Vertical Transitions

[sww]

Does anybody know of any standards or guidelines for designing vertical transitions for changing grades or simply loweering track onto a less ballasted siding?  I know there has been a lot written on horizontal curve easements suggesting about two car lengths as a good transition length, but what would be the length of a transition into a 2% or 3% grade?  What would be the length of run to lower a siding off or an HO 3/16 inch roadbed? Any thoughts would be appreciated.

[mlehman]

The biggest issue is your motive power. A steamer with a long wheelbase on the drivers tends to be less forgiving that a diesel with two trucks that can swivel around a bit. \

As a general rulle of thumb, you don't want to exceed your ruling grade, but a "vertical curve" (the technical name for this transition) often is less than that at the foot of grades in order to smooth the entry into the grade itself. Pretty much the same applies to entering or leaving track lower than the main, except you end on the level most times.

Keeping that in mind, you actually have TWO vertical transitions when you do that, entering the grade down and then leveling off, but they may be scrunched together so it seems continuous. If gentle enough, it'll work.

[mobilman44]

On my current and previous layout, the max grade is 2 percent.   I use the "cookie cutter" style in making a vertical transition, and that's worked very well.  Typically, a two foot slice into the 1/2 inch plywood will bend up to about 1/4 inch at the end, and then the rest of the grade at 2 percent is blended into the transition.

 

[doctorwayne]

Vertical transitions using cut-out plywood roadbed are actually pretty easy to accomplish, with not much math involved.  If you have known upper and lower elevations and also know the length of the run between them, then you can easily determine your grade percentage.  While the grade percentage with vertical easements won't be constant, for the purposes of establishing the easements, we'll assume that it is.

Fasten the roadbed in place at both the top and the bottom of the grade, then find the mid-point of that run and, using a riser, fasten the roadbed there at a height one half that of the total climb - you may need to raise or lower the roadbed at that point to accomplish this.  Next, without raising or lowering the remaining unsupported roadbed, add sufficient risers for proper support, simply setting their tops at a height equal to that of the bottom of the unsupported roadbed.
For long grades, after adding the riser at the mid-point, subdivide the two halves of the grade again, and raise those new mid-points to 1/4 and 3/4 of the total rise, and you can further subdivide as necessary for especially long climbs.  To avoid negating the natural vertical easements which will have formed at the top and bottom, though, don't overdo this procedure - you only need to take out any overt sags.  I used this method on a 45' long 2.5% climb, using 3/4" plywood, and also added superelevation to the curves.

Wayne

[riogrande5761]

I don't have a formula but what I do try to do is have a stretch of track which is at intermediary grades to the change from horizontal flat to 2.9% grade (my max grade) is not sudden.  For example I went from 2.9% to around 4 or 5 feet of 2.4%, another 4-5 feet of 1.5% and a few more at .8 or so.  I also use a long piece of flat wood to check to see that there wasn't a major bow where the track transitions grades cause I want to avoid mis-match couplers etc. on long cars.

[BroadwayLion]

LION found the cookie cutter to be the best. Failing that, just make the transitions gentle, and if your trains balk, derail, or throw a snit at you, adjust and ease the easement. Lift the track and sand down the roadbed into something more gentle and forgiving.

You do not always get things right the first time, as LIONS ought to know.

ROAR

[ndbprr]

I think there were templates in MR many years ago. If I were going to make a template I would draw two straight intersecting lines based on the grade. Then I would bend a very thin piece of wood to create the arc between the two straight lines. Varying the distance from the intersection to the starting and finishing point would create different arcs.

[Medina1128]

mlehman

Keeping that in mind, you actually have TWO vertical transitions when you do that, entering the grade down and then leveling off, but they may be scrunched together so it seems continuous. If gentle enough, it'll work.

The issue with the transition is making sure the transitions are gentle enough to prevent:

• So motive power doesn't contact the rails when entering the upward transition.
• And, so the couplers don't uncouple because of vertical alignment of the couplers in respect to the next car.

[HObbyguy]

I don't know if there are any standards for vertical transitions, but I do know they are needed for all the reasons mentioned.  The design software I use (XtrackCad) has functions for curve easements, but not for grade easements.  I just set gradual % grade changes for at least a couple of feet until I reach the desired rise and that has been working well.

Its a good question to ask, because often those designing a first layout forget about vertical transitions.  They can take up a good bit of track leaving less for the actual grade.  This results in a steeper rise than desired if not considered and planned in.  Its especially important when considering a small layout since space for this is at a premium.

 

[sww]

Thank you all.  It sounds like I should try about a two foot transition into my grade as a start, try some equipment and lengthen if necessary.  I'll try about the same on lowered sidings.

[Choops]

2% grade to change height 3/16 would be 9.375" long. 

0.1875 x 100 / 2 = 9.375"

I have seen someone glue down the cork roadbed and then sand it down to nothing to create the grade.

Another easy method would be to cut 2" wide strips of a clothing box (thin cardboard).  Then cut them to lengths (10", 8",6",4",2"long pieces) then stack them to creat the grade down to the plywood.

HTH

Steve

[riogrande5761]

I made my staging yard the base elevation and then with open grid benchwork was able to simply raise the elevation of the subroadbed based on the grade calculation I made, starting with more gradual grade at first (~ 0.8% and increasing to 1.4% etc. until grade was 2.9%.  The following under construction photo's illustrate:

Above: the middle of the long sections are 2.9%. 

Above: The portions along the end have gradual and intermediary grades, climbing from the bottom up and from the top down.

 

[7j43k]

If you are considering having a siding drop down off the height of the main, you would do well to have the switch ENTIRELY at the mainline height.  And also the siding track, for a car length.  THEN start the vertical curve downwards.

It is also, generally, a bad idea to have a vertical transition curve in a horizontal curve.  No, make that a very bad idea.

 

 

Ed

[cowman]

To lower a siding I have often seen a wooden shingle used, they are usually about thje right thickness at the thick end.  Some places stock tapered shims, which are about the same, maybe a bit shorter.

As Ed mentioned, keep your turnout on a flat plane.

Good luck,

Richard

 

[Czarstoo]

In the March 1979 Model Railroader Magazine, page 147, there was a discussion about calculating vertical curves, flat to constant grade or constant grade to flat. The length was identified as: %age grade change times a constant "K". K values are: 3.2 for N scale, 4.4 for HO scale, 8 for S scale and 12 for 1/4" scale.

[sww]

Thank you, found it.  That March 1979 discussion would suggest just over 13 inches for a 3% grade, so my default two feet should be safe and probably look better.

[Anonymous]

sww

Thank you, found it.  That March 1979 discussion would suggest just over 13 inches for a 3% grade, so my default two feet should be safe and probably look better.

 

This topic is also discussed in Model Railroad Planning 2016 on pages 86-90.