Grades

Answer depends on a number of factors; locomotive(s) being used, length of train and type of cars being pulled, grades mixed with curves (or all on straight track), type of track you are using, etc.  Most modelers try to keep grades lower than 3%, but if you're using strong pulling engines and small trains, you probably will not have any problems.

Chuck

I am using Atlas O 3-rail track.  One of the ramps is starts on 64.5" of straight track, then goes in a half circle made of O-81 curves, goes straight for 20", then goes over 2 O-81 curve sections and then ends after another 30" of straight track.  The other ramp starts with two O-81 curves, straightens for 11.75", goes over four O-81 curves, straightens for 99.25", goes over four more O-81 curves and then ends after 40" of straight track.  The largest engine I plan to use on it will be an AC-12 Cab Forward but the average size will be closer to a 2-8-2/4-8-4 for steam locomotives and EMD E7s for diesels.  As far as consist size goes, I'm in the mindset of "as long as possible".

What length of track did you allocate for transition at both ends?

30" to transition between grade percentages at a minimum.  For both ramps, at the bottom, it goes from 0% to 1%, 1% to 2%, 3% to 4%, then transitions back down to 0% at the top.  Each of those sections have a varying length but no less than 30" since I figured that with longer locomotives with the Ac-12s the wheels might not like anything shorter.

I think you'll have no trouble. Your transition allowance is very generous.

What do you think about the grade itself in terms of consist length?  I would prefer to be able to run 20-30 car freight trains and 10 to 15 car long passenger trains if possible but really don't wanna damage the motors.