what make up a frieght train

[Anonymous]

hello guys. how's it going. my name is deron. can i was wonder can you help me with this question if you can.

i know that a freight train is made up of the locomative and the frieght cars that it pulls that make up the train. my question is. how do they know how many locomative to use to pull the frieght cars that make up the train. that is the question i'm trying to figure out.

if you know the answer i would like to share it with me.

your friend deron williams

[ndbprr]

Every engine is rated for tonnage it can pull with a chart for grades. as the grades increase the # of tons drops. This is tested and supplied by the manufacturer. The railroad has charts for each division that determine the ruling grade to be encountered in that section. By matching the two the tonnage the train can pull is determined. Mostly the length is based on tonnage but there are exceptions. Obviously if a train of empty cars is pulled there will be more cars to reach the rated tonnage than full cars. In some cases passing siding length will outweigh the tonnage ratings so trains can pass. Railroads also need to verify that the engines can pull the factory rated tonnages on grades since curvature can also add friction reducing the rated tonnage further. Setting tonnage ratings for model engines can add another element to running a model railroad.

[tpatrick]

It takes about 4 pounds of pull (tractive effort) to move one ton 35 miles per hour on straight, level track. So a 10 thousand ton train would require 40 thousand pounds of pull to move along. Almost any engine can muster up that much tractive effort. But grades make a huge difference. A 1 per cent grade (one foot rise per 100 feet) will add 20 pounds per ton. That means our ten thousand ton train needs an additional 200,000 pounds of pull to go up the hill. Two large modern diesels can do that. Of course a two per cent grade doubles the extra effort needed, so you can see how the need for power rises.

I didn't address the need for power to start the train. There is a formula for that which I do not have. You can be sure it takes a lot more to start the train than it does to keep it running after it is started.

I hope this helps.