What is the maximum adverse (uphill) grade that a HO 50 ton 2 truck climax would be able to hall 3 log cars?
Make a test ramp for yourself and find out. It's all going to depend on how heavy said log cars are.
Sid
The engine by itself is probably good for 7 or 8 percent. I would stick to around 4 percent in order to pull a decent train.