incline, numbers? ratios?

A 1% grade is 1 inch rise over 100 inches track length.

I would avoid going over 3 or 4% so 3" rise in 100" track length. That's 8.33 feet for 3" rise. At that rise you need over 16 feet to clear a crossover.

And that does not include extra length to gradually arc into the grade and back out of it.

That makes it more like 14 feet total.

Now, you can dip the lower track at the same rate to get the 6" clearance in 14 feet.

 

Note that many say you need more than 6" clearance due to Height of Track/roadbed, and thickness of overhead structure. So you really want 7 to 8" from base to top of opening.

 

However, the trestle sets Lionel and MTH sell are far steeper than 4% so do the steepness you desire but be aware you are working your engine harder on the uphill leg.

" Lionel and MTH sell are far steeper than 4%"

always wondered about that,  "raise the bridge or lower the river" something to think about,  since am in the paper stage

I will try to post measurements and pics of my layout tonight.   I go from 0 - 6 or 7 inches in 10 or 11 feet which includes a curve and my railking engines have no problem pulling ten 40' boxcars and a caboose up the incline (that's the most which will fit on the reverse loop at the top of the mountain). 

 

I used incline starters and risers from woodland scenics and the end of the run is a MTH bridge.

 

--Greg

Don't forget, those steep grades will reek havoc on the traction tires.