I'm planning a new layout with some hills and tunnel. What is the recommended grade that I should use for designing overpasses? I have a 'Western Maryland #760' as my engine that I plan on using.
keep the grade as low as possible. 4% is the maximum I would use, 3% is better. those work out to 3/8" and 1/4" rise per full track section respectively. keep in mind that grades drastically reduce pulling power. a locomotive can only pull about 1 car up a 4% grade for every 6 cars it can pull on level track.
2% That is the correct answer max 2.5 % any more and your asking for problems especially if curves are involved!
Jack
Grades on model railroads are a tricky thing. We don't all have a lot of space but to get any sort of height, we would need either a longer run or a steeper grade. I wanted to put a grade on my layout originally but seeing as I have a 4*8 due to limitations, it wasn't practical. Jack is right that 2% is a good choice however you should be able to deal with 3 or even 4, just keep in mind that you will lose a lot of power. Also, if there are any curves, take it slow or you could find that train has taken a plunge
Most standard 'Up-and-Over' type pier sets used for Figure-8 layouts on a 4x8 table give roughly a 3% grade. This is considered steep, and limits your operations considerablly. A 4% grade is extremely steep, and generally only seen in 'back woods' logging operation type layouts.
If you have the room, grades between 2% and 2.5% should be the maximum used. Most model locos can handle them, while pulling a decent size train, with no problems. Of course, on the prototype, a 2% grade would be considered a problem, as they try to keep grades in the 1% or less range if at all possible.
Oh, if you're wondering, '% grade' is just Rise divided by Run times 100, or 100(Rise/Run), where Run is normally specified as 100 to simplify the math, but could be any distance. So a 100" run of track that rises 3" would give (3/100)=0.03*100=3% grade. Simple.
Len