Trains

I never followed-up on the question I sent out last spring about trains. I was wondering why it made sense to run those giant hundred car trains with two engines in the front, three in the middle, and one in the rear, instead of two fifty car trains. When you look at them it’s easy to imagine two fifty car trains, each with two engines in the front and one in the back, that just happen to be stuck together.

We got lots of good possible answers involving logistics, unions, bar loads, and cost analysis. The most targeted had to do with “Distributed Power” and came from a guy in Kansas who works on the railroad. Thanks to Casey for forwarding my question to him.

There were lots of details in the explanation. 143 tons per car. 4000 horsepower engines. One horsepower per ton on mostly level ground (like Kansas). Details that contributed to the credibility of the answer about Distributed Power. It all comes down to knuckles. With trains, you have to protect your knuckles. A train slows down when it goes up a hill. When the train tops the hill, the front end of the train wants to run faster as it’s going downhill, but the back half of the train still wants to go slow as it continues to go up. This creates stress on the coupler knuckles. The engineer can manage this with distributed power (engines in the front, middle, and rear of the train. Don’t want too much stretching and compressing and slamming of knuckles. The front end could even start to go up another hill while the middle was going downhill and the back end was still going uphill. Distributed Power manages that.

And scheduling. Imagine the scheduling challenges to keep track of every train on the continent, making sure there is only one train at a time using each section of track. You can schedule a gazillion 50 car trains, or a half-gazillion 100 car trains. I think I’d want to schedule the half-as-many-trains option.