How many cars will a locomotive pull?

February 28, 2006

First you need to consider the factors that determine the length of the train you can run on your model train layout:

THE DRAWBAR PULL, or traction, of your locomotive is affected by its weight, contact with the rail, traction tires, motor and the power available. This pulling power is measured in pounds and ounces at the rear coupler or drawbar of your locomotive.

DRAG OF YOUR CARS depends on the number of axles, lubrication of the bearings and if there are track pickups on any of the wheels. The weight of each car is also a factor.

RADIUS OF THE TRACK CURVES is another factor to consider. The smaller the radius the more the drag. A reverse curve, without a straight line between, causes even more drag. Also remember that a clean track will reduce the drag on curves.

GRADE OF THE TRACK can be a major factor affecting the pulling power of a locomotive. Grade is the ratio of distance forward compared to the change in height. A forward travel of 100 inches with a rise of one inch is a 1% grade. A rise of two inches is 2%, three inches is 3% and four inches is 4%. You wouldn’t want anything steeper than a 4% otherwise you could experience all kinds of problems. (no more than a 2% grade for garden railroads).

So, the number of cars a locomotive can pull will depend on a number of factors.

As a summary here is are some important guidelines to get the best from your train set: Aim to have a heavy locomotive with adequate power available.If you want to run really long trains then it’s best to have clean track that is level or with only gentle curves. Keep your trains well maintained. The wheels on the locomotive should be keep clean, traction tires clean, bearings lubricated (including side rod linkage on steam). Have the locomotive motor checked regularly. Rolling stock should have clean wheels and lubricated bearings. Couplers should move freely to maintain alignment.