I have also considered this layout plan for a while as it does have some interesting points.However,its featured 9 3/4 in. curves didn't suit my steamers so I dropped the idea.But depending on what you plan on running on it,it may be a good choice.
You say you have lengthened your benchwork an extra six inches.Let's say you concentrate this extra length at this end of the layout so that your smallest loop benefits from this increase,you'd have an extra foot of trackwork to work with,giving you almost eight feet of total run.You'll need 1 5/8 in. clearance from railhead to bridge structure and with a structure of about 3/8" thick,you'll need a total of about 2 in. rise.Now,two inches climb in about eight feet of run gives a nice approx. 2% but you have to consider that the whole rise is accentuated by a pretty sharp 9 3/4 in. curve wich makes the climb somewhat steeper.You could also steal a bit of run from the other loop by moving the bridge so that the intresect points is more to the left,wich would give you more track run without much penalty to the other loop.Just an idea......
Unfortunately, you won't have the full 7 feet -- for reliable operation you need a bit of a transition at each end of the grade. But assuming you only need to allow for one end of the transsition in the 7 foot length, you might end up with roughly 76" of run. A 3% grade could raise the track just enough (76" X .03 = 2.28") with a thin bridge for the upper track.
A good approach would be to look at dropping the lower tracks a bit also to split the overall grade between the upper and lower tracks.
Of course, a really good approach might be to look at a different track plan for the same space that might be a lot more engaging in the long run. But people seem to focus on those Atlas plans ...
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Besides revisiting sixth-grade math lessons, one needs to know the amount of clearance (rise) is required. For instance, say one needs 2 inches of clearance. In addition to that 2 inches, one needs to account for the thickness of the roadbed/bridge as well as ties and rail. If three-quarters inches is needed for that thickness, the total minimum rise of the rail is 2 and 3/4 inches to achieve a 2-inch clearance. If one divides that rise by the grade percentage, say 3 percent (.03) on average, one needs a run of nearly 92 inches (2.75 divided by .03).
Mark
3% is 3 in rise in 100 in of run.
Another rough rule of thumb is the % grade is the number of inches of rise in an 8 ft length.
Convert the run into the same units as the rise. So if you want a rise of 3 in then the run has to be in inches too. 7 ft = 84 inches.
Divide the rise by the run and multiply by 100 to get the % grade. 3" rise in 84" run = 3.6% grade
Multiply the run by % grade and divide by 100 to get the rise. 84" run of 3% grade = 2.52" rise
Divide the rise by the % grade and multiply by 100 to get the run. 3" rise with 3% grade = 100" run.
Dave H. Painted side goes up. My website : wnbranch.com
Howdy.
I'm building an Atlas N-18 Gulf Summit layout with flex track. Increaced table size 6" longer and 12" wider. I don't really like the 90 degree crossings and would instead like to make a over under but not sure if I have enough room for the incline. How would a person not gifted in math skills be able to figure this out? I have about 7 feet of track on the shortest inside loop. Is that enough? This is my first post to this forum but I sure like reading all the ideas. Thanks for any help I can get. scookam.