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How to determine the inner radius of a curved turnout? http://www.fast-tracks.net/forums/viewtopic.php?f=5&t=805 |
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Author: | ulf999 [ Fri Jan 25, 2008 4:57 pm ] |
Post subject: | How to determine the inner radius of a curved turnout? |
Hi all! I've bought a few #5 TwistTies that I plan on building with an outer radius of 100cm (40"). What I'm trying to figure out is how one calculates the inner radius. Any input appreciated! /Ulf |
Author: | emccamey [ Fri Jan 25, 2008 7:25 pm ] |
Post subject: | |
Ulf, Calculating the diverging route curve would be very dependent on the uniformity of the curve(s), and also the use of a straight vs. a curved frog. You can however, layout the 'straight' section along your 100cm outer curve - and then marking the centerline of the resulting diverging curve. Take a ruler and draw a straight distance of 1cm just touching the curve centerline points. At the midway point (50mm) carefully measure to the curve offset (location of the curve at that mid-point). This is the mid-cord ordinate. The offset can then be plugged into the formula for determining the resulting curve radius: L= Length between curve points (base) z = Max Offset ( ~1/2 base to intersect) r (effective radius of the curve) = (L^2) / (8z) + z/2 Thus if the offset is say 2.6mm (EXAMPLE VALUE ONLY): r = (100^2) / ( 8 * 2.6 ) + (2.6 / 2) r = (10,000) / ( 20.8 ) + (1.3) r= ~ 482.07mm (or close to 19" radius) If the offset is only 1.5mm at the mid point along a 100mm cord you'll end up with about a 33" (836.33mm) radius. Note: That's NOT the answer - just an example - the actually measured offset would need to be put into the formula. You can see that the measured mid-cord ordinate offset will be very small and getting good accuracy in measuring is important for reliable results. |
Author: | Dan Armstrong [ Fri Jan 25, 2008 7:36 pm ] |
Post subject: | Curved radius |
I get a little over 18" in 3rdplanit. You can take a straight turnout and flex it to any desired radius. |
Author: | ulf999 [ Sat Jan 26, 2008 3:40 am ] |
Post subject: | |
thanks guys! |
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