LastspikemikeAnd round and round we go.
Time to get off the merry-go-round. Perhaps you should try visiting the fun house sometime for a change.
SeeYou190This dead horse can be put to bed.
Yep, I agree. And I'm sure - like a bus - another one of these threads will be along in another 5 min. But, until then...Happy modeling everyone!
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
The real OP's question:
SoupyA number of years ago I read that 1:1 railroads do not use a fixed radius for their curves but calculate them from a formula. Does anyone model curves using that prototype formula?
Lots of garbage for what was an easy question, that had nothing to do with superelevation.
Answer: Yes, some people model curves that do not have a fixed radius.
I think Sheldon covered it all quite well.
This dead horse can be put to bed.
-Kevin
Living the dream.
SeeYou190 Doughless Just asking, would the superelevations and easement lengths be different? Hi Doug, I know my answer will be different than most others. I try to work in superelevated curves where possible, even in un-prototypical locations, to give me the opportunity to use the scene as a photo-location. In the picture, you will not be able to see it is actually a yard approach, but it gives me a place to make an image that looks like big-time mainline railroading. -Kevin
Doughless Just asking, would the superelevations and easement lengths be different?
Hi Doug,
I know my answer will be different than most others.
I try to work in superelevated curves where possible, even in un-prototypical locations, to give me the opportunity to use the scene as a photo-location.
In the picture, you will not be able to see it is actually a yard approach, but it gives me a place to make an image that looks like big-time mainline railroading.
Yet another twist to the plot.
I simply don't think there are that many situations where modelers have the space to model a curve accurately, so the goal is to pass the eye test.
Sheldon uses 16 inch to 18 inch easements heading into a constant radius curve. I doubt that would pass most high speed mainline civil engineering requirements, but its a representation that works given the space limitations.
- Douglas
Doughless 7j43k Doughless If you want to pretend to be a railroad civil engineer that lays out his trackwork the same way, I guess that is a fairly narrow interest in the hobby that I would think would preclude such answer to be very helpful to the OP. So I see this as a bunch of calculations that don't matter. How nice of you to inform me that the way I lay out my superelevation is just plain silly and unnecessary. You DO recall the OP asked, and that's ALL he asked, was whether anyone uses prototype formulas to lay out "curves". I do. And I believe I told him that. He asked; I answered. He's not been back with more questions. The method works for me. It is very accurate. For some, it is difficult to grasp. Or irritating to use. There are other methods, that also work. I enjoy doing it my way. I hope you enjoy doing it your way, if you choose to do it. Ed Well, I'm coming from the opinion that its not a universal answer, where as sometimes presenting mathmatics to answer a question often implies absolutes. Would the answer be different if the curves were in different situations? A Texas Panhandle main line curve? A West Virginian coal hauler with maybe 2% of its mainline track actually straight? And the model railroader's most common situation, two 90 degree curves that enter and exit a yard....where the speed of the train SHOULD be about 20mph? Just asking, would the superelevations and easement lengths be different? And would you use the same formula for each curve with the same vigor?
7j43k Doughless If you want to pretend to be a railroad civil engineer that lays out his trackwork the same way, I guess that is a fairly narrow interest in the hobby that I would think would preclude such answer to be very helpful to the OP. So I see this as a bunch of calculations that don't matter. How nice of you to inform me that the way I lay out my superelevation is just plain silly and unnecessary. You DO recall the OP asked, and that's ALL he asked, was whether anyone uses prototype formulas to lay out "curves". I do. And I believe I told him that. He asked; I answered. He's not been back with more questions. The method works for me. It is very accurate. For some, it is difficult to grasp. Or irritating to use. There are other methods, that also work. I enjoy doing it my way. I hope you enjoy doing it your way, if you choose to do it. Ed
Doughless If you want to pretend to be a railroad civil engineer that lays out his trackwork the same way, I guess that is a fairly narrow interest in the hobby that I would think would preclude such answer to be very helpful to the OP. So I see this as a bunch of calculations that don't matter.
