Ok folks, can someone please draw me a connect the dot diagram on creating easements for curves?
Seriously, I'm pretty good grasping alot of concepts, but I just can't get my head around this. How much offset does one need and for what length?
For example sake, say I have a min 30" radius needing to make a 90* turn (around the walls type layout), can someone walk me through this?
Thanks
Kev
There is really no rule for easements, less is more than none. More is better than less.
More or less It depends on what kind of room you have.
It may be debatable, but on an extremely slight curve, I don't personally believe you need them. An extremely slight curve is an easement on its own. There are those that will disagree with that. They are not wrong. More is always better than less and less is always better than none.
Tighter curves, you definitely want them. Unfortunately sometimes on a tighter curve you don't have room for them. That's why one ends up with a tighter curve in the first place. But then again, this is where careful layout planning is really important. It can prevent a situation such as this before it happens and it's too late to go back to the drawing board
TF
You can make a conceptual drawing, certainly, but I found it so much easier to use John Armstrong's yardstick method for easements-- what you want is a smooth, gradual, spiraling transition from straight (tangent) into the body of the curve, so fix around 6" at one end of the yardstick in place where the track is still straight, then gently bend it at the other end until it matches the curve radius you're after.
Hope this helps.
Track fiddler Tighter curves, you definitely want them. Unfortunately sometimes on a tighter curve you don't have room for them. That's why one ends up with a tighter curve in the first place. But then again, this is where careful layout planning is really important. It can prevent a situation such as this before it happens and it's too late to go back to the drawing board.
Tighter curves, you definitely want them. Unfortunately sometimes on a tighter curve you don't have room for them. That's why one ends up with a tighter curve in the first place. But then again, this is where careful layout planning is really important. It can prevent a situation such as this before it happens and it's too late to go back to the drawing board.
I have a hunch that if you had a properly eased tight curve (say 18" in HO), more rolling stock would accept that than a non-eased slightly less tight curve (say 22"). I've never put that to the test, though.
Phil
Thinking of this a bit more complicatedly for a moment: negotiating a curve at a given 'track speed' involves a constant angular acceleration (as in orbital mechanics). What you're doing with the transition spiral is smoothly accelerating laterally from zero (at the end of the 'tangent') to full (through the apex) at a tolerable rate. (This is the same sort of thing you do when driving your car, turning the wheel at a constant rate until reaching the apex of a turn and then unwinding at constant rate until going straight...)
MR published a 'spiral' template that did this well for typical model radii. This could be simply copied from the magazine and cut from plastic or even card stock for the gauge.
The alternative is to use a drafting French curve to get a smooth transition -- starting of course further into the 'straight' tangents on either end of the curve -- and use the result as a centerline. You could also set off about half model track gauge and make an inside-rail template if you like that method better.
Pay very careful attention as you bend the rail, whether in Flextrack or handlaid, not to kink it. It is very wise not to have rail joints, soldered or not, in the area being spiraled unless you have the tools and experience to bend rail accurately net of springback to precise shape.
Incidentally both in real life and in modeling there is a comparable transition curve for vertical accommodation, both in raising an outside rail for superelevation and as part of compensated grades. This is generally easier to implement (with careful roadbed design and track securement) than lateral spiral, but I think it is just as essential to smooth running.
You will find "Easy Easements for Model Train Track" at this MR site under How To / Track Planning & Operation. Apparently edited in 2017, as I used a prior version dated 2010. It is easy if using flextrack. It does not have to be a precise formula, just directionally better than a sudden change from constant curve to tangent. The track looks more realistic and the train running through an easement looks more realistic as well.
https://mrr.trains.com/how-to/track-planning-operation/2017/05/easy-easements-for-model-train-track
If you have it, there is a similar explanation on pg. 31-32 of How to Build Realistic & Reliable Track MR Special Issue (2009).
Paul
Modeling HO with a transition era UP bent
Easements are highly over rated, depending on the trackplan. They look much nicer but function wize do little unless you have a large engine. I boils down to what are you running.
Easements are so ridiculously easy to do, and improve appearance so drastically, that there is absolutely no reason not to use them.
Disclaimer: This post may contain humor, sarcasm, and/or flatulence.
Michael Mornard
Bringing the North Woods to South Dakota!
Brass steam locomotives can be a challenge on any radius under 32", depending upon the actual model in question. I had a 1968 Balboa SP MK-5 2-8-2 recently that really did not like anything under Kato 28.75" radius track. I had a W&R/Samhongsa (1999) 2-8-2 that was designed for 24" to 26" radius, depending upon individual installation of cab curtains. Other W&R/Samhongsa 2-8-2's are designed for 28" and 30" operation, depending upon the model and detailing. They come with an instruction sheet.
