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How to Calculate Pulling Power for Locomotives

The pulling power of a locomotive is usually considered to be the tractive force the engine exerts on the train track. The train's engine exerts tractive force through the wheels to move the train along the rails. Tractive force is calculated by the formula T=(d^2 x L x p) / D, in which "d" is the cylinder diameter, "L" is the stroke length, "D" is the drive wheel diameter and "p" is the effective mean pressure on the piston.

Instructions

- 1
  Find the diameter of the cylinders in inches. You can either measure, or find this information in the train manual. For example, a Buchanan passenger engine has a cylinder diameter of 17 inches.
- 2
  Find the length of the stroke in inches from a measurement or your manual. The Buchanan engine has a 24-inch piston stroke.
- 3
  Find the diameter of the driving wheels in inches from a measurement or your manual. The Buchanan engine has a wheel diameter of 68 inches.
- 4
  Find the mean pressure of steam per square inch from a measurement or your manual. The Buchanan engine has 80 lbs. per square inch of pressure from steam.
- 5
  Multiply the cylinder diameter from Step 1 by itself: 17 x 17 = 289.
- 6
  Multiply your answer from Step 5 by the stroke length in Step 2: 289 x 24 = 6,936.
- 7
  Multiply your answer from Step 6 by the steam pressure in Step 4: 6,936 x 80 = 554,880.
- 8
  Divide your answer from Step 7 by the driving wheel diameter from Step 3. 554,880 / 68 = 8,160. The Buchanan has 8,160 lbs. of tractive force at the rails.

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