Easements!

Argh! I'm trying to figure out the correct dimensions for a spiral easement into a 36" radius curve, and the online resources I've found so far are just giving me math anxiety.

I understand how to bend a stick, all I really need to know is how to determine the amount of offset between the circular curve and the straight track, and the length of the easement from an point with the same x-coordinate as the centre of the 36" circle. Most of the references in magazine articles and books I've read give information for circular curves no larger than 30" radius. It seems quaint to call those "broad" curves by current standards.

Anyone with any useful advice please help.

Regards, Andrew

Reply to
Andrew Jeanes
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Hi:

Although the theory behind easements is complicated, for practical purposes, installation is quite simple using a metal rod (rail) for the bent stick method. Offsets can be calculated from the equation in the NMRA sheets.

Since I use a 36" minimum radius for mainline, you might find some useful information and examples on the first site below.

Hope this helps.

Thank you,

Budb

Author of:

MODELRAILROAD TECHNICAL INFORMATION

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PROTOTYPE TECHNICAL INFO FOR MODELRAILROADERS

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Moderator of:

MR TECHNICAL HELP GROUP

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COUPLER HELP GROUP

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Reply to
budb

If you have a copy of Armstrong's "Track Planning for Realistic Operation" the general formula is in there.

-dave

Reply to
Dave Curtis

And Mallery's "Trackwork Handbook" has a template for up to 48" radii, IIRC.

Reply to
Larry Blanchard

If that's your response to what you found on the Internet, I hope you didn't see my spreadsheet!

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But to give quick answers for the math-phobic, here are some offset figures calculated by the aforementioned spreadsheet, with various lengths of easement from tangent to a 36" radius:

6 .042 8 .074 10 .116 12 .168 14 .229 16 .300
Reply to
jpurbric

Andrew=A0Jeanes wrote: Argh! I'm trying to figure out the correct dimensions for a spiral easement into a 36" radius curve, and the online resources I've found so far are just giving me math anxiety.

---------------------------------------------------- Perhaps these sites will be helpful:

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A valuable reference book, "Track Planning for Realistic Operation" by John Armstrong:

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It's 30% off list and free shipping on orders over $25.

Bill Bill's Railroad Empire N Scale Model Railroad:

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History of N Scale:
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Links to over 700 helpful sites:
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Reply to
Bill

Check out this easment printing software.

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I downloaded it and printed some out, then glued them to some 1/4" plywood and made myself a very nice template.

snipped-for-privacy@tracer.consecol.org (Andrew Jeanes) wrote in news:c5dc62$ga$1 @driftwood.ccs.carleton.ca:

Reply to
Kelly

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The book "Track Planning for Realistic Operation", by John Armstrong,

3rd Edition, Kalmbach Books, gives a method for computing easements based on proportions of the radius. Best book around for planning topics. There is no "correct" dimension. One that looks good to you and that works for your rolling stock is correct. In HO a scale few inches will be hard to detect a real foot from the track. Have fun with it.
Reply to
Dave in GA

On Mon, 12 Apr 2004 06:15:30 UTC, snipped-for-privacy@tracer.consecol.org (Andrew Jeanes) wrote: 2000

For a quick and dirty setting offset the curve center by 1/2" (36-1/2 inches from tangent). Measure 12" either side of the start of the curve (PC). Tie your spline to the tangent up to 12" before PC and tie your spline to the 36" curve beyond 12" past the PC. I use several nails to make sure the spline follows the tangent and the curve. Accurate enough for what you want.

Reply to
Ernie Fisch

Hello Andrew;

I don't know if you have been able to do your curve with the suggestions you have had on your inquiry, however; if you can give me an approximate length you would like, I can quickly draw / plot an easement on AutoCAD at my office and send you the drawing.

I've done some long curves for friends - 36" easement into a 48" curve and just cut out / pasted the print on the subbase. It also acts as a layout template and I offset the centreline to the outside of the ties so it's as simple as putting the track inside the lines. One time we did an entire yard this way.

All I'd need is your mail address....

Ian Mathers Great Northern Sand & Gravel Company Yellowknife, NT

Reply to
Ian G. Mathers

just cut out / pasted the print on the subbase<

Ian, Didn't you really mean a 48" easement into a 36" curve ?

Reply to
Jon Miller

Perhaps he's easing away from using set track?

Reply to
Gregory Procter

No, I meant a 36" long spiral into a 48" radius curve. Looked very nice.

Ian

Reply to
Ian G. Mathers

Ok. Interesting, not wanting to start an argument but I always thought the definition of easement was a large radius curve going to a smaller radius curve. Could be I have never understood the definition.

Reply to
Jon Miller

It is. Normally the lenght of the easement is given.

Perhaps a drawing could enlighten you. Have a look at

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Sorry for the Danish text but I think the drawings explain it sufficiently. The upper drawing shows the banking of the outer rail, while the lower drawing shows the track midlines of the easement.

Reply to
Erik Olsen

Would going from a small radius to a larger radius be a "diseasement"? ;-)

I think the intent was a _36" long_ transition from straight to 48" radius curve.

Regards, Greg.P.

Reply to
Gregory Procter

If you look at it the other way, it is a 48" radius curve leading into a 36" helix.

Reply to
wannandcan

The length of the spiral is not the radius - it's the distance travelled during the transition from the tangent to the final curve. The spiral begins at an infinite radius (tangent) and as it develops, the radius diminishes until it matches the simple curve in the middle. At the other end, as you come out of the simple curve into the spiral the same thing happens in reverse until you are on tangent again. So the curve is 3 parts.....spiral in....simple curve....spiral out.

About a year ago, I did some AutoCAD renderings of a curve. They are at :

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These might help - seeing the thing is easier than describing it. The spirals can be any length, but for the best appearance, I think 1/2 to 1/3 of the inner radius is visually the best.

Ian

Reply to
Ian G. Mathers

Thanks Erik!

Strangly enough, I was going thru my old RR information this afternoon and came across your origional easement posting from Sat, 23 October 1999 05:11 PM EDT. In that post you gave the formula for Danish RR easements. The graphics you have posted here are a great help in understanding how to calculate the offset.

Tusen Tok,

Ed

Reply to
Laser6328

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