Bender says that the tightest curves on Baxter Pass were 66 degrees. Neither of the mikados were designed for such curves -- that is why they stayed on one side or the other. To get over the pass the Uintah used Shays, two 0-6-2T locomotives for the passenger trains, and then the 2-6-6-2Ts.
I would think that both of the mikes were disassembled for the trip over the pass. And then, maybe the #40 was selected to be brought back over the pass because it was lighter than the #30.
The degree of curvature on a railroad is the central angle of a 100-foot cord. The higher the number, the tighter (smaller) the radius is.
1 degree curve = 5,730' radius
5 degree curve = 1,146' radius
10 degree curve = 574' radius
20 degree curve = 288' radius
22 degree curve = 262' radius
30 degree curve = 193' radius
60 degree curve = 100' radius
66 degree curve = 92' radius
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