Switchbacks

Model Railroader Layouts and layout building
1

Gentlemen,

I have 2 questions I’m hoping someone can answer without alot of percentages.

My son and I are building a layout that will have a logging area which will rise up to 3 inches above 2 inches of foam glued to half inch plywood.

My questions are how long of a run do we need to raise up a1/2 inch at a time to the switchbacks and how wide do we need for either #8 turn outs or #8 curved turnouts to reach the the 3 inch summit?

We have 9 1/2 feet from the starting point to the first turnout by 7 inches wide to the last turnout at 3 inches.

This layout was laided out in 3rd Plan it Software.

Thank you for your help.

Yours aye,

Macdonald,RB (Mac)

2

If I understand you correctly, I still need more information. But first, I am not sure I follow: you want to rise only 1/2" at a time. What does that mean; only 1/2" from turnout to turnout, in other words on one leg of the switchback?

How long will your trains be…that could be a major consideratoin given your space is limited…you must fit a whole train (your defined length) on the flats beyond the turnout in preparation for the reversal.

-Crandell

3

Unfortunately, your question involves percentages. Grades are expressed as a percent which is how many units the track rises per 100 units of length. For example, A 1% grade will rise 1 inch in 100 inches of length, 2% will rise 2 inches in 100 inches of length, etc. In your case 1/2 rise is achieved in 50 inches for a 1% grade.

Logging railroads used much steeper grades and you’ll probably want to also for the scenic effect. Depending on your locomotive 4-6% would be good. Also a 1/2 inch rise isn’t really very much, you probably will get a better effect if you rise about 3" or more on each traverse. A quick way to check your locomotive on grades is to lay some track on an 8’ board and raise the end up - each inch is roughly 1% - and see how steep a grade it can handle and how many cars it can pullup that grade.

Enjoy

Paul

4

I used about a 3 % grade with about 24 inches between the switches. My Shay or Climax will pull three log cars and that is all I wanted.

5

  1. The switchback tails should be no shorter than the longest train you intend to run.

  2. The tail of the switchbacks and their turnouts should be at a grade equal to about half of the switchback. (On the prototype, switchbacks with an upward grade toward the tail ends help stop downward-bound trains and retart upward-bound trains.)

  3. One needs to allow for transitioning the grade between grade changes so equipment doesn’t hit the rails, equipment doesn’t derail, locomotives don’t lose traction, and couplers don’t become uncoupled. The length of vertical curves where grades transition will be dependent upon the nature of your equipment. Test your equipment.

  4. A sharper turnout will make the tail/turnout length shorter so one can obtain greater elevation gain or use less-steep grades for a given length.

  5. The typical logging railroad used short equipment, so #4s, but preferably #5s, should be adequate. Test your equipment first.

  6. Maximum grades of 3 to 4 percent are the most practical.

Mark

6

Art nice dinning room layout…do you have a pic of your track plan? Like to canyon to the floor…great work

7

Crandell,

The trains will be 3 cars long plus an engine coming out to 26 inches long. The 1/2 inch would be leaving switch 1 and entering switch 2. The tails are 29 to 30 inches in length. While I realize that “real” logging trains have steeper inclines, I am limited by the area of my room. The area that I have to work with is 10 1/2 ft by 8 ft. While my entire room is 14 x 9 I need to have room for a yard and a escape from the yard plus an area in the middle to move while the trains are moving.

MacdonaldRB (Mac)

8

Mac, you seem to have much of it already in hand. So, when you say you want to rise 0.5" between turntouts, and that your space is quite confined, I would suggest, as others have, that you would be better off rising more, and limiting the number of switchbacks…they take up tons of room, as you must realize.

I don’t have a firm grasp of your overall plan, so a diagramme would really help. But, for figuring purposes, with tails on each end of a switchback of 29", you now need a total of 58" to effect your elevation change between turnouts of an as yet unspecified distance apart from each other…right? You could get anywhere from your desired 1/2" elevation between the turnouts and a more realistic 1" in your overall space with grades of between 2% and 5% over either 24 or 30"…your choice. I am limiting you, but you should probably be figuring on a distance between turnouts, for your space concerns, of between 24 and 30". So, for example, with only a 1/2" rise over 24" between turnouts, you get a 2% grade…close enough. If you elect, instead, to go for a full inch over that same distance, now you have a more realistic 4%. Three quarters of an inch would only be 3%, somewhat easier, but still three times the height advantage in one switchback.

Or, over 30", if you have the space between tails, 1/2" comes to a paltry 1%…hardly worth all that track. Make it a 1" rise over that same 30", and now you are very close to a full 3% grade…very doable.

Over the same 30", rising 1.5", you get a challenging, but still very realistic, 5% grade.

Returning to the total of 58" in tails, with only 24" between the turnouts, assuming the lengths of the turnouts is included in the tails measurements you have suggested to me, you now total 58" + 24" = 82" in length for one switchback. Can you fit it in? Would you have the room for 26", or even the 30"?

9

I have found 4-6% grade is a very hard incline for most engines with even a modest load.

10

Let’s look at an example. Say one has 9 feet of length to rise 3 inches. One could simply have a single grade at an average of just over 3%. Now if one wants a switchback on the same length, it is whole different story.

Let’s assume trains won’t exceed 29 inches. However, the grade change can only be after the turnout. Never make grade changes on turnouts! A no. 8 curved turnout is about 11 inches long (both tracks branch in the same direction). A regular no. 6 straight turnout is about 8 inches long (one track branches off). A no. 3 wye turnout is about 5 inches long. (equivalent to a straight no. 6 but with both tracks diverging). Assuming one uses a no. 3 wye turnout, that leaves about 28 inches (96-29-5-29-5) for each switchback. That’s pretty short.

With such short switchbacks, once the maximum grade is reached it will need to be decreased to allow for transition of grade. So, to have an average grade of 3 percent, the maximum grade may need to be about 6 percent.

Continuing the above assumptions, about 0.8 inches can be reached on a 28-inch-long switchback with an average grade of 3 percent and maximum grade of 6 percent. So, one could achieve a total of 3 inches elevation gain with four switchbacks.

Regardless, unless I could visualize the inquirer’s layout setup, it isn’t apparent why one would want a switchback in the above example since the needed elevation gain can be obtained with a lower maximum grade without any switchbacks

Mark

11

That’s why I suggested testing. If 2 or 3% is all your logging locomotives can handle, then that’s what you have to go with.

Enjoy

Paul