Is there a mathemical formula to calculate total curve radius when using curved track sections of differing radii. For example a 22.5" joined to a 18" and so on? Thanks
I guess that you could calculate an average radius or a median radius, but by definition, you don't have a radius, as it's not constant. It sounds as if you're trying to create easements using sectional track. I can't imagine that building something of that nature would operate very well, as jumping from one radius to one measureably larger or smaller is hardly "easing". You'd have better luck (and better operating characteristics) if you use flex track for that.
Wayne
I personally wouldn't do it unless it was for the layout under the christmas tree. You're better off going with flex track IMHO, using two radii will make the train look like its wobbling around the curve. Flex track also allows you to superelevate your curves and makes for a smoother transition when going from straight into the curve and vice versa
Fergie
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If one could roll back the hands of time... They would be waiting for the next train into the future. A. H. Francey 1921-2007
Measure how far apart the straight tracks are. Divide that by two for the functional radius.
But then again, LIONS do not use sectional tracks. Nor do LIONS really care about what radius his tracks are just so long as the trains run. LIONS are rather practicle that way.
ROAR
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Here there be cats. LIONS with CAMERAS
I'm not sure there's a formula. Each arc would start tangent to the next, and if they share the same radius, they would also share the same arc center. But when, for example, a 22R arc segment is connected tangent to an 18R arc segment, those arcs do not share the same arc center. As you build on this, you can see it will begin to become complex.
I think CAD is your friend here, to be really precise - or you could just lay the track out on a flat surface and measure.
Ed
You can't get anything meaningful from "...total curve radius...". What you want is the mean, or average, radius, and that would be derived simply by adding each section's radius that is used to form your curve, and then dividing that total by the number of sections, or individual radii, used.
-Crandell
ndbprrWhy would you alternate radii?
Alton Junction
richhotrainAnd, why would you want to know the "total curve radius", assuming it could be calculated?
my guess is to know how much space is needed?
greg - Philadelphia & Reading / Reading
I have seen some posts that indicate that using a section of 22"r curve going into an 18"r curve will help some long cars ease into the curve and not derail. The problem is that the track would not come back to parallel if you do the same on both sides of the curve as the degrees of the arc are different with the different radius track. Need some flex track somewhere to get things back together.
Have fun,
Richard
Poor man's easement - but it is better than no easement. Some cutting and fitting needed.
--Randy
Modeling the Reading Railroad in the 1950's
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Using decreasing radius curves is a shortcut way to get an easement effect without laying out the easement with flex track. As long as the different radius pieces have the same number required for a half circle then an exact half circle is possible. For example using 22" and 18" radius pieces that are both say 8 sections to the half circle, you could use 1 or 2 22" pieces at each end of the half circle with 18" pieces in between. If they aren't the same part of the circle then you'll have to figure some combination that is, possibly using unequal numbers of the larger radius at the ends and/or using half pieces. You possibly could even use 3 or 4 different radii pieces. The chief disadvantage of the system is that you'll mosty likely wind up with a wider curve since most easement offsets are usually only around 1/2" on each side.
At some point, you should use flex track as is gives a smoother easement.
Good luck
Paul
IRONROOSTER....As long as the different radius pieces have the same number required for a half circle then an exact half circle is possible.....
I don't think so: a train traversing that curve would change its compass direction by 180°, but the curve is not a half circle if its radius is not constant.
I've never understood the need to make a simple task complicated. Get a piece of flex track (or two or three or fifty) and bend it to join the two points which you wish to connect. If you use really flexible track, such as that offered by Atlas (perhaps not right at this moment, though ) the free ends will form the easements for you. This is one of those places where you need to "just do it".
doctorwayne IRONROOSTER ....As long as the different radius pieces have the same number required for a half circle then an exact half circle is possible..... I don't think so: a train traversing that curve would change its compass direction by 180°, but the curve is not a half circle if its radius is not constant. I've never understood the need to make a simple task complicated. Get a piece of flex track (or two or three or fifty) and bend it to join the two points which you wish to connect. If you use really flexible track, such as that offered by Atlas (perhaps not right at this moment, though ) the free ends will form the easements for you. This is one of those places where you need to "just do it". Wayne
IRONROOSTER ....As long as the different radius pieces have the same number required for a half circle then an exact half circle is possible.....
Yep
doctorwayne IRONROOSTER ....As long as the different radius pieces have the same number required for a half circle then an exact half circle is possible..... I don't think so: a train traversing that curve would change its compass direction by 180°, but the curve is not a half circle if its radius is not constant. Wayne
You're right, I should have used the term 180 degree turn instead of half circle. Half circle is how turnback curves are commonly describe in the hobby. But to be strictly accurate, a half circle of track would all be the same radius which also means no easements.
Thanks for all of the advice and information guys. I think tailoring flex track would be best. See, I have very limited space but I would still like to keep my curves as gentle as possible so I can still operate some of the excellent new locomotives coming from BLI and MTH. I know with limited space switchers and road switchers would look more at home but you just got to admit that a T-1 pulling a PRR passenger consist would look plain cool bt it takes gentle curves.