If you want to pretend to be a railroad civil engineer that lays out his trackwork the same way, I guess that is a fairly narrow interest in the hobby that I would think would preclude such answer to be very helpful to the OP.
So I see this as a bunch of calculations that don't matter.
How nice of you to inform me that the way I lay out my superelevation is just plain silly and unnecessary.
You DO recall the OP asked, and that's ALL he asked, was whether anyone uses prototype formulas to lay out "curves". I do. And I believe I told him that. He asked; I answered. He's not been back with more questions.
The method works for me. It is very accurate. For some, it is difficult to grasp. Or irritating to use. There are other methods, that also work.
I enjoy doing it my way. I hope you enjoy doing it your way, if you choose to do it.
Ed
Well, I'm coming from the opinion that its not a universal answer, where as sometimes presenting mathmatics to answer a question often implies absolutes.
Would the answer be different if the curves were in different situations?
A Texas Panhandle main line curve?
A West Virginian coal hauler with maybe 2% of its mainline track actually straight?
And the model railroader's most common situation, two 90 degree curves that enter and exit a yard....where the speed of the train SHOULD be about 20mph?
Just asking, would the superelevations and easement lengths be different? And would you use the same formula for each curve with the same vigor?
"...its not a universal answer,..."
Well, for the question that the OP actually asked, it IS. And the answer is "yes".
As far as my method being a "universal answer", I don't think I've said anywhere that people MUST use my method. And that if they don't, why they are silly, etc.
I find, for example, the spline method interesting. But so far, it hasn't been the right method for what I want to do. In my opinion.
It's fine for you to not want to work with mathematical solutions, but it's a bit much for you to denigrate people who do. And that's especially true when the very system we're talking about is fully based on mathematics and physics.
i'm interested in these discussions to better understand prototype railroad design.
but despite the NMRA legacy data sheets suggesting model railroad design is based on civil engineering practices of real railroads, the values in the table i posted for model railroad dimensions have a maximum superelevation of 0.01" for a scale speed of 90 mph on an 18" curve. in other words, practically zero for any conceivable model railroad.
glider pilots are taught TLAR, "that looks about right" when landing (obviously no go around).
it seems TLAR is a good approach for modeling a railroad.
greg - Philadelphia & Reading / Reading
DoughlessJust asking, would the superelevations and easement lengths be different?
Eh?
Alton Junction
richhotrain Doughless If you want to pretend to be a railroad civil engineer that lays out his trackwork the same way, I guess that is a fairly narrow interest in the hobby that I would think would preclude such answer to be very helpful to the OP. So I see this as a bunch of calculations that don't matter. Now you're talking! Rich
Now you're talking!
Rich
Yes he is. And so are you.
Outsailing86 What comes first - the track or the scenery?
What comes first - the track or the scenery?
Track.
7j43k Doughless To which than begs the question, where along my 16 feet of layout does the easement actually begin and end? I'll leave out the mathematics, and say that it begins at the end of the straight track preceding the curve and ends when it joins the constant radius curve. Hopefully, no one will challenge me on that to argue about who's the better non-mathematician. Ed
Doughless To which than begs the question, where along my 16 feet of layout does the easement actually begin and end?
To which than begs the question, where along my 16 feet of layout does the easement actually begin and end?
I'll leave out the mathematics, and say that it begins at the end of the straight track preceding the curve and ends when it joins the constant radius curve.
Hopefully, no one will challenge me on that to argue about who's the better non-mathematician.
I hope that most of us are responding within the context of the OP.
If the civil engineers on the prototype take 50 feet of perfectly straight track on their mountain ROW (one that has a lot of curves like our curvy layouts) and use a formula to compute a curve that leads into the spot they can lay the next 50 feet of perfectly straight track....over 5 miles of mountaneous ROW..its not really what the OP is asking.
It wouldn't make sense to do a series of mathmatical calculations to lay out track that curves from very broad, to broad, to sharp and back again several times, and with a different sequence of radii from one series to the next.
The common sense way a modeler would represent that constantly nonconstant radii series of curves in his 50 linear feet of trackwork would be to do it by eye.
selectorAgreed, our compressed scale means our curves are necessarily ridiculously sharp compared to the prototype. But, if we want the fidelity of the visual appeal of the prototype, we gotta superelevate those curves.
