This might be the province of the BSME's in the audience...

Assumptions: Dry level track, wind resistence not existent or immaterial.

How much power is required to move a train @ a given speed? That is, if you have a X ton train @ Y MPH that needs Z horsepower to overcome rolling resistence, what amount of power would be required to move the same train @ some multiple of that speed? Would the same train running @ 2*Y MPH require 2*Z horsepower or isn't it that simple.

Assume same train. X tons, Y MPH, Z horsepower.

How much HP to move that train on a T% grade?

Superheater, I have a program that I downloaded from a web site several years ago that calculates this information. You can use any two or three of the criteria and it will calculate the others.
PM me and I can work out a way to share it with you. I might even be able to find the original web site. It was the site of a BNSF hogger who used to post a lot on the internet, but I haven't heard from him lately.
PM me.
Mark D.

http://www.alkrug.vcn.com/home.html

Here is a link to the calculator..

http://www.alkrug.vcn.com/rrfacts/RRForcesCalc.html

That program works for scale livesteamers also.
I input your basic Colorado narrow gague info for a 1/4 sized K-36 and the average train it would be hauling up a 2% grade and the answer is within 10% of all my calculations.

Here is what I input;
Loco Hp 30
Car Count 20
Train Tons 20
Loco Tons 1
Car Face Area 5'
Grade% 2%
Loco Eff% 85%
Axles per Car 4
Curve Degrees 20

Here are the results;
Speed = 2.6 mph
Rolling drag = 2350 lbs
Grade drag = 840 lbs
Curve drag = 420 lbs
Total drag = 3610 lbs
Rolling Hp = 16 hp
Grade Hp = 5 hp
Curve Hp = 2 hp
Total Hp = 25 hp

Thats a neat program. Can we download it from somehwere?