Scale dimensions are easily calculated but, scale weight is simply not possible. What is the accepted ‘rule-of-thumb’ for weight in HO and/or O scale?
Actually, weight does scale down… but it is kind of tricky. Scale factor is based on dimension, but objects are three dimensional. If a scale model is built exactly like the prototype using the same materials, the weight will be equal to the prototype weight divided by the scale factor to the third power. This isn’t really accurate for small scale models, since they are usually built out of less dense material (such as plastic instead of steel) and only represent the exterior of the prototype, not the exact details of the interior. This formula works very well for finding the expected weight of larger scale live steam locomotives since they are typically built from the same materials as the prototype and are very close to scale inside and out. For small scale models, follow the NMRA recommendations for reliable operation. But if you want to know what a HO or O scale model should weigh, just take the prototype weight divided by 658503 for HO and 110592 for O scale. This is equal to 87 cubed and 48 cubed, respectively.
I hope this helps you out…
- James
So, accepting your computation on faith, my HO model of a double-sheathed wooden box car with the posted light weight of 47,300 pounds “should” weigh 0.072 pounds, or 1.15 ounces, less than one-third of the NMRA recommendation. No wonder the prototypes could haul longer trains than us small-scale modelers.
Mark
Well, you did list the weight of the empty car. I looked up a double sheathed box car in a book I have (with a light weight of 43,500) and the capacity was listed as 80,000 lbs. So it appears the total loaded weight would be around 120,000 lbs. That scales to 0.1816 lbs or 2.9 ounces.
The NMRA recommends for HO scale 1 ounce plus a half ounce for every inch of car length. A 40 boxcar is about 5.5 inches. Thus the NMRA says it should weigh 3.75 ounces. It’s a little higher than true scale, but not too bad.