Easement Values Needed

[HAZMAT9]

Does anyone know the length of easment and offset for curves greater than 30 inch radius? I've got the Track Planning book from way back and only talks about easements...it doesn't give any info on what to use for offset/length of easement.

I need length of easement and offset for curve radius from 30 inch up to 45 inch. Any help would be greatly appreciated. Maybe a table or chart on the web that has all this? Steve

[selector]

Steve, in theory, ANY radius greater than the mean radius of the curve IS an easement. Practically, adding only and inch for an easement won't help a great deal, so if you were to add between 2-4", you would be fine. In fact, the real easements are incremental from zero radius, reducing to the desired profile over the first third of the curve. Picture placing the end of a straight thin cedar stip in a vise, and placing your finger on the free end. You deflect it by several inches and note how the stick bends ever so slightly at first, and then accelerates the curvature until it gets to your finger. Railroads try to get that profile into their easements. However, unless you are laying flex-track, it will be difficult to do that. Practically, use Armstrong's diagram and add, say, 6-8" to the inside of the iniitial curve radius for the first 20 deg of curve. Then slip up to the true (intended) radius, slip 1/2" toward the curve, parallel to the axis of approach to the curve (the entry straight) and fini***he curve. In sectional, you could just as well use a piece with a radius 2-4" longer than your intended radius. The kink at the join should not be a problem.

I hope that was not confusing. That is how I visualize the procedure. Some use the bent stick approach, some do offsets, etc.

Others will hopefully jump in and explain it in simpler (maybe even more correct) terms.

I would like to get a better handle on it myself.

[HAZMAT9]

Kinda understand, what I've got so far is from the "Easy Easement" article written sometime ago which says something like for example "30 inch radius, offset 1/2", length of easement 18".......which I understand in terms of using the bent yardstick method.....just wondering how to figure on a radius greater than 30 inch since the chart only goes up to 30 inch. I revised an Atlas sectional trackplan to flex and want to broaden the curves a bit and have added a passenger mainline which proposes 45 inch radius curves...just want to make sure that I add in an easement for more realistic looking operation as well as keeping the wheels on the track. Just need to figure out how they come up with the offset and length of easement (if a chart isn't available and I need to figure it out myself). Thanks, Steve

[Adelie]

Steve,

I don't have my copy of Track Planning for Realistic Operations with me, and that would have some of the larger values (but not all). So, having time to kill here at work, I fired up CadRail and had it do eased curves for the various radii. I have found that it is very close to what the book says (fraction of an inch). He is it's verdict, all in inches:
Radius - Length (Total) - Offset
30 - 19.8 - 0.543
31 - 20.46 - 0.561
32 - 21.12 - 0.579
33 - 21.78 - 0.597
34 - 22.44 - 0.615
35 - 23.1 - 0.633
36 - 23.76 - 0.651
37 - 24.42 - 0.669
38 - 25.08 - 0.687
39 - 25.677 - 0.705
40 - 26.4 - 0.723
41 - 27.06 - 0.741
42 - 27.72 - 0.759
43 - 28.38 - 0.777
44 - 29.04 - 0.795
45 - 29.7 - 0.814

[dgwinup]

Simple rule of thumb is to use half the actual measurement of the gauge of track as your offset value and half of your radius is the length of easement. For example, if your gauge is 2", your offset is 1". If your radius is 18", your length of easement is 9". This will establish an easement that works for your trains. You may want to double the figures. 2" gauge, 18" radius = 2" offset, 18" length of easement. That will give you a more prototypical looking easement.

Darrell, simpler is easier, and quiet...for now

[HAZMAT9]

Fantastic! Thanks for the info Mark, just what I need to get them curves mapped out on the layout tonight. Steve

[Adelie]

Glad I could help Steve. Glad it was a slow morning around here, too!

[ericboone]

Check out this web page:
http://www.geocities.com/budb3/arts/tech/ease.html