I agree with superelevating - Lastspikemike is the one who seems to think we should "get real" and not bother with it. I was pointing out that we can't "get real" with such tight curves anyway, but that the curves they represent would have superelevation (implying that it makes since to use superelevation).
The problem isn't just potential stringlining.
There's also an absence of a flat plane for the locomotives and cars to sit on.
When you twist the track, which you have to do to gain the elevation for the superelevation, you are providing an uneven surface for them to be on, as they move through the area. This wouldn't be a problem if we had fully equalized equipment, but that's more and more rare these days, and never really happened to most locomotives.
By lessening the amount of superelevation, and by stretching the easement out longer, the out-of-flatness is also lessened. And derailment chances lessen.
I know what I did hasn't been a problem. Sheldon wants to go higher. He may or may not have a problem. I'm hoping not.
BUT there certainly is an upper limit to how far you can push this. How about a 3/32" superelevation introduced with an easement that is 2" long? I don't see that being a good move.
CSX Robert - "...The prototype wouldn't have a 217.5' (HO scale 30") radius curve on the mainline, so there's no way to "get real" with our model curves. The curve that the 30" radius HO scale curve represents in many cases certainly would have superelevation."
Agreed, our compressed scale means our curves are necessarily ridiculously sharp compared to the prototype. But, if we want the fidelity of the visual appeal of the prototype, we gotta superelevate those curves. I have always said less is more, or at least better, when it comes to superelevation. A suprisingly little goes a suprisingly long way in improving the visual appeal without seriously compromising the ability of a hefty string of dangling cars to stringline. In fact, in that image of mine above, it's overdone. My judgement.
MATHEMATICS ALERT:
Notice in Greg's sample chart the the increase in superelevation is non-linear. It increases proportional to the SQUARE of the velocity increase.
Extrapolating out along the 217/30" line, 7" for 20 MPH will give you 28" at 40 MPH.
To get from 40 MPH to 60 MPH superelevation we multipy by 2.25, and get 63 inches--perilously close to the number I got from the calculator.
I see the chart chickened out and stopped at a 10" limit. Probably a wise practical move.
THIS CONCLUDES OUR MATHEMATICAL ALERT.
radius in 1:1 ft and ho scale in. rad\mph 5 10 15 20 25 30 130 18" 0.72 2.89 6.51 159 22" 0.59 2.37 5.32 9.47 188 26" 0.50 2.00 4.51 8.01 217 30" 0.43 1.74 3.90 6.94 246 34" 0.38 1.53 3.45 6.12 9.57 275 38" 0.34 1.37 3.08 5.48 8.56 304 42" 0.31 1.24 2.79 4.96 7.75 333 46" 0.28 1.13 2.55 4.53 7.07 362 50" 0.26 1.04 2.34 4.16 6.51 9.37 391 54" 0.24 0.96 2.17 3.86 6.03 8.68 420 58" 0.22 0.90 2.02 3.59 5.61 8.08
Drifting back into mathematics, I found this fun plug-in tool for determining amount of superelevation.
https://www.calculatoratoz.com/en/superelevation-in-railways-calculator/Calc-10650?FormulaId=10650
I plugged in a decent mainline speed of 60 MPH, and the radius of 217' (see above), and the superelevation came out at 66 inches (5.5 feet).
LastspikemikeMaximum realistic superelevation for most eras would be in the order of 6% which is very close to 1mm.
For most North American railroads the maximum superelevation is 5" or 8.8%(page 18-26):
https://railroads.dot.gov/sites/fra.dot.gov/files/fra_net/19085/Superelevation.pdf
LastspikemikeOn a 30" or so radius quarter length curve (45" long or so) you deduct at least half for the easing of the superelevation. You get two feet of full superelevation and for half your quarter curve the superelevated portion will be less than 1 mm high. That's also a shortening of the prototypical easing of superelevation by 3/4 of the lengths used when it's really done. In prototype a curve that short would have no superelevation. That's what I mean when I say get real
The prototype wouldn't have a 217.5' (HO scale 30") radius curve on the mainline, so there's no way to "get real" with our model curves. The curve that the 30" radius HO scale curve represents in many cases certainly would have superelevation.
