Trying to reproduce a railroad curve. Stumped. Have done a few over the years but dont recall of seeing pc and pt stationing like this. Could anyone smarter than me shed some light on how to reproduce this? Thanks!
Thomas Smith, post: 328988, member: 980 wrote: Trying to reproduce a railroad curve. Stumped. Have done a few over the years but dont recall of seeing pc and pt stationing like this. Could anyone smarter than me shed some light on how to reproduce this? Thanks!
Not Sure that there's enough information on the drawing.
There IS a derail and ROW variance down "around" the PT, with varying "offsets (25ft 35ft) but without digging into it, it might be tough (or even impossible) to solve the geometry. It would help to have some stationing data on the 35ft offset, and also the "right hand" divergence point "downstream" from the PT (25ft offset).
Any ASSUMPTIONS that you make to resolve the geometry, will need to be backed up with a cite/reference or two.
Sorry,
Loyal
Thomas Smith, post: 328988, member: 980 wrote: Trying to reproduce a railroad curve. Stumped. Have done a few over the years but dont recall of seeing pc and pt stationing like this. Could anyone smarter than me shed some light on how to reproduce this? Thanks!
I believe you are looking at a 561.91 foot long spiral. Total ëÓ = 25å¡48'07" with entry radius defined by a 4å¡00'00" railroad curve and exit radius defined by a 4å¡36'00" railroad curve. What type of spiral formulas this railroad may have used would be what I would try to find out next.
EDIT: If this is the case computing the center line alignment and right-of-way offsets through a spiral could get a bit complex. Knowing specific spiral formula used for the C/L alignment will be a start. Then computing the effective radius and radial direction at a given station may be required. Once you have that computing an offset along the radial line should be easy.
Thomas Smith, post: 328988, member: 980 wrote: Trying to reproduce a railroad curve. Stumped. Have done a few over the years but dont recall of seeing pc and pt stationing like this. Could anyone smarter than me shed some light on how to reproduce this? Thanks!
The map you have is a val map, these were azbuilt maps the railroads produced to catalog their property so it could be taxed.
The tracks will have already been in place, maybe for decades before the azbuilt.
This of course means that the ROW was long established by the time of the val map, usually either by a deed or a map.
So there is probably a deed in the courthouse or an older map (these maps can be almost impossible to get, but there are some resources to contact) that explains the ROW.
I'm lucky, I have val maps and deeds.
One thing about the val maps is they show track centerline, but, at least where I am, the val centerline of track and the deed ROW centerline are ALWAYS different.
The ROW centerlines on the deeds are ALWAYS simple curves and on the val maps they are spiral curve spiral since they are showing the centerline of track and the tracks will of course be spiral curve spiral.
My guess for yours (assuming its the same situation I have) is that the centerline of the ROW is a simple 4d railroad curve, the bump out to 35' is along a property line that you will have to figure out since the railroad probably guessed somewhat at that, it may be a section or interior section line or an old property line. Figure out the tangents, apply a 4d railroad curve, look for ROW monuments and it should work (its amazing how good they surveyed 100+ years ago).
It's rare that the ROW is a spiral, it does happen, but it's very rare.
The only ones I've seen were produced by non-railroad engineers that didn't understand that the tracks would be spiral curve spiral but the ROW should be simple curves.
My grandfather retired as a conductor on the Lehigh Valley RR after 50 years of service. During the depression, he bought a house, a new car, and the family ate meat every day (mmmm, sausages). When the valuation maps were made, the railroads were about the most powerful organizations in the country. They could afford to hire the best, including the best surveyors. It is amazing, though, how well their product works.
Shouldn't there be a table on the valuation map listing the vesting deeds into the R.R? Moe's right about the 35' offset - I'd start by pulling the deeds for parcels 19, 20 & 21.
I'm confused (an all too common situation) by this map, though:
L = 100(delta/D) = 100(25.8019/4) = 645.05
But: 525+85.55 - 520+24.64 = 560.91
Oh, wait: 100(25.8019/4.60) = 560.91
I'm POSITIVE there's somebody smarter 'n me can 'splain it....
BTW, valuation map centerlines were chained on the slope, so that's 0.2'/1000' on a 2% grade. Longer lines = more tax revenue.
My 2å¢
SS
Thanks guys. All very helpful info. I did not post that I do have a deed for the siding. That part is reproducible. I think I have the centerline figured out. I figured it as a simple curve. What was throwing me is the pc calls for a degree of curve of 4 and the pt as 4-3600. I used the pt and the Delta to figure the radius. As a last ditch effort, I scanned the sheet and used it as a background in CAD. Using the radius I figured, it overlays perfectly.
As a precaution, im going to check with DOT as the rail lines are now owned by the state. Hoping an engineer there might have been asked that question before.
Thanks again guys!
Thomas Smith, post: 329151, member: 980 wrote: Thanks guys. All very helpful info. I did not post that I do have a deed for the siding. That part is reproducible. I think I have the centerline figured out. I figured it as a simple curve. What was throwing me is the pc calls for a degree of curve of 4 and the pt as 4-3600. I used the pt and the Delta to figure the radius. As a last ditch effort, I scanned the sheet and used it as a background in CAD. Using the radius I figured, it overlays perfectly.
As a precaution, im going to check with DOT as the rail lines are now owned by the state. Hoping an engineer there might have been asked that question before.
Thanks again guys!
"I used the pt and the Delta to figure the radius."
I would be very unusual for the Degree of curve to be an odd number, remember they were laying them out using that number, the chord pulled and turning 2d every 100' for a 4d curve.
What happens if you disregard all the data on the plan set but the 4d curve, locate the tangents and lay out a 4d curve?
You would expect to see the tracks slide inside the row curve, but usually it's only a small amount, say a 1-1.5' difference
Sergeant Schultz, post: 329079, member: 315 wrote: My grandfather retired as a conductor on the Lehigh Valley RR after 50 years of service. During the depression, he bought a house, a new car, and the family ate meat every day (mmmm, sausages). When the valuation maps were made, the railroads were about the most powerful organizations in the country. They could afford to hire the best, including the best surveyors. It is amazing, though, how well their product works.
Shouldn't there be a table on the valuation map listing the vesting deeds into the R.R? Moe's right about the 35' offset - I'd start by pulling the deeds for parcels 19, 20 & 21.
I'm confused (an all too common situation) by this map, though:
L = 100(delta/D) = 100(25.8019/4) = 645.05
But: 525+85.55 - 520+24.64 = 560.91
Oh, wait: 100(25.8019/4.60) = 560.91
I'm POSITIVE there's somebody smarter 'n me can 'splain it....
BTW, valuation map centerlines were chained on the slope, so that's 0.2'/1000' on a 2% grade. Longer lines = more tax revenue.
My 2å¢
SS
You are obviously smarter than me. I couldn't wrap my little brain around that length discrepancy.
Plus, you can do the cents symbol.
alt 155
My 2å¢
B-)
Vern, since I do model railroads in HO scale, can I get 1/87 of a å¢ ? 😀
86 more smart-a$$ remarks and I could get the whole penny!!!
yay! A new goal in life.
E.
Loyal, post: 329256, member: 228 wrote: alt 155
My 2å¢
B-)
:snarky:
