The Right Weight
Of Rolling Stock
Improves Reliability 

Derailments ruin the enjoyment of model railroading.

Having the correct weight will make freight and passenger cars stay on the track better. This is particularly true in the smaller scales such as OO, HO, N and smaller.  Taking extra care when laying track helps and weighting cars helps even more. Sometimes it is also necessary to add weight inside locomotives to improve traction on grades.

In larger scales such as O and G scale the cars are usually heavy enough to track well.

  • Light cars tend to derail too easily, especially when pushed through turnouts or curves.
  • Too heavy cars can pull a train over on a curve.
  • Light and heavy cars mixed in a train increase the likelihood of derailments.
  • Car length can be a factor when short and long cars are coupled together.

Visual calculation

model train weight calculating boardBoard with weighing marks

The National Model Railroad Association (NMRA) in Recommended Practice 20.1 proposed one ounce weight for an HO car plus an additional half ounce for each inch of car length.

Here's a handy tool you can make to check that a car is heavy enough at the same time as you  adjust couplers height.

The length of the board should accommodate an 80' passenger car, auto-rack or the longest car you plan to run. 

Put a re-railer at one end to help set the car on the track. Then mark a ruler in inches starting at the coupler. Got back and mark in the ounces and/or grams at each inch mark. You now have a quick and easy reference.

Notice that I have installed a Kadee height adjustment coupler at one end of the test track. If you plan to also use this as an electrical test track for locomotives, be sure to gap one of the rails in front of the Kadee height adjustment coupler, otherwise you'll get a short circuit.

Car weights

model train car weightsMy car weighing setup

There are commercial stick-on weights available. I use fishing weights, discarded pieces of metal and even pennies now that they have been discontinued in Canada. Whatever works.

See my weighting list options below for more ideas.

Weight chart

A chart was published in the NMRA Bulletin (now called Scale Rails) in March, 1987 and was supplied by the Garfield-Clarendon Model Railroad Club. 

You probably won't want to be quite as accurate so round up or down the numbers to the closest whole number. The NMRA data sheets cover recommended weights for most scales.

The chart below is for HO scale models.

HO scale feet Length - inches Weight - ounces Weight - grams
30 4.14 3.07 87.03
35 4.83 3.42 96.96
40 5.52 3.76 106.60
45 6.21 4.11 116.52
50 6.90 4.45 126.16
55 7.59 4.80 136.08
60 8.28 5.14 145.72
65 8.97 5.49 155.64
70 9.96 5.83 165.28
75 10.35 6.18 175.20
80 11.04 6.52 184.84
85 11.73 6.87 194.76
90 12.42 7.21 204.40

Where to add weight

fishing weightsFishing weights
weighing model train carsWeighing setup tools

Many cars are too light. If you're building a kit, figure out how you'll make them heavier before you glue the car together. 

There's nothing worse than going back afterwards to put weights into a closed box or tank car.

Here are some of the things I like to use, depending on the type of car. Fishing weights come in various sizes. BBs are also useful. Meltable low temp alloys that can be shaped helps in locomotive boilers and shells. I bought a product called "Liquid Gravity" that can be poured into cavities in model train rolling stock and boat and plane models. It was expensive but just the thing for special occasions where nothing else seemed to fit the bill. (www.deluxematerials.com)

  • Use a kitchen or postal scale to weigh cars.

I use Walthers Goo, Pliobond, matte medium or carpenter's glue to keep metal bits from rattling around in enclosed cars. Weights can also be hidden under loads.

Weighting options list

Fishing sinkers:

  • Fishing sinkers are a good choice for tank and hopper cars. 

 They are a little bigger and not useful for N scale but can work in HO, S and larger scales. Secure them with carpenter's glue or Walther's Goo.

 White metal:

Strips of white metal with a sticky back work well on the inside slopes of hopper cars and on flat cars where they can be disguised under a load.  These come in 1/2 ounce (15 grams) portions that can be cut off. A pair of pliers can be used to bend them back and forth until they snap apart. A sharp knife will cut the sticky backing tape. White metal is safer than using lead weights. 

  •    It's best to avoid handling lead weights too much due to the health risk of lead poisoning. 

   I remember when I was much younger and didn't know any better and I melted some lead cows and toy soldiers to make lumps of metal for my railroad cars. Not a good idea.

Pennies:

Pennies are also good for hopper and box cars. You can't get much cheaper.

Soft metal:

Soft metal is available that can be molded inside cars and locomotives. It works like putty.

Metal washers:

Metal washers and linotype slugs (if you can still find them) work well inside closed cars. Use two-sided tape to affix them to the floor of the car (or Walther's Goo or equivalent).


Weight cars to lower centre of gravity

Try to keep whatever you use positioned over the metal trucks (wheel sets) to keep the center of gravity as low as possible. If the weight is too high in the car it can spoil the result you're trying to achieve.

Sometimes you can put the weights underneath the car if you're more interested in operating than in fidelity to the prototype. This doesn't work very well if you have delicate brake rigging underneath the car. 

I once spent a few hours trying to locate a short circuit because a sticky-back piece of metal on the bottom of a hopper's slope sheets fell off and straddled the rails in a hidden staging yard. Now adding anything underneath a car is a last resort.

You may also find that changing the wheels to metal ones from plastic or putting on metal trucks will give you the heaviness you need as well as lowering the center of gravity. Metal wheels also seem to attract less dirt than plastic. They can be attracted to magnets if you use magnets for uncoupling cars.

A trick to add weight while keeping the center of gravity low, as on a flat car or tank car where it's difficult to hide weights, is to wrap rosin-core wire solder around the axles. Don't use acid-core.

Detachable flat car loads

You can hide some metal weight inside a hollowed out block of wood or styrene box and glue a magnet to the underside of the car. 

Now the car is lighter when empty and heavier when loaded and it is easy to remove the load. Makes your operations more interesting!

Other decisions

One of the advantages of making cars heavier is the limiting factor imposed on your locomotives. Now you have to consider the combined effects of train length, weight of train, ruling grade, and curvature of track. 

Just like the real railroads!

Most of us have a limited amount of space for our layouts. There never seems to be a mainline that's long enough. This, in turn, restricts the length of our passing tracks and that also limits the length of our trains. 

By weighting your cars to the recommended amount, you force your locomotives to work harder to pull the train around the layout. 

If you have  DCC you can easily cut in helpers on the grade, double-head, add a pusher, or run a special consist. 

It all adds to the fun and complexity to keep you and your operators busy, with fewer derailments.



Go from "weight" to adjusting couplers.

Go to the rolling stock overview page.

Go to locomotive pulling power.

Return from "weight" to my Home Page.


Return to Top


How to make Social Media work for you

New! Comments

Have your say about what you just read! Leave me a comment in the box below.
Copyright© 2008-2017 model-railroad-infoguy.com