On my new layout I have considering modeling a part where a double main from a major RR would pass over a shortline. If my math is correct, (HO Scale) I need 3 1/2 inches clearance which takes 7 feet to climb at 2%. Is that a good setup for modern-ish layout running large frieght trains and 5-9 car passenger trains? The terrian of the remainder of the layout is great lakes region with very small hills.
Thoughts?
You can often get away with clearances above the rails of just under 3", but it depends on what you plan to slide under there. Some MOW equipment, like wrecker cranes, or double stacks of containers on flat beds, the odd caboose with a high stove stack…they may jam. So, keep that in mind.
Secondly, you can split the task between the two tracks. Nobody wrote that only the high track needs to do all the altitude changes. The nether one can also dip and rise again. [I] This has the salutary effect of making all the contributory grades much less, and much less onerous on the locomotives.
Crandell
What Crandell said!![bow]
Dave
Your math is not correct. 3 1/2" rise at 2% grade requires a little over 14 feet, and that’s before allowing for a vertical transition at each end. If you split the grade as suggested, you might get it done in less space, but remember that you’ll need transitions on each grade.
Good luck.
Ok, so what is a good grade to use for HO Scale? I might be able to lower the track passing underneath a little, but not a lot. That track is going to be a branch line that will be going “beyond the layout” after it passes the under the main line. As you can tell, I am not good with grades. This is the first time I have applied elevation changes to a layout.
Most folks seem happier with 3% or less, but that will have an impact on train length. And remember that sharp curves effectively increase the grade and can create problems. As long as the transitions are adequate, you might be able to go a little steeper for a branchline that will have shorter trains, for example.
Based on the questions you are asking on this and your other threads, I get the impression that you might be new to model railroad layout design. If so, you can’t go wrong with some time spent studying John Armstrong’s Track Planning for Realistic Operation before you spend a lot of time drawing plans (of course, almost no one follows that advice).
Best of luck.
Hi
A one inch rise over 100 inches is a one percent grade, and a 2 inch rise over 100 inches is a 2 percent grade. 100 inches is just over 8 feet {8 feet and 4 inches}. To give you some easy perspective.
I would stick with 2% grade or LESS.
How do I know this? I built a small layout with a 4% grade, and found it not to work for locos pulling even short trains up it. I tore that down.
I built a changed layout with 3% grade, and found it, too, did not work well. I tore that down.
What looked good on paper didn’t pan out well in real life.
I, instead, modified my layout to have varying heights of trackage, but no over/under as I just didn’t have the space for it. My trains are happy and so am I.
As Selector {Crandell] pointed out, the lower track can slide down below the horizon for a 2% grade, while the upper track rises up a 2% grade above the horizon to gain the clearances you need.
How you accomplish what you want to do.
[8-|]
Just a thought. Maybe if the branch line ends shortly after the crossing, or is just for show, maybe it should go over the main line. You could get away with a steeper approach, an approach on one side only, or no approach at all.
Agreed, you might find a creative solution that obviates your need for much more than 2%, especially if the dead-end track is ‘far away’…in perspective.
About transitions, or the vertical curve you need at each end of a grade: the steeper the grade, the more transition. The more transition, the less grade-proper you have between them to get a steady rise. Basically, avoid grades when you can, just like on the real railroads. But, if they must be, keep them shallow. That way, your transitions are short on each end.
I had grades between 3 and 3.4% on my last layout. I came to regret them. My locomotives worked harder on shorter trains. I got super clearances where things passed overhead, but at what a cost!! So, my advice is to be creative. Ponder a bit, find a way to use a belt sander to get about 1% or a bit more out of that lower track, and then let the climber do the rest. You’ll have to live with it once it is done.
Crandell
NILE, I have a 0% grade on my layout and it works just fine. [swg]
Rich
LION got a 17 on his algebra final in high school. Him cannot count past 10 without his claws tearing all of the paper apart. Him never figured out percents on his railroad.
LION has a track here. It has to go up there. OK who cares about percentages him made a ramp and the train went up there. Locomotive could pull train up there, so who cares about grade percents.
Then LION bought subway cars, and they could not climb the grade. What to do. Him tears out ramp and makes a loop, one and a half turns, now trains can climb ramp, problem fixed.
The LION wanted to put a FOUR TRACK mane lion on that loop, him tears it out again and builds a bigger helix. Now is four track helix. Him not know what is percentage. Him cares not. Trains go up and down from one level to another.
The Helix is 5’ x 5’ round 
it must clear train on lower track. Grade is irrelevant, it must do what it must do.Train must leave this station and must arrive at next station on next level, what must be must be.
Do not be afraid to build something and then pull it out when you need it do something differently.
ROAR
I have Track Planning for Realistic Operation, and while this is a great book it really does not go into detail about grades. I have avoided them on my previous three layouts.
I can’t take the shortline over the Class 1 as I was going to put a gravel indutry off the short line right in front of the over under. I also thought the Class 1 going over the shortline would be a good way to “hide” the fact that the shortline track stops about five inches behind the crossing.
My class one will be running long big trains, so I might keep it flat. Thanks for all the great information.
Since your shortline’s track doesn’t actually go anywhere, why worry excessively about clearance that’s not needed?
This track passes under a mainline, too, but it’s part of a turning wye and extends a couple of feet beyond the bridge. At just under 2.5" it clears most, but not all, of the equipment operated on my ''30s-era layout.
While higher, more modern cars wouldn’t have clearance to pass under, on your layout it will still give the impression that the lower line “goes somewhere”, which is really the effect which you’re trying to achieve.
Wayne
You might want to have a second look at pages 81 through 83 in the Third Edition. I was basing my suggestion not only on the grade questions, but on your yard questions and other threads.
Best of luck.
I wrestled with the planning for this on my 5+ x 10+ ft HO layout as my track design was not on one but two levels, due to an upper reversing loop, part of which crosses over a lower reversing loop. I knew the nominal clearance specified (lower track to bottom of crossover bridge). I cheated on that, recognizing that it may preclude certain rolling stock making it through; but I don’t intend modern double-stack trailer cars, etc.
I checked how this turned out. My grade from under to over the crossover is 3-7/8" (rail to rail) over 150", or 2.58%, on a curve. I ended up with just under 3" clearance under the bridge. I found my Athearn DCC GP9 or BLI steamers have lots of clearance and pull a small train (8 freight cars) up the grade just fine. How many cars it will handle is to be determined (I need to build more cars). I can always go to double header locos for longer trains (I will never have a really long train on this moderate size layout.
I found myself overanalyzing the grade and crossover height, looking at roadbed plus track height, plus bridge shoe to rail height, abutments, etc. It was easy to cut down some bridge abutments to a lower height, so that didn’t need to be considered. I did a cookie cutter plywood layout (the lower reversing loop is partly on a submerged plywood arc). I put a series bridge combo in place (Central Valley girder plus truss bridges). I ended up with more clearance than expected, railhead to bridge bottom.
What I did not recognize was that my intended upper yard (within the upper reversing loop) needed to be relatively flat, which meant cookie-cutting that also to flatten it from the attached sloping reversing loop. I continued the grade past the crossover so it peaked at the far end of the reversing loop. The yard then became the lowest clearance over my lower loop, not the mainline bridge crossover I was scrutini