snippet – Swiss CRT
It was very nice to find this in a standard. Snippet taken from here.
The other Bernoulli boy and his lemniscate
When I hear the name Bernoulli I think about some funny high school experiments of spraying coloured water on paper but also about an infinite loop curve the Roads Professor tormented us in Uni. I would have bet both things were discovered by the same Bernoulli. But no. The more known one, D. Bernoulli, the…
Hallade’s broken clothoid
I mentioned in a previous article, The Cubic Parabola – a complicated simplification, that the curvature diagram of the Cubic Parabola increases linearly up to a peak point and then drops down. Only that first section of the parabolic curve can be used as an alignment transition. The curvature diagram of the Clothoid is however…
The equivalent radius (versine bending)
Prologue One of the giants on whose shoulders stood proudly Isaac Newton, is the French mathematician Renatus Cartesius. He was the first to label the unknowns in equations by the letters X and Y and also he defined the annotation of powers as superscripted labels X2 . Believe it or not, that was a giant…
Pi is never 3.14 in engineering
One alignment design homework I had for my students was to calculate the installation coordinates for a simple alignment. This was a long time ago, before Excel was a thing. We were using scientific calculators back then; a lot of typing. One of the submissions puzzled me. All the coordinates were almost correct. The length…
The Cubic Parabola – a complicated simplification
Ten years ago, one of my first British friends asked me “Why 4°?” The Clothoid is by far the most used transition curve for railway and highway alignment design. I wrote about this marvelous curve in an old article on this blog – here. Although the Clothoid is the ideal transition for linear variation of…
Straightening the equivalent radius
If we consider a circular curve of radius R2, tangent to a straight and mark the offsets O1, O2 and O3, measured perpendicular from the circle to the straight and placed at regular C/2 interval we will get something like this: The offsets O1 and O3 are the bases of a trapezoid and O2+V2 is…
What to abruptly do when you don’t have (the rule of) Virtual Transition?
I have discussed here the principle of Virtual Transition, used in the UK and in other countries with British inspired track design principles, to evaluate the changes of the cant parameters at the points where the curvature changes suddenly, without the use of an actual, real transition curve. This method of calculation is not however…
A railway track blog 