20" Curves and "modern" equipment

[Ed Kapuscinski]

I'm doing some more track planning and am trying to decide on if I can live with 20" radius "scenic" curves (as opposed to purely functional ones).

What's the thinking on 20" radius curves and things like SD50s and 89' flatcars?

Is it "you can do it where you need to" or "yeah, it'll look fine"?

[tehachapifan]

I have approx. 20" min mainline curves and am happy with them even running 89' flats. They don't strike me as being too tight but I wouldn't want to go any tighter. I would also want to make sure any S curves have a straight section of AT LEAST 89' between direction changes. Easements as much as possible help with initial (toy-like) overhang issues when entering curves as well.

[dem34]

Depends on space,  depends on the prototype if that's the goal. It passes the threshold of "looking dumb" by a fair enough margin personally.

[CRL]

It also depends on the terrain being modeled, high speed mainline or branch line operations, etc.

[Ed Kapuscinski]

It's the section along the top wall. The space between the S curve in the center is only 6".

This is all laid out using sectional track. In reality it'll be built with easements and flex.

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And in case anyone is wondering, this is what "playing out doing the NCR from Baltimore to York in my current basement" looks like. You're looking at Baltimore right now, with Mount Vernon in the bottom left and proceeding through Timonium by the bottom right (and yes, if I include Timonium, I'm definitely including the cow palace).

[wm3798]

Will you have the cow palace in odorama?

[tehachapifan]

I would try to bump-up the 6" straight section in the S curve if you want to run 89 footers...especially if using body-mounts. Less is just asking for problems....or at least a visual distraction. Otherwise, nice track plan!

[ednadolski]

What's the thinking on 20" radius curves and things like SD50s and 89' flatcars?

Is it "you can do it where you need to" or "yeah, it'll look fine"?

I wouldn't try it with body-mount couplers.

As for "look fine" that's completely subjective.   Perhaps try a flextrack mockup?


Ed

[tehachapifan]

...also, the two tracks (or perhaps just the farthest one) on the far right as you enter the yard from the bottom. Those look like they have a potentially troublesome S curve arrangement if longer stuff is going to run there as well.

[robert3985]

Spiral easements will increase the visual quality, as well as the functional reliability exponentially.  The main problem with long equipment is the sudden entrance of a car or engine into a curve, and the immediate overhang on the ends that produces.  Spiral easements makes the transition from straight to curved much much smoother.

I was going to recommend 24" minimum cosmetic curves with 18" being the absolute mainline minimum operational radius, but an "eased" 20" minimum cosmetic radius will look and function very nicely with longer, modern equipment, as will your other functional non-cosmetic lesser curves.

Another thing to think about is superelevation.  Ya don't want too much, but you want it to be noticeable.  I think Kato's Unitrack superelevated track is too much, so something less than that looks more prototypical. 

It's a huge rush to see your train with long cars and engines smoothly enter an eased curve, gradually tip slightly into the superelevated curve, then straighten out when the curve becomes straight...with the rest of the train still superelevated behind the engines.  A superelevated "S" curve is at least twice as nice, with the front of the train leaning one way, and the center/end leaning the other way as the train negotiates the two curves....YEAH! 

Although it's tempting to make all of your cosmetic curves the minimum radius, especially if you have broad 20"+ curves. As John Armstrong has suggested to us, extra-broad curves in a couple of places (or more) really add to the looks of your layout.  He called them "Photography Curves", and I've incorporated several in my layout designs that exceed 130" in radius.  I'm not talking about half circles of track, but just a 1/8th or 1/16th slice of a circle.

Also, in "S" curves, there's no reason to make both of the main radii the same radius.  One at the minimum radius, with another at a larger radius will also add to the looks of your trackwork.

Time to get back to work!

Cheerio!
Bob Gilmore

[Mark5]

I wouldn't try it with body-mount couplers.

Ed

Why not? I would think 20" would be fine (in HO scale that would be 36.8" radius).

My next layout will have 21" minimum radius on the main.

Mark

[Ed Kapuscinski]

...also, the two tracks (or perhaps just the farthest one) on the far right as you enter the yard from the bottom. Those look like they have a potentially troublesome S curve arrangement if longer stuff is going to run there as well.

Yeah, I've been watching out for those. That track is just a helper pocket, at best, and should only ever see slow speed movements onto the non-diverging route. Unless you're talking about the one coming out of the curved turnout heading into the year. I might want to reevaluate that one too.

[Ed Kapuscinski]

Another thing to think about is superelevation.  Ya don't want too much, but you want it to be noticeable.  I think Kato's Unitrack superelevated track is too much, so something less than that looks more prototypical. 

Interesting thought with that, but I think I'll skip it. The NCR was decidedly NOT high speed railroading (thanks to being laid out in 1830). But that's part of what gives it it's charm!

[tehachapifan]

Yeah, I've been watching out for those. That track is just a helper pocket, at best, and should only ever see slow speed movements onto the non-diverging route. Unless you're talking about the one coming out of the curved turnout heading into the year. I might want to reevaluate that one too.

This is the S curve I was referring to...

[samusi01]

20" should look fine... at touch of superelevation will help things look nice as well. I work up to about five layers of masking tape on the main line. Branch lines, like the one described in the next paragraph, don't get that treatment.

I have one 's' curve and I simply let XTrackCAD do the heavy lifting for me. It is a 20" radius, into an easement, about 1.7" of straight, easement out the other side into a 29" radius. I designed and planned it to run body mount 89's next to 40' cars. I laid it out on a table prior to committing to the plan to ensure things would work. Thus far, the only problems I've had are the very light Kato 70 ton hoppers next to +85' cars. Other short cars - both body mount and truck mount - haven't had any notable problems.