Measuring the weight of a consist

@Gregcz1 posted:

I have found posts that explain how to test the pulling power of a locomotive, but my question is how can you weigh the amount of the consist to make sure it is not too much for the engine?  For instance, if a locomotive has 2.5 pounds of pulling power, how is that measured in the cars it will pull?

Apples and oranges.  The number of cars you can pull will depend on the cars rolling resistance to a significant degree.  If I'm curious about what drawbar pulling power it takes, I hook a scale to the lead coupler and see what I get.  Also, you can compress the coupler slack and pick up a major boost in the initial startup capability.

Truthfully, I find this out most of the time by hooking up the consist and seeing where it'll go.

You'd be surprised what some locomotives will pull.

Hey, John.  I noticed you are missing a few tank cars.
  Dennis

@Hartman posted:

Hey, John.  I noticed you are missing a few tank cars.
  Dennis

Maybe one or two...

Above: "Also, you can compress the coupler slack and pick up a major boost in the initial startup capability."

And by doing so, add a realistic touch to your operations; this "taking slack" was common in steam days, as steamers were superior to diesels in horsepower, but inferior in starting tractive effort. Starting one car at a time helps a lot. Old hands sometimes pulled car drawbars out by starting a diesel like they had started steamers.

On the original question, there are articles out there that show a straight track with a pulley at the edge of the table. Tie a string to the cars coupler and add weight to the string hanging over the edge of the table until the car starts to move. That is the load on the loco’s drawbar. Curves  also add rolling resistance.  I know how to calculate it for real trains, but not models, since some have wheels that turn on the axle. You probably will have to test a few cars on curves to get a idea about how much curves add to rolling resistance. The sharper the curve, the more rolling resistance.

The amount of additional load added by grades is just a simple vector analysis. Just construct a triangle to see how much of the weight is going into the track and how much is going into the adjacent car. On level track 100% of the weight is going into the track. If the train was going straight up vertically, 100% of the weight of the car goes onto the couples. Everything in between can be worked out by converting the % grade into an angle and then working out the triangle. The hypotenuse is the weight of the car, the short leg is the load on the coupler and the intermediate leg is the load on the track.