Re: Porter 1203

Diesel #21 now at the Loop is a 44 ton locomotive riding on 2 axles, thus each axle is acrriying 22 tons, each wheel 11 tons. Its problems come not from its weight, but its axle loading and the fact that its is only about 18 feet long (thus the weight is very concentrated). #21's short wheelbase causes it to "hunt" (basically wiggle back and forth) at speeds over about 6 miles per hour, this is especially pronounced when entering curves. The faster you go, the worse it gets. All of that weight banging back and forth puts alot of stress on the rails and its derailments have been caused by the locomotive literally pushing the rail out of gauge as it bangs from side to side.
Remember, this locmotive was specifically designed to be used as an in plant switcher in a steel mill, not a road locomotive.
Diesel 1203 weighs about 70 tons, but rides on two 3 axle trucks. Each axle carries about 8 tons, each wheel about 4 tons, or less than half the weight on each of #21's wheels. More weight per wheel means more stress on the track.
For comparison, "old Loop" locomotives 130 and 140 weighed about 57 tons which works out to 14 tons per axle or 7 tons per wheel. The passenger cars used by both the past and present Loop operators weigh about 11 tons or 2.75 tons per axle, 1.5 tons per wheel.
Jason Midyette