Now that we're officially going down hill, I'll note that it's fun to look at superelevated/eased curves on layouts when there ISN'T a train. For some of us, anyway.
The graceful curves are very attractive. Curves. Attractive. Hmmmm....
Max Superelevation is 7" per the FRA
Spirals are calculated by running off the superelevation.
Superelevation is a function of train speed. So mixed corridors (heavy, slow freight) and Passenger become a whole new issue. The Railroad will slow train speed based on the actual superelevation.
In the model world... you are looking for the illusion. A doublestack doesn't need as much superelevation as a 40' boxcar to look superelevated.
On the Kato track, I'm sure they came up with something and the end track in the curve runs off the curve elevation uniformally in the degrees. It is settrack afterall.
Don't mistake the model world for the real world. We do things differently in the real world.
Keep having fun all!
richhotrainToo much point-counter point nonsense on this thread, but isn't that the way a lot of threads go downhill nowadays?
Yep, they all go downhill nowadays.
Nobody read the reference I posted, did they?
Talbot uses the clothoid as a guide for easements, but he does not dictate that the clothoid is a replacement for the whole curve, or even a major extent of it. It is relatively easy, as with French curves, to find a section of spiral that is tangent to the straight on one end and just tangent to a fixed radius curve on the other end for any length of gap between the two (some of the 'mathematics' establishes that but I'm not going into math here as no one seems to like it)
You'd get appropriate sections of the curve made as gages (I suspect some versions of French curves would work, or ship curves bent to fit) and just use them as tools.
In my opinion, even a little is better than none.
Douglas,
Seems to me, I was the one who said railroads use lots of non fixed radius parabolic curves to which I recieved some resistance.........
I'm going out to clean the tractor now.......
Sheldon
richhotrain ATLANTIC CENTRAL OK, I'm worn out. Well, if you notice, Soupy has not even bothered to reappear. Too much point-counter point nonsense on this thread, but isn't that the way a lot of threads go downhill nowadays? Rich
ATLANTIC CENTRAL OK, I'm worn out.
OK, I'm worn out.
Well, if you notice, Soupy has not even bothered to reappear. Too much point-counter point nonsense on this thread, but isn't that the way a lot of threads go downhill nowadays?
While I'm sure that the popular Hot Take on this would blame Mike for the discourse, I've noticed lately that when Mathmatics show up in the threads, arguments ensue over who is basically the best mathmetician.
All the while knowing what Wayne, probably indirectly has pointed out, that precision is achieved when building a layout, not planning it, where precision is defined as "what looks right" and planning is often times simply a "strong suggestion".
As far as the topic of curves, curves exist on our layouts for a number of reasons, one of them being that if the track keeps going straight like the prototype, its going to run off the benchwork or hit the basement wall; and th other would be when you want to actually model a prototype curve.
Lance Mindheim models flat Florida where there were very little reasons to not make the track perfectly straight and flat. He maximizes the straight part of the layout by having tight 24 inch curves around the room. The are scenic wastelands, ignored, just placed there, in order to get the next run of 16 foot straight track ASAP.
OTOH, if you're going to plan a layout in a mountainous region, where Mike astutely observes that topography dictates what the trackage looks like, I would wager that a section of the railroad that had a series of sharp curves going through the mountains had very few opportunities to lay perfectly straight track.
Connecting a series of sharp curves, which is what our layouts do, with a series of perfectly straight track makes all of that mathematical precision a waste of time. To make it look more like the prototype, those series of sharp curves in a mountainous region should probably be connected by a series of very gradual long curves of varying radii if you bothered to calculate them.
Soupy's not much into replying. The last time he replied to a post was June 21.
If he's still lurking, he should be learning a lot about superelevation.
And about British trains. And about camber on roads.
I have taken to just scrolling past posters or replies that don't interest me. Even topics.
And when I get even more exasperated, I go play with trains instead of being here.