Grades & track length

[Tedshere]

    In an article from Model Railroader Magazine there's a graph and example of how to plan raises in elevation.
    According to the graph, in order to achieve a 2.5% grade and the 2 1/2 to 3 inches of clearance in order to run an HO train under that overpass, my calculations come up with a necessary track run of about 125 inches. That's almost ten and a half feet.
    However, the example shown with that graph indicates only 50 inches which is just over 4 ft. I'm working with an 8 X 4 layout and am wondering if my calculations are anywhere near correct.
    Thanks in advance for any advice.
    Ted

[jonathan]

To put it simply ('cause I'm simpleminded), percentage of rise is measured by the amount of rise per 100 inches.  So, a 1% grade is 1 inch of rise for every 100 inches  of travel (a pinch over 8 feet).  On a 4X8 layout, a common grade is 3% (3 inches of rise for 100 inches of travel).  Due to lack of space, it can be difficult to set up a more gradual grade on this size layout.

I use no more than 1% grade on my mainline, but my branch that heads up to the mine uses 3%.  Smaller trains travel this route.   

Regards,

Jonathan

[jward]

regardless of what the magazine says, you are going to need at least 3" of clearance between the upper and lower levels where they pass over each other. i say at least, because you need to add the thickness of the subroadbed or other support for the upper level track to the 3"......i try to make my upper levels at least 4" to compensate for this additional thickness.

2 1/2% works out to 40" track per inch rise, your figure of 125 inches is in the ballpark for 3" rise. my calculations show 120" or 10 feet.....

there is a table in chapter 8 of the atlas plan book "Atlas HO layouts for every space" which breaks down the grade into rise per section of track (9" straight, full 18" or 22" radius curve) as follows:

rise per section    approx grade      #of sections per 3" rise
1/16"                         0.7%                   48
3/32"                        1.0%                    32
1/8"                          1.4%                    24
3/16"                        2.0%                    16
1/4"                          2.8%                    12
3/8"                          4.0%                      8


btw, 3" rise in 50" run is a 6% grade, far too steep to be recommended.

[ebtnut]

A handy rule of thumb for model RR grades is this:

1" in 24" = 4%
1" in 36" = 3%
1" in 48" = 2%

For small layouts, try to stick to no more than 3%.  In the case of a typical 4 x 8 layout, though, you are probably going to have to use 4% to get up and over with sufficient clearance. 

[Doneldon]

Ted-

There is a way to fudge a little which will effectively cut the steepness of your grade in half. Instead of just using half of a figure eight, for example, to gain the elevation necessary to clear under an underpass, put your low point under the overpass and half the rise you need beneath the surface of your layout. Thus, the entire length of your mainline is used to get up and over, not just half. You can do the same thing from grade as long as the high and low points are co-located (other than elevation) and your grade runs the full length of the available track.
                                                                                                                    -- D

[ebtbob]

All good advice here,  but there is one thing that has not been made clear.  The amount of Clarence you need where one track crosses over another should be measured from the top of the rails to the bottom of whatever is above it.   Using track,  set on cork roadbed sucks up about 1/4 inch of space vertically,  so if you measure from the board up,  and need 3 inches,  then actually you need 3 1/4 inches of vertical space.

[jward]

don,
while i agree that you can often fudge parallel tracks by distributing the grade between the two tracks, this will not work with a figure 8. the grade will remain the same because the track length between the high and low points remans the same. the best way to do a grade on a figure 8 is to count the number of track pieces between the upper and lower levels where the tracks cross, and use the table i provided to calculate the grade needed....

as a practical matter, setting the grade itself is a simple matter of using a 2 foot level and pieces of 1/4" moulding strip stacked on each other. every 1/4" is equal to 1% in grade. for example, to make a 3% grade you'd stack 3 pieces of moulding on your subroadbed (track board), set one end of the level on the stack, then raise the board under the other end of the level until it reads level. secure the subroadbed at this point, move the level up and repeat until you get to the top of your grade.....

[Tedshere]

    Thanks guys! As usual I appreciate all the advice. This board has been a great help with this and other questions that have kept me away from the hobby for years.
    My nearest hobby shop is 40 miles away and there's not always someone there who knows about trains. You guys have made a definite difference for me and other newbies like me. 

