I’m in the process of planning and building my next model railroad. I have been doing some research and found that there is actually an easement transition from straight to curved track. I will be using pre made radius tools to lay my flex track curves. I was wondering if there is a standard or at least a recommendation for the radius of the Easement going into the curve. For instance, if I’m building a 36" radius curve would I use double the radius at 72"? Triple at 108"? And so on. Any information or insight on this subject would be appreciated.
My recollection from John Armstrong’s Track Planning for Realistic Operation is that an easement allows for a tighter than optimum radius to work. If you have room for 36" radius, I wouldn’t lose much sleep over creating an easement.
In Armstrong’s Track Planning for Realistic Operation, he describes two values, x & L, defining an easement. He lists values of x and L for 3 radii
3/8" 12" 18"
7/16" 16" 24"
1/2" 18" 30"
normally, a curve would meet a straight track at some point P and R is the distance between P and the center of the curve.
Armstrong suggests increasing the distance between P and the center of the curve by x, 1/2" for a 30" radius curve (i.e. 30.5")
But he also suggests changing the point where the curve ends and becomes straight by extending the curve L/2 beyond point P. and the curve starts deviating from its normal radius of R at roughly L/2 from point P.
So the easement begins ~L/2 from point P and ends L/2 beyond P with the center of the curve R+x perpedicular to P.
Greg. Excellent putting John Armstrong info there. Since I go with 30 (or lately 32") minimum radius, I use the half inch offset with approx 9 inch x 2 transition. Have it memorized. As for easement radius, you don’t use a much larger constant radius as the op supposes, but rather it is a spiraling radius.
If you bend springy flex track starting from straight to the half way point and then the rest of the way until it matches the 30 inch curve, the transition is a gradual spiral from straight until it reaches a constant radius at 30 inches. That method works very well for me.
I put 3 finishing nails into the center line of the curve and 3 more on the tangent (which has been offset by Armstrong’s numbers). Then I use spring clamps to hold an aluminum yard stick against the nails and draw the curve with a sharpie. The point of the sharpie is about the same size as the nails so the curve lines up with the tangent and radius.
Works great and requires no math.
BTW, Greg mentions it but I think the point needs emphasis - you want the easement to be a spiral, not just a larger curve. This way the transition from tangent to curve is gradual.
This is where flex track works so well. Even if you cut and used only 10-12" of it and fashioned your own easement, it works sooooo well! You nail it down with the tangent line you drew previously, and make it meet your pre-curved portion on the other end. Draw the outline of the tie ends along that eased portion it makes naturally, and then lift the flex track. Cut the flext to fit and place its ties within the outline. There’s your easement.
Draw the centerline for your tangent (straight) track. Draw the centerline for the curved track - so that the two lines cross.
Attach a long piece of flex to the tangent space, perhaps 6 inches or so before where the two center lines cross.
Take the other end of the flex and hand form it so to center on the curved centerline and follow the curve from there.
Where you attach it to the curve centerline will obviously determine if your easement is sharp or gentle. I’ve found that “letting the flextrack” flow on its own will give a very nice result.
Yes, I would definitely solder flex track on curves…
O scale is about 1.8 times as large as HO. That 8x12 layout would work out to about 4.4’x6.7’, so it should fit in a 4x8 layout. The width may be a little tight.
Yeah but… Lionel locomotives and rolling stock are designed to run on WAY tighter curves than HO stuff is. The Lionel plan (did you miss the fact that he said Lionel?) he’s working from could have curves as tight as 27" DIAMETER (that’s what O-27 means). Almost NO HO stuff will run on half of that.
Here’s an example of an 8X12 Lionel plan I found online. The inside curves are 36" DIAMETER. That would come out as a 9" radius if you halved it to fit on a 4x6.
The poster is looking to convert O Gauge (like Lionel), not O scale. The difference is important, as O Gauge trains have compromises to let them go around very tight curves relative to HO (or O scale). Merely scaling does not tell the story.
Nope. The actual relationship is 48/87.1
And even more importantly, again, the O Gauge curves are much tighter relative to scale than are HO curves. See a more-detailed explanation in the poster’s other thread. http://cs.trains.com/mrr/f/11/t/158326.aspx
So if I did a 5x8 or 5x9 table would I be able to do this layout to HO, i already did the layout and ran large engines on it in the O gauge, so again can it be done and if so can I use 18 inch curves?
Your rolling stock’s manufacturers’ stated minimums will be the determining factor. Large steamers…probably not. Longer diesels…maybe. Heavyweight and modern long passenger cars, say those in excess of 75’, probably not unless you revise their coupling mechanisms.
It isn’t the track plan so much as the cars and engines…they’ll let you know, one way or another. The best way is to mock it up somewhat and run trains forward and in reverse with the most typical combinations of rolling stock. If they’ll go through the turnouts you have and the curves you are forced to use, you’re on the way to the races.
Easements help when trying to run on curves too sharp for the equipment. For example running 80-85 ft passenger cars on 24" radius - sure a lot of manufacturers make them to run on this radius, but you’re pushing it. So an easement helps. For 36" radius you probably won’t notice much difference. Keep in mind that on the model we have much fatter wheels and looser track standards than the prototype (unless you’re doing Proto87) so we can get away without the easements in most cases.
Yes, you can use larger fixed radii. While an easement is a spiral curve, you can use larger radii to mimic that. For example, a section of 36" radius followed by 30" into 24" curve. Even better is to use short sections of track with smaller changes, i.e. 36" into 34" into 32" into 30" etc. until reaching 24.
With flex track, an easy way to do spiral easements is with a template. These have been published over the years or you can make your own. Draw the track center line and lay roadbed and track to it.
