Trying to bring my rolling stock up to standards before I complete testing for max grade. I’ve got my digital scale, the lead weights and my rule. My question is which NMRA standard should I use. RP20.1 (Car weight) has no direct listing for On30. They do have On3 (1.5 ounces + .75 ounces per inch) as well as S (2 ounces + .5 ounces per inch) and also Sn3 and HO (1 ounce + .5 ounces per inch). Which standard (technically “Practice”) should I be using. Any thoughts on the matter would be appreciated since I really only want to do this once. Thanks
I would think the On3 weights would do the trick quite nicely. 30" gauge equipment would not be all that long, so they wouldn’t be very heavy. If the cars are built to represent 3’ gauge equipment, as most On30 models are, then the On3 standards would apply. If they are truly 30" gauge models, then I’d use the S gauge standard.
First, the NMRA numbers are a Recommended Practice, not a standard. Second, the RP was developed back in the early '60s (maybe earlier). Back then, sprung metal trucks and die-cast metal locomotives were aspired to. Extra weight made the trucks work better, and the heavy locomotives could handle the extra weight up grades.
Fast forward to now. Rigid frame plastic trucks and plastic shell locomotives dominate the commercial landscape. Quality of track work is improved. There are many HO modelers successfully using car weights that are about 75% of the RP. In HOn3, lighter than the RP has been the norm for years due to limited pulling power of the tiny locomotives up narrow gauge grades.
Lighter weight does reduce the wear of the needle point axles on the plastic truck sideframes. And it increases the number of cars a given locomotive can pull up a grade. Heavier (NMRA RP or heavier) car weights allow sprung trucks to work better, and smoother automatic coupling. There seems to be less incidence of Slinky-motion of trains with heavier cars (my experience).
If your rolling stock and locomotives are plastic, I would use the HO numbers. If primarily using metal sprung trucks and metal locomotives, I would use the On3 numbers. But that’s me.
I’d go with the S at 2 ounces + .5 ounce per inch. On30 cars (at least the ones from Bachmann) are very close to S in size. The S formula will result in less weight per car than the On3, which is more in keeping with HO track that On30 runs on.