Track Elevation Change Easements

[Kudlor]

A lot has been written about track easements coming in and out of curves.  I haven't found, however, articles or posts about track easements going into and out of an elevation change, e.g., going form 0% grade into a 2% grade.  If no easement, the change is abrupt for locos and cars.

Can anyone refer me to an article/post on this topic or provide a formula or instructions for determining an elevation change easement?  I'm modeling in N scale if that matters.

Thanks.

[cuyama]

Yes, vertical transitions are needed. This topic comes up about every three months. Using the  "search community" box to search for "vertical transition" yields a number of threads, probably the most recent is:
http://cs.trains.com/mrr/f/88/t/219308.aspx

In which I wrote:

cuyama

Just to reinforce a couple of things already mentioned. You will need transitions from level to grade, so allow for them in the overall length.of run.

I typically allow one car length of transition for each percent of grade, using the longest car or engine as the measuring stick. For an HO grade of 2.5%, this will be close to Alan's suggestion for your transitions.

As mentioned, curves add to the effective grade, so you may wish to allow for that effect. This means that you must either decrease the grade in curves in order to maintain 2.5% overall or set a lower nominal grade so that the curves at that nominal grade do not exceed 2.5% effective grade. The effect of this extra effective grade is increased when the full train is in the curve.

The very old rule-of-thumb for HO is to use 32/R, where "R" is the radius in inches. The resulting number is added to the nominal grade to calculate the effective grade. So for 24" radius curves, the value is 1.33%.. This makes a 2.5% grade effectively about 3.8% through that curve. 

If you decide to reduce the grade through the curve, again transition between the two different nominal grades.

 

[hon30critter]

cuyama

Thanks for re-posting the formula for calculating the effective grade on curves. I had forgotten the ratio.

Dave

[peahrens]

Here's a post from last year that includes the vertical transitions subject, in case any tidbits are useful in addition to what's already been suggested:

http://cs.trains.com/mrr/f/11/t/203837.aspx

[delray1967]

Use your longest cars to test for vertical movement of the couplers; you probably don't want less than half of the coupler height to be engaged at any time, some couplers droop a bit and will make this worse too.  If you don't have any long cars, borrow a couple passenger cars or use it as an excuse to model your favorite passenger train and buy your own. :)

I've found out over the years, cars that have the trucks set in from the ends behave differently than cars with trucks closer to the ends, if only your cars will be run on the grades, try several combinations.  If others' cars will be run, like on a modular layout, then try to guess the worst case scenario (two or three 89' auto racks?).  Passenger cars with touching diaphragms will have to be considered too, maybe a piece of clear styrene over the opening will prevent them from snagging on each other.