Yeah, its a dumb question. Everyone else knows what it is. Except...me. I feel like it is one of those things that is often discussed in the hobby but goes with the general assumption that everyone knows what it is. The reason I'm asking is I see that it is supposed to visually improve something about trains and curves, and I am all about that. So...what is it and why is it used?
I'm beginning to realize that Windows 10 and sound decoders have a lot in common. There are so many things you have to change in order to get them to work the way you want.
An Internet search for "model railroad easement" will yield lots of results, many of them useful. Here's one from our hosts:http://mrr.trains.com/how-to/track-planning-operation/2017/05/easy-easements-for-model-train-track
The horizontal easement is basically a spiral curve transitioning from straight track to the desired curve radius. Easy with flextrack or handlaid. Longer easements work best, but even a short one helps. I try for a length at least equal to the length of the longest car or locomotive -- more if there’s room.
Edit: One also needs vertical easements when changing grade. The steeper the grade and the longer the cars, the longer the vertical easement.
Layout Design GalleryLayout Design Special Interest Group
An easement is a gradual adjustment vertically or horizontally to change depth, height, grade, or radius to a smoother transition.
Think of it like this,.... If only the roller coaster was just a little bit more of a smoother ride. You probably wouldn't want to go on it anymore, but trains love this.
Imagine 2 pieces of sectional track, one straight, one an 18" radius curve.
There is an abrupt change, there is no easement.
Now imagine you have a wooden yardstick. Instead of a normal yardstick, this one is only 1/3 the usual width, so it bends without snapping.
Bend it into a curve. It is a different shape than the curved sectional track. At first the diameter isn't as much. It increases to match the desired radius. You don't see the lurch as your train hits the curve.
John Armstrong explains it here:
https://books.google.com/books?id=hubQI-Ojsi0C&pg=PA14&lpg=PA14&dq=john+armstrong+transition+curve&source=bl&ots=-ZdGgdAsLX&sig=pYAmUislQJnEwf2uSBTYJkBfNPs&hl=en&sa=X&ved=2ahUKEwjj6rjxiubcAhXtxlkKHdAgC5gQ6AEwB3oECAgQAQ#v=onepage&q=john%20armstrong%20transition%20curve&f=false
Henry
COB Potomac & Northern
Shenandoah Valley
You know what I never understood is easements are only considered in curves or radius. Easements should also be considered in grade adjustments. Adjusting from Flat (level) to the start of a hill. There is an easement in the beginning of a grade as well.
Track fiddlerYou know what I never understood is easements are only considered in curves or radius. Easements should also be considered in grade adjustments. Adjusting from Flat (level) to the start of a hill. There is an easement in the beginning of a grade as well.
Vertical easements are considered by thoughtful designers -- but ignored in many (most) published speculative plans.
Forgot I had made this graphic
Track fiddlerYou know what I never understood is easements are only considered in curves or radius.
My bad, I only think in one plane at a time. Given what I read in an unrelated thread, I have to take responsibility for this omission being the beginning of the end of the hobby.
BNSF UP and others modeler ...I see that it is supposed to visually improve something about trains and curves, and I am all about that.
...I see that it is supposed to visually improve something about trains and curves, and I am all about that.
That's true. But it's not just the visual part. Your trains will run better, too.
Here's one reason: Grab yourself a couple of 89' trailer flats, either really or just in your head (really is better). Now, wander over to some trackage where some straight track meets a (non-eased) curve. Put the two cars on the track, one on the straight section, one next to it, on the curve.
You will see some pretty impressive off-setting of the couplers. This ain't just visual. And it ain't just the couplers. It affects the whole car as it goes from the straight to the curve, compared to its neighbor.
What an easement does is change from straight to full-curve gently. And, in doing that, it lessens the amount of offset of the car ends and the couplers.
A longer easement is always better than a short one. My buddies all like a 12" one, because that's the length of a passenger car. Or a trailer flat.
On my trackage, I stretched that out to 18", because it was easy to do, under the circumstances. It looks great. And it works great. Zero derailments.
Ed
cuyama Vertical easements are considered by thoughtful designers -- but ignored in many (most) published speculative plans.
