Acceptable grades

[nachoman]

I have a 4% on my layout, but it is narrow gauge and is actually prototypical. For my rod-engines (2-8-0s), that's about 2-3 cars and a caboose before slipping. For my shay, I can pull a few more.

From my experience with previous layouts, 4% is about the maximum you can do. My childhood layout had a grade around 6%, the cheap trainset locomotives could barely pull themselves up the grade, but a heavier Athearn could pull a few cars. Model steam engines are slipperier than diesels. A pair of heavy 6-axle diesels may be able to handle a decent train up a steeper grade, but to run any decent-length train behind a steam engine I would do everything I could to keep my maximum grades to 2%. And if you are going to have a steep grade, it works best if it is straight. Curves on steep grades are usually a disaster.

I like Mountain Man's suggestion of a switchback. The railroad that I am basing my freelanced road after replaced some long wooden trestles and steep grades with switchbacks.