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.
Paul
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
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!
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.
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).
Modeling HO with a transition era UP bent
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 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
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
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