Those green things are vertical curves, not easements. Ideally, the beginning and end of each vertical curve will have an easement. Note my useage of the words "beginning" and "end". Yup, an easement at each end of those three green curves is appropriate.
Is
Are real easements necessary here? Probably not, if the curves themselves are gentle enough.
Ed, it is both. It is surely a vertical curve, but it also qualifies as an easement. It serves as an easement into and out of a constant grade (there is no lurch we need to worry about). We are concerned only with the secure grips of the couplers and the lower lips of the pilots on the locomotives. Well, I guess the trip pins as well.
It's a vertical easement that keeps things from being suspended (spinning drivers), separated (couplers) or grounded (trip pins or low pilot leading edges).
Tom,
I see how you can say that putting those curves in so that there isn't a "corner" could be an easement. 'Cause it certainly eases things compared to having an angle.
But it's not the kind of easement we're talking about. THAT kind of easement has a gradually decreasing radius of curvature. Which is not noted in the example. As far as I can see, it's a simple curve of a single radius.
I certainly agree that having the curve at all is a HUGE improvement. And I again assert that a true easement is likely unnecessary.
Think of it this way if you're going to go to a steep 4 degree grade from level. You would start from a zero degree grade to a 1 degree grade to a 2 degree grade to a 3 degree grade to your 4 degree grade all gradual.
If you go from a tangent into a radius the same thing applies. Instead of jumping right away into a 24 radius curve. Start with a 30 adjust to a 28 go to a 26 to get to your 24 radius curve.
Gradual gradual gradual
7j43kThose green things are vertical curves, not easements.
The term "vertical easement" is used fairly widely in the hobby for spiral curves leading into and out of grades.
7j43kAs far as I can see, it's a simple curve of a single radius.
Edit: I think I drew them as spiral curves with a CAD program. It would be pretty hard to bend that plywood into a true circular curve in any case -- ½" or thicker plywood forms its own (near) spiral curve when bent (if properly supported).
cuyama 7j43k Those green things are vertical curves, not easements. The term "vertical easement" is used fairly widely in the hobby for spiral curves leading into and out of grades.
7j43k Those green things are vertical curves, not easements.
Technically, those green things are called vertical curves, and they are parabolas, not spirals. They form smooth transitions to and from the forward and rear tangents. Calculations are based on the specified (or desired) length of curve and the algebraic difference between the grades of the tangents and a special constant called the k value.
Robert
LINK to SNSR Blog
ROBERT PETRICKTechnically, those green things are called vertical curves, and they are parabolas, not spirals. They form smooth transitions to and from the forward and rear tangents
If you say so, I'm certainly not a mechanical engineer (nor do I play one on TV). In actual practice, bending thick plywood roadbed (just like bending a stick for a horizontal easement) forms a reasonable approximation of a spiral curve -- and most importantly, it works great. Folks have been calling it a vertical easement for a long time in the hobby.
Edit: I think that the most important thing is that these vertical transitions (by whatever name) are necessary for smooth operation, even more so with steeper grades and/or longer cars. The majority of published speculative track plans don't include them, which effectively makes the grades shorter and steeper (sometimes comically so) than claimed.
BNSF UP and others modeler Yeah, its a dumb question. Everyone else knows what it is. Except...me. I feel like it is one of those things that is often discussed in the hobby but goes with the general assumption that everyone knows what it is. The reason I'm asking is I see that it is supposed to visually improve something about trains and curves, and I am all about that. So...what is it and why is it used?
I am in the middle of building a new layout, and my desired minimum radius on curves is 32". I have a number of Ribbonrail track alignment gauges with a 32" radius that I fit into the sections of flextrack that make up the curve. What I have noticed is that the beginning and end of these curved sections are actually broader than the 32" radius in the middle of the curve.
So, in my observation, the broader radius at the beginning and end of the curve "eases" the locomotive and trailing cars into the 32" radius in the middle of the curve instead of doing it abruptly. That said, I still can't define an easement.
Rich
Alton Junction
as a corollary to this discuss of vertical easements, if you are using the WS incline system, is the vertical easement built into the system?
Bear "It's all about having fun."