Any brass engine with a 4-wheel (two axles) lead truck or trailing truck can be a problem, as the truck may hit the cylinder block on some radii or else piping details under the cab. You may find that you need to replace the springs with tighter springs to keep lead and trailing trucks from derailing on "tight" radius such as 24".
The old PFM brass model catalogs clearly state the design radius for most of those models, BUT that assumes you have virtually perfect trackwork and NO vertical kinks, as brass engines do not like vertical kinks at a track joint. Also, replacement of factory original brass brakeshoes with plastic can enable the model to negotiate tighter radii, as in some cases it is the brakeshoes that short as the radius is decreased below 30" radius. I just sold some brass steamers because they could not handle portions of my layout that are 26.375" Kato radius, and I can't rebuild them, so I'm very familiar with the limitations of brass models.
If using sectional track, Armstrong did recommend using one section of a larger radius at each end of a curve to provide the easement effect rather then trying to curve by eye or other methods.
Also, it should be noted for those using Kato Unitrack that they now actually have superelevation transition track and fully superelevated curved track available for purchase, and I did just use it to relay part of my mainline to better accommodate brass steam locomotives, and it does work very well--but it is NOT flextrack, and at 31"+ radius for the largest available you get the superelevation transition but not the horizontal "easement". However, this DOES help with the operation of gorgeous 89' autoracks from Atlas and Intermountain that my son has. Kato accomplishes the superelevation transition within one section of track.
Superelevation transitions and actual horizontal easements are both necessary in real world railroad engineering to eliminate sway and derailments of large/long cars. Either one in the model world can be helpful. In the real world design engineers generally try to match the superelevation transition to the length of the spiral easement.
John
Years ago I made my own templates using the spiral easement formula. I find the templates make laying out the easements very easy to do.
The October 1969 Model Railroader has several easement templates that can be used.
But I also find that setting up a temporary oval with sectional track (no easements) seems to work just fine if the curves are appropriate for the equipment.
Bayfield Transfer Railway Easements are so ridiculously easy to do, and improve appearance so drastically, that there is absolutely no reason not to use them.
Appearance is the operative word here. Easements do improve appearance and something else that really can improve appearance and remove some of the toy like look of a MRR is to change the radius as you go through the curve. Too many track plans just look stamped out. As an example, if you start with a 32" curve opening it up to a 40" as you go through the curve, it is very appealing to the eye.
Brent
"All of the world's problems are the result of the difference between how we think and how the world works."
Also visually an inside curve can look fine but not so much an outside curve with the same radius.
Offset in HO scale is 1/8". I didn't bother measuring length on my last layout. I stopped spiking a foot and a half or so back and just bent the track into the curve. The easement shaped itself naturally. Also, if your offset is more than 1/8 inch that's okay. I eyeballed everything after the first one or two.Really, I cannot overstate how simple it is to make easements.
I like the idea and the appearance of easements, especially since I have a twice-around folded loop with a central operating 'pit' and enjoy photography. Rather than do the math and draw the centerline, I just let the flex track make it's own approximation of a spiral curve. It does a passable job. Also, I don't have problems with kinks in the middle of curves if I have to have a joint there. I stagger the sliding rail and use half-joiners (cut with a jeweler's saw that I solder. This allows me to leave more ties in place with those important little spikehead details that help to generate a smooth curve, kink-free.
This is a photo of tracks in my helix, last layout. This joint had to be good and reliable as it was all inside a large 'mountain'. I hadn't cleaned the area after soldering and filing, so it's untidy. You can make out the half joiner leaving enough room to obviate having to remove any of the ties. A fair bit more 'bother', but it made superb curves.
That's awesome selector. I never thought of half joiners and that you stagger your joints is a great idea. And I see you kill two birds with one stone with your feeder wires there as well You must have some kind of trick to do both at one time without the feeders wanting to come loose during the soldering process?
Now that I think about it a bit more, I'm pretty sure it's actually a 1/3 joiner, at least in that photo. A half joiner would still be too large to fit between two tie spikehead sets, especially since they move somewhat closer on a curve...as designed.
The feeder was added later, and just happens to be co-located with that particular joiner. Don't recall why I chose that spot...
Track fiddler You must have some kind of trick to do both at one time without the feeders wanting to come loose during the soldering process?
This here should help:
Rio Grande. The Action Road - Focus 1977-1983
Bayfield Transfer RailwayEasements are so ridiculously easy to do, and improve appearance so drastically, that there is absolutely no reason not to use them.
