. So like some of our compatriots in this thread, my personal minimums on my last and present layouts are 32-inches, but really that is so I have the freedom to operate a wide range 70’s and 80’s era rolling stock, including long freight cars and passenger cars.

But I also know those 32-inch curves still look very sharp, and even if I could have all 36 inch minimum curves, sure, that would improve things for much of the rolling stock but even those still look sharp under those 89’ cars, which I le

This was one factor in my switching to N scale many moons ago. I wanted to be able to sometimes “launch 'em and let 'em run” and even 30" curves were going to be hard to fit into the space I had, especially when I allowed for easements. That was especially a consideration because I was planning on modeling mid-40s Pennsy, mostly steam. T1s, M1s, and maybe even a J1 for good measure needed as gentle of a curve as they could get. That was when the switch to N happened.

The best “train space” I have had of three (never finished) layouts was in our last house. The space allowed me to use eased 27" curves in N. When I switched scales I also switched eras a bit, to the late 50s, so the motive power does not tax the minimum radius quite so much. Still, I have two passenger trains and the cars look better on wider curves. The current project has minimum 18" curves on the main, which translates to about 33" in HO.

We are contemplating another move, and I may get the chance to add a space for my railroad and office. You better believe I will be looking toward the 24-27" radius range (44-48 HO equivalent) if for no other reason than it looks good, especially the passenger trains.

In fairness, the current eased 18" curves have been trouble free, even with an Athearn Big Boy that makes an appearance sometimes. So reliability for my 1958 era equipment is not really hurt by the compromise. But when planning, I always run with “wider is better” for the main, and cosmetic curves sure look good. I generally design in one or more 5-degree curves (roughly 84" R in N, about 158" in HO) as an alternative to a long straight section.

Of course, using that philosophy can cause me to rethink the complexity of the plan, but I don’t consider that a bad thing, either. I would compromise that philosophy pretty quickly if the available space left me ro

The original poster really needs to specify scale as the 30-inch radius title is very much tied to scale and means completely different things to N scalers vs. HO.

Just saying…

He did. You just need to do a little math.

When I started designing my new layout (UP north of Ogden) I started with 28" curves. However I didn’t like the way they looked when I did some proof of concept testing. So I went to 32". And then 36". And now 40+“. I basically ran out of real world real estate at 40” so it’s going to have to do.

Enjoying yourself there? (as my wife would say) The fact that some have come in here speaking about other scales which are unrelated to the original post, it’s clear having the scale stated up front plainly would have been a good idea. But whatever…

Well, also, an 85’ car wouldn’t have horrible overhang if it was in N scale with 30" radius curves. That’s almost a 60" radius in HO, and if your equipment doesn’t look decent on a 60" radius in HO, I don’t know what to tell you…

[:D]

–Randy

One person mentioned N-scale, and it’s clear if you read his post that he knew the OP was talking about HO. He shared the OP’s opinion of the HO-scale 30" curve and explained that was a factor in his conversion to N.

LOL. Yeah…alot of us just don’t always think of how the real world translates dimensionally into scale (I’m one of them). And most of us just don’t have the space to accurately shrink reality. And now for another twist in the knickers. Railroads, as well as highways, the curves are spiralled. Figure a railroad curve being something a little more like a wide parabolic curve…having a slowly shrinking radius to the center of curve.

I remember reading years ago that Sand Patch Grade in PA had some curves in the order of 6 degrees…or about 955’ R. Not too far from your numbers. I’ve often wanted to build a layout with accurate curvature…but that would take at least a small warehouse. Oh well.

Mark H

When I was taking drivers training way back at 15, the instructor told us that the road curves were laid out at a constant radius so that when you were in a curve, you could hold your steering wheel basically at the same position through the curve. I found that to be true most of the time right up to the present day.

Railroads - maybe a different beast? I do design in easements into my curves following John Armstrongs info in Track Planning for Realistic Operation.

Regardless, I still think it would have been helpful to state clearly in the original post what the scale was. One of the downsides to the MR forums is it’s a general forum and very often people don’t state what scale they are in - so often we have to infer it from the content - which often doesn’t make it clear. Sorry, I ain’t crying uncle [oX)]

Roads are somewhat self-eases since generally the lane is wider than the vehicle and you can adjust the turn-in so it feels comfortable (and your passengers aren’t flung against the doors). Trains on the other hand corner like they are on rails (hey, wait…) so any easement in the curve has to actually be built in to the track. If you look at Armstrong’s explanation in Track Planning for Realistic Operation, his “coefficient of lurch” (no, nothing to do with the Addams family butler) is less for 18" radius curves with an easement than it is for 24" radius curves without (in HO). The same car or loco will LOOK better on the 24" vs the 18", but the 18" with easement will give better operation - and take less space.

–Randy