Oct. 1969 MR has an article about easements and includes fold-out templates.
Dave
Just be glad you don't have to press "2" for English.
http://www.youtube.com/watch?v=zQ_ALEdDUB8
http://www.youtube.com/watch?v=6hqFS1GZL4s
http://s73.photobucket.com/user/steemtrayn/media/MovingcoalontheDCM.mp4.html?sort=3&o=27
richhotrainthe broader radius at the beginning and end of the curve "eases" the locomotive and trailing cars into the 32" radius in the middle of the curve instead of doing it abruptly. That said, I still can't define an easement. Rich
Actually Rch you pretty much DID just define it. The easiest way to think about easement curves is to think of sectional track -- a straight tangent piece meeting a fixed radius curved piece. That "pinch point" where tangent meets curve creates the amusing "lurch" of tinplate trains and poses the challenge to our scale rolling stock. A locomotive that might be able to run on a perfect circle of 18" radius curves could well derail at that pinch point, because in essence that pinch point is like a tighter curve, a much tighter curve. Easement curves are, therefore, not just cosmetic features that make our track look more realistic. There are actual practical benefits.
Flex track can create its own easement curves. It is not possible to curve a piece of flex track to exactly replicate that perfect tangent meeting the perfect and pure radius curve. It, well, "eases" into the perfect radius curve. And you can use that attribute of flex track when building a layout. If by chance the flex track piece ended exactly where you intend to start a curve, you'd be better off cutting the flex track back a foot (so yeah, "wasting" a bit of track) so that a single piece of flex track occupies the entire transition between tangent and curve.
Some guys have used the offset tangent method. That is, imagine where the tangent would be if you had a pure radius curve - no easement curve - and section track. OK, now imagine moving out that tangent a couple of inches, parallel to the old tangent. Now "connect the dots": shift the curve so that it meets the new, further out tangent. There is your easement curve. It is not a mathematical easement curve (railroad engineering uses trigonometry I think) but is a mechanical easement, good enough for our purposes.
What I did was cut my plywood and homasote subroadbed into tangent pieces and "pure" curved pieces, almost like sectional track, marking in the 2" centers for my 40" and 42" radius double track. I then cut a series of parallel cuts into the edges of the subroadbed at the end of the subroadbed piece, so the width of the saw kerfs are making it "curvable." More properly, slightly bendable. I'd fasten one end and the middle of the curved piece of subroadbed to the layout and then push out the far end. That makes an easement curve. I'd fasten the end of the tangent subroadbed to match and meet the end of the curve and then slightly push it in, creating and even slighter easement curve. It was mechanical rather than mathematical but it works. It is easier to show than it is to describe. I do a clinic for NMRA divisions and regions on it.
Flex track also helps create its own verticle curves, by the way. Imagine a 2% grade (using the Woodland Scenics incline to start the 2%) and two pieces of straight sectional track. If the elevation begins right at the meeting place of the two pieces of straight track you'd have a kink. Possibly enough of one to affect operations. Now imagine one piece of flex track instead. Unless you deliberately "kink" it too, in bending up for the rise it would have a natural easement verticle curve of its own before reaching 2% elevation -- actually it would be hanging in air a little. Imagine filling up that little gap with shims or whatever and there you have a verticle easement curve. And that is also why it is good practice to have a single piece of track where flat meets incline (or down slope) rather than have two pieces meet at the exact spot of the change.
Dave Nelson
There is a spiral easement curve calculator on the bottom of this page:
https://www.jglrr.com/engineering/software/spiral/index.html
Easements can be a gradual curve into a curve or elevation.
Another easement that railroads might use are LEGAL EASMENTS...
An easement is a legal right to use someone else's land for a particular purpose. For example, the municipal water company may have an easement to run water ...
A utility may have an easment to run pipes/wires under the right of way. A railroad may be granted an easment to run wires or something across someone else's property.
This is different from eminent domain where a government entity (such as a commuter railroad) to seize property (at market value) to ecpand from two tracks to three tracks or something like that. States use this all of the time to realign or build new roads. It is not proper for a government to seized private property under eminent domain and then give it to some other entity (on the pretext of improving a neighborhood)
In Bismarck there is a private house in the middle of the hospital parking lot. He would not sell out to the hospital, so they just built the parking lot around him.