Generally I agree, and use easements on many of my projects for others. But not all, because occasionally the extra length and width of an eased curve, even with a tighter radius enabled by the easement, can be a deal-breaker in some situations. This is particularly true when a turnout must be fitted immediately at the end of the curve.
An example:
Byron
Layout Design GalleryLayout Design Special Interest Group
cuyamaGenerally I agree, and use easements on many of my projects for others. But not all, because occasionally the extra length and width of an eased curve, even with a tighter radius enabled by the easement, can be a deal-breaker in some situations.
Byron makes a very good point. Easements are great IF you have the space. If you don't have the space then don't beat yourself up because you don't have easements.
I also think that part of the issue is train speed. Tinplate O gauge is a prime example. If you are running trains at 150 scale mph on tight radii then the jerky movements that are a result of the lack of easements are obvious. Slow the trains down and the effect is not so pronounced.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
cuyamaGenerally I agree, and use easements on many of my projects for others. But not all, because occasionally the extra length and width of an eased curve, even with a tighter radius enabled by the easement, can be a deal-breaker in some situations. This is particularly true when a turnout must be fitted immediately at the end of the curve.
Right, but if the radius equivelent of the curved part of the turnout is broader than the curve radius it is connected to, it can give an "effect" of an easement wouldn't it?
BTW, speaking of curve equivelent, do you know about what it is for a code 100 large Peco streamlined turnout? Subsitution radius?
riogrande5761Right, but if the radius equivelent of the curved part of the turnout is broader than the curve radius it is connected to, it can give an "effect" of an easement wouldn't it?
Yes, but only for the diverging leg – not for the straight leg.
riogrande5761BTW, speaking of curve equivelent, do you know about what it is for a code 100 large Peco streamlined turnout? Subsitution radius?
All of the Code 100 Streamline turnouts have about a #4½ frog. But they seem to handle larger equipment better than would be predicted, perhaps because the curved diverging leg is gentler than a straight diverging leg. The diverging radius for a PECO C100 “Large” is 60”. The substitution radius is roughly 45”, but it’s not a perfect curve, of course, owing to the straight track at the points end and the point rails themselves.
cuyama Yes, but only for the diverging leg – not for the straight leg.
It appears you can still have an easement up to the turnout so the straight portion is after the easement is finished. Solution no?
Now OTOH, do a mirror image of that turnout around so the end of the turnout is the finish of the curve but bifurcating to the right.... As long as the substitution radius is much larger than the curve radius, I would think that would be provide an easement effect. And there is no non-easement in that part. That scenario was on my last layout - probably hard to see but in the upper left of the photo just above the green and yellow box cars.
The substitution radius is roughly 45”, but it’s not a perfect curve, of course, owing to the straight track at the points end and the point rails themselves. Byron
That seems fine. I am mulling over the other end of my staging yard and trying to efficiently allow the line coming off the bottom of the helix to split apart. Assuming the last part of the curve at the bottom of the helix is flat, I could start with a Peco large turnout there.
riogrande5761It appears you can still have an easement up to the turnout so the straight portion is after the easement is finished. Solution no?
Of course, but then you are back to the extra length needed for the easement itself. No free lunch. But depending on the overall track arrangement, sometimes that works.
riogrande5761Assuming the last part of the curve at the bottom of the helix is flat, I could start with a Peco large turnout there.
Again depending on the track arrangment, one might also consider a curved turnout. But in your case the inner curve of the PECO C100 part is right at (or just less than) 30", so it might be tighter than your minimum radius. Where both legs of the curved turnout are broader than the minimum radius, both routes provide some easement effect.
cuyama Of course, but then you are back to the extra length needed for the easement itself. No free lunch. But depending on the overall track arrangement, sometimes that works.
No extra length (to speak of) in the example I gave. It might not be a "proper" easement but somewhat of the effect. It worked.
And that is food for thought. My mainline minimum radius is 32 inches, but in staging I may make a compromise down to 30" on parts of the ladder. I don't think this should cause an operation problem with the equipment I have. However, I may want to configure the ladder so trains do not have to pass through 30 inch curves.
riogrande5761No extra length (to speak of) in the example I gave. It might not be a "proper" easement but somewhat of the effect. It worked.
OK, I guess I just don't understand what you are describing. If it works, it works.
Take the turnout in your diagram and flip it so the diverging route faces to the right rather than the left. "Easement" where the curve joins the tangent through the turnout to continue to the left - the diverging route continues to the right.