Railroad Curve-101
If No Spiral Specified, The Track Gang Would Field It In
And if they didn't build it with a spiral, the moving train would do it for them;-)
If No Spiral Specified, The Track Gang Would Field It In
> And if they didn't build it with a spiral, the moving train would do it for them;-)
Yep, similar to setting the gauge..we'd set it a 4'-8 1/4" and let the train take care of the other 1/4"
Mike, not so fast
Assuming that the rails were laid out, as the plans said, in a simple curve. The train itself would make the sprial, curve, and spiral, which is why, today, we lay out spiral, curve, spiral, so that it best fits what the train wheels are going to do in the first place.
Joe Glidden explained this much better than I, and upon a great deal of research, I agree with his findings. For this reason, when replacing RR, I use tangents and PI's and radius and the center of the track through the curve is just where ever in the hell it happens to be. 🙂
We use the tangents to fit the curves as best we can. Even with locating the rail every 5 feet with the trolley. Another thing to be aware of is the interval at which the rail is located. In the tangents, 50 to 100 foot stationing might be ok, but we always make it shorter going into the curve and through the curve/spirals.
Mike, not so fast
Yes, I think we agree, except that the plans have little to do with the track location in the curve and that wasn't an accident.
Maybe in the early days of railroad design, but it probably didn't take long to realize that simple curves wouldn't work.
So the railroads (in my area for sure) intentionally laid out the rights of ways with simple curves and laid out the tracks spiral-curve-spiral. They understood that the centerline of the track through the curve would slide to the inside.
I just wish highway engineers would do the same.:-/
There are of course exceptions, I'm working on two different boundaries, one with simple curve right of way (legals filed in the courthouse 1900's showing simple curves), and spiral-curve-spiral track (valuation maps showing spiral-curve-spiral which I can ignore for right of way). The other boundary has a railroad with that rare document acquiring right of way using spiral-curve-spiral.
Mike, not so fast
There is ZERO reason, in my opinion, to put the ROW into a spiral.
Mike, not so fast
:good: :good:
All the discussion of the track adjusting into a spiral makes sense, but if you eyeballed the result and tried to fit a simple circular curve it would make the apparent degree of curvature less (larger radius) and the apparent delta larger.
No one has offered any theory on why the mark-up to the drawing increased the degree of curvature from 3 degrees to 3d 15'. Surely the layout wasn't that far from design?
reviving this old thread based on a new survey i am working on. we are working along this RR curve as shown in the attachment. Another retracing surveyor (in 1974) has computed the curve radius to be 5730 at CL, I compute 5729.5. These numbers are assumptions that it is a circular curve, does anything else on the RR plat show its spiral? what does the "1d 00' C.R." mean ?
Mike, not so fast
There is ZERO reason, in my opinion, to put the ROW into a spiral.
I wish the Alaska Road Commission and/or Bureau of Public Roads had felt the same way.
