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Seth Kittredge
Posts: 1
Location: Vergennes, USA
Joined: 9/15/2012
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Computing old railway R.O.W spirals? |
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I am surveying a tract of land that adjoins a rail line. The rail line is old, probably established sometime in the 1850's. The railway valuation plans I have showing the right of way and main line is from 1907. The rail line in my area of interest is "spiraled" but the spiral information on the plan is limited and leads me to believe it comes from an early method of computing spirals (possibly AREA 10 chord or something even pre-dating that). Some of the information on the plans are as follows:
"All curves 1 degree and over are spiraled"
I have a tangent in and a tangent out, with the total angle noted on the plan.
The curve actually starts with a "PC" and ends with a "PT" (This curve is a spiral, NOT circular).
Do any of you know where I may be able to find information (old text books or articles) that maybe cover this type of thing in detail with the computations used? Or have any of you ran into a similar problem like this?
Any suggestions or discussions on this topic would be appreciated.
Thank you,
Seth
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Saturday, September 15, 2012 at 8:21:04 AM |
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Loyal.Olson
Posts: 1
Joined: 1/5/2011
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Re: Computing old railway R.O.W spirals? |
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I would be more than a little surprised if an “original” 1850ish Railroad was spiraled. I am NOT at all surprised that the 1907ish Valuation Map shows spirals though (quite common after turn of the century).
Out here in the West, “VAL Maps” often show BOTH the “original” (simple curve NO spiral data) AND the later Curve Data WITH Spiral data. The vast majority of the spirals used out here in the early years, were Searles Spirals, or an occasional Talbot. Railroad “10 Chord” spirals show up from time to time, as well as a few “Railroad Company Specific” spirals.
In most cases, the ROW is NOT spiraled, but in some cases it IS. Figuring out the when, where, & IF can be tricky.
On shallow, “short transition” curves, it doesn't “usually” make much difference. On high degree, LONG transition curves, it can make a LOT of difference.
Of course the contrary can be shown, and IT DEPENDS.
Loyal
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