Adding weight to some of our models can be challenging. I’m working on a couple of HO scale gondola kits and both of them need additional weight. Adding weight with a load is one avenue but I want these models to be run when empty, too. Time to review some options.

The National Model Railroad Association (NMRA) established weight recommended practices (RP) several decades ago and were updated in 1990. You can download a PDF of these recommendations through the NMRA site.

For HO scale, the recommendations start with an ounce for a car, then add a half ounce for each inch of the model. A 40-foot box car is about six inches long. Following the NMRA recommendations, the car should weigh about four ounces. Some modelers like to overweight their models and some keep the weight shy of the recommendations.

I target my freight cars to weigh about 75% of the NMRA recommended practices. That 40-foot box car would weigh three ounces for my layout. I am using trucks and wheelsets that roll better than most of the equipment used when the NMRA RP was established, and when it was updated. I also use smaller steam locos and want them to pull or push an appropriate number of freight cars. Set your own standards and practices that reflect what you want from your layout.

Open top cars

Adding weight to gondola and flat car resin kits can be a challenge. With the current two models on my workbench, some underframe details are sacrificed to add weight. When weighing the models during construction, make sure you include all the final parts and trucks for an accurate weight.

I cut sheet lead to size for these models. Please use caution when working with lead. After handling lead, wash your hands and tools. Do not touch your eyes, face, or mouth after handling lead. Lead can be toxic if you are exposed to it at length.

The Westerfield Models Pennsylvania Railroad GRa gondola, has fishbelly side sills that obscure viewing underframe details. I cut slabs of the lead sheet to fit onto the underframe and on each side of the cross members. I created a paper template to use for cutting the lead. This reduces the need to trim pieces to fit. The extra weight brought this model to three ounces.

The other model is an ancient Funaro & Camerlengo B&O O-15 gondola kit. It has straight side sills, so lead pieces can’t be stacked like on the previous gondola kit. I cut lead to fit between the two fishbelly center sills and to fit between the floor stringers.

Once these lead parts fit into place, I used Barge contact cement to glue them into place. I applied the cement onto the parts and the weight locations on the model using a microbrush. After 15 to 20 minutes, the parts were set into place. For the center sill weights, I glued those together as one unit before installing them in the center sill.

The model weighs in at two ounces now. It is about an ounce shy of what I want. I’m tempted to install a thin sheet of metal between the underframe and floor castings. The shallow interior depth would take a hit with the extra thickness. I’m still mulling over this approach.

On a previous gondola kit build, I used Liquid Gravity by Deluxe Materials. These are very small beads that can be poured into place and secured using cyanoacrylate (CA) glue. This model has deeper areas between the stringers, which accommodates more of the material to weigh the car..

Even after adding the Liquid Gravity to several areas on the underframe, this Nickel Plate Road gondola remained underweight. I added a slab of 26 gauge sheet metal under the floor, as seen in the above photo. I’m considering adding a similar piece of the sheet metal for the B&O gondola noted earlier.

These are just a few ideas to install additional weight on a light freight car kit. A load can easily disguise the extra weight but I still want the freight car to run well without a load. Each model will have a challenge. Sometimes you can use an old technique, try something new, or use a combination to push the project towards the finish line.

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18 thoughts on “Weight”

  1. Eric, there used to be a #12 shot for “varmint” rounds, Snake shot, whatever. It will fill in very tight voids. I’m still looking for a source to buy some. I’ll let you know.

    1. Thanks for the link, Paul. I bought some shot for weight back in the late 1980s. It’s one of many things that has yet to turn up as boxes are unpacked. You mention it’s pricey, but if you are only using an ounce or two per car the cost boils down to 27 cents per ounce. – Eric H.

    1. You make me blush, Kevin. Especially when I recall a few self-inflicted issues with the recent gondola kit builds. I felt more like Shemp or Curly after those moments. – Eric H.

