All right, so by the Davis equation, my math formula set-up would be as follows:
w=50,000lbs (200,000lb max weight by 4 axles)
n=4 (4 axles on a covered hopper)
With that information, this should give me: R=0.6+20/50,000+.01(10)+0.07(10)`2/50,000(4)
Which should mean that to move one covered hopper at 10mph R=0.70096lbs of resistance, or did i do my math wrong?
And if I did my math right, then it only takes about 70.096lbs of tractive effort for a single locomotive to move a 100-ton covered hopper at 10mph... so something like a GP38-2 which makes 61,000 lb-f of TE could theoretically move 87 hoppers all by its lonesome. Again, if I did my math right.