riogrande5761Take 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.
That's a completely different situation than I was describing, but OK.
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cuyama riogrande5761 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. That's a completely different situation than I was describing, but OK.
riogrande5761 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.
Ah, I though there was discussion of how a turnout could be the end part of an easement. I mentioned one I used that did not require extra space. Apologies if I missunderstood a specific application.
Rio Grande. The Action Road - Focus 1977-1983
Lastspikemike...You need much less easing into the curve than you might think and by using less easement length you get the benefit of a longer minimum radius for more of the curve.
I don't see how having a longer minimum radius is a benefit, unless you're working with very restricted room.I didn't have a track plan when my just barely-started benchwork was relegated to a much smaller (and oddly-shaped) room.
I decided that I needed a couple of parameters within which to work, and those turned out to be maximum radius possible wherever curves were necessary (and with 10 corners in the room, there were lots of curves), and non-confining aisle-space.
I didn't do any calculations for easements, so simply let the Atlas flex track "relax" itself at the point where I thought that the actual curve should end.
While the minimum radius turned out to be 30" (on all three legs of a wye, and again, I think, although it may be 32", on a double track section around one of the outside corners of the room.
Everywhere else it's 34" or greater, up to 48' in a couple of areas (used simply because there happened to be enough room at that location -ya gotta have some places for nothin' but track and scenery).All of the curves have easements, and most have superelevation, with vertical easements in and out of all superelevation, including that on S-bends.
Of course, in-truth there was more room for most of those curves, but I didn't want to sacrifice scenic areas on the limited area which was used for the actual layout - wide curves look great, but even not-so-wide ones look pretty darn good when located in an interesting setting, the latter being of more interest to me.
Oh, and as far as aisle space is concerned, I achieved my goals pretty-well throughout the layout room, with one exception. It's fortunate that I'm a lone operator, but even that "pinch-point" would allow two of me to pass without coming in contact. For larger folks, most could probably maneuver through, as there's nothing to catch one's clothing nor much of anything on the layout there that could be bumped or catch clothing.
Wayne
The tradeoff with easements is between absolute radius requirement, like rigid wheelbase or restricted truck swing or coupler engagement, and smooth lateral acceleration into and out of curves (reducing jerks between zero and curve lateral that potentially cause derailment or improper motion).
The racing line is largely determined by weight transfer and stability, with heavy braking up to the apex and high acceleration coming out of it. Naturally you want to limit peak force on the tires to available adhesion (as brakes don't brake the car, and steering doesn't steer it) so the 'line' follows the longest smooth curve through, but you assuredly don't jerk the wheel from straight right into that curve...
All the references I have seen, specifically including the Rolls-Royce manual for chauffeurs in the late '20s, call for the wheel to be smoothly and continuously moved when entering the curve, up to the point of constant turning, and then equally smoothly and continuously unwound 'just' to where the car goes straight at exit. In practice this is more or less exactly what a 'spiral' transition does: it increases angular rate up to a constant number of degrees per second, then decreases it smoothly again. The human inner ear interprets this as a constant pull, like gravity and resultant with it, and consequently as a smoother ride; on the other hand, short little jerks in direction, no matter how smooth the subsequent 'turn', are annoyingly prominent. I had to break my kids of the bad habit of cranking the wheel abruptly into turns of constant radius as if driving on snap-track; fortunately the knack of smoothly winding the wheel and then unwinding again is easily learned, just like feathering the brake as you approach a stop.
LastspikemikeMy point was only that easements require tighter radius for some part of the curve than if no easement is used. Simple geometry.
since the easement is a transition from a straight to a curved track it is not tighter in radius than the curve. while it replaces a portion of the curve, it requires more space. you don't tighten the radius of the curve to create the additional space required for the easement. the curve and easement require more space
the easement is a transition that gives the trucks a chance to slightly rotate and each car to develop an angular momentum so that the wheels remain centered between the rails and the wheel flanges don't touch the rails
greg - Philadelphia & Reading / Reading
I think he means to add "to fit in the same space" to that. As Byron showed, a tighter radius plus easement can take up more space than a larger radius with no easement. SO if for example you have a 30" radius with no easement, but decide you want you want to add an easement to the curve, but not make the benchwork any larger, you have to use less than 30" for the middle radius of the curve.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Lastspikemike...Geometry requires that any easement reduces (shortens) the radius of the curve that is eased....
If it's the curve that's being eased, then the easement actually increases the curve's radius at its extremities, as most modellers with any forethought would decide on their minimum-allowable radius, then add the easements as the track exits that minimum.
doctorwayne Lastspikemike ...Geometry requires that any easement reduces (shortens) the radius of the curve that is eased.... If it's the curve that's being eased, then the easement actually increases the curve's radius at its extremities, as most modellers with any forethought would decide on their minimum-allowable radius, then add the easements as the track exits that minimum. Wayne
Lastspikemike ...Geometry requires that any easement reduces (shortens) the radius of the curve that is eased....
Lastspikemike Ah yes, that magical extra half inch...which becomes one inch to get the whole train turned around.
Ah yes, that magical extra half inch...which becomes one inch to get the whole train turned around.
Now wait while I pull out my magic wand...
Your conundrum would be true if your curve ended parallel to the benchwork on each side. But ah, I found a solution that magically fixes that problem. My curve on both sides of the 180 turn around continues around past 180 degree's on either side, inward enough that I can avoid the half-inch requirement on both sides of the 180 turnback at benchwork sides - the easement occurs further around the curve and is natural result of the benchwork lobe bending inward as is true on many layouts. Yes, I thought about where the easement would fall while I was making the scale drawing of the layout - they fall enough past to avoid the needed extra 1/2 inch; this ain't my first rodeo ya know.
But as pointed out by Dr. Wayne, savvy track planners can build that extra half inch on either side for the easement during planning stages. So I give the Jedi Hand wave and don't struggle with the acadamia aspect of this. I look at the big picture, come up with my givens and druthers, look at the room and what I can fit, come up with acceptable minimums and design away, and have enough slop that a half inch here or there isn't going to cause a problem ala Dr. Wayne.
Track fiddler
I think this was a great answer to the OPs original question.
The rest of this thread has made my head hurt.
rrebellEasements 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.
I agree. I did a lot of experimentation with Kato Unitrack and my fleet of HO equipment.
My minumum radius will be 24 inches in the hidden track. I did a spiral easement into the 24 inch curve with a piece of 32 inch radius, then a piece of 28 inch radius. This revealed that these are the only advantages:
1) Smooth entrance into the curve.
2) Less diaphram seperation on full length passenger cars.
I had one engine, a 4-8-4 that did not like 24 inch curves. With easements, it still did not like them. I got rid of that locomotive.
-Kevin
Living the dream.
SeeYou190The rest of this thread has made my head hurt.
I posted John Armstrongs figure from his book on the first page of this discussion. It makes making easements fairly easy and understandable. It really is and I try not to get too bogged down in to the technicalities. His bent stick method works quite well. Atlas flex track does a decent bent stick approximation however.