[jward]

we were all new once. hopefully we can steer you away from the mistakes we made, and save you some of the frustrations we dealt with.

[Len]

Woodland Scenics has a .pdf file at http://woodlandscenics.woodlandscenics.com/images/instructions/InclineInst.pdf?KeepThis=true&TB_iframe=true&height=500&width=800 that has the grade charts from their Subterrain Foam Riser incline sets.

It shows it takes 12ft to get 4-1/2in vertical clearance from the table top, which allows for roadbed, track, bridge structure, etc., with a 3% grade.

This stuff's a bit pricey, but it works as advertised if you're looking for a sloping hill effect rather than using piers or trestles to get a grade.

Len

[railsider]

There are two reasons for limiting slopes to 2% or at the most 3%. One is that it's prototypical. Much more than that just looks unrealistic. But, on the other hand, we make compromises all the time in model railroading, and sos you can sometimes exceed the real-world slope.

The other reason is related to the actual real-world reasons: can your train make it up that hill without stalling? Pure and simple physics -- nothing to do with what it looks like! If it can (after all, your freight cars, even if properly weighted, are not as heavy [in scale] as real ones), you are ready to roll. How do you find out if it can or not? TEST and VERIFY, that's how.

Take an eight-foot board, 2x4 or even 2x2, and add about 5" more at one end with a 1x2 splice on each side. You will now have 101" of wood. Lay exactly 100" of track (whatever your scale, etc.) with a safety bumper at each end. Remember, this is a test track, not for looks; just make sure it's sturdy. Now cut a series of 1" high blocks wide enough to raise one end of this test-track by 1", 2" and 3" (4" too, if you think you'll need it) and a single block that is 1/2" thick. Connect a power pack to the track. Load up a train and put it in place on the track. By stacking boxcars on flats and gondolas, you can simulate the weight and keep it short. Now lift one end carefully so you don't derail anything, and put a black under the end. Fire up the juice, and see if your loco can pull that weight up that slope. If it does, back up, add a lift block, and repeat. When you reach the point of "no-go," substitute the 1/2" block for the last one in your stack. If that works, then you have found your limit. If not, then take it out and count what's there.

By using a 100" track and 1" blocks, the calculation is no problem: 2" up in 100" = a 2% grade, and so forth. Experiment with shorter trains if you need a steeper grade because of space problems (and don't forget, a grade can go around a curve). Once you know what a given engine can do, keep a notebook of how many cars it can pull up how much grade, and you are ready to design your layout to operate on as many levels as you like, knowing how each will perform.

Obviously, it's a good idea to build a "safety factor" into your numbers, and to keep the engine(s) well-maintained so they always deliver as efficiently as when you tested them.

[jward]

we diesel fans can always add another unit to get us up the hill. but HO diesels pull surprisingly well. for example, i have a couple of walthers tranline locomotives which will pull 14 or more cars up a 4% grade.

[Jerrys HO]

I'll throw my 2cents in if it helps. I have been reading this post for weeks now taking everyone's advice and still had troubles. Not that the advice wasn't good, but I got frustrated and decided to checkout Lens idea on the woodland scenics grade. Man I have to say this is the best stuff since peanut butter and jelly. I bought the 3% grade (19.99) and the 4% grade (13.99 difference of 6 dollars?). I find they are both great I used the 4% grade on the climb and trimmed to the 3% grade to match for the decent. I have about 6 ft. between them. My diesel form my digital commander set has no problems with the climb,neither does my 0-6-0. Hope this helps you also. 

[jward]

i just helped design a friends layout. in one area we had to drop 18" from an upper deck to a lower one. the amount of run needed to to this much of an elevation change is incredible. i was able to come up with a way to do so while keeping the grade down to about 3%if he builds it the way i designed it, it will be one spectacular piece of railroad, and 90% of it is out in the open.

[WGL]

 I gave up attempting a grade under which I could even have a road.  If one needs 100" to raise a track to 3" with a 3% grade, he needs another 100" to get back down again, 200" in all!