Any one with the NMRA standards for the rise for 2% or 3% grade starting a new layout and trying to keep it prototypical as possible. Or anyone with the plans to build your own gauge . Thanks, gondola1988
Grade Percentage = 100 x rise / run. If the rise is 1" and the run is 100", you have a 1% grade.
I don't know if there's any NMRA standard for vertical easements into grades. I personally allow the length of my longest car (aka one unit of easement) x grade percentage, split equally in both directions from the theoretical grade-level track point. With cookie-cut plywood, the easement forms automatically if there's no joint in that part of the cut cookie.
There should also be vertical easements where the grades change (become more or less severe.)
For a summit, the total length of the easement must take the entire grade change into account. If you go from a 3% upgrade to a 4% downgrade, the easement will be seven units long.
Someone once determined the radius of the necessary vertical curve. IIRC, it was about 12 feet for US prototype rolling stock in HO. Since I don't run long passenger cars or TTX flats, I can get away with less.
As for total rise, unbroken grade, it would be theoretically possible (but not very practical) to model a seaport in the basement, farmlands on the first floor and mountain resorts/mining camps on the second floor, all connected by one continuous helix with about a thousand feet of first track.
Chuck (Modeling Central Japan in September, 1964 - with LOTS of vertical transitions)
Model railroaders and prototype railroaders have different perspectives on vertical curves. Modelers' principal concerns are that the trains don't catch on the track, uncouple, or measurably lose traction at points where grades change. For prototypes, the problems of car crowding and forces on the couplers come into play much earlier than the type of things modelers are concerned with. On the prototype, sags (change from negative grade to positive grade) and to a lesser extent summits (change from positive grade to negative grade) are the most critical.... The prototype uses parabolic vertical curves, which are also created when one bends plywood or a wood spline for a layout's subroadbed. Now, that's convenient. This is one reason I use plywood as a subroadbed and not rigid foam.
tomikawaTT As for total rise, unbroken grade, it would be theoretically possible (but not very practical) to model a seaport in the basement, farmlands on the first floor and mountain resorts/minimg camps on the second floor, all connected by one continuous helix with about a thousand feet of first track.
As for total rise, unbroken grade, it would be theoretically possible (but not very practical) to model a seaport in the basement, farmlands on the first floor and mountain resorts/minimg camps on the second floor, all connected by one continuous helix with about a thousand feet of first track.
And if operating an HO train at scale speed, it would take at least one-half to one hour to transit the total length of the helix.