Anyone have some information on math to do cubic spirals?
I have the equations, but not sure how to put them to use.
Equations from Paul Mallery’s Desigh handbook Of Model Railroads.
Y=S cubed divied by 6RCL
S= RCL divied by RI
RI=RLC divied by S
D=YPC divied by4
Not my strong point ( MATH)
Thanks
When it comes down to it, it’s all a lot of overkill for model railroads. You can achieve a more than close enough approximation by using the ‘bent stick’ method. It’s laid out in Armstrong’s “Track Planning for Realistic Operation” but basically you have the constant radius of the curve plus an offset. You need a flexible stick, like a yardstick or a piece of lathe strip, fastened along the tangent up to the point of the start of the easement. The other end gets bent to follow the circular cuve. The natural springiness of the material will for a spiraling curve joining the two, Mark along this and lay your track.
It’s why some people prefer spline roadbed, it tends to naturally form easements as you go from the tangent to the curve.
If you don’t have a copy of TPfRO, get one. The single best source for concepts and ideas for coverting the prototype into our always limited model spaces.
–Randy
I agree with Randy 100% That’s way too much math, I use John Armstrong’s bent stick method to determine my easements.
Nick
Thanks Randy and Nick.
I have used the Armstrong system. I was just interested in the real math way.
Woodone