66 Collectable Model Trains: Track Laying: How steep can I make a grade?
Description
This article is from the Model Trains FAQ, by Christopher D Coleman with numerous contributions by others.
66 Collectable Model Trains: Track Laying: How steep can I make a grade?
Grade is rise over run. For example if a real railroad climbs two feet
in 100 feet of track it is on a 2/100 or 2% grade. Lionel graduated
trestle sets rise about 0.5" each track section, 8.75" for O-27,
making it 5.7% grade. This would be a torturous grade for a real
railroad, whose normal heavy grade is 2.5 to 3%. For most beginner
train sets this is steep, but manageable. No steeper is recommended.
Also remember a curve in an ascending trestle makes the grade about
twice as hard for the engine, depending on the tightness of the curve.
Curves also introduce the problem of cars being pulled off the track
to the inside due to the tension between the engine and the rest of
the train. To alleviate this somewhat, cars should be ordered by
descending weight. Furthermore if your track is in less than ideal
condition, a curve on a grade will be the prime spot for a derailment
on your layout, due to the unusual stresses placed on the track
joining pins by car wheels.
If you want to run trains longer than about 10 cars you're going to
have to make your own trestle with an easier grade. You can make your
trestle out of whatever you like so long as you firmly attach it to
the track and preferably also to the benchwork. The smoothest
operation will be attained if you make the grade taper up from zero at
the bottom and back to zero at the top with the normal grade in the
middle. This eliminates the wack of the wheels at stressed joints at
the top and bottom as well as pilot (cowcatchers) catching the center
rail at the bottom and longer locomotives rocking over the peak at the
top. At minimum there should be support at each rail joint. For curves
there should be support in the middle of the section also, to prevent
your prize locomotive from bending it over enough to topple. The best
support is 1/4" to 1/2" plywood strips under all the track. I use 4"
wide strips supported about every 9" by a short section of 2X4. This
can be hidden with paper mache', plaster, simulated stone, or whatever
scenicing process you prefer. I also grade 1/4" rise on each track
section or 2.9%, steep but not too bad.
If you're really ambitious you can build a prototypical one from balsa
wood. Use 1/4" square stock laying one under each rail parallel to the
rail. Use shorter sections perpendicular under the first about every
2" to 4". Cut 1/4" dowel rods to length and run four of them from the
support to the ground as pilings. This is of course a basic design.
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