At least he has good security there.
ROARING
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
Yeah, its a dumb question. Everyone else knows what it is. Except...me.
I never learned about easements from train forums. Train forums didn't even exist when I learned about them - which was from a book you should get:
John Armstrongs: Track Planning For Realistic Operation (Kalmbach books).
Do yourself a big favor and get yourself a copy. /problem solved
Rio Grande. The Action Road - Focus 1977-1983
dknelsonSome guys have used the offset tangent method. That is, imagine where the tangent would be if you had a pure radius curve - no easement curve - and section track. OK, now imagine moving out that tangent a couple of inches, parallel to the old tangent.
Two inches is a big offset. Using John Armstrongs Track Planning For Realistic Operations, I've found that an offset of approximately 1/2-inch is in the ball park for a 30" radius curve. John has a table which he gives a few example offsets based on some common curve radii. I modify his table slightly for curves that are of a different radius. It works pretty well for me on the last couple of layouts.
His table also shows the distance you need to go either side of the offset to get the begining and end of the easement. I've found that nailing the track down on the tangent up to the beginning of the easement allows me to then gently bend the flex track so the center fall on the mid point and then bends in until it matches the curve radius I draw at say 32R. It is basically John Armstrongs "bent stick" method but just using the flex track instead of the bent stick. The cork can do the same thing more or less as well although it may not bend as evenly, it works well enough.
As I have said before, riogrande5761, I try to save money where I can in this hobby. So, if there is a great model railroading community out there, why not just ask them? I dont just sit here and take, take, take either. I contribute to other threads too. Thanks everyone for the replies! I know what to do for my curves now.
is there mechanical reason for an "easment" on a full-scale railroad?
greg - Philadelphia & Reading / Reading
gregc is there mechanical reason for an "easment" on a full-scale railroad?
There is, both for easements and superelevation.
For superelevation, it's so you can take curves faster. Like a banked track on a car racing course.
For easements, it's for at least two reasons:
For a train going very slowly, there will be less relative offset between cars as they go from straight to full-curve. With that lesser offset, there will be less demand on the fittings between cars. Couplers and draft gear in particular.
For a train at speed, the change in lateral acceleration will not be abrupt. Meaning that both equipment and load will have a lessened "feeling" of getting kicking in the head as they enter the turn. Or leave. Or, put another way, their Martini glasses are less likely to tip over.
7j43kFor a train at speed, the change in lateral acceleration will not be abrupt. Meaning that both equipment and load will have a lessened "feeling" of getting kicking in the head as they enter the turn. Or leave. Or, put another way, their Martini glasses are less likely to tip over.
are you saying this is just for passenger comfort and there's no mechanical benefit?
gregc 7j43k For a train at speed, the change in lateral acceleration will not be abrupt. Meaning that both equipment and load will have a lessened "feeling" of getting kicking in the head as they enter the turn. Or leave. Or, put another way, their Martini glasses are less likely to tip over. are you saying this is just for passenger comfort and there's no mechanical benefit?
7j43k For a train at speed, the change in lateral acceleration will not be abrupt. Meaning that both equipment and load will have a lessened "feeling" of getting kicking in the head as they enter the turn. Or leave. Or, put another way, their Martini glasses are less likely to tip over.
It is actually a mechanical necessity.
In theory, trains would work without flanges on the wheels. The wheel taper centers the wheelsets between the rails. Then the wheel taper allows the rigid axle to go around the curve.
https://www.scienceabc.com/eyeopeners/how-do-train-wheels-turn.html
The value of rail travel is the very low rolling resistance per ton. As soon as the flange hits the rail, that advantage is lost.
Easements allow gravity, forward motion, and the wheel taper to change the direction of the wheel set gradually, without the flanges crashing into the rail. This keeps the ride smooth, and the friction low, so the locomotive can pull a similar load around the curve as compared to what in can pull in a straight line.
At any high speed, trains would simply derail if thrust into a curve without an easement. They would continue going straight (basic physics) and the flange would be no match for the forces, the wheel would simply climb the rail.
Sheldon