  2. Look for ‘used shot’, it’s a lot cheaper. Jeff Adam was selling this stuff, you might check with him.

    Another good choice is 1/32 lead sheeting from a masonry store. That’s a lot easier to cut than steel, as well as being more dense 🙂

  3. I have also struggled with ways to add weight to cars. I typically aim for the 3.5 to 4 oz. range as they track much better. I have avoided resin kits as they are so troublesome to add weight to (boxcars excepted). I have settled on moldable lead, lead flashing material and steel birdshot pellets (available for ammunition reloaders) eschewing some detail. Every car is a little different…

  4. Hi Eric,
    So rhe NMRA “Standards” were upgraded 30mYears ago but the recommended weight of a 40 ft.
    boxcar really didn’t change. Frankly, from my point of view I’e always felt a large part of the weight issue was determined by track issues. If proper care is given to making certain your roadbed is smooth and even with regard to vertical and horizontal issues and even the slightest easement is used entering ad leaving curves, especially less than 30 in. radius, I feel that 80% of eight problems are eliminated. Most of the rest are questions of “rollability”. In other words making sure to use decent trucks with their journals trued, machined metal wheelsets and checked for proper swivelling and limited ablity to roll. With these factors addressed properly I’ve never found it necessary to weight a 40 ft. car of any type to more than 3 ox. maximum. When I belonged to the MIT Model RR Club fifty years ago there were still a few caqrs known as “Guano cars” around. These were a dump or gondola car (can’t recall which) that were weighte with parakeet gravel and about 1/2 lb each. Some of them with Zamac cast truck frames had literally worn their journals out and had to hvae their trucks replaced. That’s carrying things to the exteme but in their own way I’ve always felt the NMRA standards carried things to the extreme as well which could have been reduced with more attention to other factors.
    Always enjoy your great blog, Don Valentine

  5. For my open cars, I generally use sheet lead between the subfloor and the scribed flooring. It reduces the height of gondola sides, but it is not really noticeable. I’ve done that several times with F&C gondolas. With closed cars I use either self-adhesive wheel weights or lead shot.

  6. rotometals.com sells lead shot in many sizes(down to #9 it appears). 25-lb bags go a LOOONG way for $53… but not nearly as far as a 3000 lb bulk shipment. ($4899.00).

    They also have bismuth shot (in 1-lb “sample bags” for $19).

    Perhaps most on-topic… lead SHEET as thin as 1/64″ (.016″)…

  7. I built a couple of HO scale resin kits over the past winter, a flat car and a gondola. A friend suggested Deluxe Materials liquid gravity which is really fine beads of tungsten. Using the nozzle on the bottle I put a layer of the beads in the gap between the two sides of the center sill. When I did this, I had the car body upside down on my scale so I could determine when the weight I wanted was achieved. Then I ACC’d the beads into place. The next day I ran the car on my test track which is five feet off the ground. When looking under the car from either side I did not see any weight, just normal freight car underbody details.

    1. Ray, I bought a bottle of Liquid Gravity from you at the 2018 MARPM event. It’s featured in this blog post. – Eric H.

  8. The NMRA Recommended Practice for car weight was developed in an era before RP25 wheel contours, and with trucks using blunt axles in metal sideframes. It’s quite obsolete, and I can’t in good conscience recommend it, but nobody has stepped up to do new research.

    That said, I find two constraints on car weight: First, weight needs to be fairly consistent to avoid stringlining on curves, with heavy and light cars faring about equally if consistent. Second, weight combined with standing friction needs be enough that one can couple to a standing car. This varies by the coupler used, as well as the materials of axle and sideframe.

    I would also observe that a lot of us are removing weights from our locomotives to make room for DCC and sound, which biases toward lighter cars so our locos aren’t slipping wheels with embarrasingly short consists.

    Anyone who wants to do new research — in any scale — I’ll gladly put you in touch with the right people in the NMRA.

    1. Bruce, I had thought an update was long overdue. While the current document has a 1990 revision date, I know I was following the same data points in the mid-1970s when I started building kits. – Eric H.

  9. Hi Eric
    I enjoyed this post…nice work on that cut lever for the NKP gondola!

  10. On a Westerfield N&W hopper build I added more weight by replacing some simple components with brass parts I made from scratch. I’m no expert by any means when it comes to making brass anything, but this wasn’t too hard and good practice for when I tackle a larger brass project. Not as heavy as lead, and I ended up adding some of that as well, but every part of an ounce helps. Still haven’t finished that kit…but from your blog I’m reminded that I’m in good company there too!

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