Lego Train Track "Medium" Switch Concept
Switches/Turnouts/Points are one of the weakest areas in building realistic and reliable layouts. The TLG R40 switch is quite limited in potential configurations and has severe geometry due to its R40 radius. It does not combine to make a crossover at a nominal 16-stud centreline and the diverging route does not integrate into a nominal curve radius. To overcome these limitations, I have designed a switch concept called a "Medium" switch. I chose the name "Medium" because it fits in between the TLG R40 "Short" switch and a (yet undesigned) "Long" switch. The design requirements were as follows:
▪ Nominal 8s interval boundaries
▪ Integrates into a 16s centreline crossover without modification
▪ Integrates into a 16s interval radius
▪ 22.5º crossing vee / diverging route angle to support return curves
When designing this switch, it became apparent that the 16-stud convention and 22.5º sector angles do not overlap well from a geometry point of view. Designing a switch to make a clean crossover was easy. Designing it to support a return curve back to a 16-stud centreline *and* within an 8-stud lateral grid was not! It turns out that in addition to the switch itself, a new straight track element is required to realign the geometry of return curves back to a nominal 8-stud interval grid. After some analysis of various track configurations, a "2/5 Straight" or "6.5-stud Straight" element was required. In actual fact it is 6.48x studs long for minimal alignment error; however, even at 6.5x it is within the mechanical tolerances of track construction. This element is very nearly the familiar ratio of 2/5 which we use for SNOT building techniques. It is in fact a partial ratio of the standard 16-stud straight, i.e. 2/5 x 16 studs = 6.4 studs. This new straight element makes possible a variety of return curve configurations with several standard (R56, R72, R88) radii as well as providing alignment for stacked yard ladders.
In future, I intend to design a so-called "Long" switch which has a diverging route at 11.25º. I haven't worked out all of the geometry; however, I am hoping it will fit within the "system" similar to the "Medium" switch.
You can download (at your own risk!) these "add-on" elements for BlueBrick from my website at www.brickdimensions.com/resources/trains.
Happy layout planning and feedback/improvements/suggestions/etc. more than welcome!
Lego Train Track "Medium" Switch Concept
Switches/Turnouts/Points are one of the weakest areas in building realistic and reliable layouts. The TLG R40 switch is quite limited in potential configurations and has severe geometry due to its R40 radius. It does not combine to make a crossover at a nominal 16-stud centreline and the diverging route does not integrate into a nominal curve radius. To overcome these limitations, I have designed a switch concept called a "Medium" switch. I chose the name "Medium" because it fits in between the TLG R40 "Short" switch and a (yet undesigned) "Long" switch. The design requirements were as follows:
▪ Nominal 8s interval boundaries
▪ Integrates into a 16s centreline crossover without modification
▪ Integrates into a 16s interval radius
▪ 22.5º crossing vee / diverging route angle to support return curves
When designing this switch, it became apparent that the 16-stud convention and 22.5º sector angles do not overlap well from a geometry point of view. Designing a switch to make a clean crossover was easy. Designing it to support a return curve back to a 16-stud centreline *and* within an 8-stud lateral grid was not! It turns out that in addition to the switch itself, a new straight track element is required to realign the geometry of return curves back to a nominal 8-stud interval grid. After some analysis of various track configurations, a "2/5 Straight" or "6.5-stud Straight" element was required. In actual fact it is 6.48x studs long for minimal alignment error; however, even at 6.5x it is within the mechanical tolerances of track construction. This element is very nearly the familiar ratio of 2/5 which we use for SNOT building techniques. It is in fact a partial ratio of the standard 16-stud straight, i.e. 2/5 x 16 studs = 6.4 studs. This new straight element makes possible a variety of return curve configurations with several standard (R56, R72, R88) radii as well as providing alignment for stacked yard ladders.
In future, I intend to design a so-called "Long" switch which has a diverging route at 11.25º. I haven't worked out all of the geometry; however, I am hoping it will fit within the "system" similar to the "Medium" switch.
You can download (at your own risk!) these "add-on" elements for BlueBrick from my website at www.brickdimensions.com/resources/trains.
Happy layout planning and feedback/improvements/suggestions/etc. more than welcome!